<%BANNER%>

Time-resolved infrared studies of superconducting molybdenum-germanium thin films

University of Florida Institutional Repository
xml version 1.0 encoding UTF-8
REPORT xmlns http:www.fcla.edudlsmddaitss xmlns:xsi http:www.w3.org2001XMLSchema-instance xsi:schemaLocation http:www.fcla.edudlsmddaitssdaitssReport.xsd
INGEST IEID E20110114_AAAADE INGEST_TIME 2011-01-14T16:35:18Z PACKAGE UFE0008001_00001
AGREEMENT_INFO ACCOUNT UF PROJECT UFDC
FILES
FILE SIZE 2276 DFID F20110114_AABYRI ORIGIN DEPOSITOR PATH tashiro_h_Page_080.txt GLOBAL false PRESERVATION BIT MESSAGE_DIGEST ALGORITHM MD5
2f8310ec9a8f5fdd6b312234ef7c65b5
SHA-1
0f4862aaae2180c1bff56e5b507b71b0367567fb
285074 F20110114_AABXHE tashiro_h_Page_166.jpg
01553e3bc1f32a2b7daed5cd2423f2af
30f5c3cc1a2b49bc7721e766cd28acf763ee999e
1821 F20110114_AABWXW tashiro_h_Page_170.txt
d28456def8962675a25ef99b43691a06
fd69be90bb704a9d8d7b04898143fe1ca47df3cc
171810 F20110114_AABXUP tashiro_h_Page_187.jpg
4de362ddd248e48dcf39d3ff18dfeeec
3ca5ae477ee4ed666bc89a330ee5234d949ece49
1630 F20110114_AABYRJ tashiro_h_Page_081.txt
f08e3dacf94f3e87366789112a0662d4
88f3e56ac589f7ef32d009d0bbc8b4d4e1d7ed84
54113 F20110114_AABXHF tashiro_h_Page_079.pro
1e6c0b6c0a6c9b689ce4dafe23acec65
6c6ec0797f80eba2ae66690ed1087c0b4eb22993
40312 F20110114_AABWXX tashiro_h_Page_046.pro
8da3faa7c74a81c1529ff8077502bd92
9c8b51b8a8ff0207a7af9b8a4f103ede16a1ded4
200102 F20110114_AABXUQ tashiro_h_Page_188.jpg
f58572588eab1e2fe6b204a8176c76da
c7c88f884426e82d3accce6da5ede3fd3b74f923
2007 F20110114_AABYRK tashiro_h_Page_082.txt
c709b58e70ca99b6f6035895c88b1320
433d471b163e3eb2f47963f3547d32ecca5e4d42
97658 F20110114_AABXHG tashiro_h_Page_055.QC.jpg
922e4cfb61c1a5a79e14a546d5937ca7
cbd22ff41556977077ec7ed449859e1d8e67cfec
170626 F20110114_AABWXY tashiro_h_Page_068.jpg
4d0651c569325a3e2659cc0ff088db74
1ed0996e68639ddba31cfa8af11b88fe288bfda5
260997 F20110114_AABXUR tashiro_h_Page_189.jpg
938a6a563f941f4747a57add3d7f46f5
c4776ba036ff82dafa1396749e5d9e1150ac8632
2165 F20110114_AABYRL tashiro_h_Page_083.txt
538897247b7beb9b9848a6fbdcf4f13c
78387674318360a16697e8246ca6bfcbeb39832c
141160 F20110114_AABXHH tashiro_h_Page_211.jpg
96f5fbe2ad3c14ff6334b9d1e0fd226d
3d1959b51591ac8ab559d501b4c12106fe98cd56
1051948 F20110114_AABWXZ tashiro_h_Page_216.jp2
5f03de81875c968ee7373985ac9528e8
7b667b0abbba496cfa30447594ba85bd5752f1cd
25271604 F20110114_AABYEA tashiro_h_Page_058.tif
fed37d080dd231709013edd22b48585f
381be81795336e6a2912bb9c52df76be97b288e4
210182 F20110114_AABXUS tashiro_h_Page_191.jpg
c990309322911976da9e4bb41447c5b8
0b43ffd59b94385b1c4eb9f498a4ec7f01311f47
1686 F20110114_AABYRM tashiro_h_Page_084.txt
160c7db0f89bf2394fd263d768b011a6
19130f2a64e98128c0e57ac064643599f7ecf612
113185 F20110114_AABXHI tashiro_h_Page_186.QC.jpg
985e2b23ca29f8ea58e0749bbd6ed2da
a53fc2528c03c0bd62d9c9967a3083e76525c05e
F20110114_AABYEB tashiro_h_Page_059.tif
37f3b74c3d789b8c04b73e5906afc1f1
44e6c877cff7485cc8c55fd4c153804c43684e76
210101 F20110114_AABXUT tashiro_h_Page_192.jpg
8eb7eeda19927ae50083e320b976c217
3891cb590e5c49d3a981e37eed402891be874f89
1942 F20110114_AABYRN tashiro_h_Page_085.txt
eafe7680d65e0abc63a40fda56fdf17a
c48f54f0c62f6ae91b692d7bb412e02d0f39fced
43643 F20110114_AABXHJ tashiro_h_Page_032thm.jpg
fd80d5c92201ba9fe8464636177cea99
39062dd93a71d9f0cfa0da7b8beadbf847286dbf
F20110114_AABYEC tashiro_h_Page_060.tif
0442214c167eee85d4335b32d84c1537
2cbde44ff48de70d01924439d4a0c0c047a5e303
230730 F20110114_AABXUU tashiro_h_Page_193.jpg
aba3151a0885a19871221cf3419ba854
bef43c45679c3989640d93e53434894e969a2e06
2185 F20110114_AABYRO tashiro_h_Page_088.txt
ce11fb38fd6d46e7cba2efc95c0589aa
a1fb0b763db12ecfe6fe5ea2be1275d66d1c4668
51176 F20110114_AABXHK tashiro_h_Page_149thm.jpg
c2c577bfca56988f88993a31bfb7fe02
6cab66396da0749f266dd82adf24eeb6ff825a6e
F20110114_AABYED tashiro_h_Page_062.tif
9ab9946a9016c9843256afd44dcb93e9
dc593b884082c2939f8e0a55f4566745ac79a94e
233267 F20110114_AABXUV tashiro_h_Page_194.jpg
eab61cea01ab3ad931fe02661f9ae8e6
2e464558c07e6b2fd7320d18fc06ae4d0cd09627
2095 F20110114_AABYRP tashiro_h_Page_089.txt
43cbb3fce96228f583ecafbece5dd37e
d56300916f5696dd59f619f4740c0790c3e93c8a
1051955 F20110114_AABXHL tashiro_h_Page_098.jp2
bb096d4f4bd37bf9c2a69798562bdfe4
e4372620c57985afa2845c84f2a3b689dd4b328e
F20110114_AABYEE tashiro_h_Page_063.tif
9635d228ddcbfed44662c1bfb0452fac
ec74f11c909f951d7844b747d7d587b933cbf37a
251331 F20110114_AABXUW tashiro_h_Page_195.jpg
f49ab7ee2bf2909c8e30680e14b5c6f8
7ee4ed61250eed10c407c67fed35fbc17383a3f2
2203 F20110114_AABYRQ tashiro_h_Page_090.txt
4b36fcd6aa799c842cceaa8dce262baa
0818ef0ad8ed5be552ede644322e784f94678dde
29991 F20110114_AABXHM tashiro_h_Page_052.pro
322b7e62a81fe49b5fc66ed3b9d164cd
c83e5ed87f43a0e87767ee05c5f838e1d7bb95c2
F20110114_AABYEF tashiro_h_Page_064.tif
68c59e9a7d432b428a1a23d46eff42fa
cce5d456c475034c5a286ba9196d3ca3667a551b
232999 F20110114_AABXUX tashiro_h_Page_196.jpg
97287c52f3e3a1a63143c637d7a2126f
19a95ba4277d500d11fa40e95b71cc79c5a6529c
2412 F20110114_AABYRR tashiro_h_Page_091.txt
43971be5aa76084da15c138f4b32ac68
679ef75af52b1cf31ad99048eaf5c4e4aab23749
63338 F20110114_AABXHN tashiro_h_Page_005.QC.jpg
2c43653c41239531e6d59dfb335ce301
05bc42414291dc1b647f1a29bcfc1b9408496d5c
F20110114_AABYEG tashiro_h_Page_065.tif
71ee0d3376c50d79f8666eb2423440aa
947c99c16caa62fabadfb39197674eb92016c3bb
249816 F20110114_AABXUY tashiro_h_Page_197.jpg
abf81fb74e935372f0c2d79fb90c5a5b
f57ffbcaddb2cb12806b641d313c5bdc8413ce65
98617 F20110114_AABZBA tashiro_h_Page_078.QC.jpg
fa1f5e5927cac1adb03bbd3b7acaa7d3
57cfc6db3e9e90e62b1b58711539218565342531
2069 F20110114_AABYRS tashiro_h_Page_092.txt
1a439d4038fa2039efc9be11fc71ef27
21f8b4702e406fa14294edf09da5a823b4629cd6
115833 F20110114_AABXHO tashiro_h_Page_071.QC.jpg
a8189a9cc5dd03f51a3031f4571e3405
d7a8dbfa1baebdc0da2bdc6bfd86c0a25e62c9a4
F20110114_AABYEH tashiro_h_Page_066.tif
2feb299d4aab9ba4d0c40a5130f0dcd1
32896070291ea7b9183895ad2c4e6c6a2b09f9db
183162 F20110114_AABXUZ tashiro_h_Page_198.jpg
b79992147592a89fd13dbed7d11bcb55
64a32defd5b67dcbb9e7450924a95ec5d5ae0a76
44741 F20110114_AABZBB tashiro_h_Page_080thm.jpg
4d4bfe14669f218c598a0809f843f4de
86d7302e5f7bf92f78348cdb6af0c5b0a330e5d1
1725 F20110114_AABYRT tashiro_h_Page_094.txt
89ee253348ebbe6868a4a92db1d6949a
a9a3716453b83288eb21111467e38a8a5d1ea699
112203 F20110114_AABXHP tashiro_h_Page_066.QC.jpg
06d96bd9347579f62a86df0f3a94b5b6
bdbc099e60a4632b5fc84f619ce816b9d85e9c20
F20110114_AABYEI tashiro_h_Page_067.tif
ed605d40152cd5c5856c498c56aff8b8
6ac5883c8d21e6b8847a97a1db5b1731bf04dc02
46039 F20110114_AABZBC tashiro_h_Page_081thm.jpg
d0aeecb75b04f21e263ac510c2fe786f
b0a122cacce22477b5afe07001bf865e1919e555
1747 F20110114_AABYRU tashiro_h_Page_095.txt
bf438b6854430c69791c0d612cc07692
1ffedd0044c3386debd78db2bf15c857869cf431
710846 F20110114_AABXHQ tashiro_h_Page_225.jp2
62780c6bb0e1e5333edb0a3732bea8f1
a1ca6cde67b8242ce33836bdc79b4338fce99b47
F20110114_AABYEJ tashiro_h_Page_070.tif
82574cbaa1d00d0f321f8ca64919c4ce
fa19075d18ead1a5bd287a2f421b7b7977e69c74
86818 F20110114_AABZBD tashiro_h_Page_081.QC.jpg
927b9a7f34a4231fd152503c811b40d5
bf84d9efc5922a9b35e08f0c5aa2d1fb4dde42fe
2343 F20110114_AABYRV tashiro_h_Page_096.txt
4114869792608c79b94a98d9349a8947
f78e8f7e08b2a9b089b0c53d38b2d5a6e7c71c37
49840 F20110114_AABXHR tashiro_h_Page_069thm.jpg
d6ca84a0dd8ac66959c8e1e136ad5fe0
b3610089a3fb36b62d32db3d352ce032838e6e15
F20110114_AABYEK tashiro_h_Page_071.tif
b38a81f4237d8e058e406cb48ae4d1e6
78c015d6b3c3f67b110f7d851c8ac779fde949a2
49238 F20110114_AABZBE tashiro_h_Page_083thm.jpg
2114e410dd046c13e192f1a2a640c71a
abce0851a5434ebb54d32c4d0dd02a18cb43605d
2279 F20110114_AABYRW tashiro_h_Page_097.txt
712f0386c483015fc471b5131f7d6b38
6aee54d14812dde7522ff8e23201a9d779b54727
1051976 F20110114_AABXHS tashiro_h_Page_221.jp2
3acc000ea691e19f0ab7572fbf73e36a
8cbdd27e94e6842c930e255a7570b9a94e33afb9
F20110114_AABYEL tashiro_h_Page_072.tif
9fbb50a629a2ee03626a5605518f1287
7f642a00c9da17b5bcaeba4e12ae6dadefea47ba
102665 F20110114_AABZBF tashiro_h_Page_083.QC.jpg
b5d4c59deaaa444fab2c06036234e303
ea12891ac15220918124e9e4e78417f90a5eda8a
2257 F20110114_AABYRX tashiro_h_Page_098.txt
924b050a6b4d79fa2d7e76180d6e0d50
f554b30f73424e7f0dea80a8f59e0e6e11552798
96431 F20110114_AABXHT tashiro_h_Page_075.QC.jpg
534cc6a258fd6635f4538ddcb1bb40f8
d6f4843a7a7b14bd3e12e41058892f5f6c95015f
F20110114_AABYEM tashiro_h_Page_073.tif
6f4b9cfa8d2b94db07165ff3b173e036
e45d16abc45d6c18534608c32a6ff82ef6696838
86388 F20110114_AABZBG tashiro_h_Page_084.QC.jpg
99e3db8a768f3d69d931baa64231e26b
4165004fd97cb3463c75a143427edbd5baa7f002
1533 F20110114_AABYRY tashiro_h_Page_099.txt
08dfb0cfc169e27f7a3f6da0da0ff382
38c6c222032db0376098b72915fc13f400c6a45c
48700 F20110114_AABXHU tashiro_h_Page_139thm.jpg
9f48eb55f3e0ea265aab4d912526016b
0a9dea8d6b7ecb32f019deb6b0082adee6034fb5
F20110114_AABYEN tashiro_h_Page_074.tif
4f38f76a802eb608f3fc898921a4ff09
bae4e8ecd2b9add3e7a7cf61681be99d2ce309c5
46343 F20110114_AABZBH tashiro_h_Page_085thm.jpg
fdd3bb160faa2ae4ffde50057786e010
19343140f78aa605268b12614fdc54253a9284f4
1988 F20110114_AABYRZ tashiro_h_Page_100.txt
7661ff70d1810fec65440c954ab3aaea
8c8c4b827c1083a0f6c7efab61f67aa161ef4bb8
46680 F20110114_AABXHV tashiro_h_Page_157thm.jpg
45102acf83aa68098fad96829f1f2f38
0973d95fbea662d416a925a00427606cdd92d046
F20110114_AABYEO tashiro_h_Page_075.tif
4ad321554972454396ebf1c36d3ff0d7
95903e574284db3747a26ee429e3f374dd6064e0
93757 F20110114_AABZBI tashiro_h_Page_085.QC.jpg
6a4a0aece54ed3ce38ab5f25c51c8b76
04d2093fad87b5f76b6c197b2465d9e42f8e7b95
52538 F20110114_AABXHW tashiro_h_Page_158.pro
7157f6518c32b507d621e5c9d9ddb34d
96fc2d7807425319ac534621e02dd6f8388c4495
F20110114_AABYEP tashiro_h_Page_076.tif
a7805adce7ee2ff351a2ac6e9f5c2a6b
bb65fb78d576031f1d833245f6f5852c53c6c94d
46569 F20110114_AABZBJ tashiro_h_Page_086thm.jpg
54d269c20f04c3933429b4f3bbaedca5
b0b8388a08fb44a4e513068094f000e71c64fe5e
118630 F20110114_AABXHX tashiro_h_Page_115.QC.jpg
7690c9a295c309184a6c430532dac314
08e76fc125de55f4c966f173b93475cb169126fa
F20110114_AABYEQ tashiro_h_Page_079.tif
1b2ada40cbcb4ed5c277a6830c793dd9
9b3c5ced39a6212b8f0db3892ef7f3d6e207aa21
47917 F20110114_AABZBK tashiro_h_Page_087thm.jpg
c78213338ba1ace8fce43e733d36e8b9
81bdd5daf62b4594a65d749635b52003bd14d0ca
33510 F20110114_AABXHY tashiro_h_Page_233thm.jpg
113481f5f536593e757d1c5a5d6340ae
e45065b48c4cc02af0773420faa253016bb10c20
F20110114_AABYER tashiro_h_Page_080.tif
a94c059ee5ea5e4c4f2c72eda4c8a24d
3e9a300bc0842f3a97caf74f09a6e162af4648d8
100187 F20110114_AABZBL tashiro_h_Page_087.QC.jpg
6f160dbaa38a8f521ee36b7e35c77bba
10f5c328180ce141dbc677438464cae6fa154fce
40178 F20110114_AABXHZ tashiro_h_Page_051.pro
2175d5cd34df560b38ff5552cbee352b
f3aaa37c8a3dade5aa4eec01b4148b704f31a904
F20110114_AABYES tashiro_h_Page_081.tif
98d392137f26337d0ce5ee020852c5d8
95c1fd92bbf7649675416ebd27222cd08c4f4411
47721 F20110114_AABZBM tashiro_h_Page_088thm.jpg
ab398e1a84c9702f7bfb3418e47aa63c
a9d8836ced090bd6d6ba11fec6f1306ff7b38ee3
F20110114_AABYET tashiro_h_Page_082.tif
ee875c2ec7cf973772a1c248c75f18e0
e9b7bf7e65a556e6f93b6d5c6eb9f3d444ff51ae
103648 F20110114_AABZBN tashiro_h_Page_088.QC.jpg
a74466b2659ff7f6f647d938d8835da8
a5d31c033a956f77b9a6b3b718fa113295df3dcf
F20110114_AABYEU tashiro_h_Page_084.tif
853967c5d1df408305ab5c880cadbd65
b6d8b940ab507e806f2cef1498b955d6c727ca01
48716 F20110114_AABZBO tashiro_h_Page_089thm.jpg
6988e329bc6e2f4bc9d9c43016a4c631
f91805248d37010c30746cf8f07c4c5efd702bc3
F20110114_AABYEV tashiro_h_Page_086.tif
e7f5f8b370297a812b0b2f710fe219f8
0584248349d1bcecb1103fb15dcd756535bbffa0
48115 F20110114_AABZBP tashiro_h_Page_090thm.jpg
a6430f374bc1758bdd4e325baaeca9a2
3904eeebf65ca5e386d72aaba26b39f70ebbbce1
107675 F20110114_AABYXA tashiro_h_Page_159.QC.jpg
9537d016af12c039cfeafd42b2ca7aee
742ade58a985eed284eded6e9318c4d92b8f00d5
48525 F20110114_AABZBQ tashiro_h_Page_091thm.jpg
16961684bf569fa48b2b2acecde31ed8
ee9fbbf06bf200b1dc6505f0d4f4c5d904982898
F20110114_AABYEW tashiro_h_Page_087.tif
751a181b686d774d018f4b335579c56b
a2f783d8f0cb9dd2d3d4fd90aaaf48755a31c533
120799 F20110114_AABYXB tashiro_h_Page_060.QC.jpg
236a2577bca930d0851e9998952d35ea
6f789d33ecaa6c2d842c351d2ff733a2f36296f6
107366 F20110114_AABZBR tashiro_h_Page_091.QC.jpg
97f4d7a31b43c2d4b6c75757db77f9af
88ca5346a78ead22c26df57caa585571944eda4e
F20110114_AABYEX tashiro_h_Page_088.tif
567cd6c256eacbba3bc3644520410f8e
30874f29a80458e723a8e5389208d87c38e02614
87376 F20110114_AABYXC tashiro_h_Page_050.QC.jpg
253c59f2a3f3c8f1145032562e7f09d3
9bf137720960170f196ee07a1b40a4d820d6c623
F20110114_AABYEY tashiro_h_Page_089.tif
d11bba426c6ea797c5768fb123abfce5
7d7c1a2af878d23730839adfa4e1ca21baa8cb77
124425 F20110114_AABYXD tashiro_h_Page_119.QC.jpg
7ab6fd1bf93407073c337239b95a87fe
0175265e427421143ef97e53729b10168ca06d93
46206 F20110114_AABZBS tashiro_h_Page_092thm.jpg
797a58c8d1fbb88e6442c4fe4f2d59fd
7ca7499049818a4a5c3b84e2d43e3cfae13353d8
F20110114_AABYEZ tashiro_h_Page_090.tif
196e27242b58011ef35292102b43639b
4bf4248bd7edc785ab5bd66b4b43fa0368b1f039
49573 F20110114_AABYXE tashiro_h_Page_118thm.jpg
5b6a5294c4baccfa48cc8b24763cd678
5e59883afe549ebce9ea8f5c1a75d0b1d0d4e264
89509 F20110114_AABZBT tashiro_h_Page_092.QC.jpg
6e3ee4bcfaa278f019e18b0442a415bc
b04cf4f570675ad6ff2bf59a9e3e7594e23c9e56
45341 F20110114_AABYXF tashiro_h_Page_036thm.jpg
50016a13662a3d546c596ef5d67e6ef8
aba5b051f91e9d9c600fd3f9d281f35cc78e6934
45659 F20110114_AABZBU tashiro_h_Page_093thm.jpg
df510bea306370542ef69608b7f2fef2
f9082806e7a20e0080c398dd24b50ab19fcebaa0
60792 F20110114_AABXNA tashiro_h_Page_148.pro
37fa19d9ab9c6ce909016e53ad3ea908
4f6839e4a4d286b0354c41d6a696ae37bd8dac93
46052 F20110114_AABYXG tashiro_h_Page_134thm.jpg
f39a4af0e95d1e13fe49a49ad0ff763d
85f5ac2ffa7ee1b731258ef186311eafb8fecde7
85097 F20110114_AABZBV tashiro_h_Page_093.QC.jpg
554211c61b726361de7d1546cbc258d8
23383b5e177168352bef96cf358089c425c710a7
47701 F20110114_AABXNB tashiro_h_Page_178.pro
3a1af6dd3bf37fa64d61490bd426ccfa
8b8d28231fd04231ad63ea5e2be3e6a542a71562
80873 F20110114_AABYXH tashiro_h_Page_182.QC.jpg
8ce80657b42d2d9ea4a37cfac1bf8ba5
6e1f7c934d0b6819914cc93f2c90923940483b53
46971 F20110114_AABZBW tashiro_h_Page_095thm.jpg
1c93c7e4541218b44ef07028302f16eb
d4b85cb044f148e59d4120429ebe297ecc67421c
1051972 F20110114_AABXNC tashiro_h_Page_174.jp2
64c491f93739129d96a3527efabc94a6
6d4c3a8d72af70a02b247023c62f1002ead9391b
121716 F20110114_AABYXI tashiro_h_Page_140.QC.jpg
4c348bb474f98e2686b5904ee84fad65
571cfa12440f957bd9df27375f63cde4f35848b8
114091 F20110114_AABZBX tashiro_h_Page_096.QC.jpg
a72c93efb4821de43c35f07e70547e12
a3e167ad3c5fe948e09c479d20df79a8111fd42d
108615 F20110114_AABXND tashiro_h_Page_064.QC.jpg
797f3bab1247d872d980a9ebd6d89f9e
58a3535be753e747d8f22115b4d5fe925326c733
109418 F20110114_AABZBY tashiro_h_Page_097.QC.jpg
55cde56a412a9e576763453a8a99478a
3cc6eb1511d2fb31b192c645d682b2c1b0dd5cc1
1846 F20110114_AABXNE tashiro_h_Page_077.txt
7129eb452871f177eb76ded5b03c90dc
eaf379583ed54c6af432e1f490602f2ef225d190
108208 F20110114_AABYXJ tashiro_h_Page_059.QC.jpg
a4aebef502216439b60a68ba1bec5a39
4dd34e65c28609da45337b401a015be989e258e0
49292 F20110114_AABZBZ tashiro_h_Page_098thm.jpg
cf246f6f1842436cdd751d18721f4877
696656459214b033bd33fdd85b4e6517d29af9d9
98258 F20110114_AABXNF tashiro_h_Page_033.QC.jpg
a654f40019cff4b10c4e48ce1689959f
24681c415b74e8a34736156ddec1d6a3805c5135
2090 F20110114_AABXNG tashiro_h_Page_074.txt
87b2c827875812eb03bff5057b24d420
8da41bc2d91b35a26c484226b4a79de53b96acee
350280 F20110114_AABYXK UFE0008001_00001.xml FULL
f9cbbf1c75497af819476e9b85d1ac2d
45232bbc6674176de18e59b72f64a11fd24a06a3
52621 F20110114_AABXNH tashiro_h_Page_174.pro
34a4e82cc9021aa18c89c680d11c01b1
b6a884584199a6b1ada66d6d4daafee58db2e745
37120 F20110114_AABYKA tashiro_h_Page_034.pro
df88c33f4c8b6891b2a8c3fd070c6451
e8ced32b85e6a07d3172ca6f8962044c9e88f47a
32290 F20110114_AABYXL tashiro_h_Page_001thm.jpg
f83984e7f73786b2ad0d177eae1600c4
9da80aa6e9ee6c49a22af5521679d62deb7c38bc
204018 F20110114_AABXNI tashiro_h_Page_036.jpg
1bd512d68fbeda1cefdd547bed76b8f1
b04829a764cfd4cc5553a80a3a213f11f353d6f1
46449 F20110114_AABYKB tashiro_h_Page_035.pro
2ac274b69089c6c6f7849b4a14bacf9a
00769fa824414022014b7b6740c57b0d15970b99
28521 F20110114_AABYXM tashiro_h_Page_002thm.jpg
2af0f558ae9dbe9ffd9caa8ed06e3003
d651814a380431a5650cc0909913d548bf57d1ab
1051936 F20110114_AABXNJ tashiro_h_Page_087.jp2
dc51fb0494f3c37accb1b0821e2160f0
dbd3c99b58933bb589467341c1ce783c610211f5
40840 F20110114_AABYKC tashiro_h_Page_036.pro
612fd8742b607dd546ca88c9832336d4
5e2538b16f56316304bd20d518d7fa9b1ab08361
30740 F20110114_AABYXN tashiro_h_Page_002.QC.jpg
ff41f26e011fa51022eafdf0dffc7daf
c941b15465ea3da01e01325b5adfe0db9b643d2e
219991 F20110114_AABXNK tashiro_h_Page_173.jp2
177c64485e4a39f8ff09af8ed2c99ce0
8ef2364191e01401b86a747eabf95f1e147e1640
40489 F20110114_AABYKD tashiro_h_Page_037.pro
40ab5aedca96abd1cd847db16f2ae9ed
407d766173876af2280a6d249750f24990c6bd5a
28227 F20110114_AABYXO tashiro_h_Page_003thm.jpg
5a7348f5ab083ebda5d169e15325b2c6
758c8cbad09fcec1fbae3187f75831d29009da56
2620 F20110114_AABXNL tashiro_h_Page_127.txt
5ec155d457f599e464b728ee78d4b560
d3da499eeff66dd4b9f911f9a3b6d5e73b245548
48142 F20110114_AABYKE tashiro_h_Page_039.pro
3b5f1470a7198364ab86875e00c8e7cb
46009036e3cbd04b308cfe272cbb1bf1b4c0bf8a
51345 F20110114_AABXAA tashiro_h_Page_017thm.jpg
4fd500590c1ea3ae5ec4ff728d2a4d75
b42ad8f7c71630a8d7abede9663066f0d3af73cc
30579 F20110114_AABYXP tashiro_h_Page_003.QC.jpg
b82516d04679f7d8615722cd1687faad
de0b8af518efc3349a66e07dc5f01a4a703a2ad4
52058 F20110114_AABXNM tashiro_h_Page_145thm.jpg
7ee18bb3ee01e1b88731d78e3d566548
5039cf02630292ce4269ce612efce68ff44a98f4
42774 F20110114_AABYKF tashiro_h_Page_042.pro
1313adb49cb6aef06526d1775795abbc
113496e2607fae5718e346bf1eb77f99a6eb094c
214734 F20110114_AABXAB tashiro_h_Page_137.jpg
f5d22e42130444277e2ced1321c5f7ae
9a000981cb220d6d68f0e85260ef50002b23a2c2
49241 F20110114_AABYXQ tashiro_h_Page_004thm.jpg
1d1ded2e06287bfedc64b27f292d3dd0
108126a1c506c97b5552dcc50cdbf9c2de8bf4f7
F20110114_AABXNN tashiro_h_Page_136.tif
561edb51a86610576469b745ad9ddd8f
36e9059e2e0c78d02643d2f4f88836ce704dba91
42286 F20110114_AABYKG tashiro_h_Page_044.pro
2dc3b0cf272b48c0bf6013b392a01f74
1e4a6537c7e8eea10454786c68ffc1fa198925e0
2289 F20110114_AABXAC tashiro_h_Page_221.txt
c4ab26e0bffc3df0d78901b29ec2fdda
d30d1fac0e4318ab9bb6640ddc46537f77ecef55
106931 F20110114_AABYXR tashiro_h_Page_004.QC.jpg
e016090f3371d854d85a0aeee5839fdb
35c1c852a37e68567c2b2c3ff56a4f52dcc41a79
F20110114_AABXNO tashiro_h_Page_107.tif
124d247543221519f6396270b9944e9a
e776c8b75b16193a92c95cdec6a04a1ebc09fdef
46345 F20110114_AABYKH tashiro_h_Page_047.pro
4938ec677420f40c8e88e367e222470c
13588f7f8bb4fc0a8bb340a81847f735aaddd879
48735 F20110114_AABZHA tashiro_h_Page_205thm.jpg
4a78cebf2812d37b7ea4f58022aaefba
5db79ed9d38d55f8f480ce009b1cbe333cbbba16
1446 F20110114_AABXAD tashiro_h_Page_063.txt
c3bc431caa918235c0fd7984004ca224
db7a61ad02d3462b1c824b91a5b1b092f2f7931b
36757 F20110114_AABYXS tashiro_h_Page_005thm.jpg
d185edeab2296100560a863ab1bc3c10
01c5ebe661ac02eaf4c10c7c9cbc8bf46ca8d146
48362 F20110114_AABXNP tashiro_h_Page_078thm.jpg
e620f1e6e3d1d8e55df00605e5da167b
0e2d9282be6b791b5b500ce2e1d442ac563ebd6f
42652 F20110114_AABYKI tashiro_h_Page_048.pro
24d7dbbeddd3b9c88eba6b92838d625b
bd23bbc4f8a4b6c6d34cf91ad3e26336f1a79816
97927 F20110114_AABZHB tashiro_h_Page_205.QC.jpg
665feb5e3d813c0783ba15aa6d9553d2
c8eb9dfb698addaba830ea0a2be9ad74e11f5494
F20110114_AABXAE tashiro_h_Page_215.tif
dc48ca276160ddcd06a4320621e9daee
0aef9c8383c91ac8f38110cd21e14afac8893230
46005 F20110114_AABYXT tashiro_h_Page_006thm.jpg
0845a2d4912d7df2fb49ad1afc138165
630033afa8c8d72fe3da84109c8ad399c2fc3960
85535 F20110114_AABXNQ tashiro_h_Page_024.QC.jpg
83aea1fc9e7ef34c0b2346c8ac277caf
e931f05ea0a0030774899ac5d859e56416ee6dcd
46804 F20110114_AABYKJ tashiro_h_Page_049.pro
1f205e8bdf172ee32fbef228508d55a6
9f408e3751100a477136da5b0a132a06e90f85fb
49250 F20110114_AABZHC tashiro_h_Page_206thm.jpg
cbcd47085b4fc96f2b15345c2bffa7c3
b0f7597821c8bb6c862ea645f1b0eb38791083dd
996147 F20110114_AABXAF tashiro_h_Page_049.jp2
ef2e999c19c25233146f63f3c96fe66b
5872bcfd466f78980d5b891fb30c8d1664bf2046
93406 F20110114_AABYXU tashiro_h_Page_006.QC.jpg
c21a7dbfc28388f2e24fca9c6c689fdf
5bcb39d2fe33dcec9f8261b9d9e445c746f325be
236359 F20110114_AABXNR tashiro_h_Page_122.jpg
ca4d4412e9ac24855f1a9290163639ab
e953ea8856a95346ff6c1be7da6cb41541143216
54274 F20110114_AABYKK tashiro_h_Page_053.pro
08d3ce364b7839f5c7d17c13720c089f
27077286f8072b128043a937ec14312b912ac67f
101383 F20110114_AABZHD tashiro_h_Page_206.QC.jpg
846b1c878dcc8ef771dce2b5f78a1029
5af90225eaad978bcca66a75ac8d00165a7795ee
97117 F20110114_AABXAG tashiro_h_Page_086.QC.jpg
547b4deda8852c656b2bc8193c59c48c
8046aa487b38a0c2e6e319b8795c06460536cff6
51180 F20110114_AABYXV tashiro_h_Page_007thm.jpg
9fc902764bebea2a80f0816cfed5818e
3311e9b776d86080c6d0049052c4ce719a20d3ea
F20110114_AABXNS tashiro_h_Page_117.tif
53d14d6d5b3b5c7825b4767dee414a14
d209cda2436eba89b015143d53930d7fb4a0baa4
30587 F20110114_AABYKL tashiro_h_Page_054.pro
2213fc7576622faafdea9eee5f0fb49e
08f800f2ca8968416e7fb0ccd84e245127213210
50738 F20110114_AABZHE tashiro_h_Page_208thm.jpg
50f1b27626a7ee16c1eea6cf00da6888
45b37c2fa4853c04a1ddf888cce91d8c7afe7764
52672 F20110114_AABXAH tashiro_h_Page_102thm.jpg
6fc317a6ea3828a9e2486dab52e27961
16d2f90481ff07e147c511472cd38f8275446b05
117942 F20110114_AABYXW tashiro_h_Page_007.QC.jpg
b0546d36d789315ac5d623dc251e9019
bb3c099dea47ccba91b6a53b7d460b11bfc4fb19
48622 F20110114_AABXNT tashiro_h_Page_220.pro
75f20db245e83a517c7373ce1a6113db
0e9183e587faad7291b1b4989676239455b3c5dd
49753 F20110114_AABYKM tashiro_h_Page_056.pro
cd9e2253897e5632b0420e44c0dc4510
99cb75c37b405007bd3602e1a310c9c1c5b99e35
118881 F20110114_AABZHF tashiro_h_Page_208.QC.jpg
4870b026059bcdd1e6dae7673bf0bd28
a46d6ec8a7b3db1d763a53e6bcdfe5e9c05f6196
101048 F20110114_AABXAI tashiro_h_Page_061.QC.jpg
4f41b0e9bb62f1dccdd30c3382d9d24e
3391127ac4d743b543df793329680339d3798ac3
50348 F20110114_AABYXX tashiro_h_Page_008thm.jpg
8fea50c62a1437bdb473eb4615c4272e
ca12a51476da73c23618af59c84aa90f0be907e2
F20110114_AABXNU tashiro_h_Page_155.tif
55c60b3210d2d575fa9dd1b48e0678dc
8f57ab00e5d74983e8b92b2e3559e6d414f41d44
53126 F20110114_AABYKN tashiro_h_Page_057.pro
d74254d48e87b72ef5dca7b109fedc56
6f0c6b3b547fae4df620ad72ff9b52abf9dc7946
50764 F20110114_AABZHG tashiro_h_Page_210thm.jpg
84a9e4acd1b5a1e47485726a9672f8a3
fe7fcd6672f261eb0dab3b85d102df5a80d8c1ed
2402 F20110114_AABXAJ tashiro_h_Page_118.txt
df8fbe81a45f8ab5edd1d1aa77d76530
7ef1e75cbb7c493980d6c8ba44053883d2ac32eb
111015 F20110114_AABYXY tashiro_h_Page_008.QC.jpg
e046b97d2c6d4c3ac543b7b7f742c00e
94ee92adfef8c569529eb04f8d3158e9cc69f8cf
1885 F20110114_AABXNV tashiro_h_Page_021.txt
1100c03cb94e4d3c8ba54c9f5178cab7
32784215b51455103f729772472e36079f519db3
52342 F20110114_AABYKO tashiro_h_Page_058.pro
1e11ee969f063717a2714a7540084abd
9c4bd509fe57b20f3a08d6459f569017d7c250c2
114985 F20110114_AABZHH tashiro_h_Page_210.QC.jpg
fb1bd8354ec027cd0d8a038398768621
7e963a389e6f4049d64ca6213c7b5f6bfb23d543
240305 F20110114_AABXAK tashiro_h_Page_104.jpg
a01529c150ba1abfe53d49f3347b8292
e22f0cdefeab31c7d92f513428c98e4bcd5e32d2
37973 F20110114_AABYXZ tashiro_h_Page_009thm.jpg
6d1a275fd82bb262ead869b0d43c5dc5
da6e94aea4ac37b1b6feaf15aa2b02c053e83001
229546 F20110114_AABXNW tashiro_h_Page_086.jpg
25639147053a7be7ef937c41973e2279
ae00d312bbc5970b34c977bac57a089c593d8221
63439 F20110114_AABYKP tashiro_h_Page_060.pro
52ef34e70a3e4746883adedc38a85e36
93c87bdd68e29a97e9c4f73775ce73753e54e582
66786 F20110114_AABZHI tashiro_h_Page_211.QC.jpg
8cafec08a501d85698c4d42dc00577be
087e248ebfb23d69c1f9b9ba2a48b20312df6dba
54297 F20110114_AABXAL tashiro_h_Page_135.pro
e2990452c0fa9a4964ffd4e51aef9b27
fb4fc21db09f1dd9e27e0bf31561dfe214a344aa
1051982 F20110114_AABXNX tashiro_h_Page_122.jp2
af358392a36b3ec58facc7b1a9f85dc3
86670345b954cbf9968ed1f89775e07d3abb428a
55474 F20110114_AABYKQ tashiro_h_Page_061.pro
7bd00f7abf04fb2ba11743a4a9577d0e
96860216b867fb3514a8c96a06748d221a462618
74025 F20110114_AABZHJ tashiro_h_Page_212.QC.jpg
4ad29e1476f21d82eeded70489c5c9c8
082bb6dc6cc7ddf8a01ef11c68922445ae22a8e1
50169 F20110114_AABXAM tashiro_h_Page_216.pro
32ef9d1b5772b9affdbef1b9c4c5f9e5
307d1d1e9a5844cda6b1c7180dfaa0215ab663ff
F20110114_AABXNY tashiro_h_Page_061.tif
06b9ecddfb0b23db1f7d192aa3807ad9
544fe9a607b9f692956a5bc37a68589f48eda861
45192 F20110114_AABYKR tashiro_h_Page_062.pro
9df6eae27751032f420fab2902c3f3f3
51c0d40efecc60522871e39015672488c009e325
43724 F20110114_AABZHK tashiro_h_Page_213thm.jpg
cd2e661a0d10bde5ddcf1051f83fb029
92eaa92160eb8d72fd533dc9c7c7e87e50a5450a
76407 F20110114_AABXAN tashiro_h_Page_126.QC.jpg
a095fb735c8d49105ea99e6687442987
6ab19427fd66e86b79f1e4212d1dfa8c4a635415
114159 F20110114_AABXNZ tashiro_h_Page_103.QC.jpg
f3f6d513d2a1bff8bd63fe32cf9432fc
040ec21cc8eaec79879660cfe4fc7c0f942cc1ec
52121 F20110114_AABYKS tashiro_h_Page_064.pro
6d9af790ad9b6106ac8f0ba167c29ab0
81b054c4d1ac6c787f939e8fcdc504ca90219788
83242 F20110114_AABZHL tashiro_h_Page_213.QC.jpg
0a575598a44df65ec4886321fb701d58
2670a0a13e6ef0967fb43482ba9f60c5799ba94b
1939 F20110114_AABXAO tashiro_h_Page_180.txt
9afcbe754f7c3d1bfef6e6718d72100c
96239db18c4f8566b4df08eead8fbafc62709dae
45248 F20110114_AABYKT tashiro_h_Page_065.pro
ce49f4ea05b724c2de3f9ef8de14c9f2
b49685719684849d964e7327d3bbdbe74171c57d
45282 F20110114_AABZHM tashiro_h_Page_214thm.jpg
1b7dac0caf37e8c90fd59ed3f4035eaf
666f79eb6f5c447dcb8715c0c725cfd6e88dccc0
48887 F20110114_AABXAP tashiro_h_Page_072.pro
0d52680567aa1d4fb90c4ca150f24246
71a08a22c3918c358e8679bfb1463c3f1ae23aa5
53559 F20110114_AABYKU tashiro_h_Page_067.pro
05ed712a9a205e93ed7b898283a83e79
9cc586616137e65927cff0e589d1ae061a5db3b3
48358 F20110114_AABZHN tashiro_h_Page_216thm.jpg
025ea4de8e707d387f4057ea958211c0
27762c905f582cf1706200a48709cd47625cb254
180053 F20110114_AABXAQ tashiro_h_Page_040.jpg
c80a49aac0c61201a61f7bbd5929e56b
b7328cb69e16a3c2a4494f23323d2c1a578777d4
35826 F20110114_AABYKV tashiro_h_Page_068.pro
21f1900f24776f3305593bd32c017ad7
257072d5a6d31ebe3af595f312d09157d4021439
47889 F20110114_AABZHO tashiro_h_Page_217thm.jpg
d108d381cca4f3978abab0207941d8d5
9b192bd5fb8a9180848925d31903b1d05efb643a
1051958 F20110114_AABXAR tashiro_h_Page_089.jp2
61a38eba77510cb5b671ae6aaf56bfa4
57148322bcad1693e74a8d4dadeb9814ee246eb9
58832 F20110114_AABYKW tashiro_h_Page_071.pro
4ceebd3c2e3d8dda21466967d9b30840
710b6c68334e879fe3a060d3fd99ba3e00fdf70b
101677 F20110114_AABZHP tashiro_h_Page_217.QC.jpg
c3a088a407afbbf9c4a30205b8422ecc
c9e1f8467cb5ff441e383baca068c93bcbceae92
47953 F20110114_AABXAS tashiro_h_Page_041.pro
008952064db2882b08851db88f138cbb
8ca75ad001f7f4a3fb8f6608f2931e2730d31497
58195 F20110114_AABYKX tashiro_h_Page_073.pro
f9b543359d1fd5cb49dceb1a11906f87
1c3b0e79877ae73125197c57c055936d7aecc56c
48754 F20110114_AABZHQ tashiro_h_Page_218thm.jpg
54deed43dec5d904d8bf50f8baa00830
169edc26749d20b749fec356825923a8176cff89
42351 F20110114_AABYKY tashiro_h_Page_074.pro
8692a46dc8aaf81c219993950219f46e
381b3693a696fcad93c846dd078b7bdad1eec5ba
47180 F20110114_AABZHR tashiro_h_Page_219thm.jpg
2b438e989817bb4630bdd587811758d0
f3157e26b810f803ff08a08313a5d553335a8846
47338 F20110114_AABXAT tashiro_h_Page_041thm.jpg
9e986e9d45e0ae3fddf293d5cd9e2db6
0cf6f96dfee670b2e7a3afb691d3ccc0bbaa0f0a
46647 F20110114_AABYKZ tashiro_h_Page_075.pro
f17dd7e8015e51cfe2c429e1bb1ef7a1
3960268932b91c4607407e3d00f7bd9bfe46361d
102915 F20110114_AABZHS tashiro_h_Page_219.QC.jpg
997ff3f039ba66b804163c0159a79ca7
9ee1a4def125284e6ebe5610dee31c3553201f7d
F20110114_AABXAU tashiro_h_Page_140.jp2
deb9c018fc3ab106c1630ac3f1426b9e
7766439422c287f63c16ba4bff14adc3db9c7f41
99519 F20110114_AABZHT tashiro_h_Page_220.QC.jpg
08b5557d2f597d21c1f8c75022b3a74f
ec1c58eee0289cd5a565885ab9c1efbe679e8524
53808 F20110114_AABXAV tashiro_h_Page_069.pro
1a8119209779acaadf9d314308c611a4
5619334ca26ab06bfdc4de853a3f811383437fbb
275438 F20110114_AABXTA tashiro_h_Page_130.jpg
0c1d9e0d443f007285e8a7176fd97aeb
0b9b1b41c26fc42f83c11d3a044e83f831aef952
51667 F20110114_AABZHU tashiro_h_Page_221thm.jpg
0be51cdbf66686709a8a9a37f7d89953
4e10735fb2bfedb00fd1518ac74e840d24e83daf
43251 F20110114_AABXAW tashiro_h_Page_123.pro
9200a94e7ecfb7a07e4c8bbb50ef2f59
ce0a5e3a8aca489cdd9e0211cc756419a4bf88e4
234963 F20110114_AABXTB tashiro_h_Page_132.jpg
021949225a9e22bf070894b095ba4a3c
6573dd3c46cde0f474246049e6794b5567355208
111466 F20110114_AABZHV tashiro_h_Page_221.QC.jpg
0567ca5512212a0fd76b426a25f72374
3b1c2a05c6ffa3751c570ca40cc8058fd8bf72ad
58822 F20110114_AABXAX tashiro_h_Page_154.jpg
1b77531e9cdf8195c626dcbbb17ef125
1fda07af1fc7f365c856f622400e49cdd5bae9e4
244999 F20110114_AABXTC tashiro_h_Page_133.jpg
99fb4d568b5f311b80a9fba388ede6c6
c8648ebc63fbab74e72d6c081e98578e390cb143
38100 F20110114_AABZHW tashiro_h_Page_223thm.jpg
3e682f566611f3dd104e8091ff2274e6
192150daefd788630eff855e590e94c289c6f21d
253561 F20110114_AABXAY tashiro_h_Page_053.jpg
e2c1647d465b13db162e19a33c7d2f7c
69b612b31a99b8e470b3443ac010a9e32db59c03
250336 F20110114_AABXTD tashiro_h_Page_135.jpg
2be726a8f38aa31e929280ae9e457e82
ec880ff4f084894d3f905372b28855b2224a0c64
68285 F20110114_AABZHX tashiro_h_Page_223.QC.jpg
f935b8a53711a297fe535f3bfff6fab0
e5d89a4fef9d6bcd086e9df3ed468f75443d77d5
2183 F20110114_AABXAZ tashiro_h_Page_019.txt
f26dbd1f9c2894525d871f6fdddc9431
de4d64391b40214aba67eaeba47a2350924f6490
193084 F20110114_AABXTE tashiro_h_Page_136.jpg
0ff2ae0414ff5009a30d95e3ffdb0503
62ba9b992c02aef2927dc0ad9c55359dee77861d
247081 F20110114_AABXTF tashiro_h_Page_139.jpg
1c91b6bad0c0827dc6c98b1411e9da49
ed3d3adc31986850eea766110c0acd909015a4b2
41476 F20110114_AABZHY tashiro_h_Page_224thm.jpg
5ab3d0c8cddcd6c96d98c285259dc577
767ebb26bf2f4fa2d3a65fe4cea60b4dd408f1a7
76021 F20110114_AABZHZ tashiro_h_Page_224.QC.jpg
5f05b5f5bf069852579520fcfe49205a
d8355308d9b00fb3617722a62d318869e7bbf296
261659 F20110114_AABXTG tashiro_h_Page_141.jpg
d1aaed8658f8edb1506b307e3dc52f10
7ff88138a52989257f9261978f34e319afaec592
F20110114_AABYQA tashiro_h_Page_029.txt
bf1383643576bcf328f9ca709513b997
ce32508ff623d9c42ca10a3790421e592c682dc1
263711 F20110114_AABXTH tashiro_h_Page_142.jpg
d1f5370257caa6ec7f9c3fb06ff10eef
80710869523901b0a0e4c7427d89c0fd70312123
2261 F20110114_AABYQB tashiro_h_Page_030.txt
93bb01154e5fe94b01b0c64174fd94db
740970b0f8842e0b81f88bb8b2c337cc86817eee
210721 F20110114_AABXTI tashiro_h_Page_143.jpg
27f39a55d481d190bcd75713a75c65df
00776ad25b4b2ec10433e79e5da1a17e18da9ae8
263707 F20110114_AABXTJ tashiro_h_Page_144.jpg
e241721561c02e6dd70909029e33be8f
4be9d14d05dbbe9153b7e941a3042930bbbb4088
2169 F20110114_AABYQC tashiro_h_Page_031.txt
5455eb87018a2bd34c5b7733e8968fb4
52ad0abfa7d31eb5a7d5ee7f19e74281b9a3394c
283607 F20110114_AABXTK tashiro_h_Page_145.jpg
779c7722d4388fb23dc78b8a91e4d8ec
61e2433c786b67f7c2bbeb019bf64b79d902de19
2037 F20110114_AABYQD tashiro_h_Page_032.txt
873d35b92479a96e2e1705941b7528b0
bccad8cd846a2fd920c18e5b09cc749e50e86834
201020 F20110114_AABXTL tashiro_h_Page_146.jpg
eb0440c47e9e1c7975657f3063f99ac1
fb6994c4ae26dd8f1ec3c903610530fe104f3887
1693 F20110114_AABYQE tashiro_h_Page_033.txt
57ad05a0eece57d682a8c02a7fa14490
e2faddea2ce45a63a5975908ff550e4f6af5eb22
1051954 F20110114_AABXGA tashiro_h_Page_162.jp2
d32d719eabc030c6f37d67e7c4e47a6b
fa1389420c69d6139e33fafd7517c49e6720928e
252967 F20110114_AABXTM tashiro_h_Page_147.jpg
5a425402b7a454ac5117504dcab19af8
69a06c024552a11216c447df8be646b7e28c76a1
2281 F20110114_AABYQF tashiro_h_Page_035.txt
587f5f0b92e651434b03276bf3b1590f
efa613cce7ce21581be5492647e44e9e763e9c09
64167 F20110114_AABXGB tashiro_h_Page_101.pro
33a7dae212ea25cfbead64159b3e257d
9b62bb0e1f134f7981c7d186a96dd7e6c0032dcf
270465 F20110114_AABXTN tashiro_h_Page_148.jpg
5530a110266d14ee81fda610838a7ccb
90aa24caf2ee7db3ef03926b117b657f300be431
2044 F20110114_AABYQG tashiro_h_Page_036.txt
a164bac161f0b95c7184452a33ed804a
f08353dbe0fa2314b531ca54f35be7121ae87504
63827 F20110114_AABXGC tashiro_h_Page_103.pro
89bb751266fe3b75ad9228a43679748f
a1a88b2c317e618ffef54762b8272f413ca66f89
253914 F20110114_AABXTO tashiro_h_Page_149.jpg
1c43c572bc38ad7c0a26cac7f3dee362
ae81dba3a2a23f0ba3ec650565e4cf2c5e341c76
2106 F20110114_AABYQH tashiro_h_Page_038.txt
6bb63cb66ebacf71400f7d579a0b7bd8
251cfa401ca58e0b8b1ba16a2c0cf56e31c2481a
48442 F20110114_AABXGD tashiro_h_Page_222thm.jpg
c218e7ac853776270c7c18775ceda7c8
c64d4999f43bc87217b0f5e158f9962ce51c7a69
241301 F20110114_AABXTP tashiro_h_Page_150.jpg
4cac4b4cde61e2f149f54d9330f35121
f03f9ef303ae3e0a6b6b8efa1b3c372c2b1da599
1923 F20110114_AABYQI tashiro_h_Page_039.txt
f0630398f70efbc708dd876c70031582
862d357b056f064bb9112ddb26cd615074959d2c
1021 F20110114_AABXGE tashiro_h_Page_234.txt
d73a6e666adb086226bf3c58127438d4
3687b2cf9f22926d0b4d8c07e0486223c746f107
252629 F20110114_AABXTQ tashiro_h_Page_151.jpg
49a6b2441bd1cc9778bee732d620f353
2a4889bf85545b66b55c06634f026f4c68906990
2075 F20110114_AABYQJ tashiro_h_Page_040.txt
e2b301c7555527a2bdacbce3c36ee7db
bef79381a410c27131d5cd3ceefe4d8fbd4c3499
52212 F20110114_AABXGF tashiro_h_Page_140thm.jpg
ad42e6008c293ec7f8dd546e99083dc9
aa65312dc8e995cd5d577d84855acdcbb571bb77
255341 F20110114_AABXTR tashiro_h_Page_155.jpg
1fafe5d40ef8813745a9b35e18375671
3e36ccb655f702da9741d7a1a0047fb735a5f081
2202 F20110114_AABYQK tashiro_h_Page_041.txt
d3e5e6aeb7e96cc098cd36f535ac928f
f5edf2e11835607a1a2719bb664f32494c988826
48863 F20110114_AABXGG tashiro_h_Page_104thm.jpg
79c2dbb85b5466ed1c130aa5d6a86aa2
1e724bdef47c73ebc210f67c93206ec0c64650bc
273271 F20110114_AABXTS tashiro_h_Page_158.jpg
e616f4f8970b4acdf4dbe3fe05096636
2331b96bc16e28c7ac5cfa3872fe47f39ce8c7e4
1959 F20110114_AABYQL tashiro_h_Page_042.txt
a2e6e2a11f819b1a43f63d6b5b2d8c8b
1cb855f156ba8d3059d1822cf5c4612a65be0fe6
952870 F20110114_AABXGH tashiro_h_Page_037.jp2
d06773ddbbbe74c45ff835f6d463d19d
1d93473f8cd9b031f7afe393db7116019eab4d2e
F20110114_AABYDA tashiro_h_Page_026.tif
efb97a14fbf159be3c6118af301bf94b
51d523a3301f5879a70cf08af66ffbc400dc6664
235576 F20110114_AABXTT tashiro_h_Page_161.jpg
0907e7a0b9091ecc848eb8e5f2893e82
b52d237657fd3a3926a25e5a39d765d4d47c10ed
1924 F20110114_AABYQM tashiro_h_Page_043.txt
2539638d17a49235b47666ec419a83e3
3cf06a7071fba759627851fef1c13be2f2300ca6
44537 F20110114_AABXGI tashiro_h_Page_047thm.jpg
adde7817e0ce1260b0314fe25f46a40f
b9907ade3c9f1e37b209742ac4aa0ab9fbbdfb69
F20110114_AABYDB tashiro_h_Page_027.tif
a31a17484fe2d6141f68fde004dc75af
ec70f9cec5984f6ea824cbbecf08935a6994648d
2208 F20110114_AABYQN tashiro_h_Page_044.txt
013cb9c86286fee28ee63427f940a1d9
5f63e4b2361d079748e2d1d55d0e734cfc163174
31515 F20110114_AABXGJ tashiro_h_Page_203thm.jpg
9e514496b4f6fa19259fe31c4c9ae6a5
fc14bb7f8a2ed6a4e8b34d72dd2205548d90cb3c
F20110114_AABYDC tashiro_h_Page_028.tif
4ef8f5127fde588890e1426dd753d467
bea0c4c9a951d0da0f6d7fc468f2fd11af241ae4
240449 F20110114_AABXTU tashiro_h_Page_162.jpg
80a1acc7d17a041f0bb280899c43353a
2c87d19c6ca547f33b8739ab9507dec820a80c29
1825 F20110114_AABYQO tashiro_h_Page_046.txt
004da0da40be0e243815da65ed571b5a
77abdb2d8ebb07710b6fe54b87c29b4a471c08b2
49222 F20110114_AABXGK tashiro_h_Page_204.pro
c5c1246c698295a3f106e6a1c11709c7
c71f69f2390bca7ceb86b7d30f0aa2f460e7ae0a
F20110114_AABYDD tashiro_h_Page_031.tif
c96c6653147576e1f68c821357061b55
2c420b2feb5ca216a80d5de7109f2d0d24eafd3c
269234 F20110114_AABXTV tashiro_h_Page_163.jpg
7b3e2510f292a99738460db16389f262
f32260d950126ae186482cefcb32f713d3b23503
1741 F20110114_AABYQP tashiro_h_Page_048.txt
df254c6ada755a7e52a16b585343e6a8
bce3513eb64570c896ef1e1102fb219ef721695d
109584 F20110114_AABXGL tashiro_h_Page_141.QC.jpg
c29926dd5e1aa983a5887bd06036afd0
15015cf3bc6d89080dca1e87e1a09bbd08bff77c
F20110114_AABYDE tashiro_h_Page_032.tif
b617969f223371691fdb160c867ee1fd
6d36d08afc3e8e32f5056f71b9829efe66e3ca21
214598 F20110114_AABXTW tashiro_h_Page_164.jpg
1619b0a8094f2fffde8323a29b63ac5c
edeedc8d201ed240bdd3934c826fe2db6d66be19
F20110114_AABYQQ tashiro_h_Page_050.txt
5794336f5344a43fa09a1f1757536a04
b040233587c10a09dd9f69098c75bfaa55e16504
85090 F20110114_AABXGM tashiro_h_Page_026.QC.jpg
552aeb175cf5828be49d14a1789eee59
2cfd2b34a1246271ac00886fca8925010a13d892
F20110114_AABYDF tashiro_h_Page_033.tif
55c9fced965329e600f9085cf8303817
d3db8fede5c38126a3de243e2210e831478b5362
240089 F20110114_AABXTX tashiro_h_Page_165.jpg
736f9b21e88ab076a27acd633859642d
e2a1166a899ad56170c8640cbc9ed3a1a46c7e49
1829 F20110114_AABYQR tashiro_h_Page_051.txt
6067b8a9132c7c4ac280bd680545f447
f60f27b0a6052c175e876df7017d638292803dd0
F20110114_AABXGN tashiro_h_Page_001.tif
04be4759e1357b29d7218ded8fe8bf48
3971041f6204a2fff83b456597a66eeb7cf4e00a
F20110114_AABYDG tashiro_h_Page_034.tif
b4f7dc718c2b0631074fee0302748739
afb442594b6256ac2a73ff2771e96c1af9530e39
226376 F20110114_AABXTY tashiro_h_Page_168.jpg
15968909e0e304e058e5dd1efd3df5dd
86386b13ca25e5f1d7ed720f39731be3711266d7
110618 F20110114_AABZAA tashiro_h_Page_056.QC.jpg
a53bda00a3739fbdb935f909a0370cb3
2929cec2c3cc01e1733b38ff9f00fef0fd43bd2b
1319 F20110114_AABYQS tashiro_h_Page_052.txt
f4d8b970f1aded12f24476b90d099e34
d60731b85193be8cffd5d827bc7208c3a5d220fa
254198 F20110114_AABXGO tashiro_h_Page_098.jpg
89d3855a27fc4fbf172cb2bc94ba5fc6
50043cf35d757973a5246a919c823a9c2d0e26b0
F20110114_AABYDH tashiro_h_Page_035.tif
fbc9a44e380da3546b4dfb2835845df0
68a4e3f975e9a2f803f21212767ee60c27a79f95
231786 F20110114_AABXTZ tashiro_h_Page_169.jpg
00d0d5c9a094266484f8ff5ca48c2b3c
9cf7cef95ff7997c1b70f713f7bd47bf65d64805
49414 F20110114_AABZAB tashiro_h_Page_057thm.jpg
d003f97aed46302bb1d00287a2015428
61e374b067b4c3df6624da32356c7987fb7418fc
1494 F20110114_AABYQT tashiro_h_Page_054.txt
e986f8c914dd4ba5cc46696c1221656a
0ec20a9bb209e58598ffbe072215b7446869eaca
F20110114_AABXGP tashiro_h_Page_219.txt
ba83eb4c699d1e08dbd80b6592dda02d
9c5683fc565bcfce6c36a55f0e493fa84abbbbe3
F20110114_AABYDI tashiro_h_Page_036.tif
4474f20044d3a8b6ece613956eb3057a
6f7e066fa54d558c0386b8ec1b3b7790cb85bab4
48569 F20110114_AABZAC tashiro_h_Page_058thm.jpg
b974eac8244c9910814a3bb98e051455
f5f788c2bd83e6bc568329150ae4a1d74b7449ac
2022 F20110114_AABYQU tashiro_h_Page_055.txt
73dba6d8d568201f7b2d8718f3b0600e
116277fca43efb50f6f13cccf7eae887f3d769c6
F20110114_AABXGQ tashiro_h_Page_155.txt
2172edf41ba92356a34f835dd4520957
90ce9e2c73eabd211afbdf7e3aa9708dbecd74d5
F20110114_AABYDJ tashiro_h_Page_037.tif
c026783e5329e314ccf3870d061d2023
68e9f38de6d2e6516fa6252a60b0b2effae0e732
102388 F20110114_AABZAD tashiro_h_Page_058.QC.jpg
29826ac709e5a7ae30eca4893a8c31b0
6ab0cddc487a34816396e17bdf1fc5ea5965d825
2157 F20110114_AABYQV tashiro_h_Page_057.txt
10c6c4dbc7968ac9a0bd1cc5be37ef6f
23e495d4330f44efb10e520ffc2c4c88eae4dbd5
187054 F20110114_AABXGR tashiro_h_Page_081.jpg
1f46dcffeda71b6bb507d0de6efd0f02
4e3e1e63bc4f389e700e7d55c8c1219838a48934
F20110114_AABYDK tashiro_h_Page_038.tif
2edb077856b49d5979ce706eb8b07d4f
652a990d252664d42e602507d2565ea5e0a6075d
48891 F20110114_AABZAE tashiro_h_Page_059thm.jpg
0327c6a7348782771ac394d2c51cd539
013c2c4dbb526d6a436917595b250bd7f42fa7da
2224 F20110114_AABYQW tashiro_h_Page_058.txt
c1d956ebf1dd4a3f10edd695a3302cc0
56c1ad1c5e9e0cbb8faae26d0c882b1d7fb5850c
1051967 F20110114_AABXGS tashiro_h_Page_142.jp2
a3fd2860f85ea4b0101598a712c38b5a
968966d4cbe85ef0c30d7d7fe3aba097ef1f5b6c
F20110114_AABYDL tashiro_h_Page_039.tif
4fe9e6e9e34fb4e30c8f4e28596ad9aa
57e05580b51b63a5ec1e811c4d2beb68bec29f3c
52312 F20110114_AABZAF tashiro_h_Page_060thm.jpg
dce5a81315e6bf26a5774b50a4b1a607
11d8c0d9f43487b1e237b09a8d9ae108cc44a3b3
2284 F20110114_AABYQX tashiro_h_Page_059.txt
fc7e2411a744f97733046ec046bf81bf
1e775e1e1526b064ecf983621a58eec5f65c8281
51752 F20110114_AABXGT tashiro_h_Page_184thm.jpg
11f35bf75923f9122820ab2e794e4555
32f508c96beedee55319e2eae9117d61a374ab41
F20110114_AABYDM tashiro_h_Page_040.tif
0cc4b60327c847dd83a6095d383b7714
dd8027ceecc61212eb78a626b08dc8de7d1a3c96
44682 F20110114_AABZAG tashiro_h_Page_062thm.jpg
d91afb43f234ade9a0106a677eb46442
1244d42c4d104d57b73947221896a7afa7dcd863
2551 F20110114_AABYQY tashiro_h_Page_060.txt
54d697856fb567cbbb8cdafe5f9b01f1
3221fc435e14345d50dde47beeba6ce9f098d14a
233142 F20110114_AABXGU tashiro_h_Page_088.jpg
cfdbd21c041a026fe74a5f184f9acf68
e416a58967b4cd9bf275319f10759e59b7a7cf88
F20110114_AABYDN tashiro_h_Page_041.tif
eb0585128d089319202be83d7bd5b9d4
6b727d0713a43aa1bb523be8ce03165b4e3e475d
92428 F20110114_AABZAH tashiro_h_Page_062.QC.jpg
62011dac09ea1747cbcd61c29f9f2203
0418718d87981913a72f8b253b5e09c59dd7b970
1993 F20110114_AABYQZ tashiro_h_Page_062.txt
58d8cf1543723f2fc79542e38531835f
3c87e1692719ea3dc897076185b055c66c46cc35
50097 F20110114_AABXGV tashiro_h_Page_111thm.jpg
6ffe3ee4c163e52959fa1dd9ed65b898
a795fbc00474979c050f71539bf1b459daa93455
F20110114_AABYDO tashiro_h_Page_042.tif
f1851192333f548b34ee3295241e8cec
d5e5605557b0613619f9747d72f2394fbfc83ba1
40706 F20110114_AABZAI tashiro_h_Page_063thm.jpg
ee2d0ff647b65ca20969a600590b6a79
6870108b05c63ff488454b09acc34acd61c0fd2a
276129 F20110114_AABXGW tashiro_h_Page_131.jpg
e453eafb082fae0fb3f046bf955d4665
37bb17d21fbf70ea98222a3b4d749837d58c2593
F20110114_AABYDP tashiro_h_Page_044.tif
76b5479997023c96894172198768b7b0
d76af44358982d54c43f2de24458f817810ecc01
78909 F20110114_AABZAJ tashiro_h_Page_063.QC.jpg
ab234bf916ae575b6058412380e22322
b14d9f5820f66df3d263dd41bdedf8fffd2896c4
2374 F20110114_AABXGX tashiro_h_Page_061.txt
6e088639c03726264ffead8f16019734
360894002b83942b02dad0b46f2feac9b38c802d
F20110114_AABXZA tashiro_h_Page_102.jp2
dc6e8b159f785858b1040054b5489751
1a8a2cec83ef11dd3d8638b16b014a05a16be481
F20110114_AABYDQ tashiro_h_Page_045.tif
4f48d904aaeaee0e520bc2871eca8d40
6ee2773b872b18c1cd0f99e6cb44012e820eeb7e
45544 F20110114_AABZAK tashiro_h_Page_065thm.jpg
f96bce1451a18ca87387deb12f0d84bf
a16fd84431423e297a4d3c07f8b45e15027d48d6
117427 F20110114_AABXGY tashiro_h_Page_017.QC.jpg
30cea8e0f881d8e09ef866ba1603a480
2f87b1a44e4645bafb887e949b468fbbc5ced74e
1051973 F20110114_AABXZB tashiro_h_Page_103.jp2
316a871825203ba1b945bd19d1b4ddee
76ba89c467f246d1c3c6171a5940ab299139b40d
F20110114_AABYDR tashiro_h_Page_046.tif
e97818eed70d4a82246f3f1f98f7f105
2679123775c7a32e7209528e6416c92eec5d7720
49894 F20110114_AABZAL tashiro_h_Page_066thm.jpg
e0058412d53fbecadbd9db3695734437
3e69452930af399c81a316aaf50b68051339e6db
F20110114_AABXZC tashiro_h_Page_104.jp2
5df66afb2fd112a86aff8638b9b6bdfa
26d8082e1a8dc980ae27ac2ed82897894160172d
F20110114_AABYDS tashiro_h_Page_048.tif
13757368b6737ba3b85b31f8f9f1d95c
f4c8492d47aadda7378a8f00a0a1aafeaaac67b4
49086 F20110114_AABZAM tashiro_h_Page_067thm.jpg
d7cd93151654dd085ee277f75ae71b0e
f259481e0d8638a363408898417cd7fb5acc5ee6
50030 F20110114_AABXGZ tashiro_h_Page_178thm.jpg
7a888eb5fcd3db2e63ef6012d508a015
b9e98fbb96dd8330cf2b26410b8d898dce0994e1
F20110114_AABXZD tashiro_h_Page_105.jp2
13c3284a2481af4bb82a2d1aa2e96204
2339d643ff565993413b64e3465ffab6f89d3e43
F20110114_AABYDT tashiro_h_Page_049.tif
ba837a67a8a81736c2be72f579618993
3f8a137c5b529e1e16a4de82494eb477b6014c06
107098 F20110114_AABZAN tashiro_h_Page_067.QC.jpg
16133caf8c2fbaef4f9bc3238697e74f
723f9dcb9c52e6eb5d612128119e1e82d6240316
F20110114_AABXZE tashiro_h_Page_106.jp2
94f709c4bda8fcad69100772c56af412
7c420551950b6f5c12452aa4f137ace4fc8fc937
F20110114_AABYDU tashiro_h_Page_051.tif
0f389fb116742e5bfe55497755eae0ca
47ead28bc7a6ed1be9c46950d909e76441c6d5ba
42649 F20110114_AABZAO tashiro_h_Page_068thm.jpg
c43558bb3ef77672558a18688e8dabaf
8d2221cd34b24244a47fa3c67e2d1c6373ca2731
1051981 F20110114_AABXZF tashiro_h_Page_107.jp2
e3a52ac1db8e8c53385a21f861e9cb49
9431e93933ab115a7651587c63dc3982b8b36276
106712 F20110114_AABZAP tashiro_h_Page_069.QC.jpg
f6c3d4be4ac5699ac7101b0554629d39
156344e58ef2579529443c23748d536175521c1a
1000664 F20110114_AABXZG tashiro_h_Page_110.jp2
06391abe6c4e7879195608eaf9120c47
f571d45a67a4b0fc0f416c9297f243ac979e1a14
F20110114_AABYDV tashiro_h_Page_052.tif
7a27e4866e53ba9e0c50341e928c9477
da0f2e69e84c7551efd17e80d406188284d1dd65
94655 F20110114_AABYWA tashiro_h_Page_164.QC.jpg
1bdb2de77bc3986fac354446e76a2641
f9defca01c9510350581b4a51c9827271273506f
49769 F20110114_AABZAQ tashiro_h_Page_070thm.jpg
740a7c2f578f2beb080c6835c714e09f
86b0ce273f1d7552a7e5197bf5ee15d0c9dfa969
1051965 F20110114_AABXZH tashiro_h_Page_112.jp2
cb9e59e7b97ea5bc2861c6f297637a64
df8d9b58ab7354a5372f89e300cd90c7ff68177d
F20110114_AABYDW tashiro_h_Page_053.tif
7f09a01581fb36aef445b9e67b15fb9e
8d223ba6bd8389bdc6ecf9d0dce77db9a5977b6f
96635 F20110114_AABYWB tashiro_h_Page_094.QC.jpg
706a9657232d152414daba5fe3cd09c9
ca59953dfb4fab94f88b1530d000b8dbaf0c9956
1051964 F20110114_AABXZI tashiro_h_Page_114.jp2
44374b41404f80d5e31e35262550d908
31f9cdabf2b6897a428f7d138c118250e78e6097
F20110114_AABYDX tashiro_h_Page_054.tif
31bee5c9d21527d4f3cb678c63241f80
eb4bf299e11936930cec66e872acafeae4e00352
49879 F20110114_AABYWC tashiro_h_Page_195thm.jpg
f165a0b25b2918142b822f48b149dc3d
90b72cccddf1d54f4daaace1a2b6c52c617a221c
46524 F20110114_AABZAR tashiro_h_Page_072thm.jpg
4ffeed92e55a4815ddfd145de47150df
35aababb8f5b768e64e7e8888751f48dd52b8343
1051983 F20110114_AABXZJ tashiro_h_Page_115.jp2
633f03f0ac4a978e56213e85d5cc230a
5e701a41799d1cdfd0dc356b2b371fac322087df
F20110114_AABYDY tashiro_h_Page_055.tif
1d1a4386d977e506c9b73338410cd921
e4875069d5a98d85bc1f02e292cb0e6e4f171056
48202 F20110114_AABYWD tashiro_h_Page_033thm.jpg
276f1b456cc396a7642976ad22b1d6b2
5a155d0754f445861188c4036ec498e482c15391
94298 F20110114_AABZAS tashiro_h_Page_072.QC.jpg
eb3e71630147ebfa7091549cc3077f98
a5a4bfc26edcb3c41f91c4993183d4747596eea2
1051961 F20110114_AABXZK tashiro_h_Page_116.jp2
9810465f272609b065d02bbbf76f4666
f092b25af5bc7d4b1c6b04cf021ef705d948047d
F20110114_AABYDZ tashiro_h_Page_057.tif
d26c1930603a2ccf436508d6d39886a5
666cb9527cb366d2a8ca3cd72b9c959d7807f45b
103838 F20110114_AABYWE tashiro_h_Page_222.QC.jpg
46ebbc8bae4f9234568f138c682b21c4
0733203679ae4944779c9dc3944748ee463561db
50864 F20110114_AABZAT tashiro_h_Page_073thm.jpg
94764439afb8717c34508a931e158ad9
a433b3b4332de7b29764d96ca58a2f8eef9bcb1a
F20110114_AABXZL tashiro_h_Page_117.jp2
3ed5255d3ba3c12c26d23d65b4a653a7
905dd4739c3808616a3fac3d19845728d8578db3
79436 F20110114_AABYWF tashiro_h_Page_052.QC.jpg
06d7ea297ffb69540faf4f0e3b2835b0
e9e32a2ca37f052f6ef8ae2bf3540ffd4507b2c5
114156 F20110114_AABZAU tashiro_h_Page_073.QC.jpg
5b96ff43d952980ea9182dcf48bf694c
7a4d5409e8b69910e5d38eacbe3570f86a8de18e
900293 F20110114_AABXMA tashiro_h_Page_188.jp2
552e5751743107d4911c16094b4a208a
7ad6e3f773618a8ac793b6c8c8051ef2107860e4
51799 F20110114_AABYWG tashiro_h_Page_128thm.jpg
0d01a8a83266f5508cf31b38915c791e
851628bbbbe5218763db235537e48b6d0d58068d
87863 F20110114_AABZAV tashiro_h_Page_074.QC.jpg
b300c29a549748b3dee02005d013d331
7da6374b577e47d31dd5cbd0e23ee45966e24220
F20110114_AABXMB tashiro_h_Page_124.tif
22b7f97227ae03222f47fa2746507770
7cd5bd037ce5396479877f71304ac69bc8ace867
1051969 F20110114_AABXZM tashiro_h_Page_119.jp2
071ed29279a5700fbd341acb6d303eb2
c99e343b3b0532602cc9196d31d348a469a92bf1
49905 F20110114_AABYWH tashiro_h_Page_129thm.jpg
7cde2a7cd13e0bc5fc4d533089282945
673648b24d7cd197b8e48a3becf35bc4a77fadbc
47315 F20110114_AABZAW tashiro_h_Page_075thm.jpg
c2c16f604b9779259d5f6b24127d02aa
e867ceea0fb9deea16ba78dc172a89cc71efcaa2
206357 F20110114_AABXMC tashiro_h_Page_157.jpg
60195d73e6423fcc9576d7412a37e3c2
27d900bf69897e85635f49ccdb57cf911ca95cb9
1051956 F20110114_AABXZN tashiro_h_Page_121.jp2
c15a42190fb6ceb7ad11ec8291dabb85
ac6a4acd5a5580e10b8bf8a401c28996e9ee5015
87530 F20110114_AABZAX tashiro_h_Page_076.QC.jpg
792766d8fb1e62d6fd1a1dca61b12647
135cabbcc9befe61ccdfc9f58954a6c2709c80d2
101506 F20110114_AABXMD tashiro_h_Page_218.QC.jpg
7fbd44307e3003b136b13aaf9a2f3a2c
ec397f0ddbd428ad11bb56702fbbed4b0f32344d
925251 F20110114_AABXZO tashiro_h_Page_123.jp2
9045eca8de5a710ea6d117885d3f4489
bd01c8402bb7a8c8c4af8740dcc0649aca17f5ed
52932 F20110114_AABYWI tashiro_h_Page_231thm.jpg
cfc8dc36f2ed610b5f90a15137ae5af9
1c70238abe75df8211a93bc66cabb0b7f0e59ea5
46337 F20110114_AABZAY tashiro_h_Page_077thm.jpg
3546d490c0fe746caaffc28c7b28ebc6
95b86592f5f0a1fc1dffd6c93e5dfb4dc79f8396
195664 F20110114_AABXME tashiro_h_Page_028.jpg
195a8172d63e197b9a30b42851a2f5db
2fc04f2f2025d9706244aa7f59c5075b922ec65e
1051974 F20110114_AABXZP tashiro_h_Page_124.jp2
b284f72975e08578a18026070db05096
822d3c379505bf2d31f0c9f21685db674af728e5
42251 F20110114_AABYWJ tashiro_h_Page_034thm.jpg
d14f12493ef8f66701a1c9304161b48d
240e3a1cb5eff2314c620ff166ce7ae2ed9372db
98865 F20110114_AABZAZ tashiro_h_Page_077.QC.jpg
ff39337522abe55cb5811c62b9fa5089
3f9489b63b3bec93137519651bbb0637ba7a1ece
90586 F20110114_AABXMF tashiro_h_Page_181.QC.jpg
e438797ae9acc8b7f5d7b13ed4b3f2cd
62eec244721cb0ba7c5c5b9defa05edc8d93b991
F20110114_AABXZQ tashiro_h_Page_125.jp2
41de0291a17a6d8758912d3d66e55842
c0b7323e7da6c690ab02d588a67580b82a44a375
49627 F20110114_AABYWK tashiro_h_Page_108thm.jpg
a37a64af7f6ae7e84e75a4a8b0442f6a
8755812dd81c268e2631b612c946b0e5e7172102
215000 F20110114_AABXMG tashiro_h_Page_095.jpg
239dfdaae7a4a63038d66ee80f57a391
210df55cab2578cffe379f21ed795a9e461c3bf7
727999 F20110114_AABXZR tashiro_h_Page_126.jp2
3699fa3783bdee3a0e5c82324eb4376c
a6c6b929ffed56df5afb54abab69f8761301de07
49702 F20110114_AABYWL tashiro_h_Page_159thm.jpg
d9e7d087ce30be73a9aa2783c8168058
2606f74d897ea1310a84cada962d87a22ecd6535
1051985 F20110114_AABXMH tashiro_h_Page_127.jp2
748f87dead0db05a30f8121d173503ba
d810469df95051dc73d0d034e0357c19772b24c4
1202 F20110114_AABYJA tashiro_h_Page_002.pro
13d31979654066cb932578b6918de5b8
91ba537bdfe157be72a986505f9dfa5d118b8fd4
1051975 F20110114_AABXZS tashiro_h_Page_130.jp2
5f680a389460d7ce64b22de781d67ed0
83624640b815bca661b7374a8fa62666948b015c
51685 F20110114_AABYWM tashiro_h_Page_229thm.jpg
a4b2bcbbd53e08cb6d1a7ea9df4ff2e7
bdfd4296dd890d201c362fdef6c8677e45ec0384
99106 F20110114_AABXMI tashiro_h_Page_065.QC.jpg
ec86d84ed4d993a3587a3f7131bc0414
18ccbd4b3720b54e90c505a686f0fa0c044f84fe
1016 F20110114_AABYJB tashiro_h_Page_003.pro
aa96dcf56576257d51ef9b53ba33db5a
0926c413aa0965f96c45d97c0ed2dd61cfaaa729
1051945 F20110114_AABXZT tashiro_h_Page_131.jp2
99c1ad30d43d1dd0911e4b3a3dc7556b
ab80e240e9e25069ee1d66cdc0835a4130a327b6
45577 F20110114_AABYWN tashiro_h_Page_074thm.jpg
7fe344a50165865264bf48eeef5f309c
d7ec5991c3d422635aa54981ebd39007b4fafe14
35714 F20110114_AABXMJ tashiro_h_Page_136.pro
2f6b3097503ff3be31e15f32c9d78da7
4a4dd38e3feaa26fcfb562cac64004a1b61517d9
22028 F20110114_AABYJC tashiro_h_Page_005.pro
c2e81767667696fdd3150eb331ea1075
d75a0be713560a22f3fc88013758cdb0914dc1df
1051984 F20110114_AABXZU tashiro_h_Page_132.jp2
48e3d6711319ab395e29980a0a7b5641
e2a74d658a185525e67179af2c33267933fb064d
48093 F20110114_AABYWO tashiro_h_Page_055thm.jpg
121a42fd8de6d2f709ad6e43d3bb0b6d
0dec870108caa5a6bc7516f7c43ce69a3e3dab78
110672 F20110114_AABXMK tashiro_h_Page_158.QC.jpg
0ee5d2a84e6a39bc9a734b7ee89a27e8
8849868f14a8e3f34104c19dcf37766f13b90926
60489 F20110114_AABYJD tashiro_h_Page_006.pro
12cfc079ac75d71b1207f5685b1d75ca
7661fdeb2409426d5fee6e2d425acdf20d6dcb32
1046643 F20110114_AABXZV tashiro_h_Page_134.jp2
7497361ee83239e2dfb7ed20a274f460
2c03cdd854a4858931689d51b994b8d2a82c29ea
95784 F20110114_AABYWP tashiro_h_Page_095.QC.jpg
9357def924446c86f7427e7ed1e55363
9cd4453c56e145ea96133a588b449a333a526c62
1051949 F20110114_AABXML tashiro_h_Page_163.jp2
13b61e7214850a3a29e0dd6110c6d810
76a032aa2a769b26fa25e8ae42adbf41d474db18
66445 F20110114_AABYJE tashiro_h_Page_007.pro
8a172752c1f288ee4480d196747d4db3
d3afcc33cb4f5fe3271b400fe47d218d173000dd
F20110114_AABXZW tashiro_h_Page_135.jp2
941def27b7186cc75430bf60cbdaebb1
2b0cf8f29f662227aad341aa171fb2954a7ff47a
102252 F20110114_AABYWQ tashiro_h_Page_132.QC.jpg
b5ec82c92f0ab0597debd45d1ba21fc3
cf65e3755e0385c006d13c75c65f8bf639c81acd
443 F20110114_AABXMM tashiro_h_Page_001.txt
7078c5c3169e109c36b6a0436aaf8b4d
6adc830bcbf3a55a622caeb15749b5f064aad18b
71666 F20110114_AABYJF tashiro_h_Page_008.pro
6fc9ebf306f73002467b4a1c10026abc
30a2286addb20bdd4bc36758cc713c9b4aacf44b
1051971 F20110114_AABXZX tashiro_h_Page_138.jp2
fce373e5c4fe18bad2827dc5d0342a0d
8b05a3407ba07a5d0f50cbcbca06f8ad3e425f1b
51342 F20110114_AABYWR tashiro_h_Page_202thm.jpg
e6c9d7e02d77669d74458dde95d5f1de
7b10ee12611884c6bf74faf2891519c571c598ad
F20110114_AABXMN tashiro_h_Page_224.tif
ae29f3285fe5332347abdc1398c83f06
a6122c4ca713f7ef72849f275d3cc727a015719f
32743 F20110114_AABYJG tashiro_h_Page_009.pro
b43ea71832da9b7e5ed1dc730b37de4d
fe3a1344ae08ab7dcdd381da0ff22836e3fdc884
1051922 F20110114_AABXZY tashiro_h_Page_139.jp2
94d61fdf9ca184789c4af7b3edd77c6b
753339a69d53cb791237cca5316eea9cc23dd8f3
126411 F20110114_AABYWS tashiro_h_Page_209.QC.jpg
3ead36cf7fc68a2d4946c61d1472668e
b375cf5f8d088e02af27b1519bea5f9548f00028
1051986 F20110114_AABXMO tashiro_h_Page_232.jp2
2da1d3df500774da116700d86db34b58
eb0c0d10cbd4ae28ceef521d609eba205e93c7cd
52209 F20110114_AABYJH tashiro_h_Page_010.pro
aa35471bbcf16f632c983239d24b22cf
78f4245890526483dd01825080d14d5c7754c47e
1051916 F20110114_AABXZZ tashiro_h_Page_144.jp2
2e574e17a6cb2f83df94d490dc298fa6
7eb58496a70bc998b51ad0a69e9641a099603690
44220 F20110114_AABZGA tashiro_h_Page_187thm.jpg
647a95164560504ada0b69218939cb91
e0c52c1eb1a53a8157892d452d1592f0407fea2e
110912 F20110114_AABYWT tashiro_h_Page_070.QC.jpg
e02f23da0739a1edda55b13a3c61322c
4f9f926fc6a23502a8a8a4db2caf7b7ee339a598
41458 F20110114_AABXMP tashiro_h_Page_050.pro
4e933616b5879b96f953cc60391a2825
67c2815e87c477e6a3b6b0529a693a0c5e517e98
25657 F20110114_AABYJI tashiro_h_Page_011.pro
72323fdbb511930b546ec9f4fd74667e
fbd276a658a1a68d353c40bffe93ba6e180db103
83502 F20110114_AABZGB tashiro_h_Page_187.QC.jpg
dfddaef520a4402141eebf70a0bc3b98
56805c976cc029c23509c66490b07f06a34a7a82
98447 F20110114_AABYWU tashiro_h_Page_030.QC.jpg
b33ad9d25352203797931a1fb568f4cb
607c75397bb75b37301da34339c260621b6d360d
F20110114_AABXMQ tashiro_h_Page_050.tif
82bf638df694f006e5f84d045343e58c
39a593aa17b929368ffe126055b9c3a646e30df2
63102 F20110114_AABYJJ tashiro_h_Page_013.pro
5191470bff9c166f72421b39d91539e7
bac98ead810bddbe5261c23de61781225db7ec47
46966 F20110114_AABZGC tashiro_h_Page_188thm.jpg
cb0f52a5c02e49d77c2126b8617ecfe6
f362d6b7b511cf1350e957177e0986ac87d5dc13
100727 F20110114_AABYWV tashiro_h_Page_207.QC.jpg
7373d96c9b952863e95196f69c8d3ea0
c98c1b3e140cc14aa513b912bdc93b8a479b279e
102828 F20110114_AABXMR tashiro_h_Page_090.QC.jpg
243828e0af85705cb5df4aaf232f6eb1
1a847c5b74dd24b7b7b56951cf2f81d4ecac8d86
35098 F20110114_AABYJK tashiro_h_Page_014.pro
8edfce924d061c1eab4200ff9c60487e
c30af04922972be86955e25b110f82bbb92a8ade
87319 F20110114_AABZGD tashiro_h_Page_188.QC.jpg
6836dbec59c4650b95e8cde1f4bc17eb
2d8e272190472d6594b058c0ca5b9096e7123bac
108190 F20110114_AABXMS tashiro_h_Page_232.QC.jpg
585966c4bbf18a516c02e05c369cefd0
3e2de28394ca3cf1955e96582f211f28a80c66dd
42068 F20110114_AABYJL tashiro_h_Page_015.pro
2521f7a1a4c58cffe23ca88cd2a39cd6
7570ba6475dc6b2f2735b45765791ffcd133633c
50476 F20110114_AABZGE tashiro_h_Page_189thm.jpg
030ab25203529e69915c17adffd3d0d2
0807ab0436f3ff83695fd63aaab153c84a6d3abe
49747 F20110114_AABYWW tashiro_h_Page_097thm.jpg
3deed7fa76216e7557f05af5429832e4
1f4949ecfa070778e91bc2e8fd48b75239ff4a37
56782 F20110114_AABXMT tashiro_h_Page_171.pro
bac7ba8ed552aa427ed2c37f0118e94a
faa7e8ff53f8a97de73dcc260d64e535d0810aea
52639 F20110114_AABYJM tashiro_h_Page_016.pro
5f40987b05b602d4a61fc7ee5f9b86a8
d05b384df0400ff438c7bba3f7a6617f51e133ab
110146 F20110114_AABZGF tashiro_h_Page_189.QC.jpg
c029757afb387d1f169c5c08eaaa9287
d4c71a44e3eebbe18625c82fe05d8aa070e93179
111588 F20110114_AABYWX tashiro_h_Page_098.QC.jpg
96ce4dd265abf9742e69374e7056b7c1
a8626a14e7387dbb910c56c32808aba953699b09
45642 F20110114_AABXMU tashiro_h_Page_050thm.jpg
d4a1e46569060be5d00bfd821ecebb7e
07fe5158e834e3dd61aaf6e9f6d2bea64f6ab19b
61041 F20110114_AABYJN tashiro_h_Page_017.pro
aeee2f3643957bc05c9934694ce196b3
b45bd9b8a0934bcb465290fafcd5efdd8a2a97bd
45622 F20110114_AABZGG tashiro_h_Page_190thm.jpg
0a6a389083614c8b29587d800cabc2f6
38377bf39c2e5a1fa1f14eb9e1c639a83c7b0ebf
51230 F20110114_AABYWY tashiro_h_Page_071thm.jpg
95243b3b969e3542ce58f26778032a33
bcef16193b6909eb7033bed93688af8b83b2f9d4
58941 F20110114_AABXMV tashiro_h_Page_066.pro
9d0eb9d253a0a8979dca31f127e061f9
1cf3b86763e82ed3101636fef7dd951e74bad591
56977 F20110114_AABYJO tashiro_h_Page_018.pro
d390c62fa5dc5f7b6c0f222ef9b98dad
12c49d009c4a3bafc0555b7f739dd1a8162cab4e
85316 F20110114_AABZGH tashiro_h_Page_190.QC.jpg
5667743013c90594bd4e7992d7b982d5
0978f856ee53da03f0f5b5459af61f04b8a9b763
46442 F20110114_AABYWZ tashiro_h_Page_215thm.jpg
c194df80ef86d82d702497e31993ae23
3299e5c73e6ab0eab82af9f58b25eead9eb2ff8f
104797 F20110114_AABXMW tashiro_h_Page_216.QC.jpg
449acbbc592d4fa491a8f705060a8a3c
102bb996795c3055dfd5a3d28fb21004f3d76647
52339 F20110114_AABYJP tashiro_h_Page_019.pro
d5758c109b6cbade5c88919ed75a1e95
a723ab6c47d8ac65f448278993f3dde3056a9402
46035 F20110114_AABZGI tashiro_h_Page_191thm.jpg
26591b3437c9f6566a5ca55d9fc8876f
4e02784e9b03eee800f64fe499a3f58578f57530
2258 F20110114_AABXMX tashiro_h_Page_231.txt
3ff14aa3e08ff75e459cbef12e3eb1c5
4c85b636a97c47a49ab54d0a11b2b963704bcce5
57195 F20110114_AABYJQ tashiro_h_Page_020.pro
83a27b9ccc34b965024e8f10968e4743
f3bac2bc44a1d247a87bb5b9979a56333a845d74
91661 F20110114_AABZGJ tashiro_h_Page_191.QC.jpg
e67f0cc522074224b423f0f083d3255f
65509107844faaf25d986f578eaa3722ca98f1ad
958803 F20110114_AABXMY tashiro_h_Page_137.jp2
afbc489f44995dc2ae285bf77704eed6
01327d28a8a0afd08f79be2ee47c87393b43cf32
52082 F20110114_AABYJR tashiro_h_Page_022.pro
132599e38b2851187d3a4375e830b983
eeb51e89c8f26e5cdb823a1586ed2872792c3cf4
91871 F20110114_AABZGK tashiro_h_Page_192.QC.jpg
a9cfcaf9e5b3707832612b2c9f64ee3c
e588b058753c40e1e7234f552c799643af9d5c56
48873 F20110114_AABXMZ tashiro_h_Page_228thm.jpg
aa266087194683cafb1656323c812d8c
97ee29f1f3527efa69f630522d167b01d0165a74
44800 F20110114_AABYJS tashiro_h_Page_024.pro
4311ef69afc58ecf92e8d7bcda93d30e
da57f3d45dd03078240a410569abef38d498b0eb
49008 F20110114_AABZGL tashiro_h_Page_194thm.jpg
c06cb0c10a723b1c11c14a0fb3e70f29
5874e1ce650e32ab68df7b6ff05f59780e1ef55a
36455 F20110114_AABYJT tashiro_h_Page_025.pro
824c24b142acff0b3bad1b7bb257700b
afd65496ea7a847fe290ba5ea357a67b04c95099
103165 F20110114_AABZGM tashiro_h_Page_194.QC.jpg
41d96b2bdd71b5c80d2d571e8126ae0e
1b78ba5f622fbb7a453ece8efbc879f4e2751925
40277 F20110114_AABYJU tashiro_h_Page_026.pro
bb13423762257b57d839f10dd3b0aecb
dce852d1bcfe40be3e76732bb2f02dbdc963733f
104836 F20110114_AABZGN tashiro_h_Page_195.QC.jpg
83a2ece4447b4ef440fd4bd6c9b4699a
549c8074c0c165e71570ded0b3bd958707544844
44598 F20110114_AABYJV tashiro_h_Page_028.pro
e4828334a3c4d8d5a1fac1bd8769b9c6
65d6fff359d070c72d84032e94234bac6e4aee8b
47857 F20110114_AABZGO tashiro_h_Page_197thm.jpg
eff686918539f5cc7f066c394ae237d3
e603c1d93b75ac201891692fe3c5e89be1887456
46177 F20110114_AABYJW tashiro_h_Page_029.pro
88065f7fd878fba20ccf67fa54247d58
eb4a55e81680773d0ab1c193805491213aaf488a
102141 F20110114_AABZGP tashiro_h_Page_197.QC.jpg
c925f61dad5d385636e4ddde2095e968
80506356bf3fd575a3fb3bcdb7c5659b8890dbad
49629 F20110114_AABYJX tashiro_h_Page_030.pro
dae6c3f8345373ad7219739b11834882
7047dee1b32bfb1b4c383fa2013561d266e18b51
79980 F20110114_AABZGQ tashiro_h_Page_198.QC.jpg
95d68c6966965c892bdda7331bf33251
9eec97265a32312648e4ee776c3b9698bd68ebc3
48522 F20110114_AABYJY tashiro_h_Page_031.pro
50b2d8d24c2269813973c9f26d1ba240
42aed78c76cc71c022c9f638c733983b630bff93
50464 F20110114_AABZGR tashiro_h_Page_199thm.jpg
b54fcbd34959765c56d332ef3795514e
ecb6c4fc27540c01f0f5d5f5378bd1358001255b
39448 F20110114_AABYJZ tashiro_h_Page_032.pro
07ea62e0197d4f359c232b26fe478e76
c89bf74ad47e224c28b8fe629086211bc04ee499
108366 F20110114_AABZGS tashiro_h_Page_199.QC.jpg
b5bdd179477f5041d5c3ea573f7fd20c
ff788f6cf7fe764ed467775fe466ef4347be700b
48620 F20110114_AABZGT tashiro_h_Page_200thm.jpg
4e04dfe884f8124c36fe2371b65e19a9
2818cc5e07c674fd8d1dcafbfe63204c54872023
219555 F20110114_AABXSA tashiro_h_Page_094.jpg
a6f7e668833dceb202ba335284a7c1d5
4e77a6e61bc8bb4687a99df3eba8a18c3b7cbec4
101422 F20110114_AABZGU tashiro_h_Page_200.QC.jpg
24ec6b1e4bc899da2463ece78c107f4a
29abf2c479437dd2a80263fa7bd90dc0ee495e1e
190383 F20110114_AABXSB tashiro_h_Page_099.jpg
11cfbad26a61b7c89523dab14a1ca412
975644f46d6cddc16c815ba593b96a469a57bde2
47717 F20110114_AABZGV tashiro_h_Page_201thm.jpg
ff08f15190325f92aabaf4f5d5376e1c
ae28d15a8242087f05c0ec5e62769101ae7e617e
224324 F20110114_AABXSC tashiro_h_Page_100.jpg
5b965bb4709a585073156a43280096b8
ff452893287ad5c832ecc42f0c645b9c21777913
96866 F20110114_AABZGW tashiro_h_Page_201.QC.jpg
d53ea1c6d5508fa32e1c8a1e36bb8fe4
ca7c0e935aec753329bde528dfb48c0b1e7cd34f
295713 F20110114_AABXSD tashiro_h_Page_101.jpg
582e5559f0f97b74ccd2aefb8d91fa89
8d898f4429daefa7dc54a3dc9de77032d4fe345d
297446 F20110114_AABXSE tashiro_h_Page_102.jpg
d49f8df69ce994f1be16593f5c81e8d7
511641b9ec5b63bb21be495a804123bad8287322
117936 F20110114_AABZGX tashiro_h_Page_202.QC.jpg
0d38ae9e20cbd0831dad9596879f7013
e19a6d518601b90df05d79b77298debea337b6b4
47427 F20110114_AABZGY tashiro_h_Page_204thm.jpg
4c0597bc38cf1ecda0b0ad590e1141cc
a0969db3e3c565da37736dd4512cb721e619525e
283239 F20110114_AABXSF tashiro_h_Page_103.jpg
1c4fcba7cde5a2b52f1ef75aba4027d2
0a7305595159771ab5a75607ea2631e1ea54b4a3
103653 F20110114_AABZGZ tashiro_h_Page_204.QC.jpg
9c6294dae4c325c21f3c9d179b8245e9
a785b0660ff8dcce458b2d6e5572260172cdb0ae
262659 F20110114_AABXSG tashiro_h_Page_105.jpg
a83a9ca43320f2cd5c91dd2f3bba7517
2c5d219cedae1535c95bc77b76dec6a4258bf632
50285 F20110114_AABYPA tashiro_h_Page_222.pro
37b0b338422ce83fdc23a1ecd391c98e
d0e8d0d9babbd060738ade0ffde6356c39b6f37f
257284 F20110114_AABXSH tashiro_h_Page_108.jpg
73f060823c3017e36243e42667bc6cbc
638d530667ae27d68964601fdd3503bd5e0475a4
260573 F20110114_AABXSI tashiro_h_Page_109.jpg
ab42929d7f13809e4970efb0ef65f220
cc000b99108a10f90ad0b0296e59ec513261a9a1
26553 F20110114_AABYPB tashiro_h_Page_223.pro
c09264d6b180e8046071ca46fe7130c6
b50c3caeb0d11b740715ef4b73d30852cbe42090
212437 F20110114_AABXSJ tashiro_h_Page_110.jpg
3f880f12b385c8644648080baa89c983
563227a84698392d493f67a404c963827e5737cf
37972 F20110114_AABYPC tashiro_h_Page_224.pro
0a74a35468291a1686bcb80d69515508
320e4e2ad7bf8ec001ccd4a2792db7ce33eeeb69
271877 F20110114_AABXSK tashiro_h_Page_111.jpg
dd5dbb3fa885db906ffdb38aa8bca989
6138e6e06e192b2464c9c903207885aef94c7c52
34822 F20110114_AABYPD tashiro_h_Page_225.pro
42fa309e6575c99a9df447fcd0551c80
cc0ab4049d92e0e7d26dcaa1fbbef9d7477dbaaf
285876 F20110114_AABXSL tashiro_h_Page_112.jpg
ada0246db057ebcc83011e9ddffa32bc
3696584742a2a93ccb3427ef66dfa9c26e0cd26f
13830 F20110114_AABYPE tashiro_h_Page_227.pro
039312c315c0eadb14b6b81e2b24eec5
604f96e3dfae4d82472980102c8d8f98e683e435
1879 F20110114_AABXFA tashiro_h_Page_113.txt
8b6a0be4f04321aade8eb274af7271a9
fef87648e250867913f0df73d881a1a0e44e9a35
217688 F20110114_AABXSM tashiro_h_Page_113.jpg
2571912ad3ab8b95ce59c43a89a2866a
20bdf5dfc046d25f388bf72e151ef8ff7b6233d0
52130 F20110114_AABYPF tashiro_h_Page_230.pro
fd331ef87417927c43da3c7da97e277b
ea60babd9cbaead6da2e77a535ac3fffdf028366
2196 F20110114_AABXFB tashiro_h_Page_056.txt
6f872d05223c481d661d12fede08b720
9ef000192aaa0ecc64d781bbda8461f68088e981
283107 F20110114_AABXSN tashiro_h_Page_115.jpg
6b3e8b0d0fea8fe032a7fe429d1a7ddd
df3231beb9e13a40137fc6e97c39eeeb2ee33f43
51099 F20110114_AABYPG tashiro_h_Page_232.pro
a9df37d520502431594411075fa63bd9
fbe1d20f5c2e016bf59347f1b69dd2551275c3c6
85444 F20110114_AABXFC tashiro_h_Page_082.QC.jpg
5d4f6c50df6c8bb1bcb5abc07ad3fd9c
41f1b5a6b30721ad5aa68e8b3cd2e47cb27472c1
244782 F20110114_AABXSO tashiro_h_Page_116.jpg
267c970238917b813c75ce263e40e1d1
1d576db15d86befbf71db4968e52812715f75633
12117 F20110114_AABYPH tashiro_h_Page_233.pro
3916e01ab2a6b61ea664067f1aee0c33
0f58e930d9d16bd2866968d9f96919d7bf685956
F20110114_AABXFD tashiro_h_Page_119.tif
2f1577d4fb2763eb3704f852c182573d
99ad60858696c1638e7d6fd7aa2e4b5b5d537901
231372 F20110114_AABXSP tashiro_h_Page_117.jpg
7f1c71ce9b4d5519c570775e4a95c8cc
df6aa0aea2cc75f192752ebd8c3326ba77c3d46c
111 F20110114_AABYPI tashiro_h_Page_002.txt
b8477ec41025a240c067d55f59f39605
3968d6958a796f192d8c448f1cbde0934900c94c
111520 F20110114_AABXFE tashiro_h_Page_142.QC.jpg
767162899c949fd06bc5dbf3488f472c
924811578031ecf7164da2f1aa312f762dfd5bb2
252012 F20110114_AABXSQ tashiro_h_Page_118.jpg
57673ab1568459351c62eb33be47760f
54f8ba17fd7ce44526ed3074fd66fc7786374249
2133 F20110114_AABYPJ tashiro_h_Page_004.txt
7edf05eb7be5643c44ee89cfa7c8b722
b8e96cb23027ca99890b76e6305676d0a1cee522
1570 F20110114_AABXFF tashiro_h_Page_087.txt
82802775648bdf49909af2c1c055e234
7b43569073551431bd9844522fcde0c6a1d84ccc
298695 F20110114_AABXSR tashiro_h_Page_119.jpg
c2a480a6c7eaafec247339bd16253aad
553bfb16ee74efeda714c824ca289206ce0ba5b7
2724 F20110114_AABYPK tashiro_h_Page_006.txt
28260507340f4f7351d51e5589909baa
025879c22a0de05bda8a5f46e32cfc4111c71608
556010 F20110114_AABXFG tashiro_h_Page_234.jp2
286f7a3c8aa92e9496e80037f0d9c2f8
a8169a2a2bd7ca9dc28963b5b200fba6f33c33f2
234602 F20110114_AABXSS tashiro_h_Page_120.jpg
05e3b0f028240433165f78087b269df2
71551a75bfc8f6391fb827a79aa58804427b7795
2852 F20110114_AABYPL tashiro_h_Page_007.txt
0634a1225047eaad8f878bb3c55b391b
41594b0a231ea5f94c3136bd312db11ffd6217fe
2512 F20110114_AABXFH tashiro_h_Page_101.txt
3d2c38982f046740b12066f6d24a1844
bec34b32dcb4dbbb3ead77c99a042863135f8e28
F20110114_AABYCA tashiro_h_Page_222.jp2
3ab040d5380cfff1be662ba08df85ade
a624655cb1fed2d2ccc3fd75bef50f37667ef7f9
286013 F20110114_AABXST tashiro_h_Page_121.jpg
aa1316ad9cd2460b7821413591961bd8
6619b84cf3b5601b730c1393050075cdecb7782a
3020 F20110114_AABYPM tashiro_h_Page_008.txt
94fdf951e7f4fb534ebe9326023274e4
6cabe990890f12f19ac5551023663835a046d7c7
F20110114_AABXFI tashiro_h_Page_148.jp2
b56bcb5adb15a24711a41eeac7c0ed00
361ab2390a1c16e2a6d78dfe0c84f1380b423770
605360 F20110114_AABYCB tashiro_h_Page_223.jp2
07e3aa8fb5630955611965e3c6453496
946785884f4f2091d820f5e09ca076a73fb01665
205229 F20110114_AABXSU tashiro_h_Page_123.jpg
b6105e871761f99e78966b6747e18916
e8fa5e36f14e493a945d16f3c7a279c1cc68b0eb
950 F20110114_AABYPN tashiro_h_Page_011.txt
d514d8cc51d1a2b1d3cb8a98d62e0482
e3ff026a8d8be0d149d6198820103699363f16dc
242290 F20110114_AABXFJ tashiro_h_Page_090.jpg
4ec3b562fe174f109cc0415ff4e644f6
1ecebdde4518af767d2292d62e176ad5284b9ce2
777959 F20110114_AABYCC tashiro_h_Page_224.jp2
cd70cf4d24dd36d33362442e1d00e736
916729fac32c16eca0fdd0548e993c35d62dfbf0
261995 F20110114_AABXSV tashiro_h_Page_124.jpg
a74479d6e8f614f11117dd6735771599
856481c7180f2fb34cb215adb45e1239a7d7f64d
2170 F20110114_AABYPO tashiro_h_Page_012.txt
dadc3d7252a7e34c6708f05876f88094
4b47aefb5bc2e4ea83f8b7b2ae3de5137ab503ef
994156 F20110114_AABXFK tashiro_h_Page_029.jp2
4908f3e68807dee21164e531b9e574c4
fb7b56976c8c96d1f6bbfe4e4a3c46aaffb6f298
245966 F20110114_AABYCD tashiro_h_Page_227.jp2
d1fef00c6cf90429eb1e1c160a07df2e
50c95f23a2716b79acef9070005877553a0982b2
235380 F20110114_AABXSW tashiro_h_Page_125.jpg
441ca6dcaa7d7b135346225f9a61f835
5055e95ba59bb95b5a8dc286d62ae081b815e342
2562 F20110114_AABYPP tashiro_h_Page_013.txt
1246255774429ad7e1b41f8f79729a96
6475ef8f1b50ea8e01941142a83c3b870acabd72
43968 F20110114_AABXFL tashiro_h_Page_107.pro
8b42cec7caa30f38f9868a5870e7d6f6
1cff763db4d1c7bf6766680c1fccf69c3f8664e7
1051899 F20110114_AABYCE tashiro_h_Page_229.jp2
73d040f07e42c3715ecccee4854210b2
a6d3d925f9b32eaf30ec04f124b72cc74aeeba30
167603 F20110114_AABXSX tashiro_h_Page_126.jpg
2cbb56681b50ce9e26eb4e40253524bd
99c9c3900f24474fd4fcb470d9c2b8e71f58d13e
1343 F20110114_AABYPQ tashiro_h_Page_014.txt
a14ca4b43d697a8be5eeba2dfc69a4f5
413c92e4d419cf2dedf678fa1dad3a3259ca7f53
F20110114_AABXFM tashiro_h_Page_184.tif
5d19823113a7331994b5061e477b74bb
02191e9db9f33a52408228cda5adab062ccd61fe
F20110114_AABYCF tashiro_h_Page_230.jp2
02483b66bd65aef2dbff5c6d4fb64f39
85d6019fe1d714d47cda47870521088b290c0e8e
284670 F20110114_AABXSY tashiro_h_Page_128.jpg
bddf0195d1900d298509b5f951f6aa2f
89045261790fc19537e064d160021683500fe58f
2167 F20110114_AABYPR tashiro_h_Page_016.txt
c1f352bb5d8fbc0a05db604962ce2a55
59ba6eb1ce5b9472e5a6ca424b815a99981489a9
F20110114_AABXFN tashiro_h_Page_111.jp2
531e65079e5670e9848e0cd515ed71bc
a1cad0e0b9af477341db81ff8281609ddb2538bc
1051934 F20110114_AABYCG tashiro_h_Page_231.jp2
6046c40c9cdb009ff67683f780ef41ef
abbab1319c696792e30885aaf4ec1ef03e45ea36
265968 F20110114_AABXSZ tashiro_h_Page_129.jpg
bf554c37e900b87d944b8408f29dec88
fc407fd54a6fdc0e0e131d2c6795a4809017eb73
2425 F20110114_AABYPS tashiro_h_Page_017.txt
277bb1114902ae1fb0fe4cf66354edaa
e38a8b5de85adea9fb552201c0df5ba3354f8857
2230 F20110114_AABXFO tashiro_h_Page_105.txt
ad563cac1dd383f155f4090adb1c05d2
795a1f27f26de6aee7dc8ef8541272330e8e03a2
291175 F20110114_AABYCH tashiro_h_Page_233.jp2
dd5c50f1099ffb2c76956e61406b8d94
3be007f1c97e9f8157dab08afa60f32541ed8d17
F20110114_AABYPT tashiro_h_Page_018.txt
ec6fde7edc54345a2d28f2e323fb0dfa
73ba7eb50ad024472694da177ee892dbd35b1562
97689 F20110114_AABXFP tashiro_h_Page_193.QC.jpg
8738ae23238b761bcd910348d00ca103
49d30bb687fd475b0524a203e6d3dee5811c13b5
F20110114_AABYCI tashiro_h_Page_002.tif
f54383dede3fea4fadd9e25e73858307
d98b2e2d540907294bc871902716d6abd7fb9be0
2430 F20110114_AABYPU tashiro_h_Page_020.txt
c54e56b88238d3046d0e643443a7cf09
598fcbfe85a9248595f82735ca208fb6776188d8
60457 F20110114_AABXFQ tashiro_h_Page_115.pro
55a6286ee943c6d3a1ebcbe3898cc5b4
fe06f44494b9c2af755011798643b7fae6684b4f
F20110114_AABYCJ tashiro_h_Page_003.tif
3c4d070acf4e651ad5b915e7994336d9
ba00454854a88699a165af6abeeaa079b3250d7e
2125 F20110114_AABYPV tashiro_h_Page_024.txt
72f1e5144a60020d9e0ecec59b07dfb6
9fd2e8dddf56577327a3423b2da8efb87e9c8a9d
F20110114_AABXFR tashiro_h_Page_056.tif
8de6e06ed9ebfe56733809874607bb07
58ef9eb3eb129d69ef1a11e66460a42c2d99c679
F20110114_AABYCK tashiro_h_Page_005.tif
9c80980d41687f3848919b7330154419
55ba6a1e27536bfcf6ea201d3dc697a227e098fb
1896 F20110114_AABYPW tashiro_h_Page_025.txt
2247d359fafe65006900ecc907064a29
0fd5a25ee3705df61d2775ea35d462e15f070d2a
49239 F20110114_AABXFS tashiro_h_Page_162thm.jpg
542d2d28dd69183ef09ff7b783ebd202
a0d42ea4770e597087c7fa751ea6e6f260f09cf2
F20110114_AABYCL tashiro_h_Page_006.tif
9378969392c8123013d393059a3ae553
dd3ef87547e349884dfcd2d935aa951c2238c95f
2205 F20110114_AABYPX tashiro_h_Page_026.txt
27f1e7dc769626e825a93e211f4bcc3d
f749e6e90db0565bbba40fd387844c2bc4400274
F20110114_AABXFT tashiro_h_Page_098.tif
3d73dcce55bda7893f440268be03b58a
b060c32150b9a9493411ab81bf4bab36813c7146
F20110114_AABYCM tashiro_h_Page_007.tif
34d485da67f5956735ba0f75e372d6da
521ea31620d5784ad29f3313454ddd8537dd6d84
1723 F20110114_AABYPY tashiro_h_Page_027.txt
c8179db05b8638d630324968399fbad3
5a9d0b7219efe5f217a654bd34b8d5250f5bb0ea
77135 F20110114_AABXFU tashiro_h_Page_173.jpg
f9416bf123067f2e19533c60a2ac1db8
383dcb30c36c50915288767cd7897b656a1a450c
F20110114_AABYCN tashiro_h_Page_008.tif
a89e9681345dc246440f1c76d98d3c57
aa4e58f4f2d7481b49a928364e44840dbb8feb3c
2364 F20110114_AABYPZ tashiro_h_Page_028.txt
4ad93f85c81771c3dec92d4d88d88d02
b8129c646d727b224961e717bb6e7cab5e01cf69
92966 F20110114_AABXFV tashiro_h_Page_179.QC.jpg
e9aed4d227e56fb0bfd9ec2cdde434c0
1b12f6c9f634f38c487ce8b91b7e790063dbf8cb
F20110114_AABYCO tashiro_h_Page_009.tif
18a518e8fc5be470efad5405f39bbf5d
c63ede2253b4234f5cf87f13686a988ee8ea3545
1918 F20110114_AABXFW tashiro_h_Page_164.txt
5cbded4545412065fcc19bed9920ebe4
30c7aa3706b146e58dc5f9c192c7c271b8ca4956
F20110114_AABYCP tashiro_h_Page_010.tif
820f09cc5159d8d7ac08313be4ba9db7
8315eb452b49812fd2cb99339b1bfddf90930d65
49152 F20110114_AABXFX tashiro_h_Page_018thm.jpg
e9fc85c63c68e48dcac424647f21a264
28ed524971340554ce5f771922a4bfb83c387e28
1051947 F20110114_AABXYA tashiro_h_Page_061.jp2
57040283fa028d03ea2579534a752ddc
e47f6c6edabe3aa504fd41d2a67be511a1b8c668
F20110114_AABYCQ tashiro_h_Page_011.tif
06bd0f813f17527e989e33ea9adba891
8fd9cc19c943afdfc29a26d97b69265f0c9577e9
972511 F20110114_AABXYB tashiro_h_Page_062.jp2
92fe4dc1f859e5d7cfd00db442b45287
6ca95be3cc225a516f910f6ab3a0b575960a19f5
F20110114_AABYCR tashiro_h_Page_012.tif
7064e5a55360cf6ed998effb421fa60f
32758435550da659cc3a577cf721195f0ef1299e
58848 F20110114_AABXFY tashiro_h_Page_184.pro
f0bd145fd88509821b9bfa953d475133
689584dafc3186a6636d140d591d84787cd27c85
744304 F20110114_AABXYC tashiro_h_Page_063.jp2
8b687dbbb473c8c752fd01b0448696dd
dcb2675c2110607e0746fdb9b7e313a565b941e6
F20110114_AABYCS tashiro_h_Page_016.tif
2a24be97821730b5fa1f195dfdd56313
801c3e3142cd0aa988ed0852545102f59722574c
24618 F20110114_AABXFZ tashiro_h_Page_234.pro
2ced71406afc906d4f39e530d816f273
e6a7b91a52f48793e8733009c1d856f33f6888db
1051980 F20110114_AABXYD tashiro_h_Page_064.jp2
c7b3de10f80bf3a91df3e9fd0a55d27c
88304ff90c237d4e5ee62c2b2e414d001fe8292a
F20110114_AABYCT tashiro_h_Page_017.tif
6f1c188611157411a64294f24d1239a1
bb188fcc6c41a07e2bf70c73c1d93b1a1e2edf6f
1021861 F20110114_AABXYE tashiro_h_Page_065.jp2
36ad7a9b6d97a6a348a819331879f7b6
feffa25dc5cb557c72d532c800cda6d390b93f4b
F20110114_AABXYF tashiro_h_Page_067.jp2
a4cfdfa2a9d3ccf760364eaad6467238
db74153c2363e9ea1a26eb13ebd5778c8501905f
F20110114_AABYCU tashiro_h_Page_018.tif
72d81a68063d547ae7b3d0785793c1ae
30dde8f2394c02d67e51629fcb7164d8fcc6cdb7
747252 F20110114_AABXYG tashiro_h_Page_068.jp2
74c2c6fc965843f42d7a4213341c9c23
171786a974dd412faa4550f5a080a06665a87798
F20110114_AABYCV tashiro_h_Page_019.tif
2bc09179ae0f39b4f746705ee4e4b1c9
bfee1bc81a1924296bb7f460f249bc419cc1a2ba
1977 F20110114_AABYVA tashiro_h_Page_201.txt
8bc20cc9f1aea35f655055df13889ceb
6f2c6f86a779ef7136bb9b39a66955577760e354
1051912 F20110114_AABXYH tashiro_h_Page_069.jp2
403c8dace12522adb8eca61bb582215a
0d688740dcd7e53f0d5781f374ba7cd12f08ff3d
F20110114_AABYCW tashiro_h_Page_020.tif
e2363905f9f371719233ad8ec1e7bef9
041b06dd5e5cd056e23de1c1e39c9040884fd942
2542 F20110114_AABYVB tashiro_h_Page_202.txt
b9d51e8fe49beab750bb7673172a193b
88bc72b56e28cec40c91526111d40fd944ea9221
F20110114_AABXYI tashiro_h_Page_070.jp2
b8e1878622f1d7d6616692910c95d673
d4d97347321a41aa5545198bdb000fe7397ea1fb
F20110114_AABYCX tashiro_h_Page_022.tif
5691adcde8f88f7d039f9b2c8a9011b4
00366c197b8add359d592eff2cd22a25b5524f43
347 F20110114_AABYVC tashiro_h_Page_203.txt
969cc6221c73a0e707337a4aac328928
2d0d5d29636e9c2a935e673c2f3ece30d9b20bc9
F20110114_AABXYJ tashiro_h_Page_073.jp2
a49e813aaf3de87d4d4571c9fd7cc30e
88deda14fb3711b34ce2f47b7c61ecef6003dfe6
F20110114_AABYCY tashiro_h_Page_023.tif
3e38c00a5b3fa85985a92d2f6aafcec9
aed6fb95b31a795f817ccafb1321a8ee13b300e2
2029 F20110114_AABYVD tashiro_h_Page_204.txt
8ba2bb836933cbd3bb7d2119b46506df
b4b218195c21c4ee49c00ce21e1502333d15af26
963353 F20110114_AABXYK tashiro_h_Page_075.jp2
f65818c6129a71b349963941506b04a8
8fa23aa7f427e0aeaf4849fd4ee4ceca08557b93
F20110114_AABYCZ tashiro_h_Page_024.tif
38a17129393995ec0d4a74d4a787f1a3
314b4f3c16120a0ba924dccad93c5d8f88549c09
2386 F20110114_AABYVE tashiro_h_Page_208.txt
2056c5c9becfead887d0de5ba15717d3
3aa5e23b1a3444f35106493bf78a91c51bed1784
2577 F20110114_AABYVF tashiro_h_Page_209.txt
d1f373dc3a966fb6dc1c21e926706629
6775c14ccad91f2160251737ef954b33a0385ea7
43046 F20110114_AABXLA tashiro_h_Page_026thm.jpg
76e260b772075362a37ca417e104cebd
9eed999bedb45d185de9ba537ffe3273abdbbced
830758 F20110114_AABXYL tashiro_h_Page_076.jp2
81847a9436e8e3bf4b068da00e9302ca
32779c810148a7bbef3f6aea37b031cfb9cd6f26
1077 F20110114_AABYVG tashiro_h_Page_211.txt
0400b42f9f125fca1dce52cca0e626ad
6386d52d350e46a93f824bf4a9c37abee8e10c9b
F20110114_AABXLB tashiro_h_Page_123.tif
08a2ad25b0d6d5bd4c457a9e5db0015a
d63f18bb9f3c423db338853f0287d414d8bfe2ec
1037879 F20110114_AABXYM tashiro_h_Page_078.jp2
8c7f15b0f774bd9773f6e34741dd8172
8229807a1b3bf835760742a0f17db0867aec90b8
87417 F20110114_AABXLC tashiro_h_Page_051.QC.jpg
ef4bf838c17ce6d6281ce4d52c6933f6
acab16b853c336906ddfebefc134d8b73c25ae31
894563 F20110114_AABXYN tashiro_h_Page_080.jp2
34a8e87e8cd43ad7c3a7f5e9d3e53f01
50921a34d1cb16cfc68dc72bac60ce77279e366f
1763 F20110114_AABYVH tashiro_h_Page_212.txt
5d73c63238f8268ded501c07fc10d9a2
442089358c78d20d6b4e18dbb54426a2d4fbb05b
110409 F20110114_AABXLD tashiro_h_Page_155.QC.jpg
6b17f97ed0fd9644fb62497ad971f871
7462102ad33844a2f9f615bc5ec7e7dbd38039e2
F20110114_AABXYO tashiro_h_Page_083.jp2
13e56183ef46c8a4138fc072c0390643
f4b04d15017fee70f8cfcb45137327e55af16f39
2259 F20110114_AABYVI tashiro_h_Page_214.txt
c66e7234f06ad42186e39402477f048b
ca69dffadaa8a5069fa89ab62b556fb06146b202
185961 F20110114_AABXLE tashiro_h_Page_190.jpg
c35cec097a10643371af4a88ddbdd639
6093bcface2cfa6178255efbc4fc248853c24483
828696 F20110114_AABXYP tashiro_h_Page_084.jp2
4246ffa6975b5ae6371a7543f36dfbbe
643bd30e4f5647342da580c9a9f1b9ad6a84b385
2079 F20110114_AABYVJ tashiro_h_Page_216.txt
367d1e551fd65786721589c08f423d6e
39665145dc0640a5e7bed33036986dc1d195af59
2080 F20110114_AABXLF tashiro_h_Page_207.txt
337292c80b4d819b386af87b10f2ef69
fe702fd883c0b15c7b7c505d54fc1c252288f9e4
978775 F20110114_AABXYQ tashiro_h_Page_085.jp2
eed1fccfac4b7344801f156cad193b2c
ae9703292e4add6ff93dbee1adf782e2b0d13398
2002 F20110114_AABYVK tashiro_h_Page_217.txt
07c557b21b357b41200b41a4f685c0f4
820e05b59abe4ad16670d3e81c6dcd8861152abd
F20110114_AABXLG tashiro_h_Page_021.tif
7dfff0f0ce57faba5b293e2266e265c2
90251dba4887b25887324bd0592e96fb408d0327
1048159 F20110114_AABXYR tashiro_h_Page_086.jp2
235018101759cb8661457320ed62317d
9cb52983e9dd9d6479cb078e46deea1304ab1cba
2024 F20110114_AABYVL tashiro_h_Page_220.txt
dd27fcc432bf05afd3ee1af412445d7c
8223bd60e553aae0713b729161d2c85b3764897b
29660 F20110114_AABXLH tashiro_h_Page_027.pro
724fddef0e7bcb907a24cee17b806b6c
cbe488ed83dc5552f898be4a62db8deeaa250175
F20110114_AABYIA tashiro_h_Page_199.tif
f75c3300d2852533c788fdcd63341bdf
f2c3407bcbc05964dac2e8471f732f8416a04936
F20110114_AABXYS tashiro_h_Page_088.jp2
3fbfb7950e461c7a22560032adc18261
636e5d9e7b3f19a42fbcb21c7d69efd6a0c76811
1994 F20110114_AABYVM tashiro_h_Page_222.txt
15aad0ccd7f7a1105bdd06c746c90483
4b8505eb4558afb93fd283686b4ef10eae6d887f
253367 F20110114_AABXLI tashiro_h_Page_160.jpg
132fb6d29e01d5a863e00203e6b6086a
36daf6c16028f11f28ddd9f7874496f8fb4a6842
F20110114_AABYIB tashiro_h_Page_200.tif
87acc1bf5faa2f21a0368b1a4f845a88
45aeb6f62e8754a4412df8e0b11336264ddc3766
1051963 F20110114_AABXYT tashiro_h_Page_090.jp2
fd6f5a92eb6b8af317db5bed0ceee31f
6dc7d0c252a59549adf4d5f0a9fd7d2663e0b251
F20110114_AABYVN tashiro_h_Page_224.txt
9962da121b9c97342f71a5c0fe1b570e
bb5eea6f67c917f622f06dd46ad49eaf2baa3f0f
44536 F20110114_AABXLJ tashiro_h_Page_089.pro
74369fef43e271904c2d9cc14f3efd11
65ba1395c0eaff0caf714606c56bce3ac1b30c25
F20110114_AABYIC tashiro_h_Page_201.tif
2dc206363d034147fac8404a17c2bd10
050df3da789b779bdd3c33dd35d95f8b2ff47f60
1051970 F20110114_AABXYU tashiro_h_Page_091.jp2
729956ca39bbc3bfa656fcc95576c23d
715dd18b366c61a35ab1942b1ecd572756475cee
1689 F20110114_AABYVO tashiro_h_Page_225.txt
371fce3ad7080a1270d478b28334c725
08deeff8555256178d775b4ed01b8fd6db88049d
190278 F20110114_AABXLK tashiro_h_Page_051.jpg
337e00b12c79c0cb7a3a79a7561e8fa4
f8093fc479a6006d71d749ffc059cc231e2a7b70
F20110114_AABYID tashiro_h_Page_202.tif
413d3cfc3071a0ec17a31b11b91591ee
8d24769150983bce8b5b3e673c8824a8122d2d8d
933173 F20110114_AABXYV tashiro_h_Page_092.jp2
13c5a9576704a41f90bc0670a9ebcd3a
45e7f9d68c25d966e0e08d50e8fb2c45360cdc7f
1155 F20110114_AABYVP tashiro_h_Page_226.txt
24bbbc95e1bf89ed8e8f08cd0106b14a
faa5d25f7600c424bf81d220ac97c7c84cfc909f
F20110114_AABXLL tashiro_h_Page_043.tif
8a9882fde11a0bacfdf0d2e7ff2de943
007d4c7f47877f481ac8db2816aace24f1adf70a
F20110114_AABYIE tashiro_h_Page_203.tif
607c9ce556eb661180aeb74284158bb1
218f4ace1c395ed94973535b23193a5cc746a8b3
1003139 F20110114_AABXYW tashiro_h_Page_094.jp2
da8ea7366c0ca8469392fd08cda83117
092159643f25e2ce519c530767a684f15e45b74a
674 F20110114_AABYVQ tashiro_h_Page_227.txt
cbd5416cb4673809ffed5d45b066fd87
d78e0a117a845913bbad95bf79d4834f40a56245
2362 F20110114_AABXLM tashiro_h_Page_071.txt
81329497d24b3ab0685754862e9e36a0
08c56ddc434c12c1e590f2feef2c809b91adbacd
F20110114_AABYIF tashiro_h_Page_209.tif
66911813058bfbf20008e8c0f56c8ab1
82742e20bb927847552c8ff005e206ed5ef60a4c
F20110114_AABXYX tashiro_h_Page_097.jp2
c6ca47ca138f4870c8a1fcbb7c5d5904
f40611ceea8ad11a5b1466d633010f4328ca7445
2028 F20110114_AABYVR tashiro_h_Page_228.txt
8e74b104c38e44dffb2c0e1668113ec7
270e213d086587f1f7ba89d632a243dcc09869d9
874920 F20110114_AABXLN tashiro_h_Page_050.jp2
567cb0b63c8d074ea03189a98b642645
5019a1486ebe45f309ab4fcead9f831143a140c9
F20110114_AABYIG tashiro_h_Page_210.tif
b7fd327dfd6578ef4add4730cdc6cc5d
8d8ce58894c6657c684c7c8a0a966a2c0b077aea
860281 F20110114_AABXYY tashiro_h_Page_099.jp2
07f9bab14d17400a7f7466ca69642ce1
7a66a41666928c1a5f6510138ad46501fda074aa
2181 F20110114_AABYVS tashiro_h_Page_229.txt
449492c61bf3141d92ae8003a041efbc
037619f1e443c1c31df1225bd40acfe3f772c484
F20110114_AABXLO tashiro_h_Page_128.tif
93c14424df030418fd1c19a81b68f303
bb9599478e2ee3912c4cd403b6119a6e9ddd9cb3
F20110114_AABYIH tashiro_h_Page_211.tif
55753aafa8adaa9f09321e38739ee73c
80116c1735768b6cbb5e53ef920938257f2d8cb1
F20110114_AABXYZ tashiro_h_Page_101.jp2
f76eb7565a3c77b3e38e08e762ae068c
a8aaa7ce298409445856a91f46fb2009e683379f
103589 F20110114_AABZFA tashiro_h_Page_168.QC.jpg
167f94e0c53e6a0f71c93320250bb39d
dfd8336166287f11dfba5c5b23baf6118d2f3c8d
F20110114_AABYVT tashiro_h_Page_232.txt
48415f21d9d51283d09b0cfef1d8a4fc
d0130d7e06d24ba8a53637b6dcd80e02cb081ea7
27773 F20110114_AABXLP tashiro_h_Page_043.pro
ec4b7c5d9accf4580dc8be1b4c65ce9c
e9d813cc4e7d802df842807118fe443d44e6f6a5
F20110114_AABYII tashiro_h_Page_212.tif
c1e80e77704b4b6ffa26080479f0abc4
c3c8001df81fe8264668b5866c89e028858652af
50388 F20110114_AABZFB tashiro_h_Page_169thm.jpg
f868276f960b36ccc060bbc285c2c2d6
ec50c80b0b3d37340a37667048e54861ace7df7c
521 F20110114_AABYVU tashiro_h_Page_233.txt
02179f18787c62eb6c792a866eeb7b9b
5d607bbd483376bc37ceb15b96d8ab8f4220eac8
33935 F20110114_AABXLQ tashiro_h_Page_063.pro
7625244b6b3090a9973649ab62dad1d7
38812df16f59d7b179636b4b5f1d40664213fd6e
F20110114_AABYIJ tashiro_h_Page_213.tif
c98db03e06a8cc0cbc937da133f2e601
19d7d5dedac1985510b8ba5c32db57a48fe6cec8
101839 F20110114_AABZFC tashiro_h_Page_169.QC.jpg
e1b344328b4a7ec136f0c82542b1ae11
c044219435a5ea86c480f896939ae26fa33d7fef
2220576 F20110114_AABYVV tashiro_h.pdf
7041fd2a8ce74a05b455f6fe709c3dd1
37cf13f563860473cc5441f182e3710e3f7bdd00
1008076 F20110114_AABXLR tashiro_h_Page_095.jp2
264110f119a415561bdab8e7980c1fc6
0becf87ad7ab1d1482bcea709068ffa67d1b4218
F20110114_AABYIK tashiro_h_Page_214.tif
9749b973144c01d54fe75466f7c4c24b
2497883e175703e711f26d2223e943dbacb126d9
48805 F20110114_AABZFD tashiro_h_Page_170thm.jpg
7984f447ef86cf181101d99cc9568c1c
af13ceab30bbb4a83ef6ecbb58f8c5fb9daf16ed
106580 F20110114_AABYVW tashiro_h_Page_057.QC.jpg
2c09bcd306639b679547f9f204a6b6bd
f9228c06d8aa39b58ba90145ed5a6de1d427c64e
1874 F20110114_AABXLS tashiro_h_Page_183.txt
5fd90408ec92d942973fab2bbb7dad1c
4805e7319bc6377c6d1b4314225138bd53985d7c
F20110114_AABYIL tashiro_h_Page_216.tif
c52926f8c6e21ee1c4a6e976b8610919
8f587ad6d2848772c5cbf25d09353a596b4e8c4d
99642 F20110114_AABZFE tashiro_h_Page_170.QC.jpg
e25b6aa1d9bf34e2f186a584d87dbd5a
9066ae7c65842ddc5a2eff6f070b010c35a2954d
47887 F20110114_AABYVX tashiro_h_Page_122thm.jpg
5deb7dc7e7d4cf2c65c6810ad3e1cb32
1820a632ae65990c1ebe4d012a3aa3c3c43f70ac
232006 F20110114_AABXLT tashiro_h_Page_107.jpg
ca3d055707cb41a48223d853cdc8ede1
1a79b71e7d3a07739e05344e3a22d11f9ccfa459
F20110114_AABYIM tashiro_h_Page_217.tif
a606f64666fa88e3c5f6197f507f6b6d
26337fa56dd2909ba659b41195e7ad4c9da3deb3
51650 F20110114_AABZFF tashiro_h_Page_171thm.jpg
c9c4e49d9af1cf4172a7788b5599fe16
c8cd4e4ff9bfb3e58924273486f529541514f135
52679 F20110114_AABYVY tashiro_h_Page_101thm.jpg
cd40228329d0499c1c97033cf3455941
3bd6d5bac332fd2ac9bba5f6ac615ffe5a66585e
294716 F20110114_AABXLU tashiro_h_Page_138.jpg
da2f4fad7fa0180f5a6c9e8c962b0f3d
0fe01b6b66ba37bbe6b028e1c09b564ef4d2e804
F20110114_AABYIN tashiro_h_Page_218.tif
79d0a8bfa0498a7a845b552e9a3eaa3f
ed7582ee02cdfd3afa3eed50d054a74f2f08401a
109292 F20110114_AABZFG tashiro_h_Page_171.QC.jpg
10532ac1b5a18403f740e1471e353487
a1cbf626516a6d7b43727b70d90159397dc904c6
96641 F20110114_AABYVZ tashiro_h_Page_214.QC.jpg
08219a60f50bcc38157846f578f5f446
98eae97e6e538e628799cbb287eaec22481117c0
532853 F20110114_AABXLV tashiro_h_Page_043.jp2
f60f530a79081305a659db7b1c59f491
9a28316078afb4b80541ced7d2fcf7ab75ea0be7
F20110114_AABYIO tashiro_h_Page_220.tif
f4abb134152ed66314fd1074c7599acf
cdda5b44a8b650ce24edce8574b49dd9f40c0898
13636 F20110114_AABZFH tashiro_h_Page_172thm.jpg
1b4af0e553642c920e602ae6ffa67644
02fc78b149729181f2afdbaa8dd7b874ed2d5116
41918 F20110114_AABXLW tashiro_h_Page_033.pro
3f940134961de24c8be7d44351c6c0b8
553f5edfc81d2ad21e619a8cb7b5991c65b19c4a
F20110114_AABYIP tashiro_h_Page_221.tif
ce30f2b48a59d79fad578f9f2414c4bc
914de8086e40a9c0dddbc3c83f22d0a989c3c1b4
41188 F20110114_AABZFI tashiro_h_Page_172.QC.jpg
1317c8f0cacc67046f13e61d987d1a0e
b75cbd457e1ea6e68ae0591acf20bddcdf9d5f03
201615 F20110114_AABXLX tashiro_h_Page_037.jpg
592e9792afb50c4871c6f1f432e5f9ac
2bde907d2682376cbdf8413ea3d66e13917fd06f
F20110114_AABYIQ tashiro_h_Page_222.tif
c49385edcb5668b9b2d13fb4ebce8b54
a8460ce46efd6ca55b84b7de02f4ded06e8ae3f5
32848 F20110114_AABZFJ tashiro_h_Page_173thm.jpg
b76e76fc8583355fc8f77996f75838aa
49e92505f9738bc9d01eb7100058bcb03753fa27
F20110114_AABXLY tashiro_h_Page_227.tif
44ef0aea348733655e230a4bf7ef4c42
d62505159ef6ec0a9c1cc838dd5dbfc312b4d07e
F20110114_AABYIR tashiro_h_Page_223.tif
550bb5c2f52c78c3153b297357a889e6
82be2bee0956f00282fd637e6f2806b08c7c64bf
47936 F20110114_AABZFK tashiro_h_Page_174thm.jpg
b1afa89b37169a0b3636b66700db01ac
def6e99c8e64f7c3c5a38a920bea247af85d015e
176382 F20110114_AABXLZ tashiro_h_Page_014.jpg
1660423189645ef14010bbfc2471b301
62514ca3bc61e571f263fbbf71633d19c9b66551
F20110114_AABYIS tashiro_h_Page_226.tif
2bcc988d40d60e9d3fa2f04151cf40c3
3666653565ab8b9c0e8ad7250ea7463ef6904cf9
116477 F20110114_AABZFL tashiro_h_Page_175.QC.jpg
b5201167e4481a7cfff14f74ffa39406
dd5a0c9ae25919154c52dd610342b0b498b7e8cc
F20110114_AABYIT tashiro_h_Page_228.tif
781336ce2676428f0a32fa7eba6d920a
b1cb4c247130880209ae799bab56d84565d09c59
48659 F20110114_AABZFM tashiro_h_Page_176thm.jpg
4de6dd5c123fa4c1b4883f9eb9909ad7
6be6c74579eb6cace673971f1f8eda4a68b7ccca
F20110114_AABYIU tashiro_h_Page_229.tif
17cd9867ac92338614133d0ef49bc18b
a322aa7a64b6c66c9f1d1870f32fd2f1010a083a
103621 F20110114_AABZFN tashiro_h_Page_176.QC.jpg
e512f1e463840f09d4c584ec079f2728
80b613d19a21be6acae2c899309411e22ac7356c
F20110114_AABYIV tashiro_h_Page_230.tif
85dc434980c7a12d9e18c64fed47447d
6878429dc582b5d263ecf6feab0623c7b5a6996e
104276 F20110114_AABZFO tashiro_h_Page_178.QC.jpg
c5549e318f323be66b88a5c32ed67927
5319a304fd349fdc6589f836f291805da9ee1555
F20110114_AABYIW tashiro_h_Page_231.tif
27264adb6beb63e701cd9924e8a19035
81e5bac4816bf6b8946cd4ff11964575cd27ee60
45147 F20110114_AABZFP tashiro_h_Page_179thm.jpg
47cc49f698a265df3e8755628c015e45
fb0fe2e42bffd2bcdb29443c5eeaaef189d500e4
F20110114_AABYIX tashiro_h_Page_232.tif
5165d1dfd526aa4461d52d6438d305ea
6bceb25565259aaf12be1ce6ac1510c484be7960
47663 F20110114_AABZFQ tashiro_h_Page_180thm.jpg
536467698dbf9f367b51dae49a56909d
9dbace13d89c3c5060edbfc7b858e0318922553e
F20110114_AABYIY tashiro_h_Page_233.tif
8a6b3bf629b86946f5ac1cee596a579b
c7cede614585c3dc35675c36c85ee48e2b7416eb
95766 F20110114_AABZFR tashiro_h_Page_180.QC.jpg
1a5dfccadeeac289fe4440de73caebcc
fc0bd0070b57da094567ec75338c9ed301d8da91
8386 F20110114_AABYIZ tashiro_h_Page_001.pro
81609fbc3280c2909f3f1c15ef60ace5
f92295740e2ead46bc02101ab1e5696928989571
44867 F20110114_AABZFS tashiro_h_Page_181thm.jpg
8a88cb4913056b77c568676d53779b52
b9b22c50314bf91a1c6259eb66aedbe5e434b0ba
42651 F20110114_AABZFT tashiro_h_Page_182thm.jpg
0c723eab0cd49b640562a5cd5b8093f8
3a67ba9968731f1c507b02224a6761e6ba410f6b
249949 F20110114_AABXRA tashiro_h_Page_056.jpg
8de91bb35ddae36d9c8271f9b0861966
3ec6863c33d7cbf49dd43a13499c5d8d8a234505
48524 F20110114_AABZFU tashiro_h_Page_183thm.jpg
c248cd1f603f522dbeba0e9e470bf57e
30a727b4054c0015c45246ada11168a837331c2e
245281 F20110114_AABXRB tashiro_h_Page_057.jpg
85c5c2ebfd8d2e6bf184b199da26ebf1
0aded9e01d2d9890e290249b7ba097b07c8efe3c
95898 F20110114_AABZFV tashiro_h_Page_183.QC.jpg
ae73a536bb996c265642bf49824c2bfb
a386ec633808877127cef1f3e6e93fdfe9097481
244936 F20110114_AABXRC tashiro_h_Page_058.jpg
e44d7c72dc96034d3e6686bff1ef9680
74a5e139433e95caca2abe92b130b493fea261e7
288661 F20110114_AABXRD tashiro_h_Page_060.jpg
698725a579a0fce382db5117d308a8d9
d836b4621b95500f7b78a0b826c548f04649770b
116706 F20110114_AABZFW tashiro_h_Page_184.QC.jpg
c1fb4207149be6e100ce66508b6930a3
b53a3224fbab69818af1a4bb4346018b41f09f16
50021 F20110114_AABZFX tashiro_h_Page_185thm.jpg
e045872c21ed5be9d1854f20ffc25df3
2e80ec681945927d1900a2281a72b1046570f600
254746 F20110114_AABXRE tashiro_h_Page_061.jpg
0743c9c620323966c66121c830f5b792
b2d35ce01836a21ea6c4613de062afcfaac178aa
106085 F20110114_AABZFY tashiro_h_Page_185.QC.jpg
782c87e115546ac9cf43b4b2d6ee97ee
9865791a17994766ea7f31ca889724d7c4de5c10
249778 F20110114_AABXRF tashiro_h_Page_064.jpg
a5efe04161cbb6a7e0b1d7b597146a30
6b99276f83caf9a231b5c022d0027b2ec93e2de9
50279 F20110114_AABZFZ tashiro_h_Page_186thm.jpg
cf2871c49a6038fdf5b813da809b9560
ca54f1f92220edcd5a0a2af8bc6fb74f2579efaf
220160 F20110114_AABXRG tashiro_h_Page_065.jpg
156f13b84ce7f5e46e8e9956ec09add6
bb8a19db78a492d013d2ed9a4a4512c8b9067c1a
261933 F20110114_AABXRH tashiro_h_Page_066.jpg
0520a4e9007a95dcc515b3a0a58b216b
c58f30cf494d116ab96b667a4961d882c5148371
33559 F20110114_AABYOA tashiro_h_Page_188.pro
fe85edb756d16d77b66ec36ab627bfb1
c1e1e0c72004b24174e345052f93f52b95eb5df3
243329 F20110114_AABXRI tashiro_h_Page_067.jpg
76e37c7747a74951e3ac7c66ef97678d
1871156f2a571df1478eab4865412d49c76cdce6
54839 F20110114_AABYOB tashiro_h_Page_189.pro
6b90885500f76e3c0cdf9cd40dda74e2
da2b1100729faefe474f049cf1960b24afbd88b0
241540 F20110114_AABXRJ tashiro_h_Page_069.jpg
e96cb37310dcb176b4245c968683bcad
25ff3eb6b933afee56f8f943653b30197aac28a5
40856 F20110114_AABYOC tashiro_h_Page_191.pro
97d073e06578ede45d02c685b9ae3e2e
0baa7c300cc97a71c72f8063333a6f3c933a65f4
261932 F20110114_AABXRK tashiro_h_Page_070.jpg
0b9733812a90ebf2859868214f3e86e4
2aa0e12180147a42dbcba1da229cb9f31630894c
46505 F20110114_AABYOD tashiro_h_Page_192.pro
c6edb7d361a043a3a691370c4a3c2fee
3d71fab3ed3b0ba2af60ab292e4395b9e8e824b0
226293 F20110114_AABXRL tashiro_h_Page_072.jpg
07f687ae03ad67a5441892b7c7bfef14
40475343d8bafe969532fefe2829ff366289f5b4
44589 F20110114_AABYOE tashiro_h_Page_193.pro
27f77758d971ef0cc41e2e752807e4bf
7aeb22afc0cfb9979aa44e9f5f68f99cab910ba1
2134 F20110114_AABXEA tashiro_h_Page_022.txt
3cd6eacd2c011cf1e5077e21aa5ce2d0
0d5d2a307c10923113d692e2913ed3daa2bced8f
260370 F20110114_AABXRM tashiro_h_Page_073.jpg
27680e017bfe8fed8fe464562c7d4593
94a8c9aab546dc97f0265652dcef6ae7240aa4c9
52489 F20110114_AABYOF tashiro_h_Page_194.pro
802d07824371aa1cb80408ce9b893108
5eef231d1c48d1065459a783cc84ad0dd05bcda0
F20110114_AABXEB tashiro_h_Page_219.tif
2d3e6dbad33b00482d8002502880eace
9f57a46c398b71605589f298b3268b3faa337d77
192890 F20110114_AABXRN tashiro_h_Page_074.jpg
1e98d67ee2b9f02329e67a86f0f9cfae
b611e74aec2c9b2af16adc71b30f4a7f9597f017
44465 F20110114_AABYOG tashiro_h_Page_195.pro
710a5d11e21b2e899c6ef771c896d747
3f51b08487748f5e98fce76c366cc7c96afb7e6f
294049 F20110114_AABXEC tashiro_h_Page_127.jpg
ba07eb596085fb0fb00452f7887cdfad
9d5f13a5322b786a7b72ddb901647196123bbf09
217277 F20110114_AABXRO tashiro_h_Page_075.jpg
29e88ff3d9f11924b884feb37428d95b
a2f175cab18178f78953df184ee87a77fd1c6529
53787 F20110114_AABYOH tashiro_h_Page_197.pro
6650d78ff408cc7bdfab0f942331cf8f
74854c5f7348b4e5d9e36350cc05ea475b7436ba
1041577 F20110114_AABXED tashiro_h_Page_072.jp2
c8432f79644f1bfd9e69b5b662149735
0bccc23f85ffd47a76acc29d431b3c01835f247d
190033 F20110114_AABXRP tashiro_h_Page_076.jpg
259958897474aa2485471635dd3822cf
56a37656c373dc4fe049b0ffc312ec6f2d36c1f0
34508 F20110114_AABYOI tashiro_h_Page_198.pro
962472e3c91b25dd2a16823124468ca9
0f89a9b837c568f1dd1046ec412c4aec48eaed72
1051921 F20110114_AABXEE tashiro_h_Page_141.jp2
8b5642a14ad9881ebedfaf5dda7044f7
e21efaf14bf12fba510f0ef814b92ec292c509d4
219434 F20110114_AABXRQ tashiro_h_Page_077.jpg
f0ade29c193705e484c6ec3fa3c3d281
3756c191d3a2a006600440afc1ffc91229208109
58151 F20110114_AABYOJ tashiro_h_Page_199.pro
e7da5e34e2ffcecb55229e3e2ece3ed0
145084a18f1030c92e7867fbf2a4c42cc03283ab
50073 F20110114_AABXEF tashiro_h_Page_144thm.jpg
2decf0e4623bbb8bd343a15a5220b48e
cae5c6f903677b22dd2cbd21779de885db3f815f
244630 F20110114_AABXRR tashiro_h_Page_079.jpg
481f3c615bd074e48fd988b06220561b
65928cf430344578d7ec839cda342f72a1cc953c
47950 F20110114_AABYOK tashiro_h_Page_200.pro
ce499d11e150c4c61522f2083b1f376b
ce866189a3bb6e891d06c48153bbcad28fd6e76d
44625 F20110114_AABXEG tashiro_h_Page_114.pro
2ca90e225156dd12ee0b84397649a997
cb955267b573718ecc0c7379e4be274b0482eca7
200829 F20110114_AABXRS tashiro_h_Page_080.jpg
bfbee16c6193a89692773caab723cee7
08866bf7c82f949e6175c58b06c7f82781c75292
43125 F20110114_AABYOL tashiro_h_Page_201.pro
aee9ea6c477ec01c678c856b2843d08c
a1451b36c721ec3dee094cb9ca50112cbc8d2153
212200 F20110114_AABXEH tashiro_h_Page_045.jpg
e196805db10a63923ca1c256277028aa
5eb5c490adc8ca7e099b006832fbc6ba71c7bc18
1051937 F20110114_AABYBA tashiro_h_Page_185.jp2
7a7ddbbc4382a0aff6621f4d63f3be2f
632a7e23c10038a6172767a716dfedc9ef4e75b5
187728 F20110114_AABXRT tashiro_h_Page_082.jpg
ae42e6871ceb60e284cac4164c7e9cf2
841da3b8c1627ca012e510967ba5317daed20272
63048 F20110114_AABYOM tashiro_h_Page_202.pro
3e131e9200362c7b2c56815d6c4f8537
83bc25ad9fdcc7c987253a4acdf99b854f5dd3d6
51328 F20110114_AABXEI tashiro_h_Page_038.pro
a887d62e34618395da9e74398cabd7bf
123a729cdcd4ea027199c886ed6c44c7b49a6105
F20110114_AABYBB tashiro_h_Page_186.jp2
15faf240f6e696ee5697370ed86b5b5e
174b81d8eea1ff142ca793a31f8992cfce398060
242297 F20110114_AABXRU tashiro_h_Page_083.jpg
1857ab972ef40cdc2259f8d67e15e10c
078d44a89e24ed63c6737f37bb6813a6d28173a1
7691 F20110114_AABYON tashiro_h_Page_203.pro
d1a3276841839f9e5e059889ec95dbb7
b9e65f15b59b381a352d8f46724e65e677bc41b6
48447 F20110114_AABXEJ tashiro_h_Page_135thm.jpg
b36d5041d992685ca5243628ddab9ba9
85871c0f1f4ae7d166c939e17c3b9c3db0bb6b9a
721007 F20110114_AABYBC tashiro_h_Page_187.jp2
62219949b95cb830018148bedfc64529
363aaee535a8afd9032576d6314cafc931b1085e
184575 F20110114_AABXRV tashiro_h_Page_084.jpg
084dedaa9226bdf5bd97367018aba790
a29ef7f0bd9fdc0ac9bc2407ce1c9e38ae3b7b06
40761 F20110114_AABYOO tashiro_h_Page_205.pro
ab9b8ebe9a2afae51db4fda5bb152540
f32c28ac7d4be95150309781030e4708a23c8dfd
F20110114_AABXEK tashiro_h_Page_207.jp2
de5600a89a93cfca3545ccf8d85481fb
36b697520e5e9872e1f1e3399d1dab0b454c4328
1051878 F20110114_AABYBD tashiro_h_Page_189.jp2
89472230e3efc04c03b7be1b05befe18
19eef57edeb909b520e0238f8d2dc4b2768a4797
206002 F20110114_AABXRW tashiro_h_Page_085.jpg
c5dedba490e62b59c6e54e850dd0f5d9
013646ec01794c7da4fa5a0020dcf4ab3a414891
46353 F20110114_AABYOP tashiro_h_Page_206.pro
84a7c08cafe7f67728baa84d2640a653
8cdf90d9de91734674c77dff10b3022adf0b1774
F20110114_AABXEL tashiro_h_Page_205.tif
3a566616abe7926bc871fb752d771661
5c7c104bd97c7d32353765b55770724547530211
822201 F20110114_AABYBE tashiro_h_Page_190.jp2
e79d24bfaa9695062e2586218242b106
c2a9fad6c9e6e863484a38b2fd5b5efa67ac23b8
228815 F20110114_AABXRX tashiro_h_Page_087.jpg
80b19a64aaa7280178611185f350c462
41cfe26ef433d1ee59617f57c0de721ab4dc05cb
51030 F20110114_AABYOQ tashiro_h_Page_207.pro
e05ba28327686dab26efb611e4027970
c9355c2c5dc6de6dd80fb274e0e3265680e4dd8d
F20110114_AABXEM tashiro_h_Page_069.tif
740302be70a6e50a77c7cfaea92c166d
1b2c9eeb89875c570e9b7f05c755dd7570c563f7
923291 F20110114_AABYBF tashiro_h_Page_191.jp2
11f7171ef31ddb1712319499995a2787
331c54e490fc3602eb6d7b96db370abcb8f5ad20
229131 F20110114_AABXRY tashiro_h_Page_089.jpg
8ead7a0911e07b202d3ef0ea22425c17
72e6a0d3d3c9d63d66d5773d7e0cd4ba739fed4c
57877 F20110114_AABYOR tashiro_h_Page_210.pro
fe1a4aae92d1227389809a7b13ebfffb
451f8db368018ca7b2297b1e57c90a4c5d38ccd5
44294 F20110114_AABXEN tashiro_h_Page_024thm.jpg
80970a91b18322d82e8f8a2b27d7a776
db4955e14fd711733c79743b4f5b41e0ac8f9a63
F20110114_AABYBG tashiro_h_Page_195.jp2
5ba28b6e22ce8d02170f35dc14d53e3a
0cc16ab6aa703d7f9681c46a1140965822aa6bb2
250996 F20110114_AABXRZ tashiro_h_Page_091.jpg
b6486d772989795152af239efaf2896b
5b1c4e7ac5dd6ec52bd12e022a06e5d877b74bce
27116 F20110114_AABYOS tashiro_h_Page_211.pro
e71594e9f8074a68e48b0d394f26156f
8b3c9c5eaf61a3187f326c7871981db628a3b03e
F20110114_AABXEO tashiro_h_Page_158.jp2
13dc35e2c5042f17ac3d3483c3a9c6ec
70baf228345e7185e57c6b9956fc00435dc21d5c
1051923 F20110114_AABYBH tashiro_h_Page_196.jp2
7e7e46713665558ce6706776ce99655a
cd10c8be34146a1d4205a3c31d84f3391abee2f4
42247 F20110114_AABYOT tashiro_h_Page_212.pro
89d0d92440f21e6c59331983772459f8
d24168c81bed260d566fd0366c560cb5b48474c2
121730 F20110114_AABXEP tashiro_h_Page_166.QC.jpg
09661f944eb2f3ba14b96eae7f03e13e
3472d73cac4558f67b7f1977623308ea5687fdc9
1051919 F20110114_AABYBI tashiro_h_Page_197.jp2
8ae27df4b6a3c6a8f26e2079d16ae65c
86de534d675ee4508bc171932d2c44e5c044e8aa
48521 F20110114_AABYOU tashiro_h_Page_213.pro
5336c5bbafd0e3cf122a9922b6a00e01
43ea1aaf549dfe5e011e2be41d345ce840f20900
46124 F20110114_AABXEQ tashiro_h_Page_110thm.jpg
77a3cad648eb11bc8a9cc4b630958f7e
b914d554b4fe9c7f8b79c064c5ffdc68e9af9e83
846428 F20110114_AABYBJ tashiro_h_Page_198.jp2
327a32bf6b00d461db63ea01349a28c4
09c28bb0605998b213bec8c15f1890d466e55bf0
47584 F20110114_AABYOV tashiro_h_Page_214.pro
f8f69cf959e60b41edcac5a450551aa4
3bb790a618bb7c6b4a3b1fc9c487f1a551414cfd
182678 F20110114_AABXER tashiro_h_Page_093.jpg
5483f925049f311af5fb217da1b80f54
916bdedbfc68d764e9d1699311b43b9851ad1757
F20110114_AABYBK tashiro_h_Page_199.jp2
2cd0eb0f4cc2e353ce42b1855b65bb89
c562d58913c0cc35f72f50c2ea4c18fe77ed9206
40778 F20110114_AABYOW tashiro_h_Page_215.pro
077874ced6dca892f64a5c25cdbcc646
783075998129238bcde283c5e3be024ce97b42e3
68313 F20110114_AABXES tashiro_h_Page_226.QC.jpg
daa6f0b6dbcb794e45ff68535cd82c46
4243e2c1eb6013c3e229a92d85001bb5d1e0fb6f
F20110114_AABYBL tashiro_h_Page_200.jp2
9832b97d8818a02954c659e5460805ea
880ed457f88c834fceb21a345d1d719b27f34746
50524 F20110114_AABYOX tashiro_h_Page_218.pro
710e53a54f8b614af61c4228d10821eb
65e7e43fec093ee47804261e2b8b04efa7a6af2e
947118 F20110114_AABXET tashiro_h_Page_157.jp2
23165efafc9b5011dd7f1ef083be346f
93e537f743a75a1fdbb78bc0bb1ae4ec8d045926
1051978 F20110114_AABYBM tashiro_h_Page_202.jp2
e68013dcfca47059e33f206774fa1710
21e985eb4d3fcb62cbcca2ac0a7b6735ff240ff0
48838 F20110114_AABYOY tashiro_h_Page_219.pro
a5ddd60250294b89ef405a38b53450fe
538bb3c689c3f491dc271ead831f736a2051c429
F20110114_AABXEU tashiro_h_Page_083.tif
92269fcdc2ab8bcd5d5a4f515a593045
3558c0d759f8c89fbd8bff2c8ba3fb6a91a9955e
181805 F20110114_AABYBN tashiro_h_Page_203.jp2
eb8c262725ac4c232b7cca328cea0677
fa7f5acdc050617dc5393913c6fd3296989b1978
57353 F20110114_AABYOZ tashiro_h_Page_221.pro
8ae2f4e20076f34913be9de81264826a
3a771f99edc28189f2b301d651f23c122abcb60b
2514 F20110114_AABXEV tashiro_h_Page_121.txt
034cc6b195a7678a3dd586085c060aad
6c39bce183752e9a643a49f15f201f43a17bf0ea
1051960 F20110114_AABYBO tashiro_h_Page_205.jp2
f4feebe83020a3c3f19128a70df58ea5
8bbb6b669b25377cbff1e335241cd702afe0f411
1041572 F20110114_AABXEW tashiro_h_Page_041.jp2
a8b17451123bb4af81e40095cf3a5e1a
53ed115eeac5d3f8cca1b143f2e5a4346ae8638d
1051977 F20110114_AABYBP tashiro_h_Page_206.jp2
5b497b74624fa0c278bde53f1fe05c00
bfae4bcc3f434fa05b46e6f789376ec28b743047
F20110114_AABXXA tashiro_h_Page_023.jp2
37adf416123d8bec18cde5be7818de63
23f5ec467de7c91f61d81d415c4a3407fffe21ca
F20110114_AABYBQ tashiro_h_Page_208.jp2
3e932a40ee8699b1331e28b5753436e6
2415f0f92402f0403982a74c7e126d837d386c70
F20110114_AABXEX tashiro_h_Page_114.tif
1af6b615314ce98aa23d2283611543bf
8eaaae9f41a1746beaab451d248699034c8a268f
915067 F20110114_AABXXB tashiro_h_Page_024.jp2
885f8ec25068f071d43a107ade4bd7d8
6d7fbcf3c2d850c9d44da76d6c36602e6e5e5d40
610866 F20110114_AABYBR tashiro_h_Page_211.jp2
5cf230153c68257f7a9fb771a28b1c55
94178fea4f41a32e253d0538a8bed348a614f9b4
2051 F20110114_AABXEY tashiro_h_Page_205.txt
aab217c875deb5125c3ae260b8c4f170
be3170eeeceab5ba62496daee39b9d0df37cfb35
747729 F20110114_AABXXC tashiro_h_Page_025.jp2
2767a388bd6fd4bf9cfec190167ee437
6e5ffab0e9889c0dee313d093a0a91c9cfa0833c
831655 F20110114_AABYBS tashiro_h_Page_212.jp2
42252754f86a27321e1f045bc0b095e0
c1775cbcc5feabd804c82df4037e07506c565a26
2175 F20110114_AABXEZ tashiro_h_Page_023.txt
c5a485b9ef54ae5c1abcec8969b67709
579f61ea20c42c67286dee2c146a92e956a83e52
811226 F20110114_AABXXD tashiro_h_Page_026.jp2
5471692b0e1c72c014ca51bcd5f0033f
d07896bda367bc74f269e77bc87622b550ce6389
642433 F20110114_AABXXE tashiro_h_Page_027.jp2
7e360424e378e4b52ab542abe6a09a91
f7c23a674a3b9eaca695b74462c1195b2a04d122
911820 F20110114_AABYBT tashiro_h_Page_213.jp2
f85309e74c14d6fa1e8b44b4d3d90d42
5eb860ac97235983e6de406cc7ef0845a4cd61ad
909267 F20110114_AABXXF tashiro_h_Page_028.jp2
4306345f84b09bb78f59768f2f7990f0
b2041122f1b9270638f94ef04b5c14a61b6847fb
F20110114_AABYBU tashiro_h_Page_214.jp2
86c6c11f122d2d9aba0ed5d7703a24d5
46948c8f2b25b5adbb0b3b09800c82596104b00d
F20110114_AABXXG tashiro_h_Page_030.jp2
7724edd0dc567bb60ec43e50efe0cef9
4d2bb48d198eea4f89aadd7604f82a1a1cc557f6
978465 F20110114_AABYBV tashiro_h_Page_215.jp2
cbc4854440b5ff77e2d8ed1323f6cea9
eef16568052710a6a2959a6feec32b2e77fcf86a
2081 F20110114_AABYUA tashiro_h_Page_169.txt
bf316a18028354fe0c47d05b28abd52c
3171fd4ffb8d40ce8a6b37bcbaa5f7c1bec4fc8a
1032562 F20110114_AABXXH tashiro_h_Page_031.jp2
fa9bacffe9842c44bd291d7e895d27e9
fcc47b7bc4c4f5ce0fee8caf43c5097ba970aa0d
1051950 F20110114_AABYBW tashiro_h_Page_217.jp2
41a0682f59240389489dc60d0d7556ef
fc15dcf987eb326b5e59c6727c46bd063c97f700
2759 F20110114_AABYUB tashiro_h_Page_171.txt
a3a5e95cd489474384f71e86700b97f9
6fa48d8bd164307e1b054e0585c8e28f8a4e3822
827997 F20110114_AABXXI tashiro_h_Page_032.jp2
7d63369b1669eeea9cc0858af3e823cf
e0e324074b035d472edadc8eea3f1be8e3033a36
F20110114_AABYBX tashiro_h_Page_218.jp2
b9ee2aab511e3d8fca1a0418576b70e3
5e62d71f59377dd9b6cb5ca7ae78358d8158caa3
738 F20110114_AABYUC tashiro_h_Page_172.txt
e2b9883f89f386c8d4a057a0f4847c8a
56e7d52b3c6a41204e1d11962c6c24bc04c8f032
F20110114_AABXXJ tashiro_h_Page_033.jp2
d2ba6e573f812ddf550164f2464784b2
e3c7baea845712e3a1a569e27b6d535b61803cd2
F20110114_AABYBY tashiro_h_Page_219.jp2
242c37fb074b9df8ab716c9fff653c26
df31a8b67540be1a4061f6a299144818254e32a9
340 F20110114_AABYUD tashiro_h_Page_173.txt
b84a0c204f2b478f9d006e2caffc0ec7
4717b4a390323feb2fdadb23c0e8d4f03efd5747
F20110114_AABYBZ tashiro_h_Page_220.jp2
9318a87dfc7f7941e321f145871f101d
05452573c2daf16f39fec03fe45f80f9f4b110df
2163 F20110114_AABYUE tashiro_h_Page_174.txt
16613263c0f15326bf16a2b9f3b45fae
c38084f3aca9bc57c2dce6e78d881135f92befe3
758417 F20110114_AABXXK tashiro_h_Page_034.jp2
e11fb138fed70d1d0090ba1099a488b0
ec456d5b3d7f8383d28e4e4852e25af9dc46e7ad
2407 F20110114_AABYUF tashiro_h_Page_175.txt
93b3ada557964ab6e06043366e854a8b
d52ec4ec2d2da81359513f9f799350518776f8b4
829950 F20110114_AABXKA tashiro_h_Page_082.jp2
bf8b8dfaf0a7dd8cd1815952bb79206e
18fbcc4342da879dd2fec224afca192d1fb1ac29
1051946 F20110114_AABXXL tashiro_h_Page_038.jp2
bda8f83997686fe5d9b5bb22ef3e82af
16c1659d842efab040a962243a2912745a52f14a
224487 F20110114_AABXKB tashiro_h_Page_078.jpg
5dbb4249ee734db7e054788f2fc06219
94d18e2209fb4cddce306b7aa377ddf42092a7dc
F20110114_AABXXM tashiro_h_Page_039.jp2
a067029083caef16edb34c8252dff998
b7266dd77306095da69104964f9a051acd55e81c
F20110114_AABYUG tashiro_h_Page_176.txt
c19c14b5b1a04c9347d14390faa73711
deb800d2e1a4df0c599ed984263f520baf344bd2
47949 F20110114_AABXKC tashiro_h_Page_079thm.jpg
b9759e1b818f24e62b8900b78fe97662
9b2329cccc8d96beeecfbbae6b7762e8f8d9a1a7
783144 F20110114_AABXXN tashiro_h_Page_040.jp2
8d5ecde86e54477a09d3c1a6a192314d
5e13f74f17b229ffff1c7f26fae0a22cd2acd543
2607 F20110114_AABYUH tashiro_h_Page_177.txt
307af69503042bcfb44ee17077813bb0
3f6d549c3b4ca02ec91e85928423994164780109
F20110114_AABXKD tashiro_h_Page_108.jp2
9e1908a775507eba8fac1fb0f19a872b
6d6a219a00615cf1e4c4f9f24a07269096513e39
911515 F20110114_AABXXO tashiro_h_Page_042.jp2
d23f8b68278025d165ac859566e89c39
f0e6a78967bc296e09335d6c21c38df74e27454e
2094 F20110114_AABYUI tashiro_h_Page_178.txt
7b7fd25b5e322d037511122838791367
a5e8a795627417ebbf48fb261664fbb70f107129
2171 F20110114_AABXKE tashiro_h_Page_070.txt
2fdadcd1d525109395dca0768fdfe3b6
647b53b059e025392cf1c42b15cb80241db9dc2f
848690 F20110114_AABXXP tashiro_h_Page_044.jp2
5fe127f9c885bad946e42930dd003a91
cdf291523a3506ef28d70cbe159a7a9bdcf26e49
2199 F20110114_AABYUJ tashiro_h_Page_179.txt
cc13bdd418ae9f3e7c6d26d6a297b980
077b7e79e2c2b89665ac84c936db1a847c8b06fe
44978 F20110114_AABXKF tashiro_h_Page_076thm.jpg
e8e8507cae7bd4e973a49ab88ceb4686
da6451621966c57f5bcd39b4ccac77a58e953dfb
963453 F20110114_AABXXQ tashiro_h_Page_045.jp2
4de5cda613706f0b9c1d8f3cc6a4aaff
81464e81e721f1613a4faaa07457989fd5dfa2e9
1845 F20110114_AABYUK tashiro_h_Page_182.txt
846fe574f4862f5dbfdccda7633a0605
5f46c58a56d5b8e3639060318678a7965e088a65
F20110114_AABXKG tashiro_h_Page_120.jp2
9048798e64fb7c41ff87f338a72a1353
d8818237aeae5d5b54033ca7c7fe308544374f0f
869290 F20110114_AABXXR tashiro_h_Page_046.jp2
3760e5b225737689e348fb4dee5d1ab3
9b70b75d893c4c998476e1d4ba568eb91ab957e7
2342 F20110114_AABYUL tashiro_h_Page_184.txt
3f4d54aebd040761f419448fde276009
ce170c3a228984f067272a57b9a34c8aac713caf
1928 F20110114_AABXKH tashiro_h_Page_110.txt
29e73528e706d16bf85254fbd4234bc2
8a2dc8c05543d4f18c6470f3cd4d140ef3eb3966
F20110114_AABYHA tashiro_h_Page_163.tif
a3af144ab6a6d5c7e949c3a1df320c00
a680e7fa4ff09e0ea7cd4de1150da53ef0690a26
926593 F20110114_AABXXS tashiro_h_Page_047.jp2
6548392cdd2374d2e24ae072d8139929
c526d8129fe843ac2d3a16d0a03ab7c22205680a
2332 F20110114_AABYUM tashiro_h_Page_185.txt
f1f03c23958bb6c13afb40d88f580eb4
a86fc06051af48d6180f40e719d7947fe5dff760
1517 F20110114_AABXKI tashiro_h_Page_093.txt
089b433149fddccd2c1b44d3c55606d9
40ccb3500e00172b158a5ab4b80ce042928fe1b9
F20110114_AABYHB tashiro_h_Page_164.tif
750d385c34c77932325ab6ca73de684c
03f7f2d2b74f4189b77e926a385fdb59184b5335
971432 F20110114_AABXXT tashiro_h_Page_048.jp2
496a30733489ca9cd29c74227d2fe39a
a0b9e7b3cabe1a275794d940fceaa32b6b72bfd0
2530 F20110114_AABYUN tashiro_h_Page_186.txt
189ce1433bb1bcdeeb0dc96820b96218
28f2570cbaf2ec5db047e56f9d8cb84c82837e31
91122 F20110114_AABXKJ tashiro_h_Page_215.QC.jpg
4e4b2176fdd6b477dbeac2e937efe1d9
b25dd1b846277cd0dafbcf0c05ae0b45f5ad21f2
F20110114_AABYHC tashiro_h_Page_165.tif
916684c03419d89441c71711e767c29e
e0cc2f42564590772a7e9d1e64faa539948c5997
698917 F20110114_AABXXU tashiro_h_Page_052.jp2
6d6e86f87a813c047c19ae330d976287
c7a899aa6e48430a4025f24cb0a06fe6958e4559
1598 F20110114_AABYUO tashiro_h_Page_187.txt
62f2301afb5107f82b028164232b1fb3
672a455a393faa2f23ce0a1ad4c87aa76b3fe9d6
203050 F20110114_AABXKK tashiro_h_Page_015.jpg
73f9bdf1376833212b115607a9a9d2b2
2d33169ceabf0078ac9ffcfaa654e13865765027
F20110114_AABYHD tashiro_h_Page_166.tif
d87784002c8c3e09cf46792679aa93c0
1e6ebcc7aea650d4faed00a6b84ac57e60d8bf25
F20110114_AABXXV tashiro_h_Page_053.jp2
831f2383251714de6c37cc7c6dc4c1fe
2bd34691f15886f7c5a177a9ae67049c8838879a
1505 F20110114_AABYUP tashiro_h_Page_188.txt
6f14737efa4f3a810c3844ab9638b832
2e1f453a0829b5e95e995c2b2526004bf694b2ca
888188 F20110114_AABXKL tashiro_h_Page_136.jp2
58e38471f3e8ac5b61a92b2dc04979f5
db3d1f1bec570d9948691f83c51d6fc746208713
F20110114_AABYHE tashiro_h_Page_167.tif
918a30bf2d6711de11f500f76c634f46
c9cc3e4394cc19841452f81ff9558263ac6b07bf
F20110114_AABXXW tashiro_h_Page_056.jp2
e20eec9e2376b89e32614b5c86f14378
9ba52f934e4f8f28a261622d00a650c24b63c36e
1409 F20110114_AABYUQ tashiro_h_Page_190.txt
ffceb14d761cf92bccdaba4ba38ab73f
a955314adb98745604cd649f6e0b52225b310b4a
46840 F20110114_AABXKM tashiro_h_Page_161thm.jpg
45de32fef4f16bf5a0f5bf1dec44078e
528d56059f2f736557b2d60c0d9f96ab1232df17
F20110114_AABYHF tashiro_h_Page_168.tif
858e56ed0bd263c9d459106d2914be5e
2e52d6d3ad2bc872e2118fd612b0fa3a325ed81f
F20110114_AABXXX tashiro_h_Page_057.jp2
27dae0caf8595edcb3e500af0f7493ff
ffc2c7a3392de03acf27e2a5da5af78138a9d163
1739 F20110114_AABYUR tashiro_h_Page_191.txt
8d56cf1092aec0616bfa18768babeb41
1e8e6fec77dffb9ef9d523d1374accd68ff8f5bd
F20110114_AABXKN tashiro_h_Page_129.jp2
7e44bb753a28dd1fe9045a5b94ea1fe7
021c328b50096d392766ad53f4872ceb847a69ae
F20110114_AABYHG tashiro_h_Page_169.tif
86ad0dc3e10c8a66931c58c312274657
f16751092fa4cfb31d6809728270515337364777
F20110114_AABXXY tashiro_h_Page_059.jp2
97af054c816ebb5da96eff9dfafb49b7
a2613d8507b8ed78f353648d42ad00001b20ba11
2193 F20110114_AABYUS tashiro_h_Page_192.txt
77d8b583f18fba0625d568ddb7e52e1a
8b75dc40d88728dee153e8fe362e2ad2da887ef0
F20110114_AABXKO tashiro_h_Page_029.tif
a24b95ba291646607ab54b4698353105
7b6be172c7661da4f0e798b7d07563fa9798f263
F20110114_AABYHH tashiro_h_Page_170.tif
77d58df55320f3c93222ea466f3aea2f
6051d3965ee76d5bb6f6d2957f4b0dcd8e27b5d7
F20110114_AABXXZ tashiro_h_Page_060.jp2
3a0372d88d8946dd25d1aaab9102daaf
02a8572191cd263a989fccb540739166004e6b75
44159 F20110114_AABZEA tashiro_h_Page_146thm.jpg
366bf6f116666a0e0aefc12c392e2e45
5f46d311d799765205b877d34d4db0b1ba64951d
1904 F20110114_AABYUT tashiro_h_Page_193.txt
3345042bb603b731dbbead258c607a95
94dae54ac84577cdf5e97971417cc4210128ec4a
47697 F20110114_AABXKP tashiro_h_Page_207thm.jpg
aa8257ce1fa0d432b7bfa59daa936fcd
e29b24b11ef83885e8dc0406d56672d55e48079f
1053954 F20110114_AABYHI tashiro_h_Page_172.tif
12889043f399d10555f3c54726861bed
99fe4df7ffdcd7e0f030bd2a9cee8f853f210662
49824 F20110114_AABZEB tashiro_h_Page_147thm.jpg
c4be808d5408cd69077f3fe72ddddc8b
8d1d76a356e089b8aac6a3cdf2197b981aff9e9b
2166 F20110114_AABYUU tashiro_h_Page_194.txt
d59927e87548ab720767397d8354e01a
e1c543896a6a4e088e5224f6ce38283bf1c7263e
48901 F20110114_AABXKQ tashiro_h_Page_165thm.jpg
07d431081e253be004ebe9fcb1565754
0ce307cb4d1119e06ab776d3c7affa8cdec11f5f
F20110114_AABYHJ tashiro_h_Page_174.tif
2b5baae622451a7fd94e1012624039dd
fad97780b6a2ffdc06e894ec4837e8315f846ed4
111914 F20110114_AABZEC tashiro_h_Page_147.QC.jpg
5a61f0b5fa81352061a1e38928657346
3420cfb22e9cde5571afdf3b40e28afed3709557
2073 F20110114_AABYUV tashiro_h_Page_195.txt
81a81ec24136972beba7e1fe8ba7602a
fd234e5b3278603b37a7205f609d4a4a19e3c0cf
80459 F20110114_AABXKR tashiro_h_Page_025.QC.jpg
961035b4599f8f287913b52e18dc7175
e5ce3d5bf2ec41f0b00681863744f535b2c905fc
F20110114_AABYHK tashiro_h_Page_175.tif
db203b16efbc3e6e00f59e5c6dd82f8a
8e56af82caba019ff11605ede0e53627eba16351
50203 F20110114_AABZED tashiro_h_Page_148thm.jpg
0db89ab2f22f4ebf789a6803c5384767
ab39c32616ba6ce127a33497f8fce0d254ddb4d1
2077 F20110114_AABYUW tashiro_h_Page_196.txt
b5da3f5ea87a3b5d144312c724fdee81
8995894da098139c69bef79b4480a991cb088230
F20110114_AABXKS tashiro_h_Page_097.tif
a8d81ef3b0df972c8a5aa7e4905dca29
3a1b673857a0c02325510be59ca3b4d4ede4d6af
F20110114_AABYHL tashiro_h_Page_176.tif
7e153c28a7ffdd36a65a3c857b56cb28
bab1eef26d9ed2fd496d91b0dca4dd4f4a29b30b
114125 F20110114_AABZEE tashiro_h_Page_148.QC.jpg
831613d3e67f33cfb1b17fce9c524602
0c95660eee8bd41dd9c59da350e6431fe4b6fbd7
2420 F20110114_AABYUX tashiro_h_Page_197.txt
cf982a7fe10b6b0efe29e4ea9575aa72
ceeaecb270497f8c5729e4a327b4f2edcb72d9d5
40892 F20110114_AABXKT tashiro_h_Page_125.pro
a3b74192d26ca98879448d5f6f64f18e
133fbf50b9ea2208e1e70556883c85c3cd187594
F20110114_AABYHM tashiro_h_Page_180.tif
6e5a6f6aee7804af419ccc7eff7025d5
361ce26cb738ae5837a1bedc32a20392d8dbbfb3
110168 F20110114_AABZEF tashiro_h_Page_149.QC.jpg
9f784f19f6343a09f50fedc7f7534047
d0b157f11a8461c687bd3a05eaf0a984f78a3da8
2528 F20110114_AABYUY tashiro_h_Page_199.txt
a1c5092a5f13295c78f6ed01b947ee68
092ddf79a42a7ecf1dafee6384f882e6b1c5236a
45195 F20110114_AABXKU tashiro_h_Page_136thm.jpg
27b0110aefc5ed1bf67f1e862bf77f3b
faeea33e1e6a3b614b3b4abdaedb0c49aeb55da3
F20110114_AABYHN tashiro_h_Page_181.tif
690e3b607c9657ec9e7bc45295c4225e
29170dc3d959b14ed657308197d249abeb9d1d76
49409 F20110114_AABZEG tashiro_h_Page_150thm.jpg
6e69d65553b6a59c40cc7ef4baff51c7
9f09655cc3d986c9fb31f179aca7e33840f3f028
2211 F20110114_AABYUZ tashiro_h_Page_200.txt
c646c8399e1e5d10fbee640f2bf96be3
3319f55a3969c0dc026296cd7adf02deedd7e7ed
F20110114_AABXKV tashiro_h_Page_179.tif
1911772430f971b2cd7ef6336d523249
ffbacd3828c4862894b9cff857f10b2582926bbc
F20110114_AABYHO tashiro_h_Page_182.tif
e3472ca74fc3ccf3a0d487521a024171
1d3e7d5a0c655ff7b0a21e96acae9cca66a52195
105910 F20110114_AABZEH tashiro_h_Page_150.QC.jpg
204d9c85db72dca9449da1750bfd4042
734ba1546169c5e31e2fc5e1822cd6795891c431
52708 F20110114_AABXKW tashiro_h_Page_119thm.jpg
20f750b4baf23f1a30b065ed9e2cdb74
f09a5fb9fe1f3a79569e415e0c392f05e3c38180
F20110114_AABYHP tashiro_h_Page_185.tif
d1f896d0c4bd508dd725dc7fae8b02a6
87b5374aaaa5ef566d838bcdff69b17723a06f72
49099 F20110114_AABZEI tashiro_h_Page_151thm.jpg
3a843e874035689c40e7a24b9a0cd246
e829207b4d24f3879aeb80afabdf151fc3958911
208602 F20110114_AABXKX tashiro_h_Page_048.jpg
2bf4c4b6cf827ae92b69a13683558cc3
539402b16676b1c0422add4b3fe24185f005db77
F20110114_AABYHQ tashiro_h_Page_186.tif
d6de223a26d85ced42c223663b950016
affcee846004448c5f8f120d951f9321c5baad12
104422 F20110114_AABZEJ tashiro_h_Page_152.QC.jpg
b37b1f464e733b56e50f031a49fea18f
19e954a0718faa1fd75f0b95e72edc157a2401aa
89602 F20110114_AABXKY tashiro_h_Page_042.QC.jpg
aa10e5f7321086b7308aec6006b6ae9c
dca3f4f64739d9879d5a3cb8c8ebebb8541ae87c
F20110114_AABYHR tashiro_h_Page_187.tif
ac541e32a086c67a109224068a6ad09c
866b65e24784fc674200b0708009b475b7d3fda3
30116 F20110114_AABZEK tashiro_h_Page_154thm.jpg
35eb1239efb0d518e975aa87cb68b376
dd924089e3a677b9e949dc119b37039633c0caec
101101 F20110114_AABXKZ tashiro_h_Page_133.QC.jpg
e91543950e4d1f4b38eeb009db3a5db0
5e0c09079b2e18b24f90a6828aba3119976b3021
F20110114_AABYHS tashiro_h_Page_189.tif
8765a6eaa9fd152262101666b9cc86d8
04f151e291e01e9f138faef4ca6ab8c9239abc56
37584 F20110114_AABZEL tashiro_h_Page_154.QC.jpg
fab94f1fd8a81d1bdd07e4aa5747818e
4d89154e4ca31e4b0037ea8e8af49e94436a32a3
F20110114_AABYHT tashiro_h_Page_190.tif
461bdf640b02e77261763370edfd9439
787650712aca8baf2c1d5c2839802cb8449d9d24
48717 F20110114_AABZEM tashiro_h_Page_155thm.jpg
3a6433afbaab962fde63f81085c9bb9a
a5e0c592204bcf302aec9ae189f934bf471c755d
F20110114_AABYHU tashiro_h_Page_191.tif
24b306f146e477536c96d65c447a3497
bb1f6722451ab64b5044ca4fc6991d4bf7254003
51591 F20110114_AABZEN tashiro_h_Page_156thm.jpg
45d9fb08d37cbf4710e7a9fd086f7c37
c60b7277182036e24e961154a7d4deb95902927c
F20110114_AABYHV tashiro_h_Page_192.tif
2f4dbd386c0958600c900a63fc9b4350
b2241d4c7f2ea8db9ed408eae37c655fb5b2e74c
120479 F20110114_AABZEO tashiro_h_Page_156.QC.jpg
1accff1323dfab678a35669b5319e3e4
9cdac11e1fcb85738e60f6e14d97ce73f8cf82f4
F20110114_AABYHW tashiro_h_Page_193.tif
379016fa651fc70e452f649a352ab28b
7bd6f152fd77079a25f69035151bcd6d487e2c48
94171 F20110114_AABZEP tashiro_h_Page_157.QC.jpg
38134037e4db6fa49882e763081307de
6ce16a1bcff7c68e52aab1b30f44bb24bbda1e58
F20110114_AABYHX tashiro_h_Page_194.tif
fee59c6b72ef821a91215fdafd152add
ffac0f569bf20ca434186e41313e3ec6f0ac9dfd
48803 F20110114_AABZEQ tashiro_h_Page_158thm.jpg
0a3acfa8a08f849147328351d1f4d62d
8b9fdc1f749eee14d463f146f48fdaab9016408e
F20110114_AABYHY tashiro_h_Page_195.tif
6d269ed07ac462fb79d440c10c2821e4
a3bb30c2f67e6843c0c4013f90afa32103e49187
109828 F20110114_AABZER tashiro_h_Page_160.QC.jpg
8c65713417015c7b7c97bc065d9254bf
c23b0fc1185aa492ef8efb8b358d03811e1f4e0f
102481 F20110114_AABZES tashiro_h_Page_161.QC.jpg
6c2e3d36fdbf4641c29404060e99cbb1
c5152c2846ec9383872fac85744390bc118cd56a
F20110114_AABYHZ tashiro_h_Page_196.tif
209141fab759ead6cde5ade21d978288
cb6ccf19dcb748c8d4d8878413f3fd4ce7f81dd7
107181 F20110114_AABZET tashiro_h_Page_162.QC.jpg
5e31edd614c11dbcd36d74db8d601519
6be5ee908ea0fc5a6c696322d0663b3b3d81b9b6
262826 F20110114_AABXQA tashiro_h_Page_013.jpg
4ac6a9ac717616be76696284d201b553
3d033cde68fa8913befc0a708d920468ee389946
115170 F20110114_AABZEU tashiro_h_Page_163.QC.jpg
c96b29a43b5d7d6553b2759f3990ad60
dfd6de48e4768dc0c21d9d936db32dafa75bbacf
245046 F20110114_AABXQB tashiro_h_Page_016.jpg
7343139294afdce2ee058c4aefb7dbb8
7a533bd9fab85944838c15604d7e76a9ed414697
256102 F20110114_AABXQC tashiro_h_Page_018.jpg
5ec76f744d47d27b1d090be99b9bfa8d
d32601d6f9171d80a76a276a5d75a000b64a6cc5
48470 F20110114_AABZEV tashiro_h_Page_164thm.jpg
0a5a9f43b8012f69ae0262146986a89a
cb9b0bf7c5ff6531678f27a13a818e19eebf5a98
103876 F20110114_AABZEW tashiro_h_Page_165.QC.jpg
adaa4bfa7896f95925cc0320c3c34bc0
e3f64571d58b002d921b7d86c8b85cc6d2f8984f
255414 F20110114_AABXQD tashiro_h_Page_020.jpg
cb0b3572c72ced87f52a1f7c4eb3fde1
2a40ce242568557758acee548953471e0ea300a3
52483 F20110114_AABZEX tashiro_h_Page_166thm.jpg
d9026f96154ad14e3520c02febc34eca
b2ece383ed33bb25846071731712c357739ff662
236377 F20110114_AABXQE tashiro_h_Page_022.jpg
6ee3d6458dc655b043c85b367a51bbee
aa233e5df40bcb1964eb7c50f64d5a51e8b49abb
49462 F20110114_AABZEY tashiro_h_Page_167thm.jpg
3aa5590b2a9649c88dd475c4fa6199a3
dfae02cff98291217af662653ee3bbdeeb4b6f43
228779 F20110114_AABXQF tashiro_h_Page_023.jpg
8b85a8bc5452ff8a7f6c24c5499c756c
ef32dbec07804c5e7c6bdf24958750ece97d1f7c
49865 F20110114_AABZEZ tashiro_h_Page_168thm.jpg
39fb0d2a53aa4767ce6d85851d8cae7b
3694bb47f5af544a32954c972ede7b5424a44728
201838 F20110114_AABXQG tashiro_h_Page_024.jpg
db362ce56764c10fbd15f534133f1339
a3e89c9b54e907cd5b87dfcc4c626f36fec20d1d
186441 F20110114_AABXQH tashiro_h_Page_026.jpg
e0c208010ec47d3d0996ea26d3f012ab
6a959df5764f644d1a22def1aeb5a7eca1b8736a
55024 F20110114_AABYNA tashiro_h_Page_150.pro
3ee226310520f0565b6ea54e9aa7f04f
8baf177c62b0d9b6414b8d6f6d767bb553845ccd
144636 F20110114_AABXQI tashiro_h_Page_027.jpg
788adf34df01ce61af50b1bc7dc35aff
b8dd10991400c2fe33a5a9c98e637e95a95182a3
54750 F20110114_AABYNB tashiro_h_Page_151.pro
0766a91d5d5d7ed1a5b154faf2894e07
5341bfddf696219de149dc3d4b23c87a30595fff
209965 F20110114_AABXQJ tashiro_h_Page_029.jpg
dca79cfe4ec4399eb04ea7ddd2b0fd15
aa199ce18c1b3fbd4eee48941fad9119aac614a1
43651 F20110114_AABYNC tashiro_h_Page_153.pro
51f3015874fce99b2920ed91c739d821
0dbae0a2dd826718030cf81d00ce1106082ceb88
231701 F20110114_AABXQK tashiro_h_Page_030.jpg
8163f08a7804df1c00ad2a02cfe64c92
b68f3288b34dcc305b922c4cb28b916b55032224
5313 F20110114_AABYND tashiro_h_Page_154.pro
e8f94ac141672180a31e1cbd849e601e
b024f89ddd7980994fa2bdb3a87d798d60f4f095
178232 F20110114_AABXQL tashiro_h_Page_032.jpg
e6bc4b1e34bf6b615b402231622a5e02
d178f2158a9ea9fa8c0b2a786df02f49289cff4f
60514 F20110114_AABYNE tashiro_h_Page_156.pro
2f5ee252529f38fa6966013ced87b4e4
a1ce8933534b6d7db00f33e51e4e59582c582fbe
46522 F20110114_AABXDA tashiro_h_Page_113thm.jpg
a180432bcb29f96dec48455d7156a24c
38c8a52794c8e6aae59a237a035b26483ad15f65
223591 F20110114_AABXQM tashiro_h_Page_033.jpg
29f7de8b46cc882069298d3fa43e7e7d
e0f1fcbbcd9d59a1085ea4f63621a6077e2465d4
45530 F20110114_AABYNF tashiro_h_Page_157.pro
0b4013d3ffdba4d150dd338c2ccc9e68
19de74c7b461ee640f87f06668790619b53ae0d1
F20110114_AABXDB tashiro_h_Page_085.tif
47c165349818c291e903956b89aae14e
5b7f3f796a860f74c8f0db48e1dbea3cfa6a8296
211706 F20110114_AABXQN tashiro_h_Page_035.jpg
7a7d8497c0c59ee08eb33d26804ea78a
02c8164e45989b02b96c876631a12602f9290142
55296 F20110114_AABYNG tashiro_h_Page_159.pro
4c00d8b6a3d1e6e73196879d1c4864f3
d2cfc86d55057cb57db348ae185e1b1b8ee7ce80
244396 F20110114_AABXDC tashiro_h_Page_174.jpg
d57a15e70c27148375838ee8a108674f
0662622e615e3a650ba6e0edd2aa6730d53e7564
241880 F20110114_AABXQO tashiro_h_Page_038.jpg
10e937aa450ce639a6d8d6e24214f5f1
3c9244044500554ced5a5cd94bbf25fd67923687
50973 F20110114_AABYNH tashiro_h_Page_161.pro
8da33535c40533fa17c4a1cf94c7be86
cd9aaedd8af6c7bfcd4049d9c4ab4fa4aa1fcd7f
F20110114_AABXDD tashiro_h_Page_071.jp2
c3803c64215620124d6c197d8dba6522
faa6b904c6c3efa3ad22335fcd6a5cdd2089aa2b
223278 F20110114_AABXQP tashiro_h_Page_039.jpg
b3a55363f834bded46cb808bf7df4547
99f3e978bfde5dc239166ddf08f1508466af3087
52259 F20110114_AABYNI tashiro_h_Page_162.pro
fb892d3611d280389e4052f9f03c8e8f
699eb34e56455a95e6b440b9c0f93823453bc729
66074 F20110114_AABXDE tashiro_h_Page_209.pro
cc81b0f3e39c0f2d42dd0d5901fc8dca
550334055824fe0e00630943fa65116b4354f5da
231476 F20110114_AABXQQ tashiro_h_Page_041.jpg
7562b08c45451945fde812379d4c87cc
e566be82d0fb7ca1b69fd7b2abc33877dea234a9
59760 F20110114_AABYNJ tashiro_h_Page_163.pro
6ecb7fa1d7570c066e848d47e9a3146f
d84ec8b867bbc0a3b9f7a97186218ccd8497a23b
F20110114_AABXDF tashiro_h_Page_116.tif
fe434b81fcffdb97a03ba5aca6a54d76
e8d6e95847b1663f2a2733d8b06eb93f653564ae
200050 F20110114_AABXQR tashiro_h_Page_042.jpg
cd88cc0465c0a1f1387111845be880b6
fdcf05da832661e38bddacf7e5114dd6e47473f3
41455 F20110114_AABYNK tashiro_h_Page_164.pro
9627a510870bcace7c5d44ef6de8c0e6
854e9dd379f4fd672071300c8adf5652f4a70502
51306 F20110114_AABXDG tashiro_h_Page_012.pro
385ef3cde10cfbddd51264ab28b2cc3c
484228c6a00b7361fff3d59932188f2fc6fb041e
F20110114_AABYAA tashiro_h_Page_145.jp2
c162dd6b3cf243c49a518397b4d02cf3
7387d600e95f468abd11fdf51530aaf4c291618f
136484 F20110114_AABXQS tashiro_h_Page_043.jpg
e7c0cb05a649edf04f761aa562f4f71f
6bd4f514755158f31afb9e457a5f9e31dee62cd5
48469 F20110114_AABYNL tashiro_h_Page_165.pro
b715554abaa7f57a602ec2c64b2a4510
a021d9aa5df699491e5231b5975a6cf66cdabdb5
F20110114_AABXDH tashiro_h_Page_101.tif
3bbd043e7382df2e63d6b10fe8421677
f8c6f54bebcdadf451d1ca93c131306c2a382645
889230 F20110114_AABYAB tashiro_h_Page_146.jp2
adebbb6911b5744c0b321a857db792a4
0f3c01fb5632bf5c52d7c0660eef68903612b286
198920 F20110114_AABXQT tashiro_h_Page_046.jpg
f1c08e799e227b837bc235db80c4d98e
78c540f8077098e8d8ebe9541a285c92c13d0070
61168 F20110114_AABYNM tashiro_h_Page_166.pro
3ce55944e87ed8d4417d7c32e5487b09
d7edbd0d2ce714eb0577802578fdefee364a5819
42194 F20110114_AABXDI tashiro_h_Page_203.QC.jpg
f3443d2ddf841317e4a796ce9fd57d1f
c271c7daacde0033d9583c9693ef6ee3c8f87c17
F20110114_AABYAC tashiro_h_Page_147.jp2
4d1f95643290a5034892be34a19f5623
126ca6ee9ead961d73a01bfa167c733d4231921d
198553 F20110114_AABXQU tashiro_h_Page_047.jpg
bd20133d56de316a8fb42fd1f666e305
22c68249fb8b1393439e8f3daa321c67951f905a
38731 F20110114_AABYNN tashiro_h_Page_167.pro
5d9d396fe9665f92b526ba826397726e
ab5e23b1bc1d46a39019c98255f7d41e0c4f69ff
47502 F20110114_AABXDJ tashiro_h_Page_193thm.jpg
9dfad61c4153d9fd5faab6e7973a04fa
49a6c08b12a9923525792d39b9f36358490620bf
215406 F20110114_AABXQV tashiro_h_Page_049.jpg
c0106d3c099b14faa21b1dff09e2e3ac
7fe1a072b4938bedc227ea48427e4f726b7b3583
38878 F20110114_AABYNO tashiro_h_Page_168.pro
c16d5cc5b7bade10b1616d12b83038ad
e167700184ca4bfb127c9c0d764e0d893911017e
222445 F20110114_AABXDK tashiro_h_Page_134.jpg
6933a4203a66f1137f01fa3689b9fb52
ab31b594c16dc28c6ad3c29451531f8c1541b237
F20110114_AABYAD tashiro_h_Page_149.jp2
01ac779b7ed9f47edc15361f039f2008
1e747a32bc50635016271675bf5e46a7094b2582
187693 F20110114_AABXQW tashiro_h_Page_050.jpg
38fce2870c1a9a2e4bf8e6abcf616df5
dcb9e248910b24b5b01d270aa9b47f7d033c5e8d
41249 F20110114_AABYNP tashiro_h_Page_169.pro
13da38bc87ab29ead7ec75c5cf6c1a4e
fd1fb91cd8c9ad3abfa9f55c5f8bb4a41fb7c95d
44792 F20110114_AABXDL tashiro_h_Page_227.QC.jpg
2ac37cb655b24b9e83cf130bbcaf9f6e
5a1c2d0c9db44c2aed81816aefd806347574be63
1051941 F20110114_AABYAE tashiro_h_Page_150.jp2
3502a5064d3aea6cb0e6cd02f3a27532
bf455345646fed9ab812eb42785c219f67cf0a7e
163001 F20110114_AABXQX tashiro_h_Page_052.jpg
94080c14db6ed623a439c2b9698750c3
81f11d3b444bcae88cd31b6f43edebfe9bf3e76a
38832 F20110114_AABYNQ tashiro_h_Page_170.pro
7854b6fa997dd3d7313b30bd370cdf59
480d3a69b3fb74e8a10f218112bc3d8b6f4d457a
42414 F20110114_AABXDM tashiro_h_Page_052thm.jpg
2124cfab83d406c0b385ac74b4ab8865
af7a23270952a2caebbf45c6146db4c986475d04
1051903 F20110114_AABYAF tashiro_h_Page_151.jp2
e9baeb5c9fab5f89ebff0eac673f563f
4917cf6556d020ff9946247b7dfcea01b59a8ee5
160121 F20110114_AABXQY tashiro_h_Page_054.jpg
ee1dd9cae34b59134a461a2875cd397d
aecbf1ff468acccea8d12e2cd5478aef677e4830
17809 F20110114_AABYNR tashiro_h_Page_172.pro
325d920d9cb7e7c88aa7e7448dec4ce7
25894e069b06a7eea0aaa3e4ff4973486e51163e
44586 F20110114_AABXDN tashiro_h_Page_173.QC.jpg
640d81b7b437283a859a9fbd9268aef9
769ec30c584fbb7a7aa76d1007fe8a9d2b115a1e
F20110114_AABYAG tashiro_h_Page_152.jp2
7c205e9e2878bc50d430b22f2b870666
c7ac5de5a700893e3f5a433560c647745cd9fa2c
224902 F20110114_AABXQZ tashiro_h_Page_055.jpg
dbb1957bbe0651946a5a81f1c6e1018f
3af33b1a7b811729c5d0825be11fec0518112298
8079 F20110114_AABYNS tashiro_h_Page_173.pro
c4004fc1bc0df13d2ac759091e3f59b9
def798b1ce861a05ba601ddb2f2ae7e3578f7afd
38821 F20110114_AABXDO tashiro_h_Page_076.pro
5605524f80c9fa87053d99c162e299e8
4146ea018fee719bcc172f2e10fc685028c25581
1010727 F20110114_AABYAH tashiro_h_Page_153.jp2
5719378caed1c42f7482c317e02aa802
963af6644853cd1c4001427940c4ac06016bcc84
59486 F20110114_AABYNT tashiro_h_Page_175.pro
9e347dd0ad482c057b365a04d04e9129
a346aa7106fb627284b22ef4fef350c45420a721
55735 F20110114_AABXDP tashiro_h_Page_185.pro
446c19205449b645908d4739ce40fd22
744118b0cc98cd87414fb1013c4dbb5da70c6b06
130468 F20110114_AABYAI tashiro_h_Page_154.jp2
a60ed53a3d74fc921e6175a7e65dc712
33ee44f2477469f017b978d86b335aac0ec79c94
49620 F20110114_AABYNU tashiro_h_Page_176.pro
ef6946a1cf1e53dbad362e45b8843941
af41ad1f4f4372e46594dca4040796e86cada6a4
F20110114_AABWZA tashiro_h_Page_177.tif
59dbe5af16a71d81711cbb9ac53a5953
b2210f28498e9230c66380cdd2fd1ebeaf713134
60696 F20110114_AABXDQ tashiro_h_Page_186.pro
1f1ff55a2305203486a9d003051142c0
d43e835af6a4d18ebed8f986957f035d1b328e21
F20110114_AABYAJ tashiro_h_Page_159.jp2
c045caa1ac6d2a04bfd0e477b15888f6
5919ea93ccf39558375fd5585b096320e94aa26a
67229 F20110114_AABYNV tashiro_h_Page_177.pro
f398044bbd02e97835bc8676ef472585
62906d3ef0da36e8f3a8e24c70ea61e0763238ef
106088 F20110114_AABWZB tashiro_h_Page_053.QC.jpg
7f501c9f7b4390f1e8626dedf43fd6ca
ee4b3e4f9fe6e27613454d17e520ed435f785d93
F20110114_AABXDR tashiro_h_Page_055.jp2
ead89cd2f8d8f20140ecc5ce8254417a
7ccb1dea63ef37a2e82f257f9b1f26561aecc96c
F20110114_AABYAK tashiro_h_Page_161.jp2
08890a58d51315d76cf6220966e9db1e
480da7483e7120736c145d563c9db0a7f324d91f
45822 F20110114_AABYNW tashiro_h_Page_180.pro
00af962411d89d50af74afbbeaae1595
03e39b515a4b78b42733eed538b38c6c1ac00590
89165 F20110114_AABWZC tashiro_h_Page_037.QC.jpg
05a22a4332f68cad1e61e105de37b2c5
1da84265c2eba86b2bf15bba9d84a7a5c0146947
102892 F20110114_AABXDS tashiro_h_Page_106.QC.jpg
064c7722f2407421bdb484dae6eaecf7
49498bf92bd9479a9d3b10dee1994d28a94b3728
975635 F20110114_AABYAL tashiro_h_Page_164.jp2
0dea4fb487624531ff8b7bcd83924fe7
5f3a5c16790f5b7830a7509b2a3c8566a287ae9d
39841 F20110114_AABYNX tashiro_h_Page_181.pro
7f353cffd60484874d2703033a5fd700
d815e3f16fbfcbf84f5ccb584fdf4b526adf5ead
2070 F20110114_AABWZD tashiro_h_Page_230.txt
06b5b1d3b8a6ffcf1dd915ac820ac7bf
6b9bb88a9eeed0d64a47314ab70e0f1d50bcb337
2041 F20110114_AABXDT tashiro_h_Page_218.txt
e9a730377dc2a46d3f2e948d317e321f
8f407210b122455496b186b7e793a2bb4c3d3e74
F20110114_AABYAM tashiro_h_Page_165.jp2
71ac5c4f3cba94f9ac3271531ca3d510
0cf66305f8a9e26bb947dad5e8f34932cfad901d
33771 F20110114_AABYNY tashiro_h_Page_182.pro
ea3b973b78e64c77116cdad6d929e73c
986e071e910652d526b9f9fc0fa337ce9547db61
F20110114_AABWZE tashiro_h_Page_183.tif
3e8a25c721a4d0acbe907a077c38da7b
6b4cd17ef1061eda745cd3eb5b41e06978cf9f78
46112 F20110114_AABXDU tashiro_h_Page_042thm.jpg
ba5b0df6da8fac47bae2aa6ab405aee9
94daf48b9b933995dace96c5ce96d4dd0a9d70f6
F20110114_AABYAN tashiro_h_Page_166.jp2
3df0c82b8d4b719f83acba496d4f0c9f
dce834d98177db18790fc122f16ab75a25341a42
41420 F20110114_AABYNZ tashiro_h_Page_183.pro
9fda2bfcf997f50a748c567d6d3581ad
7a6e34ee9c33c97ad83ef83e4d32c154896ff343
2036 F20110114_AABWZF tashiro_h_Page_206.txt
2b0bb8dfb078ceb1e93273e2c139e054
2e5f472bf0dab9ca92ed4a57d884412ad76b27fb
F20110114_AABXDV tashiro_h_Page_171.tif
7388699d26c1407c4049dadf418f2829
a59f1564e1d662fc4fc208a6c1a67e4986952934
F20110114_AABYAO tashiro_h_Page_167.jp2
8ec80c9b16c0430b79cb4174eed30913
58447540df3ccc252e1506843c6c62cb4cc7fd7e
281351 F20110114_AABWZG tashiro_h_Page_156.jpg
92ee6ca91bf82d963ae910a3f0364547
27cae0347cc68c1f705c4f7b713e5263f57c9b0e
F20110114_AABYAP tashiro_h_Page_168.jp2
f516b9ee61ac2cc8dbc5acbeded5fb3e
8b0b889b4a7b15c12981f812daa356fd4b97655e
109810 F20110114_AABWZH tashiro_h_Page_109.QC.jpg
6d79440a636276e0db98b4d05a630239
aeee2b3630d2daceca82bce39acdaa255a47816a
2266 F20110114_AABXDW tashiro_h_Page_189.txt
0972e437f655eb9c90ce968ab1501dde
f3ac67d1e9f2a765243c40fe014c14f6958dc699
234034 F20110114_AABXWA tashiro_h_Page_228.jpg
1a72f26ffdec20d6dc1b320c55fa9cdd
cfec0559e375ad6d6a3ce25b2ca3da434d32060d
1051979 F20110114_AABYAQ tashiro_h_Page_169.jp2
7f008654643cffe53403ae6283ef0c08
82a0b892134d7256e3eca6c7b049f66d98d39a5b
F20110114_AABWZI tashiro_h_Page_188.tif
d6855cbb1302f263f97abf5a75e9d913
93d764c01aadedc9b7348c99a344f26ede8f3c09
38174 F20110114_AABXDX tashiro_h_Page_211thm.jpg
26794f61857a302883cdab556a372f31
28f369c898c624b936cc627e47ec4fb09414bef5
254253 F20110114_AABXWB tashiro_h_Page_229.jpg
c9e8c3d74623a803dad7af8a24329a5f
96d4f0b74f71e41b54f60ef2364e3224ad3002f0
F20110114_AABYAR tashiro_h_Page_171.jp2
7841d0cc2cb6910a88690e51558d58fe
2bdbd7cd58c01aa044ec1e7a3cd42debf3f3340e
2204 F20110114_AABWZJ tashiro_h_Page_053.txt
a9b1d34141b45bd245715c96228124a7
94437c231147c4c1f492d139dd843ea964f9a330
2223 F20110114_AABXDY tashiro_h_Page_072.txt
70568d53d519505bc374858a70e32769
e3b85ae0b3c412340c823b282f8b65a05c2e19bf
259830 F20110114_AABXWC tashiro_h_Page_230.jpg
6225e14138f572ca3f2f5c2326cbe521
edae9c99cb4fb9bbf04802ab9a7bc9202e5482c2
163685 F20110114_AABWZK tashiro_h_Page_063.jpg
e2222eec022d7a2a0a6868ce9ca51c20
5ace841cffd98fca14b7f75ec44321a5d52525b3
55478 F20110114_AABXDZ tashiro_h_Page_160.pro
fc20497e0f3b02a0ed304515dcea0c00
4cb87cebe5cde80d109eb4b206da695de51400b4
259850 F20110114_AABXWD tashiro_h_Page_231.jpg
54b7753f889b1f32f3495a16f4899f2e
b7bf0ec78579f75c9c6739e70f7ed8255b56a4d1
F20110114_AABYAS tashiro_h_Page_175.jp2
21848cac97298bf16c7b9fd0c9771936
1d1031c7a10154b6a21449a111f0e98d83cc6303
242733 F20110114_AABWZL tashiro_h_Page_159.jpg
7ac3f7333eede6cb7e07850daa18df0c
035b1720b4388f1ac2eff03a4c3ad250016b3571
250180 F20110114_AABXWE tashiro_h_Page_232.jpg
991daadd1153c91baea651eff3c49b5c
a2936909ac203eb6368f221865d164a01f3c83e2
1051968 F20110114_AABYAT tashiro_h_Page_176.jp2
81e8375128cd6531a03b3e219e48012f
c725d94e21097c678e1c8f2bcf613c3eb13fe46d
1774 F20110114_AABWZM tashiro_h_Page_068.txt
baa156be8f6483bd6a8f0a2535b46653
314dfc7e692ea763bf90a5a8900fbf54aa7f21dd
88517 F20110114_AABXWF tashiro_h_Page_233.jpg
4781713869bf4ad4e7eb83b970173ba1
a139c3ae3ab24a5f56dc1ef2ce11a34dcc96bb40
F20110114_AABYAU tashiro_h_Page_177.jp2
fc9a4c497f86aa6089c72b3b065f93fa
1f3102995e757b06d0a160f383e28b9f09f25107
136498 F20110114_AABXWG tashiro_h_Page_234.jpg
defb3c4e298d76ad5bd92273c4130ca1
97f73aa2f77ff992e509c5d6b9475e818c1a39ee
F20110114_AABYAV tashiro_h_Page_178.jp2
0e538f159c5b4141bb9ec61695f2a089
07455a9b814e01ae45682323c9998e40760ddd27
2238 F20110114_AABYTA tashiro_h_Page_139.txt
2ca89d008ecd2be7ef67e6f263be46ff
c18298862b366b0efbf1a83a3b3bde983cba5e2c
108055 F20110114_AABWZN tashiro_h_Page_108.QC.jpg
9fb5e8244ff9b4cae2f96c356b9b6643
e35bc23798633cf230d95a13ead0cb441a25ac50
257595 F20110114_AABXWH tashiro_h_Page_001.jp2
6ebeab45399d543af2548880731e33d0
96d48ea448dcccfaa71c8aa88a083f2bf896d840
983429 F20110114_AABYAW tashiro_h_Page_179.jp2
d1f178e516456b5d2a4eda5467054501
a381fbd2d3b1ba98dd1a16012371efb8ecd74fbd
2462 F20110114_AABYTB tashiro_h_Page_140.txt
0e960e5a69d301c7af8d6ea366b6096e
d709e9ceb9ce959906f57a269593e85d0fffd0d5
231596 F20110114_AABWZO tashiro_h_Page_167.jpg
69a2b6a81b4d4dc0676a3f2fb02bcc8a
384a2322066b3a6157b0949b00a997a7eff1bc36
31412 F20110114_AABXWI tashiro_h_Page_002.jp2
61e3c878ca0c52c2b1d3a1f85768d16c
90548ce462123fcf54f43996fc61fe2af5d0795f
1018080 F20110114_AABYAX tashiro_h_Page_180.jp2
52f692997a725c894bc28147c83ec7e9
9b82a2b8391dcfbc1db88f9c290ce88b26e71c0a
2306 F20110114_AABYTC tashiro_h_Page_141.txt
d9302e0fa6940aa596c45cc57e9bcf71
a37f25207bebf989360992f13a15c968f17c7bf4
252713 F20110114_AABWZP tashiro_h_Page_114.jpg
83f1b0218ce1398d6f8455717a660250
f2b8efb65a9ad702e5dc8e1a7afb79d4ef8b4e73
888246 F20110114_AABYAY tashiro_h_Page_181.jp2
4f495737f576146b9a101e67690c0f89
8dd68cec8918fa81b5d162b40c3b2cd009205213
2594 F20110114_AABYTD tashiro_h_Page_142.txt
53754bdcf8113493ee71b03f63d5864e
7a289f44df754044470601a1bba7a18368976d1c
57567 F20110114_AABWZQ tashiro_h_Page_124.pro
8e41ce6c5140786b1dc13cd5c516e06d
4e2863f9dd06ccef8bdc585c4a7be542cd16ec9f
26426 F20110114_AABXWJ tashiro_h_Page_003.jp2
1f4bcebc811fcf9f1b12345781d8c11f
0d29b65ac3887b73904122e71cda103e523cd967
1040932 F20110114_AABYAZ tashiro_h_Page_183.jp2
cb86b52298b0571d2dfc26fe60ba3a7a
b678f0e010e16619e991e9813998d4115e6f20ce
2057 F20110114_AABYTE tashiro_h_Page_143.txt
0611278eea72c026c77499464a632f9b
9c7cd14825a674aa0b10701a11cb9fd1ec9c6ffb
F20110114_AABWZR tashiro_h_Page_014.tif
18e9176f6d6704a4034dd85b70078376
60630df2a2f465585c81828359abaac7b7bd26f2
F20110114_AABXWK tashiro_h_Page_004.jp2
1d4d96a0c4b93902c0d5e4c913d720a3
5687d5354d731d2673fb78ffea2f82ed6c818f2e
F20110114_AABXJA tashiro_h_Page_030.tif
988ab28f7fb7012dc012634709728bd1
8a0fca2d4cb38beaf2208c06fb8f9af68dda3b23
1869 F20110114_AABWZS tashiro_h_Page_104.txt
97d675d42dcfb7e5e966ea78bcbe1dc8
6230087c18a334e9d86e56d7bdd0407e4add894d
F20110114_AABXWL tashiro_h_Page_006.jp2
ca59bd7412ae4eb7e8c19eca0bc8a2ce
bea7df264dcf133847f4db64ad0072f0bc667e51
2285 F20110114_AABYTF tashiro_h_Page_144.txt
13012f04bae2c760171d3c4ede57031b
3036f05ade30125aa112b493ce7295ee118ad3fd
498406 F20110114_AABXJB tashiro_h_Page_005.jp2
0700e5a820f2daee6ef05a9a2a595ba3
65876e320204e261d1a92b055c8442aa22f5d086
120236 F20110114_AABWZT tashiro_h_Page_121.QC.jpg
419e7ed6c18e0ba77fe14d06f8f8b442
e2190cedd0d315877f57e14035683e1ac6aa49b2
F20110114_AABXWM tashiro_h_Page_007.jp2
33e4c42275bee2a23a67147ddfe39db7
ad704df172cc61a6f5e310be192a8b6d6b284ad7
2418 F20110114_AABYTG tashiro_h_Page_145.txt
6c6890f7d94fbc693330c839e4bbabfd
c827964a1bba9118add6255d522399d2b94d407a
1961 F20110114_AABXJC tashiro_h_Page_037.txt
c1cbbb966e1197aa64fde8e49f0cd3e5
a4cef42f90dbbc4b0f2dc421eda4388bd7aa4383
F20110114_AABWZU tashiro_h_Page_197.tif
58d5488ad04561a718ec49034a6a9177
185f9b5f265e4ef08694c10fb1aa5f1cc9054e05
F20110114_AABXWN tashiro_h_Page_008.jp2
0fc96cd6cafc445c97873ce147703884
15fc49f6851d8d8e09a0a39f2a0f6e187f367053
1842 F20110114_AABYTH tashiro_h_Page_146.txt
a968afa832b9e90bca21c7f0e14f214e
77f133bececac6eb93a673eefe9c3d4f1ea91d90
F20110114_AABXJD tashiro_h_Page_160.jp2
d66fd2add098a3be3d9a0cf2552b8cd3
156c6faad3bfd9895c09605f6ea0be5cbf4297cb
51185 F20110114_AABWZV tashiro_h_Page_232thm.jpg
ee27674565d5768bc41d5437f50fd0e5
182375e5f40861f2082aa264940e45be106af90e
933480 F20110114_AABXWO tashiro_h_Page_009.jp2
868b0a085855bf4d68f6ddca5ff9e28a
04baa8fab4a3b23b12000510e741f22a7ee0b916
F20110114_AABYTI tashiro_h_Page_147.txt
54c0ca43032d38b6d542e9e1ee49e67f
9fe89718b76502efeca518daedac68c5efcdf01d
108976 F20110114_AABXJE tashiro_h_Page_151.QC.jpg
e5078fbe5ba6f67b90a33af615116864
9c843414604704775f5d0bf6920a53f4c398f710
170882 F20110114_AABWZW tashiro_h_Page_025.jpg
9cd501a00202f4c66eb7ddda786f0599
a22738c0278fbade5990adc39abee1cd1aeda53e
730415 F20110114_AABXWP tashiro_h_Page_011.jp2
aa842fb881db86b4d875db6ac620ef76
6071146d3957a382604ccd1a94c41f8335a25327
2433 F20110114_AABYTJ tashiro_h_Page_148.txt
0f8e2c13986e435171b6a7a22c6226e8
90cc4a797e4ff8f34ae9cf06aa6b5e211f456340
57344 F20110114_AABXJF tashiro_h_Page_144.pro
c16fe2df7ac5568f869b2aa7864dcf28
06101b811b09d8039a9a3417bd95f77556aeb366
869688 F20110114_AABWZX tashiro_h_Page_051.jp2
857ec73fbef0025647877fc0668b2157
9978b295b971ac439a159b8f6913de1d2c1da8d7
F20110114_AABXWQ tashiro_h_Page_012.jp2
eaa6737c3a50cc2cd7a5541a7a497a53
0e07cb3a02bcdb73b2e93668cf24e71e4f516b99
1370 F20110114_AABYTK tashiro_h_Page_149.txt
873d615b49b6cbab3065ef145ade3bb2
2ab4d06ece0c1f3b02b018b4037f02cc0ec9f5a9
246740 F20110114_AABXJG tashiro_h_Page_097.jpg
f33d686f8c7bc9b012b93015b7ba46a1
fe966a9b03e209a8ced15401afe059977fb3259c
55238 F20110114_AABWZY tashiro_h_Page_091.pro
7e2b42836b179d5833630748e73fe41a
6ea8140043767250897a16ad769a8fc921962c90
1018632 F20110114_AABXWR tashiro_h_Page_014.jp2
821f8f62832190e51d554fdfafbc794d
55dbae750aba9fb59812c5993c171cd3821b3111
F20110114_AABYTL tashiro_h_Page_150.txt
7ef8a9fbfd0e601fd85f282c409ab446
bed90cd96f768cd6c33425b422a7a35a10d522b6
45312 F20110114_AABXJH tashiro_h_Page_046thm.jpg
1cefb12fcbf71a8ff2a5705c31344307
275ea59581f205760ad119e02b86671ebb6d8692
756490 F20110114_AABWZZ tashiro_h_Page_182.jp2
fcb10c4016859fa93c2b2492fdb783d0
922d879d1618b26418ceb5c90f27be7ca4496487
F20110114_AABYGA tashiro_h_Page_132.tif
bf88ec56393d480f0156d07e10bcf682
de0064a5d8348d77a52d525158fa4c553c81ce8a
954789 F20110114_AABXWS tashiro_h_Page_015.jp2
ecb8e692213146dac2aedbd8a19033c8
f86c6e6ac5a4917d585d4414e1cb62f550371088
2098 F20110114_AABYTM tashiro_h_Page_152.txt
cec4a6a0c01f2fcb954f3d8f909555b1
a56399130574d6d17e69e81fc7bce69040466049
F20110114_AABXJI tashiro_h_Page_078.tif
54d12d7e49e59a2ec8271dbea9114911
7866435d38e0f0b2f9856852c8236ca52d7958fe
F20110114_AABYGB tashiro_h_Page_134.tif
2fd8716a0415c1829b2d4578781eca7e
ef2285d905cf6574ac82dd75849989e9c162f2d7
1051953 F20110114_AABXWT tashiro_h_Page_016.jp2
6385471cd2eb7cc945ceca6a991823c6
4c6f14d66d53c10063a42e20745d7bb9a4562ac9
1979 F20110114_AABYTN tashiro_h_Page_153.txt
f94a4e2243ce7dff56f320a6c460c4b8
8802fbcd7e50d71ca326beca09083329c45f8b59
48908 F20110114_AABXJJ tashiro_h_Page_217.pro
9eab9105aca77174b7b90ddaef5c3017
dd40b70521a649485aceddee4e9a3b558a83530b
F20110114_AABYGC tashiro_h_Page_135.tif
eeb94b4adb8ea40a9febbbf8a74cf884
39c8c9abcfc7793d55612232a7cba4e21b4affe3
F20110114_AABXWU tashiro_h_Page_017.jp2
c4dbd484cbde3159ba8dcb0c777d0a1f
9886e313e733c9da3f05f5687281698d775cc97c
254 F20110114_AABYTO tashiro_h_Page_154.txt
24ac734a13e581665c5a1584cae9cb47
d35893ed35005cd16bfb3319920675f0cee2ae2b
733564 F20110114_AABXJK tashiro_h_Page_054.jp2
2af745228ac02e3e8ea89b0ef74a4d5e
5b8eed8d4d9f2be6d174421c91db3c64351dca5b
F20110114_AABYGD tashiro_h_Page_137.tif
65235a18a8e0901faf1831aaec609e29
009a317ccec291f3af72ba7930634c350607e428
1051962 F20110114_AABXWV tashiro_h_Page_018.jp2
d05c32329e69ff094a61f8982d618dd5
c9c1883c42d8478443f31fd1149cb21f7575777e
2455 F20110114_AABYTP tashiro_h_Page_156.txt
7a0868e0c90bab63e6e2d610937aa063
0fe5ab5e8fa328d724c3978fc2aeb24df342443e
1098 F20110114_AABXJL tashiro_h_Page_223.txt
f98b1a488856499bb602d49d706f4de4
0258a9a3ffca186d1695d2945738915b8e1f6af6
F20110114_AABYGE tashiro_h_Page_138.tif
55f79b754690dacd3cd164ab01d360dd
b475ad88f18968b857f521b374339f453317e8da
F20110114_AABXWW tashiro_h_Page_019.jp2
87a1a14e4c6445e2164e6e923a5c33ba
8c91c2e3a9120a627a3751828c61865ff9c4562b
2240 F20110114_AABYTQ tashiro_h_Page_157.txt
0a7c437d860f027bdc77d57b52829bbe
34f820e21de089a2d5473193996f87cb79d8682e
F20110114_AABXJM tashiro_h_Page_010.jp2
020f9d1549385bbe6ac22abe6458439e
47a810cea883440ee008b4de870a7eec187302a5
F20110114_AABYGF tashiro_h_Page_139.tif
2cb20f66400da694b32182bb5b46cda4
c3a2d6e25ae51e41a5f05eb07e33b8617cbe2cfb
F20110114_AABXWX tashiro_h_Page_020.jp2
808f64df2ec501c54ddd3af97243d995
7efe813abbd5d4d51cdba6689e932af8d4dea16e
2379 F20110114_AABYTR tashiro_h_Page_158.txt
b1a39fefbef837bc2019453dae1c126b
0bae6119001c413a1941e9a9f48f6c5125116f0e
47241 F20110114_AABXJN tashiro_h_Page_153thm.jpg
348b9c02db3ff72f1287584318362be2
e4bb116d2f9d7be34fb4e117bd575b9c741cf00d
F20110114_AABYGG tashiro_h_Page_140.tif
a4319741a85d96d422a6f46dc758a76c
31f6cce32dce29f3a9c935556512e624dc2aaba1
920863 F20110114_AABXWY tashiro_h_Page_021.jp2
3662ff6a648747eb8b563cf5e55be486
a266587a8e3e3923dc81f2301585b5a393bbe126
45605 F20110114_AABZDA tashiro_h_Page_123thm.jpg
0e38a9c67f714a70d48a7febf1619990
cf8c7a9283a8c0195bfe03ac09e5c239fe549870
2586 F20110114_AABYTS tashiro_h_Page_159.txt
92def47afa2611fb49ec90499a45b82d
b0a17ae5f76727d982817a6236f1dfc44711a1fb
63461 F20110114_AABXJO tashiro_h_Page_129.pro
621877f509bc614a7fcb658567496a3f
0a3b6464b4de47b66b7cc422cade8af745af185a
F20110114_AABYGH tashiro_h_Page_141.tif
56fec2f1b0fb04fea508a766059c63c5
c4ac2046a3503f22e1cccacccc89d613ff51302b
F20110114_AABXWZ tashiro_h_Page_022.jp2
c73731bd36e3b739e1d61fa5001b1e6c
9b13012f87eb72645b7155290dbfbe5b96ff1ec6
88549 F20110114_AABZDB tashiro_h_Page_123.QC.jpg
d3a22cb1f3bd144df4c1b1b63d4c9a62
1fed76474ae519d18e50e09dcad550b8ed58d050
2226 F20110114_AABYTT tashiro_h_Page_160.txt
b80ab48846935c541c8f2950950a9ec5
9d3cddf7e631f21d46ec8fd74d1bf1a3252c6f70
251598 F20110114_AABXJP tashiro_h_Page_059.jpg
f442f1960a7f88a164ca366ca0d9666f
02f17cc317ad5b6cdf604930f12e4253c47afd59
F20110114_AABYGI tashiro_h_Page_142.tif
f9c0421bd39cbfc433d33c5600a9f921
ac21aff58f60fa2f295d0ade23a48f27a2af5440
50500 F20110114_AABZDC tashiro_h_Page_124thm.jpg
9012d591089353b188ff79bc508e4a7d
040d6f82bb87a4e42cb8ac11e2fc8da8bac640bd
2282 F20110114_AABYTU tashiro_h_Page_161.txt
f92c967296b6559237c0964ce3fe9306
1a8035f0e1703a347c0fa5466db3239b84b3f3b4
86206 F20110114_AABXJQ tashiro_h_Page_080.QC.jpg
aa4533e2bb3d0dc962921cc4855f37a7
b6bff634b3aa2667a946e80271ee77c660e56b65
F20110114_AABYGJ tashiro_h_Page_143.tif
1ea0e591415a58c66ef4b0729d80f54f
3d3cebc97962ba954a4238ba2175e3daafd8099c
114726 F20110114_AABZDD tashiro_h_Page_124.QC.jpg
b9358aac9bda9769ddf90715d3377b3a
220cc0481e7c40225f5955fca4ba504e66842385
F20110114_AABYTV tashiro_h_Page_162.txt
71c42e5fd80e68d20ca25d1a6829f5d8
bf855dfe832fba88739a379e90c9322030e467c9
106772 F20110114_AABXJR tashiro_h_Page_016.QC.jpg
8d69812679dd5eeb17706f1a9bddad9d
aa6e0044968d52743cc75b851f29c36a16bd0705
F20110114_AABYGK tashiro_h_Page_144.tif
c5a16fcf609d94b44368555d1a3b86a2
614128c931fb2ec8d8d5f2474b3e089308b073a1
104076 F20110114_AABZDE tashiro_h_Page_125.QC.jpg
9be8a2c7bb765827e95607de1ed8c7a2
c08c9fd3a68385b3c84f3f89d327fe8225dfea75
2416 F20110114_AABYTW tashiro_h_Page_163.txt
de86bf3a8e8a88d747d2f00fd22d9886
7abad83c2255b6decb2ccffda2ec01c4853aa54d
2126 F20110114_AABXJS tashiro_h_Page_213.txt
82ab06ab88f345913a93367f06d56a2d
035d774b16405214e8b842ccd3c61dc55aad49a9
F20110114_AABYGL tashiro_h_Page_146.tif
819fb5604fd8a14bd9efdcd472493e43
4ddfce2b1bf1d060bec98214d4c196ba48cb0be5
F20110114_AABYTX tashiro_h_Page_165.txt
f8924e12cae0100c457d7487a54ed4cc
726d7ca69c252f75015062ab8ba7868c1321a848
1854 F20110114_AABXJT tashiro_h_Page_181.txt
38123ee752c70ff3c3d708aea4c5aa11
462cb048e9291f353e0ac87ec1fd0ee89ebe634c
F20110114_AABYGM tashiro_h_Page_147.tif
d004c1a1f8805d6d77fb7885fbdf2f2b
0c6e920dced0173e1820b97a582f276b4a484386
42154 F20110114_AABZDF tashiro_h_Page_126thm.jpg
b8d4967ca81a04face745a108e557922
0d8a64a5461fc9c65f651efafda1e6f727af45f2
1875 F20110114_AABYTY tashiro_h_Page_167.txt
32c44b52cbdd31a0bbfd995acbfae443
3f0984d3124d5a5885a2c346f6800a8e6dceddd5
52274 F20110114_AABXJU tashiro_h_Page_175thm.jpg
cb7cb6c0251c5cd6e29fd11392bb312c
51615f2e4e3cbab7c0ea5dba0133b3c0d87005a9
F20110114_AABYGN tashiro_h_Page_148.tif
a1658d9dd5151449e8b50b88c107df49
f1f29d2b16abc66f29b83f7a0c41708737e0ab74
52759 F20110114_AABZDG tashiro_h_Page_127thm.jpg
2a9bc84c83077df9a9c94ab1c3ae6f40
efb12f594a4100ebaf508ab68a7ab6c134f46998
1761 F20110114_AABYTZ tashiro_h_Page_168.txt
98a4b59747f4eece38119b682c416e09
9bc6619ccb4beda6706815e4717aa389f07f7de7
F20110114_AABXJV tashiro_h_Page_198.tif
e465d639b95a95c5e1baa3722a6bdd85
7a7441898217619dec042bff0d4ac7d7a5f4babd
F20110114_AABYGO tashiro_h_Page_149.tif
6d31a8196818e8dff636d51c40ad0553
92098845ba29711106a5cadec9722acf78ae6754
123541 F20110114_AABZDH tashiro_h_Page_127.QC.jpg
8215543d13372ffc5ee540044573756a
a8ba33b03f462ed414c96d292c777046b8dcd5e7
52184 F20110114_AABXJW tashiro_h_Page_112thm.jpg
865e64a0ec4ae7d81db872c3e4c7b249
e46ac8200d7bcbde63ce9fe214c30e7d02689eed
F20110114_AABYGP tashiro_h_Page_150.tif
8c702d1e54f2582a1f000ebe19324199
8f911e24b2e802318f18e0de4895d12a53dc4cfd
119445 F20110114_AABZDI tashiro_h_Page_128.QC.jpg
16db08e3b38a7a829224b47a7da404e3
cb1d1323fb1df3ff1019a3bdedf63d0fd1529a50
48918 F20110114_AABXJX tashiro_h_Page_020thm.jpg
b4174e91611e6dffaf0b156233ae51cc
470ea33c18a88e3de062437dce488e278228860f
F20110114_AABYGQ tashiro_h_Page_151.tif
c8cac085e031c38d920d9c31bd430a15
d376e309c3bcdccd1b3118556b67f7361216df3b
112513 F20110114_AABZDJ tashiro_h_Page_129.QC.jpg
bcdf1b626046e8967edf4845fd197daf
d619c3117f8e7d10535bd6316ed8b9f32fb12ece
120389 F20110114_AABXJY tashiro_h_Page_112.QC.jpg
f8023298a724e26e99c0bdcab77b79aa
a955815b804ed6b033444e6634de7a8862796936
F20110114_AABYGR tashiro_h_Page_152.tif
e377d91726f9c393a8afec98485723bf
7e50fbf99863491c414fe79d75e38b8000d3ee68
50423 F20110114_AABZDK tashiro_h_Page_130thm.jpg
3170b2380414c342ef7f4a759b1e7f22
d84fc2adce89a41bdcbd7d6d7164507197eb2bca
F20110114_AABXJZ tashiro_h_Page_004.tif
0a66c3f9e1873a0e713cac23bab4cb41
9f10c20c260f0ab44ada8b55db06b6a3fc9bfed8
F20110114_AABYGS tashiro_h_Page_153.tif
f07ebd72af79b00d185c80e3fd535d0e
11e2b1ac980f1f0bdec889645aa18f44b8a69f80
116176 F20110114_AABZDL tashiro_h_Page_130.QC.jpg
1f8fba1b04da80d343dc56509ea1c942
70de2569b40711b870fbd8bbfd743ea60d53b475
F20110114_AABYGT tashiro_h_Page_154.tif
29d9191d57022de401c5e6c92e5a004d
b37fe70c3da1eb3446605c2d37188adba407ef31
52061 F20110114_AABZDM tashiro_h_Page_131thm.jpg
4e331ac1ea72b79d96203de72f8d6b66
6d67d70540df5a0c53614016afdedf6bdcc0a48d
F20110114_AABYGU tashiro_h_Page_156.tif
ed6fa59ed30dfac000a3473c1a9faf43
66fac90860b841403eaa22f8d529117c5262da3f
117505 F20110114_AABZDN tashiro_h_Page_131.QC.jpg
ce5b7c03ed582dcdef751d8fcd381159
28e1fd02c22b02dffbd9c60bbcb9f907dfbd97fb
F20110114_AABYGV tashiro_h_Page_157.tif
9e33e7bc601cd904bf5a2dd51a91f8f8
5224a2b9588c728c3787d6c684ed8e71fc8eb970
47722 F20110114_AABZDO tashiro_h_Page_133thm.jpg
891317c831e5449ea6be509c961a83bd
5865b31f948fc02aee57ca783606d3d704d4ff4f
F20110114_AABYGW tashiro_h_Page_159.tif
04beea6da7a6a3fce42fefb624a249cc
74b10d0ef5be0620202a4940e14a819d1758fa23
104474 F20110114_AABZDP tashiro_h_Page_135.QC.jpg
693e76fa7c61f28d4a3319e8a2061190
a00c7c64c5fd65dcdaed0c1a361334f9a033d994
F20110114_AABYGX tashiro_h_Page_160.tif
9c02d0330679183fa38915a00b680cd0
48797c37397db20b2a7a2c04c1e8bfd68a9db89f
47407 F20110114_AABYZA tashiro_h_Page_030thm.jpg
6e535f7330d9d16efc26d98988c745a7
f912bbcb9840662cbb92eb0a63c97251c67f0d56
89994 F20110114_AABZDQ tashiro_h_Page_136.QC.jpg
2165ba81a762062cf4bd5e5defae0120
80500e0284da31de8f65111d3170963a1f04a036
46791 F20110114_AABYZB tashiro_h_Page_031thm.jpg
44ee0608d3facbd4483fa719d0d7f2fe
57a21af6ae14d5144b80ac52d682d7895b73df09
46127 F20110114_AABZDR tashiro_h_Page_137thm.jpg
a04ff77624f00220d3cffa441d86e654
db04a70a764328d59adb3078894be3ddf6878ad3
F20110114_AABYGY tashiro_h_Page_161.tif
05b8598de63f504652cdd4641041b1b0
697d18187e10d574fd33406a7905f6454a445c60
98844 F20110114_AABYZC tashiro_h_Page_031.QC.jpg
f4d7761a25cdd2fc10f4d7a8d3ed31a1
c3c711284118abdcde8edfc2f47a11bae3549df0
92843 F20110114_AABZDS tashiro_h_Page_137.QC.jpg
06721f69d84dd009a8a6439bca1364d0
58ea498b05394e6c7b5eda605678b9f7cfca524b
F20110114_AABYGZ tashiro_h_Page_162.tif
d84184b6b68d6f0995dd405e75b4bfef
d995f133a07748c9aa37c0f54359cc5ef265558a
81620 F20110114_AABYZD tashiro_h_Page_032.QC.jpg
d2e810bc8b9fa05840939c05dc7bc507
9925fd269cb98e6bb0f3b8abe35ff041fd28fd38
50992 F20110114_AABZDT tashiro_h_Page_138thm.jpg
13dba6ad236de75244fd8d43c7ff4791
900e2b600a60bcfe450daf85e85793bb73b01bc3
60778 F20110114_AABXPA tashiro_h_Page_208.pro
77afc79ae833d5594034268b27e9e57c
be979d0020bfc815b42c1c1da87c68988068be10
46297 F20110114_AABYZE tashiro_h_Page_035thm.jpg
bffd53bc2143a9843354a1672d8a7676
8a98a50117262db29b969bec07bdbca77d484a0c
51209 F20110114_AABXPB tashiro_h_Page_139.pro
a878782786ab948f79b30efb6470360b
8ec7840aefaf4a79e50d3bbcf31c3c93fba5520a
92661 F20110114_AABYZF tashiro_h_Page_035.QC.jpg
3c3896b3ce5e37460b4b16442cb557bb
72555bd5dd86eeb6137856031ce2695e26fd00eb
118018 F20110114_AABZDU tashiro_h_Page_138.QC.jpg
06bac8ae999bc98500357dba44bf0426
1825fcfb867bb9b1dd4c7629239b6e075edcaa80
49563 F20110114_AABYZG tashiro_h_Page_038thm.jpg
d08e090794000756286f9700d7d42416
0ed2ea7d346097cff2bb228da6c1187dfbcb190d
107130 F20110114_AABZDV tashiro_h_Page_139.QC.jpg
cd879da583b31b64c0fb6ad75bcfd600
da7553f1a00832c33ba7470f0635b8acea0398c6
254975 F20110114_AABXPC tashiro_h_Page_106.jpg
8ca6c84971ed089d4593511f6bd3dfc2
6b92aa42648e5f687bf6c081d412dc7da10b02a5
104384 F20110114_AABYZH tashiro_h_Page_038.QC.jpg
9aff05aa761d318d5e1c3c8b484cc7ef
f6f4f1ab6ea856772d9ee0c38b19f55bd85309a6
50037 F20110114_AABZDW tashiro_h_Page_141thm.jpg
a1331a1df988f7b7acba47dbe13d5fa6
17688c1e78b879abe339136119d726b27ad61b09
39762 F20110114_AABXPD tashiro_h_Page_002.jpg
a89d85252beb2b77fc1f9cd997f02fc6
da5d99a33af92097b0436ae2c1ebafb489d744ac
46416 F20110114_AABYZI tashiro_h_Page_039thm.jpg
501f7c04861cad18bb844c25b136a608
963655b6ef3776c8666b5f6d705911a689e01246
50658 F20110114_AABZDX tashiro_h_Page_142thm.jpg
bbffcfc0b730c3cf0b81841144623527
c8c38d77b1a45bec3702699e8853a46520b41e1c
48508 F20110114_AABXPE tashiro_h_Page_220thm.jpg
470952f56c69e7d9950af5ca059ddc08
e0c052929dd2c9065e6c0a608ed988d2e7ccb2e8
101507 F20110114_AABYZJ tashiro_h_Page_039.QC.jpg
5d93c208e02d96167cb980f1b25ebf17
3fa2214b80c1a3d9f60bc66c015e7a0a4445a20c
95060 F20110114_AABZDY tashiro_h_Page_143.QC.jpg
b4bc259a771d7405c4d91d1f50c34e04
87f98e02dfba388236407dcf9c97203cd7d71100
55318 F20110114_AABXPF tashiro_h_Page_155.pro
a9035c78a0b37e0586466e1529d6a332
fa599831276126aa330a93796c80552073269691
82227 F20110114_AABYZK tashiro_h_Page_040.QC.jpg
3e5665879773898f62294512a1f5068b
2df087800ff996a5321e96ea3e5c1062583183f9
119522 F20110114_AABZDZ tashiro_h_Page_145.QC.jpg
5ea00c33f7865ef3c74a81fbb39992c0
d023b9b1a8c595a54e8199411a26f31df3c74629
1051908 F20110114_AABXPG tashiro_h_Page_079.jp2
daf959efd6ecd539ac0f97b703f7cf7e
36906f6f5a70d3cce701ae817f5a345a941ce856
45971 F20110114_AABXPH tashiro_h_Page_045.pro
7b0852453e1fe5a32997e7469a2fef52
8a7004c6bc8fc3557ad7d5adca557b907b3b0fcc
65878 F20110114_AABYMA tashiro_h_Page_111.pro
343c7850badbe4c750579efae7fd1186
22ee003c05a0fd6c9a24ad6a25bdc8e8395ca1ed
99820 F20110114_AABYZL tashiro_h_Page_041.QC.jpg
cb65d75725cb5354378192e667c7b621
c3b09ecc0f1eebb762c44e4fec5978b308b3bd88
105760 F20110114_AABXPI tashiro_h_Page_019.QC.jpg
e1f999383de0c5fc50c41980f186b554
838d55978cd4f27cba2c26c96e7fc2a7e1d40a29
64120 F20110114_AABYMB tashiro_h_Page_112.pro
55b1a24608afcaab4d2b64273caf923d
565846058d0a059e5267cbdbcaa10af89e209305
66602 F20110114_AABYZM tashiro_h_Page_043.QC.jpg
d1290b3c50b43a020ee465bb3838dd79
3bf4c91c9071944bf9ae0347642e59f2a7efffc1
969150 F20110114_AABXPJ tashiro_h_Page_035.jp2
ca4097f30edef8b70aeafa79c7476ea0
c2ec7947b3ba51b07c292ed8720b14a02e841a81
38779 F20110114_AABYMC tashiro_h_Page_113.pro
c092589afaa46e86a4ea163c7484ce71
2f3b86b261b9684c0ed7e48692eafa0dfb110049
42382 F20110114_AABYZN tashiro_h_Page_044thm.jpg
312775dcced47b9a3d43777a2c3e2198
f50a29ef4e66e7e08107ed74c4dbdd58ea3b1eaa
F20110114_AABXPK tashiro_h_Page_178.tif
152d9d4bad6397e354b908693e4e6d05
a510b7cbf10f8a54b0e69c61dab0622d557fd6d8
56794 F20110114_AABYMD tashiro_h_Page_116.pro
4e0d97220f0f8b8e202b2b168122e79a
b513f78826a0d5f02dd366b967954fb0fe19b626
81209 F20110114_AABYZO tashiro_h_Page_044.QC.jpg
8d1ef9b0ed365fce24285089bdeffae7
a94e6f4511a79e1a785caf028ff64009d5f0b628
1051932 F20110114_AABXPL tashiro_h_Page_100.jp2
cd9f3fd4b2c1af7e075ab811c12a222f
42e2637d2e834aa51b78d4b16c6d3d2f3635d7dc
47983 F20110114_AABYME tashiro_h_Page_117.pro
43e8616b560ac9b8df8ce6c74bdfa804
27fcbb2d842b6ef3f888287f7f15faccf1a2b12c
2475 F20110114_AABXCA tashiro_h_Page_166.txt
69f007c51a1fa45a15fa4daf8f322980
db63c1f2d77ee8422739c834c86cb2b9ebf154ac
45985 F20110114_AABYZP tashiro_h_Page_045thm.jpg
f8eb79e4a0fc109022cb29a755dfca81
76da6d8bfe065230450d636fdcd579a357ce845a
F20110114_AABXPM tashiro_h_Page_145.tif
38c617fa32b6503d1342c7527f874a74
59456d4be272f01d2658d5663fbc163bd4bde97f
54958 F20110114_AABYMF tashiro_h_Page_118.pro
28b1746187e2e79fd127db4bd0d6ad56
b59fa7213dca4c0c47080485c708b7e3e24257aa
41145 F20110114_AABXCB tashiro_h_Page_054thm.jpg
dd06ec5a28cac1d888faf3a8a212fe55
f3c666f75b685cc77a9bb5134c8767ff42777156
92662 F20110114_AABYZQ tashiro_h_Page_045.QC.jpg
1e6660b4c0127abfd58a34089a2a2cec
ba7a63e7753d78e26a1c34d034870496404bf43c
1051909 F20110114_AABXPN tashiro_h_Page_133.jp2
bf0dcc9bf00661c9c326fff13a33150c
94a1b4be05ee776b12fabdd57f94ea0784fc0c96
65307 F20110114_AABYMG tashiro_h_Page_119.pro
5665502252724d07010e515600e96162
ac406b25e4f84d45a00733eb7dafb3da4e99ad8f
105132 F20110114_AABXCC tashiro_h_Page_114.QC.jpg
87f7e4d1731d7e38b13ceacd20c991c2
f59420687199a1b9c86e4ad7d9dd48852ad44656
86391 F20110114_AABYZR tashiro_h_Page_047.QC.jpg
fb067fe4b3d7ddc7567d6bcee5a21190
001a62e2b0cd0a9643ac32b1b45f694902c0cd53
269892 F20110114_AABXPO UFE0008001_00001.mets
c19ea9d4a09d3e741b3d943bff6cb4e0
bb5048eb174af0c48927bfc782367eafdb4e76da
42717 F20110114_AABYMH tashiro_h_Page_120.pro
efd4445707af4049044c284feae70827
b66f542d688bfab7f0a6c04a82c9f9b7d4eba8ae
61904 F20110114_AABXCD tashiro_h_Page_131.pro
107a741591d0e54d146854bd950ae874
9d018f0ca5d57c3db2e8903aae7b713d4076f6b0
46134 F20110114_AABYZS tashiro_h_Page_048thm.jpg
83ca92898ebaf375753783d0e741d5e0
1f2cb328b7a2a6e54b63ec378f92edbed9108350
63139 F20110114_AABYMI tashiro_h_Page_121.pro
c9d263f3608104df1c8c8ed382261331
da4dd87c7be3880cf0d70479bf5db6dd6e3f26a6
F20110114_AABXCE tashiro_h_Page_095.tif
fa7100a5604ee245e584b3a9a40c6453
4eeae8527e6c637ccb69a10a66757ddf8e7031cb
94388 F20110114_AABYZT tashiro_h_Page_048.QC.jpg
d2e013ad3991f4e73e73ab6f62feb165
f11b3b9f6455c1efb6a619835472aa71c1186e29
30223 F20110114_AABYMJ tashiro_h_Page_126.pro
c21bcbbfe1ee7be89e505320c4b55bea
3702060559efb5a92eb6bde98507e9899b24f70d
1001669 F20110114_AABXCF tashiro_h_Page_170.jp2
376ca99940c0f7e25c485bc28f67af6b
217bd28a5ae5584f36ef89b2be8c70611d4e7104
44083 F20110114_AABYZU tashiro_h_Page_049thm.jpg
9ba904c6355f510c3d1053722d764ceb
a1c2e343d0b85d1eeb96c68180f776a0bb958011
77003 F20110114_AABXPR tashiro_h_Page_001.jpg
6f3f76cbc66d35348e31fb286771d3cf
a65655ca6b10bed92c55cef5e76eab66c5a11b7e
65991 F20110114_AABYMK tashiro_h_Page_127.pro
1e134f11ab26f64372455f3fe5874aa4
d98ea9b62e0d6329ed461a761d8a2c1ad79f4f67
F20110114_AABXCG tashiro_h_Page_210.jp2
5a4aba9138b1e4534c21d27ac88c4a76
2fd0386a5d1a5b7b6b01c97e1bb8b49917def552
89794 F20110114_AABYZV tashiro_h_Page_049.QC.jpg
34472280d644f773c77435ba910f0c4d
fe900d45b660d0c4b9ad25a6e1f1839100bf2e62
38230 F20110114_AABXPS tashiro_h_Page_003.jpg
70ea882615efac87856f434f59364d42
cd02109ef941d09e8056f9483167c3c95e554cdc
61541 F20110114_AABYML tashiro_h_Page_128.pro
be69e6a952ac3f9fe33dce6d2abd7d33
5410409f51d4c4a30908f2ffca3e2047cb0ab471
F20110114_AABXCH tashiro_h_Page_118.jp2
f8768a58f5933403ae14230fbffe713f
f615a584ebec2d92ca27c9a452af995cfcd2c667
45598 F20110114_AABYZW tashiro_h_Page_051thm.jpg
2b7cb7ca273bebbada767701cce35bd9
80dff6db9239792675813577ea2d655efdb1ebf5
250335 F20110114_AABXPT tashiro_h_Page_004.jpg
b9017ce4249f874df39cadd3a98e39d0
538bdd049dd744a3027a6dea5ac7aa7e8f718453
62522 F20110114_AABYMM tashiro_h_Page_130.pro
dad99fb98a19a8b7f87b93e27f2560ab
24b2e615f255540aba0ff6832637b216b7bfb4d7
41407 F20110114_AABXCI tashiro_h_Page_212thm.jpg
daccc244654f5e7a122d2961656234d9
7cc54b5d7fc7ceff9337b778e82afd199239d4f3
50523 F20110114_AABYZX tashiro_h_Page_053thm.jpg
7480bccdcce84c8727a772d5f3debb36
748083503f0d7eec9aa159aea979f5bf19507f04
123146 F20110114_AABXPU tashiro_h_Page_005.jpg
1da976a0f36ef0671ddd51138e15db60
5eb26fb74c07b3a7f9aa3dd377fa9b285267bd06
43083 F20110114_AABYMN tashiro_h_Page_132.pro
8c2fe328a179a30f8e647551c975ca25
364e0609020cc40c12b2471dd763c863682a8c07
F20110114_AABXCJ tashiro_h_Page_201.jp2
210a2a355d37331f7732ff4ef8cdb7ee
43107c08b35f6f6b90adc68bc8fe7a80521364cb
76030 F20110114_AABYZY tashiro_h_Page_054.QC.jpg
e79c6ec3c54f9f700929b248eeaa5076
fd8a39a8f061c219ecabe99c9ce96e52c1021719
332704 F20110114_AABXPV tashiro_h_Page_007.jpg
33f4ba87067c5630c5edb228969dd25f
51df6ec59ae9c143277a7f8eb3f84b28c816f5fe
49494 F20110114_AABYMO tashiro_h_Page_133.pro
d1310b66b2bb8cb55f36d5e8cc463aa4
3826a66ae5f41cc72125c5800ef546a5af73fc7a
43476 F20110114_AABXCK tashiro_h_Page_082thm.jpg
f8f0b372bce42088ba8d82a052620200
9b4d6965d45a9e58580dd228a255f639000ac1b1
50026 F20110114_AABYZZ tashiro_h_Page_056thm.jpg
04f176561d0f01e3ed108c1a4d5aa42f
976d2a89c24898b497159ee53d6027c43312f58a
310443 F20110114_AABXPW tashiro_h_Page_008.jpg
64d77cbf837761e932a400eef3ff02b0
6b4a2be112d570e2d67aa3b4275781a115e880c2
46859 F20110114_AABYMP tashiro_h_Page_134.pro
4bdf7749393131ffebbfa3cdfb44570f
337a98964090bad88807d2bd4d38cfd368e7aaf2
123278 F20110114_AABXCL tashiro_h_Page_177.QC.jpg
690152c252bcf53f912a1a3f7b0da4cd
50b122a60e32765c21bbb98bc182a0a5e4b56dad
167173 F20110114_AABXPX tashiro_h_Page_009.jpg
8e79c2e2061410fd75064aa824e32747
b25055d78163be52005547962d8226e40b94c86a
46151 F20110114_AABYMQ tashiro_h_Page_137.pro
6bab77a2a5e4836d8936c07d3f0ca070
778920bed11ef04ddc39d4ead55caafa4ac92c63
F20110114_AABXCM tashiro_h_Page_058.jp2
f3bb40dfbd90d45962237e2e91f854f7
efca5f6ecbc6db8a70c831733e8cfab028c5d01d
231838 F20110114_AABXPY tashiro_h_Page_010.jpg
4d3e8213a9d9bfb0286901929bc7944a
5bedd89a2a87de2329c136e2bcf4e556c903070b
65395 F20110114_AABYMR tashiro_h_Page_138.pro
f6b3501688389f1278407d47a5ee150d
6b3fe380285f65f4e2c027a95954dedd356bb5f7
33783 F20110114_AABXCN tashiro_h_Page_087.pro
a348d4d66a93606a4b84819394688a08
0172ff606c77661593f36c9cbaacb48553359168
265870 F20110114_AABXPZ tashiro_h_Page_012.jpg
9ebb916d5b56f53fd312539206980af2
95abf0e5348c5d42179433fcffc424f73de345d5
62868 F20110114_AABYMS tashiro_h_Page_140.pro
3696071831e70ea0b48bcf3cd3f938e4
1c605a9f90d8a623d94c79b90bfe7f5d33e30793
1051952 F20110114_AABXCO tashiro_h_Page_109.jp2
b0d35ce38759867d07e67a4899f09980
831dd992508036442a488da8c35cfc88df814c1f
58647 F20110114_AABYMT tashiro_h_Page_141.pro
324b547f6daa32aa0ad5a89236252c1b
5dec14133c0bb9819548e114b4c005266e10016d
1755 F20110114_AABXCP tashiro_h_Page_198.txt
088226598d9f8f5baa856dbf9d0b39c7
5fbc968ad50854e6a5ad02900dc8bb6c5d206380
58645 F20110114_AABYMU tashiro_h_Page_142.pro
5fe9f5bbcb3fef29a3968019cc3fd462
31da5b187acdb1015570946023a84619b3835d74
1051957 F20110114_AABWYA tashiro_h_Page_155.jp2
8850f175789cc71255922ab6cef07d45
e16ca9b106d9bd4a6900a623e35a227aa30904ee
45585 F20110114_AABXCQ tashiro_h_Page_179.pro
1fe069a6c3463503734461d80d422f2b
04edfa51ea74dfc605cbe9741c8575ef097cd21f
38645 F20110114_AABYMV tashiro_h_Page_143.pro
0b1cdec6a0857733c090789c06a5807a
2f04910a06cc213be886bb65295e3f84303d402b
F20110114_AABWYB tashiro_h_Page_234.tif
4446df4c9da5b9c8ba3d4c7162574d6b
2a2811e21f0a9f0466abc9f2ce0b3a6515fbae15
53371 F20110114_AABXCR tashiro_h_Page_004.pro
a79c60aeba6f4ca6a819c892a00c8a82
949ba1521c30c9afc21f1c8048cd1e6e2583fd13
61758 F20110114_AABYMW tashiro_h_Page_145.pro
93cf8cd08e96f16f696959bfd510cf5c
5f17bdf0b1375e28fbd5ad684e0193e107741406
F20110114_AABWYC tashiro_h_Page_103.tif
1a6d92ba54fabc176a34e13b788817fa
71c7ed0adb675cfe71369f7377f2604e4f83d33d
43766 F20110114_AABXCS tashiro_h_Page_084thm.jpg
fa0e453dc2436ba018d04d559816190c
a612909b9adc3e8e5e3723b44ecfe05d766c43c6
40086 F20110114_AABYMX tashiro_h_Page_146.pro
f88980cb370e7f0814b7d81fb26fe9b7
6c2b01be264c105d044d5f71805208e925024e7f
F20110114_AABWYD tashiro_h_Page_013.jp2
939717396470acc4b053c776fa1eb560
69b5f976780fd83370f9deab8323049b283fd518
52192 F20110114_AABXCT tashiro_h_Page_177thm.jpg
7e0053e53e79aed10459bb90dfd9c156
0ef4b9d6567823946bf4da3ad12ade5ade735431
56684 F20110114_AABYMY tashiro_h_Page_147.pro
ad71379d833cc8defa865d7e78cb9b8e
da421d64d263be0bfd80578d7d75e35d7199038b
55574 F20110114_AABWYE tashiro_h_Page_231.pro
2c5914cfa87baf2051263037ff6471dd
ae563c2dd88ddc7a238de9efa7e14a7498de5aa2
32339 F20110114_AABXCU tashiro_h_Page_190.pro
0f18640a984fcaa13e3b55e9f63733d2
a4aa03188f4b04602e2663142656529d696add36
34581 F20110114_AABYMZ tashiro_h_Page_149.pro
db302d0ebc5f9450584ae6ae8e41273d
229e6697fe7aae90645df484872474e405812b99
F20110114_AABWYF tashiro_h_Page_047.txt
f3615717480f223a8d3205945600d099
4cfb5d0cca1b7dc12a2b8aa824947ce5f060d608
55571 F20110114_AABWYG tashiro_h_Page_059.pro
51d62305dc169a534a6911f5dfe982a6
7a845b07728ff3456209e566b407194ed6a86b3d
97 F20110114_AABXCV tashiro_h_Page_003.txt
16125139853e03c398dfb46c13e82baf
d9dc4734855bf5e70fc218b4cac3253edcf8f5f3
44434 F20110114_AABWYH tashiro_h_Page_172.jp2
658d4431a5510b1c53ccb7c6d0003a3c
4ef242dfc0bd28fec995297e6606163a68babf9a
180492 F20110114_AABXCW tashiro_h_Page_212.jpg
715087233d0dd744e68dab6c55a9ec63
d9ee2bdd92aba4ca914ece91297a98c89329bb3c
253844 F20110114_AABXVA tashiro_h_Page_199.jpg
0d2ba247a0a2f1951f33c8b0e3aacbf1
fd2fb3b1563c6b3e30adfd58ba28f8e1ef9ac38d
F20110114_AABWYI tashiro_h_Page_206.tif
4c5bd18104df944de233b8e833ff107c
2bcbe713355068605bfae6beea0bbd79e4910d39
51061 F20110114_AABXCX tashiro_h_Page_160thm.jpg
eb2bf1ef69e56e2c50317e278b8241bd
c1deacffc57d48f38576b7ebc54205aa94ad03c2
222722 F20110114_AABXVB tashiro_h_Page_200.jpg
5c8279b434d60042265140b66a3b44a7
3e461cab94a0d5502b05cdced2b96952ec87c448
233937 F20110114_AABWYJ tashiro_h_Page_222.jpg
cc082208045b16e5bd028e4dba542399
681180f8250faf61a93b14b0f2c168af51146fd2
47386 F20110114_AABXCY tashiro_h_Page_132thm.jpg
3723b159046776a9e55006b8830fe438
688d3245f1bdcb1e4387319924973a39cba8a935
222481 F20110114_AABXVC tashiro_h_Page_201.jpg
22a4138d3e122758e8c798da1d41c1bc
0ef54857919d04a75d7c8d028c5ca0ccec08cf03
31808 F20110114_AABWYK tashiro_h_Page_227thm.jpg
cf0d53926675648cb293b0088d117f97
3df601c11fbb6a51faec0c963157928bb99386f1
55021 F20110114_AABXCZ tashiro_h_Page_070.pro
0ab0ef5a9d911f405eddfb5ac63c0605
a0e36fc47a30fb547d0353b146162b7ff219b947
283897 F20110114_AABXVD tashiro_h_Page_202.jpg
035cf300e8d19c48370d37d1b2cae5c9
f78e67377d3e45a3c4f286c2959da0d47fbbfd94
F20110114_AABWYL tashiro_h_Page_068.tif
460de6bdade031a24a7c5ab5c240de7a
e01ee469ad0841d6c9beaf373668dc47693fac19
69759 F20110114_AABXVE tashiro_h_Page_203.jpg
1865fd7d04942af93d492fb184e2f918
ca99c043eeac3b0493eb436b13f43c1dbd4e153c
235514 F20110114_AABXVF tashiro_h_Page_204.jpg
2a25a9d7ae6b64145517cb6df444cdcc
ec96a27bd647dfaa5921ded80055e61b918e948f
32657 F20110114_AABWYM tashiro_h_Page_187.pro
d50ce8ece6307c8ec68b543699fc7a0f
979f053b6667ea972f3b12ef2f0dd7554ecf6ea2
229180 F20110114_AABXVG tashiro_h_Page_205.jpg
a042b01024e42034b9ce385cd7ac9873
c0221cc15eb427b4d5efec55807145c8ef93a62e
2679 F20110114_AABYSA tashiro_h_Page_103.txt
9f95e4c73af9b7aaf5429a879c2ba749
fece0a9f000f76c4f95a6ab15eeadf2233d86d22
81730 F20110114_AABWYN tashiro_h_Page_034.QC.jpg
cccd51f298a75188e77a85ac318b9f2b
2c8cb9de4dfa232484e93846357c2e171cbbd461
232795 F20110114_AABXVH tashiro_h_Page_206.jpg
b39f9b2fc856eb8100ed76e89b2e9f66
2fabd748c1f0ff9d2154cc3ed07affa8668d8f25
1698 F20110114_AABYSB tashiro_h_Page_106.txt
f09f349c46b2a400d7d147f8c157b69b
a2d4f44f0da621944001f722d7e000bcbb303738
47835 F20110114_AABWYO tashiro_h_Page_061thm.jpg
b7bf86dc38843a9974efd9adb96452e6
832aee0b5380029baef8725aea1ee94ddd8d8a37
2119 F20110114_AABYSC tashiro_h_Page_107.txt
fac4a88ce3c918534f2c573ea8d7c14d
07c19bebeecbceeb44cd8903b1c81f8cc762f2b4
79768 F20110114_AABWYP tashiro_h_Page_068.QC.jpg
0f825e5e2121049d9ecb68900ff4db2f
032d3240a8fb3ba0504f08ce6619eb3bd0049a4d
236974 F20110114_AABXVI tashiro_h_Page_207.jpg
7b9310133d126377012671ce5abf75c9
af2ccd3276e2a02b6336b3e8933a476403e70f8d
2186 F20110114_AABYSD tashiro_h_Page_108.txt
162d36d911d0915ce4f810033429e44a
36750381b0a263901593fdf368a4096e52d3e81f
243170 F20110114_AABWYQ tashiro_h_Page_152.jpg
1be72a8f90ba40cbf88987d5a401c153
2bb7f244a52ba2fd08c15e20190e29605311c540
283675 F20110114_AABXVJ tashiro_h_Page_208.jpg
f4d60079c736a9ce5e143da4fc19f52c
c42ffc51b8d7809c02e094ca072ef24300d81ada
100037 F20110114_AABWYR tashiro_h_Page_089.QC.jpg
1330e0ce2509f97e117b3b559e08af33
3f1f482a469c4257e735214cca97f52fcbfa0ee1
294538 F20110114_AABXVK tashiro_h_Page_209.jpg
c696f44dda7195589b60354120439ac8
6916b8b71a54263713f832f22f5741d4fdcd5ae7
2260 F20110114_AABYSE tashiro_h_Page_109.txt
d715e26ac56cd6f2bc3216f3a4094ae9
1c2d77c374f01dff25400d5e35a0dc7df5aa9732
113277 F20110114_AABXIA tashiro_h_Page_144.QC.jpg
377507ffbe306a293e34b4ea8153776c
4c1227a7411fbf0964f40d0def39b5d0d4fba186
F20110114_AABWYS tashiro_h_Page_225.tif
cc6983a447d627145b65a8f3d4b11e9e
9132e6859f1295920118328cee26f6c35465130b
267092 F20110114_AABXVL tashiro_h_Page_210.jpg
009fb0fa63ed96246a5782ef811a8dae
8c35fce2e8212eb870dea252259459e9f877d685
2870 F20110114_AABYSF tashiro_h_Page_111.txt
a10a99a71d90a10b9a0a61ee60a31a50
67dd1bb2f00705ca7d77dacca4634045c7ec11d9
48296 F20110114_AABXIB tashiro_h_Page_196thm.jpg
9fca4b4e99bf58f088f23842c7691b20
57a5f5b2b0eea181eb998a7bc03502ca7167bef5
F20110114_AABWYT tashiro_h_Page_194.jp2
d8c179fc13770994467734f05be6ba40
81721d377ad85241d03df2db40b0f16616ae9268
197055 F20110114_AABXVM tashiro_h_Page_213.jpg
76e8b92ea257e95c7dc3c675dc735f42
82b8a4c1276cd9a3662a1b597478943c32aeeb38
2510 F20110114_AABYSG tashiro_h_Page_112.txt
68d15bf7225e8909e45c07fe8c4bba54
f2c83ae24ad9af7323d186f3e1caadf5c1419328
1906 F20110114_AABXIC tashiro_h_Page_034.txt
6ca715df63f79f18478011df6ab1cdd5
688569f57e7d3747bf0c3046ae9df7e5e9b9aba4
F20110114_AABWYU tashiro_h_Page_133.tif
ceaa8ba7927a39e4bb56fee0e1ca263a
c6a66500696e026e185e1ae885bf9386ed1849a5
230402 F20110114_AABXVN tashiro_h_Page_214.jpg
eaa010977d37f650d439b0d7a8a5fb96
a62c240f65cab11ee659a936cb716577a4987999
F20110114_AABYSH tashiro_h_Page_114.txt
f8755c31e26b8d36ec77464796bf2999
a650fa4bef9af8333b2ebb535397615f0ea68005
1428 F20110114_AABXID tashiro_h_Page_009.txt
37be4bf203e759f7f48831e99a5837b9
4229cfbad19784959457783b6b8550d2167f17be
F20110114_AABWYV tashiro_h_Page_096.jp2
41b99133e31756278a1beefc7e0495d5
6719aeafe938b40ea39aa4b4391922695c6019d6
203243 F20110114_AABXVO tashiro_h_Page_215.jpg
14689c902837b50c848e68dd89ed5e63
59afbffaee5cb5c200056144f457f81cad46265a
F20110114_AABYSI tashiro_h_Page_115.txt
feedcca3fd2988a5b2eea072e11cce87
39b0e4e4410929256bf2addfec324fc673d7dca8
975358 F20110114_AABXIE tashiro_h_Page_192.jp2
729290a2c0d357e6bc1d0c5c7131bc13
6c9b3c7d19b1241ef9adc86df3ef21fc351a7f2c
91971 F20110114_AABWYW tashiro_h_Page_110.QC.jpg
abac32fbc7c76e61b565dab1323b1331
5024c324cc40f91342408456c7e4169adb81af07
238514 F20110114_AABXVP tashiro_h_Page_216.jpg
f69f9166df09266423a1a39571900e05
36b5b74cf13fefd86d0c45a9eb13aeccb3afafc5
2592 F20110114_AABYSJ tashiro_h_Page_116.txt
258b0b82a7edb1dcd335537a80a1ca07
02dbccd97114f8785adfa9ed830fbb1216f66e91
46624 F20110114_AABXIF tashiro_h_Page_192thm.jpg
66cb6c2625efd9928a37c2f9ff1e615a
bc6e46a410b3629065cb6635c68de30b7692d30f
49542 F20110114_AABWYX tashiro_h_Page_152thm.jpg
330a18a51066b6173992789215efdec2
de9952b53d65d6892a06982cbd65c5d18bad09aa
237885 F20110114_AABXVQ tashiro_h_Page_217.jpg
dac1fa02ebe5b374131e0b240116a1b4
e8a0d6f7d3e94d8421936eb27ef94b84b37eb5e8
2218 F20110114_AABYSK tashiro_h_Page_117.txt
6bf5f989e04cac6f60025383e77d1ade
3b29856389cba9d2fa35485a48858ae0f601dddd
102858 F20110114_AABXIG tashiro_h_Page_079.QC.jpg
cab4a1219ed807bb3eb836ac0f230855
ef3f6544bd6b223f5de961d678c381bc7e956f04
2164 F20110114_AABWYY tashiro_h_Page_010.txt
bee4de518b2a04f2bcdeefae5847c548
cc7c0466809fb24e60117e20a135f3b8759abe24
236843 F20110114_AABXVR tashiro_h_Page_218.jpg
369dab2297e35b47bf01a86f9182e5c3
33ee510c57d7690f16431c4aca797ca9755046f3
1673 F20110114_AABYSL tashiro_h_Page_120.txt
3f20d345583f61efae1ee06adb269a28
98e26af6740a8035f695eaa5cc8f376f98172bed
F20110114_AABXIH tashiro_h_Page_204.tif
b858d0338ec10576e6a038963cd5fb96
8827db06169db575c45a324de05a031272ea263f
F20110114_AABWYZ tashiro_h_Page_015.txt
974b62c1db3cf34b418f4e170cb2df10
22e4edfe9cfae63cf66df8db8390cb13e16815d4
F20110114_AABYFA tashiro_h_Page_091.tif
399180c5aef547ed4dccda3913f47278
e81dc8dcab846c344d6bc7caaf00d9ef108ed27a
230268 F20110114_AABXVS tashiro_h_Page_219.jpg
5e37d0d6946f8db5eafeb3d0b2c1438a
79680e88afa12d8174ced920c932032b7d7b538c
1978 F20110114_AABYSM tashiro_h_Page_122.txt
f5e0aeb8d49c1c2ea3bd27d7c7ef66e0
fcc4f04daeb5e51e5ceca85c0858b691f8486368
50799 F20110114_AABXII tashiro_h_Page_023.pro
d6808d0ac0d4dc8144a9368ee5ab957e
72d60dcedfb1de51b8e9c101ca468e5588cd2343
F20110114_AABYFB tashiro_h_Page_092.tif
ae8831c70750fac00c4bf91a937f72fc
2b594a24c84dcf12080e4c874247fbd34633b7a0
231818 F20110114_AABXVT tashiro_h_Page_220.jpg
a6b1ad48b2dd49114ac3e01405b1c3cb
001b6870555f9561e55bbffa5ae24d79f113db0f
F20110114_AABYSN tashiro_h_Page_123.txt
a42ef597ad437b86451c419c04206c39
0e7496023b4d4b6e55e656007aaf264d980584d9
886 F20110114_AABXIJ tashiro_h_Page_005.txt
4c3f502957ae91f8fbca7e19ca4ce2cd
c28dde7f777c77b6147392e3c87c83c7945e1eb5
F20110114_AABYFC tashiro_h_Page_093.tif
e40be8e148c3cdadcafee08d0f8a79b1
c3549bb0de4e4c2b5b74d1df7ff6df66753ad046
261217 F20110114_AABXVU tashiro_h_Page_221.jpg
bcb32821e349740ddba14f64e46f2906
c679dc5c1348425750cece9f9e2094c3c75936f6
2272 F20110114_AABYSO tashiro_h_Page_124.txt
e7afd0756b105f367da970d865702448
4da26e98d979b616a731c16b6a58a4c5ee14f737
F20110114_AABXIK tashiro_h_Page_207.tif
83cababface57cc7c329d5580f87d170
86fecd054af79c87ef9573e69818c2a52f918bce
F20110114_AABYFD tashiro_h_Page_094.tif
0942a378fce1fb53bfa9e1cc6f9f9fe0
1c3155e00cdc064d9cb84180256fc3a1c1962a2f
142560 F20110114_AABXVV tashiro_h_Page_223.jpg
b3028abe1b569a1c9b01f2a64e1db85f
a7a891372fcbb2564d1a6a6c21620b2dc0bb3979
1811 F20110114_AABYSP tashiro_h_Page_125.txt
74149de647308fdc6e3243ca4dc5d4c0
9d4d06483815cbd4952a004425f70e04c2670bba
F20110114_AABXIL tashiro_h_Page_209.jp2
66e07b3a4e7842bf29dc35e4ada7bdf3
211e277f404e6b61bed3212a7892f14e12e796ec
F20110114_AABYFE tashiro_h_Page_096.tif
7d6b62f6f5aef46b0c64aa7fbd61da1a
4b1ddd6027e3794db45e4927f0f6f061a7e82aee
180831 F20110114_AABXVW tashiro_h_Page_224.jpg
8535d9450e34abcbd8334b8e7c909562
2c0642be57857033b8314c4fa4428f521b2c7255
1623 F20110114_AABYSQ tashiro_h_Page_126.txt
d1f9dc347a5aa577535ce6c1cf0b0825
a7ba909633cef390d14d48d9327568b4d56587b0
133028 F20110114_AABXIM tashiro_h_Page_011.jpg
ed2901508188134428cd4dbdd8246072
9300ddd1a2e990b68e19ece56372237557fc99fe
F20110114_AABYFF tashiro_h_Page_099.tif
05eae4acebe9366cdbade43755bc6f64
0130a1e26f93d65ea615f2a633f00687c72b83ce
172575 F20110114_AABXVX tashiro_h_Page_225.jpg
5903305de1aed1035171e08322db88fb
76d31b9837ee4a22b4e85d7af9b1980edb6ddd79
F20110114_AABYSR tashiro_h_Page_128.txt
9c70f7eaa9ba1acb8b88567198e48609
7a3fa2823fddc0622f28c23fb691cfd221ca79aa
F20110114_AABXIN tashiro_h_Page_210.txt
02525c94162ba2c464da29a1f40c6bae
fdc496cd36c12bc9a47793d28fb12f041de46671
F20110114_AABYFG tashiro_h_Page_100.tif
94bf7927a6ca1ee29c8735e36d160bfb
c85dbec9178897b4d6f57102e0f21b5509a1085d
143143 F20110114_AABXVY tashiro_h_Page_226.jpg
94038b2615b8f6012a9458b725e31649
c11ecd95ce1fe3922da73aaebc007db69d474147
88118 F20110114_AABZCA tashiro_h_Page_099.QC.jpg
0e6c706735833ae0ed4a73b0c66d9469
1d8db118fdf215cfc71b804f28d321f962a67cc0
2913 F20110114_AABYSS tashiro_h_Page_129.txt
b9210ddec0dee39a6d0e150537f8d1fe
3b2fcc08b7ab6acd2cb578de5a0af0cdb8ee6ff9
90876 F20110114_AABXIO tashiro_h_Page_146.QC.jpg
67030f720405e20352ecdf5e2e35551a
6b93142921f16848eafd923dab8e8110242b7970
F20110114_AABYFH tashiro_h_Page_102.tif
2f5b2bbdb9dba204fc33f6683e2e2136
b35a096876328b39339d2afb4791b8e761f8be56
78311 F20110114_AABXVZ tashiro_h_Page_227.jpg
68278eb3573dabf8511e6d81212f281e
73a9e40336ec3a9d1d57f3a73ca3ec526e4b639f
46727 F20110114_AABZCB tashiro_h_Page_100thm.jpg
97851f0e8712727f8cbe06688129a4af
576074eba2e10f5ad00e904c9ec37d257ef92c4b
2442 F20110114_AABYST tashiro_h_Page_130.txt
8a23230073dd47d05aef8a729796e6b7
13cb0659b7560475628bd933c5b11af4a602d239
102860 F20110114_AABXIP tashiro_h_Page_196.QC.jpg
e161dfd2c15c031dafab92a2269bc72e
a1c1df7bab789789cf8e8c5f668e0f3825995e99
F20110114_AABYFI tashiro_h_Page_104.tif
d5ae43968bf23924e8eaff54c72f8098
ec3b555d5b7f5d0c5e5c94d04cb7309ad1e7641c
99266 F20110114_AABZCC tashiro_h_Page_100.QC.jpg
125691c75930f011808e239f2b1e8c77
04ccbfad69d586f41d64d3d53d03cc8dffeac49f
2452 F20110114_AABYSU tashiro_h_Page_131.txt
ee989a2d0d481ca086058cd663a02f4b
a320be27ad9983c3dbe9e03ae51f177a41663553
F20110114_AABXIQ tashiro_h_Page_228.jp2
89400c6c831f733aba851a26f5e0bd8e
167c64a5010077c30b5ed08483474ac1878ac5af
F20110114_AABYFJ tashiro_h_Page_105.tif
41665a7142b341fb9047e4dbee86f9e3
6f9f47e23d1741e2f35355b84478000a97e28523
122632 F20110114_AABZCD tashiro_h_Page_101.QC.jpg
b0629078a8df51ae1f268400a1965d21
e5f9e42cf70214104f34b4180cce50ed0bb0e3b2
F20110114_AABYSV tashiro_h_Page_133.txt
4302cb783fe5a33e496eb3d3126c6575
7c470262b1869da085651e1fdff2c3d038731cb1
F20110114_AABXIR tashiro_h_Page_156.jp2
a583f08cf81f3af6a584151ac4390da3
dd40a128360db4938de2931b93c4784719275069
F20110114_AABYFK tashiro_h_Page_108.tif
3cc94dc0f1af32a0726cb77266a61894
eb449bcb606d94eeb1308fb6cfda4be1db3bbd7a
126302 F20110114_AABZCE tashiro_h_Page_102.QC.jpg
850bdcab115339eff12153f744ae6fd7
409652c6af8f652a4c2c7ca1fba347fad0cad1c0
2535 F20110114_AABYSW tashiro_h_Page_134.txt
bc15b82c2cf197664d00c08345bd96b5
74bda3d4074236c194c75c6211de12d58a425034
90149 F20110114_AABXIS tashiro_h_Page_046.QC.jpg
00324b39defbdfe7e102cbad4ee3d5b4
884a932772f99ad9adcaf52c0b831ea1cedc9e8a
F20110114_AABYFL tashiro_h_Page_110.tif
23dd51b5571b592d5f3a9c3f22697581
5dd03a3b9f6e3dd7b526f9d6447970f770bbffb7
50865 F20110114_AABZCF tashiro_h_Page_103thm.jpg
a572a101a45b31536609de51fc05e4e2
639864e744c1797d65120d34cfe843a2b5ac3104
F20110114_AABYSX tashiro_h_Page_135.txt
67c18be168ff90c10eac3e86df528eb3
c2496378b444f89191fc9a55f0ac2a236a377ccb
F20110114_AABXIT tashiro_h_Page_128.jp2
8771216e73650ac0948606436da211fa
6b66408a0eebd6e60cb6a9ec4f2b852aa8186038
F20110114_AABYFM tashiro_h_Page_111.tif
8a227bdc8bb460bc40e57f1caf76d0c8
c8939d6f801eafc5cf5cd7d10d8263da4f2a7c93
101387 F20110114_AABZCG tashiro_h_Page_104.QC.jpg
1433f1857c4ed9a7ae43eb5323d9aa92
3e84bf7e66a3f031e12a5f5920c35f4393b6267f
1574 F20110114_AABYSY tashiro_h_Page_136.txt
dff94e8a376f322c07c0e8f4ff563f81
41db233a045bfb9ed6890afc33eb9905dee8aba5
43448 F20110114_AABXIU tashiro_h_Page_106.pro
6a9abe5ed183e53a87300bd7a0c38c77
8a3d0020af91c273133150432c96ed004703f967
F20110114_AABYFN tashiro_h_Page_112.tif
66aed0a002d7939bd38965c57b80b0cc
606107ea90dce54c1e2ad76a6d7476688f62684d
51366 F20110114_AABZCH tashiro_h_Page_105thm.jpg
18bf8e51df1994e45f74da88c1c792b9
fab8fb830ba18a6d8ed300676b1f0eef11f0b87e
2597 F20110114_AABYSZ tashiro_h_Page_137.txt
83170e8f4fc9e191a65fbc9f6f19c727
fb6a09a9df15c84e2e1759305550bd0ccd10f62d
F20110114_AABXIV tashiro_h_Page_047.tif
266e963551cef1252624658312daf759
df2d76876fc8eb83a298543d9e91158218e5ca42
F20110114_AABYFO tashiro_h_Page_113.tif
be2e47b1b12a7cc255a1a8aee2058e99
00c02a2830df27b0e77c76cc4d8f226fea0a7004
114020 F20110114_AABZCI tashiro_h_Page_105.QC.jpg
238b46051c1b7ace9e15214ea4b43715
5a3c6df2bec5f007a3b3a1f77a09c160dcef71fd
F20110114_AABXIW tashiro_h_Page_215.txt
3a6b410ad98249712268d2c6474e9a50
d744899297b7fd2aa5da423e83ed3c950dbdb9f6
F20110114_AABYFP tashiro_h_Page_115.tif
41d3527b12a4bd2e41b9010e648e654a
2211b74ba8090d8e3e8043e4e0686fe28d538367
47821 F20110114_AABZCJ tashiro_h_Page_106thm.jpg
9ac4971b1d21757008a5e024e929d151
74a72b52592677764d4a8fd30c581e98a2324257
50403 F20110114_AABXIX tashiro_h_Page_096thm.jpg
422f404d2b669a7d0d03f67bb97fef6f
d2a01bfb0598e8cb81b28e1703b80e263abb1588
F20110114_AABYFQ tashiro_h_Page_118.tif
5fa559cf13cf2baa8fb0b3afc544c532
10c9d777c6bf945dc2eacd65304edc5c63025893
46450 F20110114_AABZCK tashiro_h_Page_107thm.jpg
9c328100e2881c0b2fda60a2358af7e4
217cb61844aa5eab281c93bf1475333a57372e2e
F20110114_AABXIY tashiro_h_Page_077.tif
8506f7633de3818904534535c652cc83
827f8fc29356e44428470cf1cddb079b742c107a
F20110114_AABYFR tashiro_h_Page_120.tif
04410a84ba914e263f2a89553a29ccc9
3de59d081321d963f18461d4d9a3555eb4ef75f3
99447 F20110114_AABZCL tashiro_h_Page_107.QC.jpg
7b904d84f80f4e18a09b1cb69f7a4f82
ff584afbbad35db6b38c309d5b6b137005df6fd9
594267 F20110114_AABXIZ tashiro_h_Page_226.jp2
805aa00570f9443f92c19c7b761fa822
0edeba3666ffd3747cac1a99626753ab64896a07
F20110114_AABYFS tashiro_h_Page_121.tif
a58c967547cb27284b1e699285010bba
afdc126ec1a2038bc5917ee57b93b853701951bf
49969 F20110114_AABZCM tashiro_h_Page_109thm.jpg
cd3847662b130b930b71c677463da3d1
97dba0ac9d09e47de88a5dabdd2f7d4030b3c1d0
F20110114_AABYFT tashiro_h_Page_122.tif
8e1f4ceb172e90b541b5fd3cb1829674
5449f6a8165c1ed8cd4fcf40281411354a99d07a
106939 F20110114_AABZCN tashiro_h_Page_111.QC.jpg
2843ae462d447342336f2976f33937f9
49ddddaf89207edbbf2350822994e7b3cf42eb88
F20110114_AABYFU tashiro_h_Page_125.tif
3c73cc0681708241bf1b66c4ed5ec77d
4de4ad1906677ded902258a1f8d385815733df32
93860 F20110114_AABZCO tashiro_h_Page_113.QC.jpg
930fc6b050842d2c7cad06d01afaf46e
e649aabb05aa09d01f9164650aa59020fb736e81
F20110114_AABYFV tashiro_h_Page_126.tif
cf828ce6a65ff73dd47bcbf727e80e9d
bc81eda12d4e9ecd30e9bff623216f26e9aa76b2
48894 F20110114_AABZCP tashiro_h_Page_114thm.jpg
197b01d3195e3caed9843bae0f20d04c
8f2744380e1f74348b262ea2bf54e9497b73c2ba
F20110114_AABYFW tashiro_h_Page_127.tif
212c353a55bf7e91166baa64075e10c0
4f67560b5ba78469265a44c8a52c3a4880438c3d
52455 F20110114_AABZCQ tashiro_h_Page_115thm.jpg
8760915b26c6e56bc7ca86c7779ad09f
21aebd1bd65e91b199e443d7bdea5527938e95cd
45396 F20110114_AABYYA tashiro_h_Page_010thm.jpg
54f09b4014817f7b5356f1c929d9b666
dc48ba3f71264cd0dd56ed19472c9cb825d7585a
F20110114_AABYFX tashiro_h_Page_129.tif
45660bc4592752959dd8995a88ff033e
711b4e9ecae484d4249058207f02e8636a46adf6
97623 F20110114_AABYYB tashiro_h_Page_010.QC.jpg
fe96bb7fec80abe48fafdd658f2616c5
37354ce7e4290c11b31176737d753a3607e2c526
47457 F20110114_AABZCR tashiro_h_Page_116thm.jpg
d74fda82d20eb7a747c166748744e410
7e67020a116a16ca64715258183886b468983c36
F20110114_AABYFY tashiro_h_Page_130.tif
d5469b19fefa8f735d8fc673e2859658
d946e6a67bd212f8cc7dd1fc8c914da95c99c6d9
36832 F20110114_AABYYC tashiro_h_Page_011thm.jpg
5c2b7acce7bf1545a5c757af342137cf
403d2713ef96a43a73c1cf657d13b8eeb4d4c1d5
101345 F20110114_AABZCS tashiro_h_Page_116.QC.jpg
2cfd27d290be60a09fbab048b823e878
359cdf58d7f8ce8df8d4f6d01fe05f8bdbad8380
F20110114_AABYFZ tashiro_h_Page_131.tif
54612aab33253ce3ecd338d2fc9880b6
0cba24edc60eee79f92aeb900993272448675ac0
63235 F20110114_AABYYD tashiro_h_Page_011.QC.jpg
906267c08e470441eeebdb467cddb0ef
f516c78055c852937503ebc5c5064de7b21178aa
49387 F20110114_AABXOA tashiro_h_Page_125thm.jpg
b7a1afad096fc2f53d9c15fa1bf70768
8f4b22c1be97b750b65fe286b49653afa8079d34
47624 F20110114_AABYYE tashiro_h_Page_012thm.jpg
68141c9ad95ad976c6a3c12ae0ea6611
849d44fdfab501f78cce796881993c668afa1acd
48278 F20110114_AABZCT tashiro_h_Page_117thm.jpg
6bac4ff5604fccd0fee1b6c02b8d760f
708211a0794e2715c69fed6c58e9e17c245e2e07
109796 F20110114_AABYYF tashiro_h_Page_012.QC.jpg
f7f6f7411af7a03484b611e782ae6f54
9d042b7d43269096f38d75eae6446397b188ba93
100598 F20110114_AABZCU tashiro_h_Page_117.QC.jpg
84aae44c3e01f5a243486e824c34cee8
92975323da01936974bb6d089d30237c774898d7
220776 F20110114_AABXOB tashiro_h_Page_153.jpg
586cf35b5bdaea669520eaaab2f53d19
9295ea2e74347f7ce5f4d312ad816118019dcc9e
47042 F20110114_AABYYG tashiro_h_Page_013thm.jpg
86592c7f01e57b8babac9a67c059b150
0d6e93e1a2f2f2ca700a93a8b4b092e2e1e4738e
103258 F20110114_AABZCV tashiro_h_Page_118.QC.jpg
054cbae9c6aa663e491ac3b2e793cd30
87ea082cda6396453bbc3a086f01418016fc8da6
F20110114_AABXOC tashiro_h_Page_208.tif
755bcd2d2ac29f34cee5274222dd5c0b
bbd729bb4473bb580451dfdaaec5799c4f401cfa
108090 F20110114_AABYYH tashiro_h_Page_013.QC.jpg
875df7d8f2c3b9a65f41454f6c3f7384
e822c67d54a104bc6c3c4d23a60e67b4ebaa1c4a
48804 F20110114_AABZCW tashiro_h_Page_120thm.jpg
d3ce7a17ff4d9be0f73c54db940d3dd6
8e3bec19a268b416a332a07d162d71ec929d89f0
38511 F20110114_AABXOD tashiro_h_Page_040.pro
d88550df57b11b385d516f6afc3d1757
f99615469ffecabc480a2e0f6f4b44d6c781a16b
77859 F20110114_AABYYI tashiro_h_Page_014.QC.jpg
9cfd47e1be0cf29024074ccb9ffdac46
f338dc32072a31c1a99a1ba5aaffb0910112c8d5
102857 F20110114_AABZCX tashiro_h_Page_120.QC.jpg
ffb45878af9f01b8ffd6ba8e82467ed7
baa046a0e6bd3071e2f1fe39251fb73f7a2007a1
41444 F20110114_AABXOE tashiro_h_Page_027thm.jpg
2e50d9fe5a9671b8505ebb13b290f476
e49aca5289128bbcc2d07c479df8b8cede85bedf
44929 F20110114_AABYYJ tashiro_h_Page_015thm.jpg
5ad06be65c31ef89b179fa42397b7c69
0fb759050a73eacb5f8365e9a5297812299ac265
50466 F20110114_AABZCY tashiro_h_Page_121thm.jpg
a9d30df950dcd9152d7fcd051fbf66f3
1b92e079a157505dfe7454a8daef1d792bbb5168
45608 F20110114_AABXOF tashiro_h_Page_037thm.jpg
3a53427e28ea08c9bc683524c67f5588
357e7c6e7a766ced49f9087cbbec464e810f6a68
102019 F20110114_AABZCZ tashiro_h_Page_122.QC.jpg
abf52e36023614408351734450207289
f208e78a849abca7aed693b31cec08e46a9528bc
F20110114_AABXOG tashiro_h_Page_173.tif
6182b68f8e3db8d7989edf5b73151080
e2871960805680b9fafc56b05d4fdf441d3b71b8
89586 F20110114_AABYYK tashiro_h_Page_015.QC.jpg
11c4dd63df23545136850339849e884a
0810ae9f47a9ee6877f6ebe1e2566ef7b0f5b795
91488 F20110114_AABXOH tashiro_h_Page_036.QC.jpg
fa3c1728325ffb3dd84513f8b0c97a56
cb86f1f4df8ade8be8ecd98c007b371d8968041d
46293 F20110114_AABYLA tashiro_h_Page_077.pro
f76faf982cc57ee42e9eec18c27af14f
3181ec3e4aadc5b4488f50559a2eecc332b051e5
47333 F20110114_AABYYL tashiro_h_Page_016thm.jpg
ba9ce89d6b44e3911dea096a0acc8fba
ba41d5b21036c77eb4f0fdb9bb3f33ac0f41694b
F20110114_AABXOI tashiro_h_Page_113.jp2
6f071298a0a168a8cbcde667e18760b2
1e6a17d3c3e9b66daa4c9109bd38fe6ebeda2499
48018 F20110114_AABYLB tashiro_h_Page_078.pro
b16668e9071d216cf1c76eddb16402aa
52ae51b81106ab768b06172b291d88d4df7fa9eb
109747 F20110114_AABYYM tashiro_h_Page_018.QC.jpg
82f94be1b8de059b33f6921d0aa2ab58
e03b0c47b54c28b92369628e12d3fad7e1998f38
F20110114_AABXOJ tashiro_h_Page_193.jp2
484c599a38bbe8332f35020c636c5b53
73bb96c2ee482cb8442432759d08999acd5fd7ff
43447 F20110114_AABYLC tashiro_h_Page_080.pro
d9f2974f8296d46600b9f7d34c900f8f
56df77bc82ef5f572a28e16ccf140f167a601a80
48611 F20110114_AABYYN tashiro_h_Page_019thm.jpg
52ba49195a4d163edd5dd713a3ca9ab9
bbefde2d548c7fe903a985d0f2b42c734556d75d
52810 F20110114_AABXOK tashiro_h_Page_209thm.jpg
15fba097e3399afa9dcb25de3f36e53b
cff3b97109dfacd97aef386805bdfcac18bbc477
35314 F20110114_AABYLD tashiro_h_Page_081.pro
7873fe8465e4d1460c603596455913c2
c7108f7f647d15696e35d8e4880f866c374e5060
110750 F20110114_AABYYO tashiro_h_Page_020.QC.jpg
b94447f4b665bba267e3c0683a6768ef
a877678f2b4a00d52184c4b1ff9abedebdf46d47
200670 F20110114_AABXOL tashiro_h_Page_021.jpg
a0c15586479c5a96130ef5c259c301f0
efa7ead61d5a00b8f0a0ad5a86336baa506b9797
39011 F20110114_AABYLE tashiro_h_Page_082.pro
bd0cc59f623321ac1611fc5e23f9827c
b51aea7a701546bfb74b394da1a88bde1e6fdedb
53794 F20110114_AABXBA tashiro_h_Page_229.pro
ea7f29cd983383382f01ffd764970ab8
717c652ef52289ff737663d629d6022b827c616c
46704 F20110114_AABYYP tashiro_h_Page_021thm.jpg
b4931cc90e045d215ccf6294b5f3f238
09ab99bebd072bda2abb90235e361bdb9f81a23d
47107 F20110114_AABXOM tashiro_h_Page_094thm.jpg
c5d0832c0c9b7b34f7bc22bb876ee9f7
5ebae76781123899d8dc4649296d7051236ac296
51710 F20110114_AABYLF tashiro_h_Page_083.pro
3f53f2f930c510e0377f318a73c3dd48
dd896d92d1fe1f14f0c6f60a828c800155a633cb
835502 F20110114_AABXBB tashiro_h_Page_081.jp2
8616f595dbf43fc40bfe6e9cf61b394a
20821f205caa068cfc9f2249232ee6f18b148cab
94861 F20110114_AABYYQ tashiro_h_Page_021.QC.jpg
e1582a2a9b33b3e1eca44a8f00f417a2
4a20aec0ee1006452bc4fe0d680daa7a052f3a3d
2572 F20110114_AABXON tashiro_h_Page_102.txt
a09d1a78fe3dbb7bf89fe7154c596fd1
a125e4897381aa27e401ee21c328cb4a10a8034b
37399 F20110114_AABYLG tashiro_h_Page_084.pro
a400b457927c27b7fc083e2799cca459
91be07bc258528a377c2220c4692e89211a688a7
104498 F20110114_AABXBC tashiro_h_Page_174.QC.jpg
7ed8d6835053ba52c5b50880642b77c8
865a9645001a01512f336db9559e83bf7ffa5976
47235 F20110114_AABYYR tashiro_h_Page_022thm.jpg
e80c14825d74b68bec6ef1155f6cb906
67a5fd0315c2aa6da4a7c24b3e49be2ca8363849
71186 F20110114_AABXOO tashiro_h_Page_009.QC.jpg
e65fa9ccd91d32925b426ad2c280f555
1b54a6c064ca540962c591cfbd1d51a081fcb8d4
43893 F20110114_AABYLH tashiro_h_Page_085.pro
d438bb9efa1bc60e39e8e519e9de5817
faa0d5a5f08685f0f8b31a30fef36ea81ecd7f5e
39617 F20110114_AABZIA tashiro_h_Page_225thm.jpg
fd01d6f71db5ea18b7c82a49a88e02d0
4f0873013919d33ad53be4c2eb9622e5174d0ae9
94332 F20110114_AABXBD tashiro_h_Page_153.QC.jpg
4f1ad23fbfaefe53be427adc48887177
0c9ef21fce6b4f22ef7ec839ae82083f8eff501a
101053 F20110114_AABYYS tashiro_h_Page_022.QC.jpg
c1f9a2cb20f62917144b2d14ebd133c1
093bb6ec19bbe328b85167bd3086ab8cdbe4787f
51885 F20110114_AABXOP tashiro_h_Page_163thm.jpg
3e73bb85c50926839d8d548898f93e52
74251bd309a55d3c6094f5f6b53637fe23b09f01
48772 F20110114_AABYLI tashiro_h_Page_086.pro
c02b537100c7f043e6762d228d9e784d
297d3413a174f6b1028c772f14f32fd59f5a73aa
39463 F20110114_AABZIB tashiro_h_Page_226thm.jpg
403b50de8c8fed9e573e8a5a9678e00f
2d49f0a356590151668b69dfb04c0d0bd0816849
48438 F20110114_AABXBE tashiro_h_Page_064thm.jpg
179cd97ab73b32694937976eaa962787
3ec28abc54672034699b00ddca1a44ec4e419692
47563 F20110114_AABYYT tashiro_h_Page_023thm.jpg
802e2dc6bca17dadfb3cf106ee0a2a6e
b38b334891dbe79732029b16d2f387ddd42d69c6
F20110114_AABXOQ tashiro_h_Page_015.tif
f66554b191e82d173b38cf938a544c06
096abcde4c2d611c6b0139d6fcb2c0e539fa8e4d
50998 F20110114_AABYLJ tashiro_h_Page_088.pro
e3caed04687d17caaafa7e7696224232
e875408fa31240b9fb170a37cf77800977beacd2
100068 F20110114_AABZIC tashiro_h_Page_228.QC.jpg
12d4b214ba1f52d278e27479c1ff99c5
298c085190cfe67ce450a14f38a2e4c24414bc3a
225172 F20110114_AABXBF tashiro_h_Page_031.jpg
a63c95c416b926f64b818a24137092b0
dd54c6d73555945eb557e7c239b324a773118cfd
100227 F20110114_AABYYU tashiro_h_Page_023.QC.jpg
d90cdc010363e5144c21b290cc3c00ac
c734d3dee6b6fbead0277756fec916f02b02b259
41235 F20110114_AABXOR tashiro_h_Page_152.pro
480343b5d914356eccffc048da792afe
b6cd336fca6cd57aa75d494926b384b5d50921d8
53592 F20110114_AABYLK tashiro_h_Page_090.pro
748339a388a3efee4b36aae7d5daa5a7
6e81fe868c15b7457df1ea71bc759cde94fac74f
108353 F20110114_AABZID tashiro_h_Page_229.QC.jpg
ad593beacb05087907a18e2fabec9f72
bd6c8f4d95a875f84212137cc32bdf302ea06a30
845089 F20110114_AABXBG tashiro_h_Page_093.jp2
f1745c124f203fae0eabf66d03443931
d3adc3a54a83acd1ab4531375851705c079efedf
42126 F20110114_AABYYV tashiro_h_Page_025thm.jpg
dd8e01c3996f323e643f2c7bf5e31b2c
9f662e7afa068ba06f460d1bf048785c4e0912f0
45528 F20110114_AABXOS tashiro_h_Page_029thm.jpg
7c9a15bacab02a2a24f2c32f88e2775b
93c692880ed790029166da538d154a109c0a0383
43798 F20110114_AABYLL tashiro_h_Page_092.pro
406002042c403a6f7b7f422da70c5175
b69baa29b7c2df6bc0261b6750ce268a3a07ac40
50122 F20110114_AABZIE tashiro_h_Page_230thm.jpg
35923c34615897a3efbb9f9bce2c4e9f
2ea38e0ab45d0f5015e3cf092feeab0eeb337e2a
2042 F20110114_AABXBH tashiro_h_Page_045.txt
1d7c738aa149636a2f9c7a9915b7adb2
d53a2ddd0586ce94422a0906a46691178738d8cb
72939 F20110114_AABYYW tashiro_h_Page_027.QC.jpg
9af45b304e7671461471d597674f7dab
0a382de261f6e2f9a5679a35afb0a966af0a563f
1876 F20110114_AABXOT tashiro_h_Page_049.txt
cec7380b1cb634d7fb89ec56054432b5
1aa8eb1c4a9fca336d954b052720c4b7c9f74d9a
34576 F20110114_AABYLM tashiro_h_Page_093.pro
5665299dd274b2aa162d5d30286faf29
aaa48e851ddb8033bf4c4c6a1f3435b66c00b2df
108510 F20110114_AABZIF tashiro_h_Page_230.QC.jpg
01fd022d0ca1902e041f9fdf6308db69
9231636863c00beb941c28534bb9254b9888754f
26887 F20110114_AABXBI tashiro_h_Page_226.pro
6919aa2763aca4f5733f20a5aef363e2
7d72c5e96de141a7d1d4a35ebfbbf49f9c4dc95f
45138 F20110114_AABYYX tashiro_h_Page_028thm.jpg
9747f4e89674096487924d1c14dfdafa
ec3b931011366d3b7124a2722b6e73c082b8740d
F20110114_AABXOU tashiro_h_Page_025.tif
e7dd2fc375bb4568eb2a98866ea900d1
4fce5c86f0ef2c16b8310d172daf36ee75d6e73f
38666 F20110114_AABYLN tashiro_h_Page_094.pro
e80232956eddffdc969b6f9ba6448560
ad1e38fc8272f1311be95ee5e747368c0bf2e3b8
110753 F20110114_AABZIG tashiro_h_Page_231.QC.jpg
9901b80862e0e88028e19460771707fe
a4b232f6ba5b5ed26b62ee1e40075747cd4dc498
43510 F20110114_AABXBJ tashiro_h_Page_021.pro
fc7d49e39aea38c6ba8b14177f5abbb4
1aef19544186105d32bc42269b9fd4814af841a4
89103 F20110114_AABYYY tashiro_h_Page_028.QC.jpg
c36dd28804e2e78a32a6306ac6e281b6
240fcaf25bf1a9708f65034a24c7e80aba63eef3
F20110114_AABXOV tashiro_h_Page_013.tif
a6fdc051533c735d831c75fe17de28fe
ac51b0a71dcf3586975c72fcd442205c855a9b06
39890 F20110114_AABYLO tashiro_h_Page_095.pro
e422259a4da4e8f6dafd4ccfc008335c
7dc20039d6912e096e636cc1dedc8379bcc1af30
49261 F20110114_AABZIH tashiro_h_Page_233.QC.jpg
300624ecfe9d7a417c333ea4d0c397fe
60a11cf5c748aaf96dde468adb51f73353959452
94533 F20110114_AABXBK tashiro_h_Page_134.QC.jpg
692aaf5e338de59c3cf9f343922b810a
f39e4588d46a5f3dba25fd1d2fa5d656fccdb906
95276 F20110114_AABYYZ tashiro_h_Page_029.QC.jpg
92aec75d65875c66474ab45e3e9a0aa7
7651b873ef1e6a67b9490147b3a21d16aaecfd1a
42783 F20110114_AABXOW tashiro_h_Page_099thm.jpg
c73d187434728332b1ad5a17b662f6e5
cb3d2b6c9a015c2cc524763a40ad97977b40b6f4
58136 F20110114_AABYLP tashiro_h_Page_096.pro
771e7e9ff8bf74fa0f747dad051a91f5
d1624284f3f484847675f5f1d432537758e9a4a3
37933 F20110114_AABZII tashiro_h_Page_234thm.jpg
4d6a83d91f94d3432c91dfd37ed9fed8
539c57adbb85331f2985e0bef314edf953976a30
F20110114_AABXBL tashiro_h_Page_184.jp2
5386128ba79924e8b65e9fc26d75adcb
b62b1231470a54317f33f7f1ee4d4b8c4cb5a20d
102657 F20110114_AABXOX tashiro_h_Page_167.QC.jpg
ea3f3f9fa40d5049fae4ff65efaa3fcb
92a6724a74394904f7fe191e0ee8b5361b1b37b0
53967 F20110114_AABYLQ tashiro_h_Page_097.pro
06cc769359b24c14e2411e02d3418dab
7939493d804e04204870dfcfa0229c78282d5b34
66818 F20110114_AABZIJ tashiro_h_Page_234.QC.jpg
4847cdb9ee1b7dc3ea146a1276cd4fe1
b8b5e51848d45f789356b2466dd526aa4cf55857
43278 F20110114_AABXBM tashiro_h_Page_001.QC.jpg
db354f3741eb52cfc8cc5ab034715122
a27adf104f9224a7e429e1d24f318330c2b81e8b
46576 F20110114_AABXOY tashiro_h_Page_196.pro
14e64a17d79dfe891f5b41d058c5090b
2e48e79b7df6ebb10c6baf6436623738e49ebc1f
56139 F20110114_AABYLR tashiro_h_Page_098.pro
f50ae048f0cb01d5979f626f7824c86d
84f8031ae89f6d13c244bd67a301006ce0071eeb
1914 F20110114_AABXBN tashiro_h_Page_076.txt
95caeb48fbb7f43175c7dd67a2d8b5a4
e762e0529d2c43d316cc10cea5d18ef6edd66071
243288 F20110114_AABXOZ tashiro_h_Page_019.jpg
d6a72f7de8551201e0bbe8d79685868a
a5c102fc0a3c6932f6f386095f19a6fb47c59348
38591 F20110114_AABYLS tashiro_h_Page_099.pro
bf040a4347d02aeedd2edc9910139d7a
9afc3504fa76523a7a369f0cacfe6cfe38f82e0c
39355 F20110114_AABXBO tashiro_h_Page_043thm.jpg
972f793734d4970e32dcf99ba9b64458
2bb858caf6da6f0bd9977a78184858d3c6684a45
47251 F20110114_AABYLT tashiro_h_Page_100.pro
cc40d0e1142410b17678d4fccaedaa46
14db77326653e12932752e580dbfe41820872523
976806 F20110114_AABXBP tashiro_h_Page_143.jp2
7f9500c5cf2181c5c1debbad4634cdd1
59eded123b632f72595f4fcf878a16822243abfe
65810 F20110114_AABYLU tashiro_h_Page_102.pro
303887bf9277857d15692a657efdd532
16504beadd9bd4f472c356200cdf964242d364e5
F20110114_AABXBQ tashiro_h_Page_158.tif
05c36845be726914ac2ec93039dbfe4e
09885e2183de16515643919cc0a6c46e4505561f
44044 F20110114_AABYLV tashiro_h_Page_104.pro
f465b49be1dd4a28152b329d8c4a981c
be65c637d13ad975cb9af06042a43479ae65861e
45750 F20110114_AABXBR tashiro_h_Page_198thm.jpg
08daa57b0684a524a5ba0937467ff4d1
4e9e9f980feea18c97938cd884c73f5fe056263b
56557 F20110114_AABYLW tashiro_h_Page_105.pro
8f53ffd175c2fb4b6c9985c8a5edc908
2bab871444ab8cfb38cf7aaafc4ae432a4f94a91
46909 F20110114_AABXBS tashiro_h_Page_143thm.jpg
42ae616719ade903effa3a56e7ce02c8
5719495eedbddc8e297d4accdc644a05acd2ba12
54498 F20110114_AABYLX tashiro_h_Page_108.pro
aea73a543b14b1f640109517ffb556ae
be5ba6d99181be377872be25605502389f27e653
2206 F20110114_AABXBT tashiro_h_Page_151.txt
f828f07e7979386995daae6424ebb436
6bc5aaa1a566a091b6e69209fad38c5a3d856ac0
57331 F20110114_AABYLY tashiro_h_Page_109.pro
93697dbf7a2518692648ba9c1e24ff58
b45065fb72bd8ed1fd388fbc19e8bde7dd824613
39992 F20110114_AABYLZ tashiro_h_Page_110.pro
cbaa41dca8e7bc6c68b28a53b8fc05b4
44c856f66739ecc7ef423c8f4938fedb5ab4f087
72176 F20110114_AABWXF tashiro_h_Page_225.QC.jpg
8c29dd947638f1bb48f7c4deac1179a7
397f2c8b971d001b48f919377f327dd7b408ac44
F20110114_AABXBU tashiro_h_Page_109.tif
362a9c2c003a026f480ad88399b25d17
e3afcfd661be8009db85e44b12b3f4fbb3a480a3
42140 F20110114_AABWXG tashiro_h_Page_055.pro
9c8f7f17ad17262ef3b9e12f2e539a77
b01a880abc88595e79a6aa5bbdb6677d2895f37c
205832 F20110114_AABXBV tashiro_h_Page_092.jpg
322bca780ab4ac7dc6928ad6b9933208
b8da3e45e3dca91b6f9f5f35cb1591541df91211
223488 F20110114_AABXUA tashiro_h_Page_170.jpg
4c6402dbd6225cec284e5839ffc284db
fbfa7efe4e22d020bf9cdbc659111ac4de2caa12
39323 F20110114_AABWXH tashiro_h_Page_014thm.jpg
3ba393ad5c472adbec0ea35327bdccd6
9547aff2d94cfc2b9d6d3bb7e45fcc7fab058961
1864 F20110114_AABXBW tashiro_h_Page_132.txt
f781bb2e0c94cce038c8ccb8e5f37675
41fd1b3b1ffec1529fa814ef1700968ad74f2042
265393 F20110114_AABXUB tashiro_h_Page_171.jpg
b10abc86041e89477c331cc25fcc430b
0c5efffd1a09be7cc9d679ab87fa9b60903b2bd3
173743 F20110114_AABWXI tashiro_h_Page_034.jpg
f82305c37c879a4bf7c0d958fe8c3e16
5bb5fb05537a589ea2fae76a71af65c1dfe5cac7
2573 F20110114_AABXBX tashiro_h_Page_138.txt
04670df7429ded838e7379148117eb89
84d37d3c9d235531f5e91772f9b6e646ff08f088
101209 F20110114_AABXUC tashiro_h_Page_172.jpg
d17e8e449f8a5aa6a9a0f5a283773ec0
2f57812c7406e3ab67eecde841af44a1e2b1df97
290184 F20110114_AABWXJ tashiro_h_Page_140.jpg
07c3d1784b0131d2177a881afdfc197e
b8025d4c7cd968ba3eae0892b090e2b08b68540a
2141 F20110114_AABXBY tashiro_h_Page_078.txt
cb4d8ca5581b8304737d5cc5aa6b5910
20e62dc887156c5a555bcc19422e01ac5176386d
271145 F20110114_AABXUD tashiro_h_Page_175.jpg
7221a55809652c1740ee25190e4fb1f8
02e7c2db37b348dd0dae4a5d459aaa24dfe500cf
888259 F20110114_AABWXK tashiro_h_Page_074.jp2
ebb0baccb6669637fb070ca16cd8269f
cb9b20918d968c20687c6a4561673c52dbf7fce1
2550 F20110114_AABXBZ tashiro_h_Page_119.txt
32013abb649f7df2ba5c005a1b1cbd2e
c56bcb4cecf9cdefe282333b219837e36d8d6888
238159 F20110114_AABXUE tashiro_h_Page_176.jpg
db67b012e362d098184e6c930842903f
356160073b9efce0ab3633f7a7ffd881e5a6c538
305424 F20110114_AABXUF tashiro_h_Page_177.jpg
039fae5143677ec740c7165c60534777
ee91ef250e842ed971467315e2fff417664301b0
1040614 F20110114_AABWXL tashiro_h_Page_077.jp2
9315d934b5c8af5aafa354f883ca7244
f6061adb6594f1dda1739fa67ea6f99486ea187e
234605 F20110114_AABXUG tashiro_h_Page_178.jpg
3b020899f3770ccd4deb065c94eb2e8c
21f8725de42e534fd05f17592f355f8ae7e871db
209611 F20110114_AABWXM tashiro_h_Page_062.jpg
ee5bdaf5583d42c566d0b3e088a7d789
ea7c3cbdf474ae59f70c8f00bf80485406fdbed3
2146 F20110114_AABYRA tashiro_h_Page_064.txt
3b4bcf66488f78217bfd1a71ca96a9d2
df113d626769a781436d44faf5c6d8dcf1c6fa2a
282407 F20110114_AABWXN tashiro_h_Page_017.jpg
78a3fe3c67ea86896e4c81827114a00f
b733549cf427d462d3d6c5ef61276c0209ed6b3b
207215 F20110114_AABXUH tashiro_h_Page_179.jpg
f48f7be48c5d5b8c004877d5c8d26935
6dbb6f20a40c9a3dd034f97e1f1b602919c96746
F20110114_AABYRB tashiro_h_Page_065.txt
ccbc4e14286b985749a70921a5ed27bb
9f7b438ccf9bdc0f75f3fb8bb1ae864c3eeb4aae
182823 F20110114_AABWXO tashiro_h_Page_044.jpg
bb80524829e459640b51cb121f8b8753
a13e3c0af3f05796d9c2595cf103549da4ce8c9a
2489 F20110114_AABYRC tashiro_h_Page_066.txt
64afaa05d56334397cd6dd51406389c5
8763d8f8f4cbea1fcbca1a202c7a94d99ee8da5a
256281 F20110114_AABWXP tashiro_h_Page_006.jpg
c7aabc368c6329065ff1a561e690076f
b3a76f034ad14c0098dc38e0c01557b1babd36ae
215312 F20110114_AABXUI tashiro_h_Page_180.jpg
df149ad5f7e6116356414e31f08d3192
e8138d667ca287854bc43ab7f4f201036310d195
268664 F20110114_AABWXQ tashiro_h_Page_071.jpg
4f1f748d7e732de31735618626064170
c954f4db127d0ed7b97d98f8635066f03adea09b
199950 F20110114_AABXUJ tashiro_h_Page_181.jpg
23590ab0be1f92347c6c129ceb6996b8
084a34fff906553363fd2e2c82a3fd21b0652928
2229 F20110114_AABYRD tashiro_h_Page_067.txt
3e2f6ee616788f53d372826e033143d7
13f562be58d174e71e02a3d7e0b2be524a348846
49327 F20110114_AABWXR tashiro_h_Page_228.pro
9f1204c816fc98ae12e40dab28b4a92a
bbd7cb15a978a124bff470f93d39ebe8c70224bf
175531 F20110114_AABXUK tashiro_h_Page_182.jpg
1b467802bbe3ece460df7cf446c5d808
14e6de491be6bbf977b1b266cd20512f0fc89e7d
2264 F20110114_AABYRE tashiro_h_Page_069.txt
edcfed169083635b5fd239b8271e3d15
ce034471dffeac0b1330e0f788d276fccce2fc06
44279 F20110114_AABXHA tashiro_h_Page_040thm.jpg
650bafe7238fe0a159fb0ffa4bd99290
82ad7aa430c438d3021de7b94e8f7166db67a33e
45261 F20110114_AABWXS tashiro_h_Page_122.pro
bebd3f7689cf4a166370cec9c23d272d
22e9b34021ea2fc432442d2e6e321a543de12467
220214 F20110114_AABXUL tashiro_h_Page_183.jpg
d31440f5c4ee760be5dc4db0c0143e57
fb6101163c61c1b0883ed0c7cacee2a09e3bda3c
2385 F20110114_AABYRF tashiro_h_Page_073.txt
c315906bcb963f18a38024027e83d902
e5fbe459234156019e99c69a53448aeffaced9c8
F20110114_AABXHB tashiro_h_Page_106.tif
a71f14ef411b308a3fda8c3359be1545
f3aa7e00e95d8209523b3f0cdcda780f49f3aca8
266138 F20110114_AABWXT tashiro_h_Page_096.jpg
ebed9ed30d011283b17ba0332af3cbfd
f00de004e53bcfbbf9577cd9658383f2b17decd2
272565 F20110114_AABXUM tashiro_h_Page_184.jpg
04a7c6d518bd95e45415ee5cfdf8d4e8
749aca79b0da48e72a3dd8515292233fd175a975
2239 F20110114_AABYRG tashiro_h_Page_075.txt
5d2e420ce078815affa38e86c5b22bd3
aa3a1fe0636a7fd96a3cca422403e5477e39700a
F20110114_AABXHC tashiro_h_Page_066.jp2
3aced3335dcb7ba7cbdf0bd4e5ce125a
bb9d5bb326a2c5640e4eb962d2ca6be90467172d
943774 F20110114_AABWXU tashiro_h_Page_036.jp2
cf0b3a2c488057cad7f81636c35a3a59
e79559d12b7a4118d3ce23b56e0989d11ad6961a
245010 F20110114_AABXUN tashiro_h_Page_185.jpg
a250ca0ddf430f09b2650ee7032edd6c
5e6f4ca3df6dc06968b561845de0e8faf96b54d5
2316 F20110114_AABYRH tashiro_h_Page_079.txt
9d316c712328ee75dce6eb6f9515a86e
9f48b67c2ff9adfc35083472140c65b273d23cdb
F20110114_AABXHD tashiro_h_Page_204.jp2
71ddee203e9453c4738398514320ed91
48a0fa60c5d229db905b326d9d3dbf6228b8aa40
2410 F20110114_AABWXV tashiro_h_Page_086.txt
380148ae0817e2bbe560bbfdd4551d23
643a568da62f4c51eff315c99c8dafc0bdbd490e
269238 F20110114_AABXUO tashiro_h_Page_186.jpg
bfd22eba218f8b37c7f519568c0e3068
0f74adc1a1078e7b75bdd7086373fcab8c520bed



PAGE 1

TIME-RESOLVEDINFRAREDSTUDIESOFSUPERCONDUCTING MOLYBDENUM-GERMANIUMTHINFILMS By HIDENORITASHIRO ADISSERTATIONPRESENTEDTOTHEGRADUATESCHOOL OFTHEUNIVERSITYOFFLORIDAINPARTIALFULFILLMENT OFTHEREQUIREMENTSFORTHEDEGREEOF DOCTOROFPHILOSOPHY UNIVERSITYOFFLORIDA 2004

PAGE 2

Copyright2004 by HidenoriTashiro

PAGE 3

Tomymother,KimikoTashiro

PAGE 4

ACKNOWLEDGMENTS Overthepastfewyears,Ihavereceivedfullofsupport,encoura gement,andvaluableadvicefrommanypeople.Here,Iwouldliketoacknowledg esomeindividualswho helpedmeinvariousways.Iwouldliketoexpressmyforemostand sinceregratitude toProfessorDavidB.Tanner,myresearchadvisor.Myworkcouldn otpossiblyhave beencompletedwithouthisguidanceandsupport.Henotonlyco ntinuouslyencouragedmetokeepgoingbutalsosuppliedmejusttherightamountof pressuretoget thingsdone.ThemanythingsIhavelearnedfromhimwillbemy treasure.Iamtruly gratefultoProfessorChristopherJ.Stantonforintroducingm etoDr.Tanner.Iwould likeequallytothankmysupervisorycommitteemembers,ArthurF .Hebard,Hai-Ping Cheng,StephenJ.Hagen,andStephenJ.Pearton,fortheirgui danceandreadingthis dissertation. IwouldalsoliketoexpressmyappreciationtoProfessorDavidH.R eitzeforhis occasionaladviceandhisstep-by-stepinstructionforusingand maintainingthelaser systemusedinmywork,JohonM.Graybealforsupplyingmeasetofsam plesand informationaboutthem,andCharlesPorterforprovidingme withalgorithmswhich helpedthedataanalysis. IwouldliketoexpressmyspecialthankstoG.LawrenceCarr,wh owasmydaily advisorattheNationalSynchrotronLightSource(NSLS).Hisgui dance,input,and patiencemademyprojecttogosmoothly.IequallythankRicar doLobo,whoisthe authorofvaluableprogramsusedfordataacquisitionandanal ysis,forhelpingmeto startmyprojectduringhisvisitattheNSLS.Additionalthanksg otoJiufengJ.Tu, ChristopherHomes,LaszloMihaly,DiyarTalbayev,GregoryD.Sm ith,RandyJ.Smith, andallofwhohelpedmeattheBrookhavenNationalLaboratory (BNL). IamdearlygratefultoallofmypastandpresentcolleaguesinD r.Tanner'sgroup fortheircooperation,conversations,andmostlyfriendship.I amalsothankfultoKevin iv

PAGE 5

T.McCarthy,StephenArnason,ZhihongChen,SuzetteA.Pabit,Am olPatel,Susumu Takahashi,andNaokiMatsunaga. Iwouldalsoliketoacknowledgethehelpofthemembersofthem achineshop, electronicshop,andcryogenicsteamoftheUniversityofFlori daPhysicsDepartment, aswellasthemembersoftechnicalstaattheNSLS.Acknowledge mentalsogoesto thePhysicsDepartmentstafortheirassistance,especiallyJill KirkpatrickandDarlene LatimerfortakingcareofthebureaucraticdetailswhileIw asattheBNL. Finally,Iwouldliketoaddressmyexceptionalthankstomypa rents,Hiroyukiand KimikoTashiro,fortheirsupportovermyentirelife.Finally ,mydeepestappreciationis duetomywifeandtwosons,Yasuko,Mitsuru,andHikaru,fortheirc onstantsupport andpatience.Theymademylifesomuchfun. v

PAGE 6

TABLEOFCONTENTS page ACKNOWLEDGMENTS ................................iv LISTOFTABLES ....................................x LISTOFFIGURES ...................................xii ABSTRACT .......................................xv CHAPTER1INTRODUCTION .................................1 1.1IntroductoryRemarks ...........................1 1.2Motivation ..................................2 1.3Organization .................................3 2OPTICALPROPERTIES .............................4 2.1Introduction .................................4 2.2OpticalPhenomena .............................4 2.3InteractionofLightwithMatter ......................7 2.4ExperimentalDeterminationofOpticalConstants ............15 2.4.1RerectionandTransmissionataPlaneInterface .........15 2.4.2Kramers-KronigDispersionRelations ...............16 2.4.3RerectionandTransmissionatTwoParallelInterfaces ......18 2.4.4OpticsinThinFilmonaSubstrate ................20 2.4.5PhotoinducedAbsorption ......................23 2.5MicroscopicModels .............................23 2.5.1LorentzModel ............................24 2.5.2FreeCarrierResponseandDrudeModel .............27 2.5.3Drude-LorentzModel ........................31 2.5.4SumRules ..............................31 3FOURIERSPECTROSCOPY ...........................32 3.1Introduction .................................32 3.2FourierTransformInterferometry .....................33 3.2.1GeneralPrinciples ..........................33 3.2.2FiniteRetardationandApodization ................36 3.2.3Sampling ...............................38 3.2.4PhaseErrorandCorrection .....................41 3.2.5Step-ScanandRapid-ScanInterferometers ............43 3.3PolarizationModulation ..........................45 vi

PAGE 7

4SUPERCONDUCTIVITY .............................49 4.1Introduction .................................49 4.2FundamentalsofSuperconductivity ....................50 4.2.1FundamentalPhenomena ......................50 4.2.2ThermodynamicProperties .....................54 4.2.3TypesofSuperconductor ......................55 4.2.4LengthScales ............................56 4.2.5BCSTheory .............................62 4.2.6EliashbergFormalism ........................68 5SYNCHROTRONRADIATIONANDPUMP-PROBETECHNIQUE .....70 5.1SynchrotronRadiation ...........................70 5.1.1Introduction .............................70 5.1.2RadiatedPowerfromaBendingMagnet ..............70 5.1.3AngularCollimationandPolarization ...............72 5.1.4RFCavityandPulsedNature ...................74 5.1.5BeamLifetime ............................75 5.1.6InfraredSynchrotronRadiation ..................77 5.1.7SourceComparison .........................78 5.2PrincipleofPump-ProbeStudies .....................80 5.2.1Laser-SynchrotronPump-ProbeMeasurement ...........81 5.2.2InterferometryUsingPulsedSource ................82 5.2.3AdvantageofLaser-SynchrotronTechnique ............84 6EXPERIMENT ...................................85 6.1Introduction .................................85 6.2NationalSynchrotronLightSource ....................85 6.2.1General ................................85 6.2.2VacuumUltravioletRing ......................86 6.2.3BeamlinesU12IRandU10A ....................90 6.3Spectrometers ................................93 6.3.1BrukerIFS66v/S ..........................94 6.3.2BrukerIFS125HR .........................97 6.3.3SciencetechSPS-200 .........................98 6.4PumpLaserSystem .............................100 6.4.1SystemOverview ..........................100 6.4.2Mode-locked,Solid-StateTi:SapphireLaser ............101 6.4.3OpticsandLightDistribution ...................104 6.4.4Laser-SynchrotronSynchronization ................107 6.5OtherExperimentalComponents .....................111 6.5.1OxfordOptistatBathCryostat ...................111 6.5.2Ox-BoxCustom-madeSampleChamber ..............116 6.5.3OxfordInstrumentsVertical-boreSuperconductingMa gnet ...118 6.5.4Detectors ...............................120 6.5.5RatioBox ..............................126 6.5.6FiberOpticCableandPulseDelivery ...............127 vii

PAGE 8

6.6ExperimentalTechniquesandSetups ...................129 6.6.1PhotoinducedMeasurements ....................130 6.6.2LaserInsertion ............................136 7OPTICALCONDUCTIVITYOF -MoGeTHINFILMS ............140 7.1Introduction .................................140 7.2Background .................................141 7.2.1InfraredPropertiesofSuperconductors ..............141 7.2.2EectsofDisorderupon2DSuperconductivity ..........145 7.2.32DModelSystems ..........................147 7.3ExperimentalDetails ............................148 7.3.1Samples ...............................148 7.3.2Measurements ............................151 7.4Analysis ...................................151 7.5Discussion ..................................154 7.6Conclusion ..................................156 8TIME-RESOLVEDSTUDYOF -MoGeTHINFILMS .............159 8.1Introduction .................................159 8.2Background .................................160 8.2.1NonequilibriumSuperconductivity .................160 8.2.2TemperatureDependenceofLifetimes ...............165 8.3ExperimentalDetails ............................169 8.3.1Time-resolvedMeasurements:QuasiparticleDecay ........171 8.3.2PhotoinducedGapShiftMeasurements ..............174 8.3.3FluenceDependence .........................176 8.3.4SpectrallyAveragedFarInfraredTransmission ..........178 8.4AnalysisandDiscussion ..........................179 8.4.1RelaxationTimes ..........................179 8.4.2PhotoinducedGapShift .......................185 8.5Conclusion ..................................187 9MAGNETO-OPTICALSTUDYOF -MoGeTHINFILMS ..........189 9.1Introduction .................................189 9.2TransmittanceRatioinMagneticFields ..................190 9.3RelaxationTimesinMagneticFields ...................191 10SUMMARYANDCONCLUSION .........................192 APPENDIXAVUVSTORAGERINGPARAMETERS .....................197 BINFRAREDBEAMLINES .............................199 B.1InfraredProgramsatNSLSVUVring ...................199 B.2HightResolutionFar-infraredSpectraatU12IR .............200 viii

PAGE 9

CLASERSAFETYANDOPERATINGPROCEDURES .............201 C.1HazardousBeamControl ..........................201 C.2PersonalProtectiveEquipment ......................201 C.2.1EyeProtection ............................201 C.2.2SkinProtection ...........................202 C.3LaserSafetyTraining ............................202 C.4Alignment ..................................202 C.4.1GrossAlignment ...........................202 C.4.2FineAlignment ...........................202 C.4.3AtBeamlineEndstation .......................203 C.5DailyOperationProcedure .........................203 C.6OptimizationoftheDownstreamOptics .................205 C.7ANSILaserClassications .........................206 DUSEFULINFORMATION .............................209 D.1FrequencyRanges ..............................209 D.2EnergyandPressureUnitsConversion ..................211 D.3Gas-phaseContamination .........................211 REFERENCES ......................................213 BIOGRAPHICALSKETCH ...............................219 ix

PAGE 10

LISTOFTABLES Table page 4{1Transitiontemperaturesforseveralsuperconductors .............51 6{1OperationmodesoftheVUVring .......................88 6{2Frequencyrangesofvarioussources ......................95 6{3Frequencyrangesofvariousbeam-splitters ..................96 6{4Frequencyrangesofvariousdetectors .....................96 6{5SpecicationsoftheSPS-200 ..........................101 6{6SpecicationoftheMira ............................103 6{7PropertiesofOxfordcryostatwindows .....................114 6{8Characteristicsofberopticcable .......................127 7{1 -MoGelmparameters ............................149 7{2 T s = T n ttingparameters ...........................152 7{3Valuesof N s and ................................155 8{1 -MoGelmusedfortimingexperiment ....................170 8{2Parametersforthetimingexperiment .....................171 8{3Fluencedependencedata ............................177 8{4 e and A atvarioustemperatures .......................180 8{5Materialparametersin R 0 and B 0 .......................182 8{6 r R 0 B 0 ,and R 0 = B 0 ............................182 8{72 0 B 0 = R 0 ....................................183 8{8RelaxationtimesandmaterialparametersfromKaplan etal. ........184 8{9Photoinducedgapshifts .............................186 A{1VUVstorageringparameters ..........................197 A{2VUVstoragering'sarcsourceparameters ...................198 A{3VUVstoragering'sinsertiondeviceparameters ................198 x

PAGE 11

A{4NSLSlinacparameters .............................198 A{5NSLSboosterparameters ............................198 A{6NSLSboostermagneticelements ........................198 B{1InfraredbeamlinesoftheVUVring ......................199 D{1Infraredspectralregions .............................209 D{2Frequencyrangesofconventionallightsources ................209 D{3Frequencyrangesofdetectors ..........................209 D{4Spectralrangesofbeam-splitters ........................210 D{5Transmissionrangeofopticalwindowandltermaterials ..........210 D{6Relationsbetweenenergyunits .........................211 D{7Relationsbetweenpressureunits ........................211 D{8Absorptionpeaksduetoair ...........................212 xi

PAGE 12

LISTOFFIGURES Figure page 2{1Rerectionandtransmissionattwoparallelinterfaces ............18 2{2Rerectionandtransmissionwithathinlmonasubstrate .........21 3{1Spectrometerclassication ...........................32 3{2SchematicviewofaMichelsoninterferometer .................34 3{3Sincfunctionconvolvedwithasinglespectralline ..............37 3{4ComparisonoftheHapp-Genzelandboxcarapodization ..........39 3{5Relationbetweenspectrumreplicationandsamplingrate ..........40 3{6Twosinewavesdrawnthroughthesamesamplingpoints ..........41 3{7SchematicviewofaMartin-Puplettinterferometer ..............46 3{8Interferogramsproducedbyapolarizinginterferomete r ...........47 4{1DensityofstatesforaBCSsuperconductor ..................65 4{2VariationofthegapwithtemperatureintheBCSapproxim ation .....66 5{1Incoherentandcoherentradiations ......................72 5{2Angulardistributionoftheradiation .....................72 5{3Angulardistributionofpolarizationcomponents ...............74 5{4RFandhigherharmoniccavityvoltages ...................76 5{5NaturalopeningangleofIRSRwiththeVUVringparameters .......78 5{6Powercomparisonbetweenblackbodyandsynchrotron ...........79 5{7Brightnesscomparisonbetweenblackbodyandsynchrotron .........80 5{8Principleofthepump-probeexperiment ...................81 6{1Changeofthepulsewidthduringthedetunedmodeoperatio n .......89 6{2ElevationviewofU12IRbeamline .......................91 6{3Transmittedpowerwithandwithoutalightcone ..............92 6{4Emissionspectraofconventionalinternalsources ...............95 xii

PAGE 13

6{5BrukerIFS125HR ...............................98 6{6SciencetechSPS-200 ..............................99 6{7OpticalschematicoftheMiralaserhead ...................102 6{8OpticalLayoutoftheU6lasersystem .....................105 6{9Eectsofthepulsepickers ...........................107 6{10Timingscheme .................................108 6{11Synchronizedlaserandsynchrotronpulses ..................110 6{12OxfordOptistatbathcryostat .........................111 6{13Custommadesamplecompartment ......................117 6{14O-axisparaboloidalrerector .........................118 6{15Oxfordmagnetsetup ..............................119 6{16Transferfunction ................................121 6{17Classicationofdetectors ............................122 6{18Compositebolometer ..............................124 6{19Structureandproleoftypicalopticalbercable ..............128 6{20Experimentalsetupfortimingexperiment ..................134 6{21Newditheringscheme ..............................135 6{22LaserinsertionsetupswithOptistat ......................137 6{23LaserinsertionsetupwithHeli-tran ......................138 6{24Couplingofdiodelaserwithopticalbercable ................138 7{1Mattis-Bardeenrelativeconductivityandtransmittance ...........143 7{2 R 2 vs.1 =d ....................................149 7{3 T c =T c 0 vs. R 2 ..................................150 7{4Measuredtransmittanceratio .........................152 7{5Mattis-Bardeentto T s = T n .........................153 7{6Measuredrerectanceratio ...........................154 7{7Mattis-Bardeentto R s = R n .........................155 7{8Opticalconductivitiesof -MoGe .......................156 7{9 N s vs. R 2 ...................................157 xiii

PAGE 14

7{10 N s vs. T c .....................................158 8{1Simpliedrelaxationprocesses .........................163 8{2Universaltemperaturedependenceoflifetimes ................168 8{3Dierential,integratedsignalvs.time .....................172 8{4Quasiparticledecaysignalvs.timeandmodelfunction ...........173 8{5Pointsonadecaycurveforgapshiftmeasurements .............175 8{6Fluencedependenceof e ...........................176 8{7Spectrallyaveragedfar-IRtransmittionvs. T=T c ...............178 8{8Quasiparticledecaysignalfor16.5nmlm ..................180 8{9 e vs. T=T c ...................................181 8{102 0 B 0 = R 0 vs. T c ................................183 8{11 R 0 = B 0 vs. b ...................................185 8{12Photoinducedspectralchanges .........................186 9{1Measuredtransmittanceratioinmagneticelds ...............190 9{2Quasiparticledecaysignalinmagneticeldforthe33nml m .......191 B{1Highresolutionfar-IRsynchrotronspectraatU12IR .............200 xiv

PAGE 15

AbstractofDissertationPresentedtotheGraduateSchool oftheUniversityofFloridainPartialFulllmentofthe RequirementsfortheDegreeofDoctorofPhilosophy TIME-RESOLVEDINFRAREDSTUDIESOFSUPERCONDUCTING MOLYBDENUM-GERMANIUMTHINFILMS By HidenoriTashiro December2004 Chair:DavidB.TannerMajorDepartment:Physics Superconductingamorphousmolybdenum-germanium( -MoGe)thinlmsshow progressivelyreducedtransitiontemperatures T c asthethicknessisreduced.This suppressionhasbeenexplainedintermsofelectronlocalizati oneectsandreduced screening.Thisdissertationpresentstheresultsofbothlinear spectroscopyandtimeresolvedstudiesofasetof -MoGelmstounderstandmorefullythisweakened superconductingstate.Theobservedopticalconductivityshow sthepresenceofan energygap.Theeectsofreducedthicknessintheselmsareto depress T c andthe superruiddensity,whilemaintainingthenormal-stateresistiv ity.Alloftheresultsfrom ourlinearopticalmeasurementsappeartobeconsistenttrivia llywiththoseexpected forweaktointermediatecouplingdirtylimitsuperconducto rs.Ourtime-resolved studyrevealstheoverallrelaxationofthesamplesatatimesca leontheorderof100 ps.Thetemperaturedependenceoftherelaxationtimeseemsto beconsistentwith thepredictionbasedonweak-couplingBCStheoryforalllms wemeasuredwithout changinganymaterialparametersfordierentthickness.The applicationofmagnetic elddidnotchangetherelaxationtimes,whichwasunexpecte d. xv

PAGE 16

CHAPTER1 INTRODUCTION 1.1IntroductoryRemarks Spectroscopyisaveryusefultechniqueforinvestigatingthep ropertiesofvarious typesofmaterials.Informationonthematerialisencodedin theradiationspectrum modiedthroughinteractionwiththematerial.Theextensiv eenergyrangecoveredby electromagneticradiationallowsustostudymanypropertie s( e.g. ,electronic,magnetic, lattice,andsoon)dependingonthefrequencyranges.Forexam ple,theconductivity peakforfreecarriersiscenteredatzerofrequency.Lattic evibrations( i.e. ,phonons) interactwithelectromagneticradiationatfar-infraredf requencies.Electronictransitions acrosstheenergygapofasemiconductorlikeSihappeninthene arinfrared.Transitions fromcorelevelsrequireevenhigherenergies.Insuperconduc tors,anenergygap developsintheelectronicdensityofstatesaroundFermiener gy.Thetypicalenergy scaleofthisgapisinmeV,whichcorrespondstothefrequencies betweenmicrowaveand farinfrared.Thus,opticalstudiesinthisfrequencyrangepr ovideanimportanttoolfor investigatingsuperconductors. Asynchrotronisasourceofhighbrightnesselectromagneticra diationemittedfrom electronsorbitingaroundaclosedpathofastoragering.Itis averybroad-bandsource, extendingfromtheveryfarinfraredtothehardx-ray.Becau seelectronsarebunched astheytravel,theradiationemittedfromthesynchrotronsou rceispulsed.Beamlines U10AandU12IRaretwobeamlinesontheVUVringattheNationalSync hrotron LightSource(NSLS)ofBrookhavenNationalLaboratory(BNL)de dicatedtosolid-state physicsexperiments.TheNSLSprovidesapowerful,tunable,ne ar-infrared/visible mode-lockedTi:Sapphirelaser,whichproducespulsesofafew picosecondsduration synchronizedtothesynchrotronpulses.Aspecimencanbeexcited (pumped)bylaser pulses,andprobedbyinfraredsubnanosecond-durationsynchrot ronpulsesfromthe 1

PAGE 17

2 VUVring[ 1 2 ].Dependingonthemodeofsynchrotronoperation,thisfacil ityprovides auniqueopportunityformeasuringtransientphenomenaontim escalesinafew100 psupto170nsrangeoverabroadspectralregion.Withpropert uningofexcitation energy,thedynamicsofvarioussystemscanbeinvestigated:qu asiparticlerelaxation inconventionalBCSsuperconductors,recombinationoftheph otogeneratedelectronholeplasmainsemiconductors,dynamicsofthephotodopedpola ronsandsolitons inconductingpolymers,andrelaxationofphotoinducedcond uctivityeectsinthe insulatingphaseofhighT c superconductors,tonameafew.Useofasuperconducting magnetalsoallowsustostudymaterialsinmagneticelds. 1.2Motivation Thisdissertationdescribesopticalstudiesonasetofsupercondu ctingamorphous molybdenum-germanium( -MoGe)thinlmsdepositedonthickinsulatingsubstrates. AllmeasurementswereperformedatthetwobeamlinesontheNSLS VUVring.Itis wellknownthatincreasingdisorderleadstolocalizationand therelatedenhancements oftherepulsiveelectron-electronCoulombinteraction[ 3 4 5 ].Itisalsowellknown thatinsuperconductors,twoelectronsformapairduetophono nmediatedattractive interaction.Thus,theenhancedCoulombinteractioninhere ntlycompeteswithsuperconductivity. -MoGeisawell-studieddisorderedsystemusedforstudyingtheint erplay betweensuperconductivityanddisorder.Itstransportproper tieswereinvestigatedby Graybeal[ 6 7 8 ],andshowedprogressivelyreducedtransitiontemperatures( i.e. ,a weakenedsuperconductingstate)asthethicknessisdecreased. Inthiswork,wehaveset outtounderstandthissystemevenfurther,andpossiblyndsomesor tofconnections betweenreducedtransitiontemperatureandthedegreeofdiso rder.Forthispurpose, werstundertookathoroughstudyoflinearspectroscopyinthef arinfrared.Then, thedynamicsofthesystemwasstudiedbyapump-probetechnique .Drivingsuperconductorstononequilibriumstatescorrespondstobreaking Cooperpairs,producing excitationscalledquasiparticles.Inreturningtoequilibr ium,thesequasiparticlesrecombineintopairs,releasingenergyusuallyasphonons.Therateat whichthisrelaxation

PAGE 18

3 progressesinvolvestheinteractionbetweenquasiparticles,w hichisoffundamental interestforanytheoryofsuperconductivity. 1.3Organization InChapter 2 wereviewabasictheoryofopticalproperties.Someofthecomm on techniquesandmodelsusedforextractingopticalparameter sfromexperimentsare discussed.Chapter 3 providestheconceptsofFourierspectroscopy.Twotypesof interferometersaredescribed:amplitudemodulationandpo larizationmodulation. Chapter 4 summarizesafewfundamentalpropertiesofsuperconductorsw ithinthe frameworkofBCStheory.TherstpartofChapter 5 describesthepropertiesof synchrotronradiation.Comparisontoconventionalthermalso urcesrevealsadvantages ofusingsynchrotronradiationforspectroscopicstudyparticul arlyinthefarinfrared frequencies.Thesecondpartofthechapterisintendedtointr oducethebasicideaof thepump-probetechniqueusingalaserasthepumpsourceandsync hrotronradiation astheprobesource.Readingthispartofthechapterpriortor eadingthefollowing chaptersisrecommended.Chapter 6 describesindetailallexperimentalcomponents, techniques,andsetupsusedinthisproject.Thespecicsofthea pparatussuchasthe NSLSVUVstoragering,beamlines,spectrometers,lasersystem,andoth ersareall includedinthischapter.Chapters 7 and 8 discussourexperimentalresultsoflinear andtime-resolvedstudyon -MoGethinlms,respectively.Eachchaptercontainsa theoreticalbackgroundspecictotheanalysisusedinthechap ter.Finally,Chapter 9 showstheresultsofourmostrecentexperimentofmagneto-opti calmeasurements. Inopticalstudies,dierentenergyunitsarequitecommonfor thedierenttechniques,frequencyranges,anddisciplines.Intheinfraredspect ralregion,themost commonlyusedunitisthewavenumbergivenbycm 1 .Itisdenedasthefrequencyin Hzdividedbythespeedoflightincm/sorthereciprocalofwave lengthincm.Inthis dissertation,thewavenumberisusedinterchangeablywithfre quencyorenergysincethe valuesfortheseunitsaresimplyrelated.

PAGE 19

CHAPTER2 OPTICALPROPERTIES 2.1Introduction Inthischapter,wewillprovideageneralbackgroundofthet heoryofoptical properties.Thechapterbeginswithveryintroductorydiscussi onofanumberof phenomenathatcanoccuraslightpropagatesthroughamediu mandthecoecients thatareusedtoquantifythem.ThebasicresultsofMaxwell'seq uationsalsowillbe summarized.Inthefollowingsection,wewillshowseveraltechn iquesforextracting opticalparametersfromexperimentaldatameasuredonsample sincommonforms.At theendseveralmicroscopicmodelswillbedevelopedtoexplai ntheopticalphenomena thatareobservedinthesolidstate.Themainpurposeofthechapt eristogiveabasic theoryandtechniquesingeneralterms,andalsotobeusedasqui ckreference. 2.2OpticalPhenomena Inthesimplestway,rerection,transmission,andpropagationar ethethreesimplestgroupsofopticalphenomenathatareobservedinsolidstat ematerials.Whena lightwavepropagatinginonemediumencountersanothermed ium,someofthelightis rerectedfromtheinterface,whiletheresttransmitsintothe mediumandpropagates throughit.Thelightalsoexperiencesavarietyofopticalph enomenaduringthepropagationwithineachmedium.Thelightraysarebentattheinte rfaceduetothechange inthevelocityofthelightwaveindierentmedia.Thisiskn ownasrefraction,andis describedbySnell'slaw.Thelightmaybeattenuatedasitpro pagatescausedbyprocessessuchasabsorptionorscattering.Absorptionoccursifthefr equency( i.e. ,energy ofphoton)ofthelightisresonantwiththetransitionenergyo ftheatomsandelectrons inthemedium.Hence,absorptioncausesreductionofthenumber ofphotonsinthe forwarddirection.Intheeventofscattering,thelightbeam isre-directedinotherdirectionscausedbythepresenceofimpurities,defects,orinhomoge neities.Thisobviously 4

PAGE 20

5 causesattenuationintheoriginaldirectioninananalogous waytoabsorptioneven thoughthenumberofphotonsisunchanged.Scatteringcanal soaccompanychangesin frequencyofthelight.Ifthefrequencyofthescatteredligh tischanged,itissaidtobe inelastic;ifitisunchanged,itissaidtobeelastic.Luminesce nceisthephenomenonof spontaneousemissionoflightbytheexcitedatomsinamedium.T helightisemittedin alldirections,andhasadierentfrequencytotheincomingl ight. Withconventionalsourcesoflight,opticalpropertiesared escribedbylinearoptics, whereitisassumedthatquantitiessuchastherefractiveindex ,absorptioncoecient, andrerectivityareindependentoflightintensity.Thisisb asedonanapproximation thatisonlyvalidinthelowintensitylimit,andpractically everythingwewillbe discussinginthisdissertationfallsintotherealmoflinearopt ics.Whenhighintensity lightpropagatesthroughamedium,anumberofnonlinearphe nomenacanoccur. Frequencydoublingandtriplingareexamplesofthesenonlin eareects,andarerealized throughtheuseoflasers.Thisisthesubjectofnonlinearoptics, whereitallowsthe electricsusceptibilityaswellasallthepropertiesthatfol lowfromittovarywiththe strengthoftheelectriceldofthelightbeam.Eventhoughno nlinearopticsisan interestingsubjectinitsownright,itwillnotbediscussedfurt her. Opticalphenomenacanbequantiedbyanumberofopticalcon stants(optical parameters)thatdescribethemacroscopicbehaviorofthemedi um.Thererectionfrom aninterfaceofdierentmediaisdescribedbythererectance R ,denedastheratio ofthepowerofrerectedlighttothatofincidentlightonthe surface.Transmission throughtheinterface,ontheotherhand,isdescribedbythet ransmittance T ,dened astheratioofthetransmittedpowertotheincidentpower.At theeveryinterfacethe lightwaveencounters,conservationofenergyrequiresthat R + T =1 : (2.1) Therefractionisdescribedbytherefractiveindex n ,denedas n = c v ; (2.2)

PAGE 21

6 where c and v arethespeedoflightinfreespaceandinthemedium,respective ly. Therefractiveindexdependsonthefrequencyofthelightwa ve,whichisknown asdispersion,andcharacterizesthepropagationofthelight throughatransparent ( i.e. ,non-absorbing)medium. Theabsorptionoflightbyamediumisquantiedbytheabsorpti oncoecient denedasthefractionofthepowerabsorbedinaunitlengthof themedium.Interms ofadierentialequation,theeectofabsorptionisgivenby dI = dx I ( x ) ; (2.3) where I ( x )istheintensityoflightatposition x .Thesolutiontothisequationisthe exponentialdecayoflightintensityasitpropagatesthroug hthemedium: I ( x )= I 0 e x : (2.4) Thefrequencydependenceoftheabsorptioncoecientisrespo nsibleforthecolorof materials. Rayleighscatteringiscausedbyvariationsoftherefractive indexofthemediumon alengthscalesmallerthanthewavelengthofthelight.Asmenti onedearlier,scattering hassimilarattenuationeectasabsorption,andtheintensity oflightasitpropagates canbeexpressedby I ( x )= I 0 e N s z ; (2.5) where N isthenumberofscatteringcenterperunitvolume,and s isthescattering cross-sectionofthescatteringcenter. Thefrequencydependentrefractiveindex n ( )andabsorptioncoecient ( ) arethetwoimportantquantitiesthatcharacterizetheprop agationoflightwaveina mediumsincetheydescribethedispersiveandabsorptivenatureo famaterialinthe mostdirectway.Therefractionandabsorptionofamediumcanb edescribedbya

PAGE 22

7 singlequantitycalledthecomplexrefractiveindex: 1 ~ N = n + i; (2.6) where n (realpartof ~ N )istherefractiveindexdenedinEq. 2.2 ,and (imaginary partof ~ N )istheextinctioncoecientthatisdirectlyrelatedtothe absorptioncoecient aswillbediscussedshortly. Afewexamplesofopticalquantitiesthathavebeendiscussedsof arprovide descriptionsoftheopticalphenomenaonlyfromthepointofv iewofthererection, transmission,andpropagation,andoerthemostusefulinformat iontomanufacturers ofopticalelements.Thefrequencydependentrerectance R ( )andtransmittance T ( ) aretheexperimentallymeasurablequantitiesfromwhichoth erparameterssuchasthe complexrefractiveindex ~ N canbederived.Themicroscopicmodels,however,usually enableustocalculateotherparameterssuchasthecomplexdi electricfunction~ and complexconductivity~ ratherthan ~ N .Therelationshipbetween~ and ~ N provides directconnectionbetweenmicroscopicmodelsofmaterialsa ndpropagationpropertiesof electromagneticwaves. 2.3InteractionofLightwithMatter Thissectionsummarizestheprincipalresultsofelectromagne tismthataresucient forthestudyofopticalpropertiesofsolids.Detailsofthesubj ectcanbefoundinmost booksonopticsandelectromagnetism[ 9 10 11 12 13 14 15 16 ].CGSunitsareused throughoutunlessotherwisespecied. Theresponseofamaterialtoexternalelectricelds E ischaracterizedbyafew macroscopicvectors:polarization P ,electricdisplacement D ,andcurrentdensity J Withinthelinearapproximation,thesethreevectorsarepro portionaltotheelds E 1 Theuseofcomplexquantitiessuchasthecomplexrefractivein dex,dielectricconstant,andconductivitytodescribepropertiesofmediumnatu rallyarrivesfromtheuse ofcomplexsolutionstotheMaxwell'sequations.Thispointwi llbeclearafterreading x 2.3

PAGE 23

8 ( e.g. P / E ),andtheirproportionalityconstantsarethelinearresponse functions whichdescribepropertiesofthesolid-statesystemitselfandare independentofthe drivingforce.Thelinearresponseisformulatedintimeandspa ce.Sincetheresponseis, ingeneral,frequencyandwavevectordependentanditiscon venienttohandleharmonic functions,adiscussioninFourierspace,bothwithrespecttotime andcoordinates,is moreappropriate.Thus,ratherthanstudyingtheresponsefunct iondirectly,thelinear relationbetweentheFouriertransformofthedrivingforcea ndtheFouriertransform ofthesystemresponseisconsidered.Also,wewillusethetime-varyi ng E inthe formofexp( i!t ),andexpresstheproportionalityconstantasacomplexquant ityto accountforthephaseshiftbetweentwoelds:areal(animagina ry)partrepresentsthe responseofamediumin(outof)phasewiththeappliedelectric eld.Inaddition,the assumptionofisotropic,homogeneousmediumwasmadetosimplif ythediscussions. 2 Thepolarizationisdenedasthenetdipolemomentperunitv olume.Withinthe assumptionmadeabove,themicroscopicdipoles(bothpermanen tandinduceddipole moments)tendtoaligninthedirectionoftheexternaleld.T hisallowsustodenea polarizationas P =~ e E ; (2.7) where~ e isthecomplexelectricsusceptibilityofthemedium,whichis oneofthemost fundamentalresponsefunction. Theelectricdisplacementofthemediumisdenedby D E +4 P : (2.8) Theabovetwoequationscanbecombinedtogiveanalternativ eexpression: D =~ E ; (2.9) 2 Anisotropiccrystalshavenonequivalentopticalpropertiesa longdierentcrystalline axes.Thephenomenonofbirefringenceisanexampleofoptica lanisotropy.Insuchmaterials,theproportionalityconstantsmustberepresentedbya tensor.

PAGE 24

9 where ~ 1 + i 2 =1+4 ~ e : (2.10) Theparameter~ isacomplexdielectricconstant(ordielectricfunction). Whentimevarying E isapplied,thereisanassociatedmotionofeachelementof charge.Thisleadstoarelationshipbetweenthecurrentdensi ty J andpolarizationas J = @ P @t = i! P : (2.11) Inasimilarwayto P and D ,thecurrentdensitycanalsobewrittenas J =~ E ; (2.12) where ~ 1 + i 2 : (2.13) Theparameter~ isthecomplexconductivityofthemedium.Generally,thecu rrent density J isthesumoftwocontributions:onearisingfromthemotionofch argesthat arefreetomovethroughthemedium J free ,andtheotherarisingfromchargesthatare restrictedtolocalizedmotion J bound Opticalconstantssuchas~ e ,~ ,and~ representtheresponseofamedium( i.e. ,responsefunctions)toaperturbingeldoffrequency 3 Alloftheseparameters, however,arenotindependent.Theyareallinterrelatedtoo neanother.Ascanbe seenfromEq. 2.10 ,~ e and~ providethesameinformation.UsingEqs 2.7 2.10 2.11 and 2.12 ,wecanndausefulrelationshipbetween~ and~ : ~ =1+ i 4 ~ ; (2.14) 3 Theresponsefunctionsshouldbeconsideredasafunctionofboth frequency andwavevector k .However,theexplicitdependenceoftheresponsefunctionson k ( i.e. ,wavelength),theso-calledspatialdispersion,canbeneglect edincasetheelds couldbeaveragedoveraunitcell.Spatialdispersionariseswh enevertherelationbetween D and E isnotexactlylocalwith D ataparticularpointdeterminedsolelyby E atthatpoint.

PAGE 25

10 orexplicitly 1 = 2 4 ; (2.15) 2 = (1 1 ) 4 : (2.16) Thusopticalmeasurementsof~ ( )areequivalenttoconductivitymeasurementsof~ ( ). Incaseourinterestisintheopticalresponsesduetothefreecar riergasinmaterials suchasmetalsanddopedsemiconductors,opticaldataarefrequ entlydiscussedinterms oftheconductivityratherthanthedielectricconstant. Later,wewillshowtheconnectionbetweentheopticalparame tersdescribedhere andthepropagationconstantsofelectromagneticwavesinam edium,namelythe complexrefractiveindex ~ N Theresponseofamaterialtoexternalmagneticeldsischarac terizedinasimilar way.Themagnetization M isdenedasthenetmagneticmomentperunitvolume,and isproportionaltomagneticeldstrength H : M =~ m H : (2.17) Theparameter~ m isthemagneticsusceptibility. Themagneticruxdensity B isdenedby B = H +4 M : (2.18) Theabovetwoequationscanbecombinedtogive B =~ H ; (2.19) where ~ =1+4 ~ m : (2.20) Theparameter~ isthepermeabilityofthemedium.Atopticalfrequencies,an y paramagneticorferromagneticmomentscannotfollowthera pidoscillationsofmagnetic eldbecauseoftheirlongrelaxationtimes.Theremainingdia magneticmomentsare

PAGE 26

11 sosmallastohavenoappreciableeectonopticalbehavior.Th us,unlesswestudy magneto-opticalphenomena,wecanset B = H Thestartingpointforthetreatmentofinteractionbetweene lectromagneticelds andmatteriscontainedwithinthefourMaxwell'sequations fortheaverageelds. 4 In theabsenceofexternalcharges,theseequationsaregivenby r ~ E =0 ; (2.21) r H =0 ; (2.22) r E = 1 c @ H @t ; (2.23) r H = 1 c @ ~ E @t ; (2.24) where~ isthecomplexdielectricconstantdenedinEq. 2.14 ,whichallowsthecurrent densityarisingfromfreecarriers( i.e. ,Ohm'slaw)tobeincludedinEq. 2.24 Weconsiderthesolutioncorrespondingtoaplanewaveoftheang ularfrequency : E H = E 0 H 0 exp[ i ( ~ k x !t )] ; (2.25) whereaconstantamplitudevector E 0 isingeneralcomplex.Thecomplexwavevector ~ k wasusedtodescribeenergydissipationofthewave.Substitution ofEq. 2.25 intothe Maxwell'sequationsyields ~ ~ k E =0 ; (2.26) ~ k H =0 ; (2.27) ~ k E = c H ; (2.28) ~ k H = c ~ E : (2.29) 4 Theuseoftheso-calledmacroscopicMaxwell'sequationscanbe justiedasfollows. Inopticalmeasurements,featuresthatcanbeprobedarethesiz eoftheorderofawavelengthoflightorlarger.Sinceasolidcontainsnumerousato mswithinthelengthscale ofthewavelengthoflight,itcanbetreatedasacontinuousm edium

PAGE 27

12 Herewehaveassumedanisotropic,homogeneous,andnon-magnetic mediumsothat ~ hasnospatialvariation.Equationsareseparatelycorrectfo rboththerealand imaginaryparts.Theseequationsarecombinedtoyieldarelat ionbetweenthewave vectorandfrequencyknownasthedispersionrelationship: ~ k ~ k = 2 c 2 ~ : (2.30) Inanon-absorbingmediumofrefractiveindex n ,thewavelengthofthelightis reducedbyafactor n comparedtothefreespacewavelength 0 (=2 c=! ).Therefore, wavevector k isgivenby k = 2 0 =n = !n c : (2.31) Thisleadstothephasevelocity !=k = c=n inEq. 2.2 .Thewavevectorcanbe generalizedtothecaseofanabsorbingmediumbyallowing n (andasaresult k too)tobecomplex: ~ k = c ~ N = c ( n + i ) : (2.32) Eq. 2.30 andEq. 2.32 allowustorelatethepropagationpropertiesoflightthrou gha mediumtotheresponseofthemediumintheelectromagneticel dsas ~ N = p ~ ; (2.33) orexplicitly 1 = n 2 2 ; (2.34) 2 =2 n; (2.35) and n = 1 p 2 h 1 + 21 + 22 1 2 i 1 2 ; (2.36) = 1 p 2 h 1 + 21 + 22 1 2 i 1 2 : (2.37)

PAGE 28

13 Eqs. 2.26 2.29 alsoshowthat E H ,and ~ k aremutuallyperpendicular( i.e. ,transversewaves),andthescalarrelationbetween E and H isgivenby H = p ~ E = ~ NE: (2.38) Theratio(4 =c ) E=H iscalledthewaveimpedance ~ Z : ~ Z Z 0 E H = 1 p ~ = 1 ~ N ; (2.39) where Z 0 isthewaveimpedanceoffreespace,whichhasavalueof Z 0 =4 =c (or377n inSI). OnsubstitutingEq. 2.32 intoEq. 2.25 ,wendthattheeldsattenuatease !x=c Theopticalintensityoflightisproportionaltotheabsolute squareoftheelectric eld 5 ( I / E E ).Thus,fromEq. 2.4 ,wendthat = 2 c = 4 0 ; (2.40) where and aretheabsorptionandextinctioncoecients,respectively.T hepenetration(orskin)depth isthecharacteristiclengthoftheelds'penetrationintoa mediumdenedby 2 = c : (2.41) Theaveragerateofdissipationofelectromagneticenergyden sityis W = h Re( E ) Re( J ) i = 1 2 Re( E J )= 1 2 1 j E j 2 : (2.42) Thusonlythecurrentthatisinphasewith E contributestoanenergyloss,and 1 representstheresistiveresponse( i.e. ,absorptionthataccompaniestheenergyloss) ofthemediumintheelds.Theoutofphasecurrent,ontheother hand,doesnot accompanytheenergyloss,and 2 describesthereactiveresponse.The~ iscalledthe 5 Thetime-averagedenergyrowintheelectromagneticwaveis calculatedfromthe realpartofthecomplexPoyntingvector S = 1 2 c 4 ( E H ).Themagnitudeofthisvector givestheintensityofthelightwaveproportionaltothesquar eoftheeld.

PAGE 29

14 opticalconductivitysincetheresponseconcernedherearisesf romtransitionsasaresult ofphotonabsorption. Wehavesofarconsideredonlytransversewaves( i.e. k ? E ).However,Eq. 2.26 canalsobesatisedforlongitudinalwaves( i.e. k k E )foranyfrequency l provided that~ ( l )=0.Atthisfrequency,longitudinalwavescanpropagateth roughamedium andcontributetotheenergylossthatisproportionaltotheso -calledlossfunction denedas Im 1 ~ = 2 21 + 22 = 2 n ( n 2 + 2 ) 2 : (2.43) ThelongitudinalwavescanexciteLOphononmodesattheLOfr equencies. Inanonlyweaklyabsorbingmedium( i.e. n ),Eqs. 2.34 and 2.35 simplifyto n = p 1 ; (2.44) = 2 2 n = 0 1 cn : (2.45) Theseequationstellusthattherefractiveindex n isapproximatelydeterminedby 1 whiletheabsorptionismainlydeterminedby 2 (or 1 ). Thepurposeofthissectionhasbeentoprovidesomeoftheoptica lconstants thatdescribeopticalpropertiesofamedium,aswellasthere lationshipbetweenthese constants.TherelationssuchasEq. 2.30 and 2.33 aretheconnectionsbetweenthe macroscopicopticalparameterssuchas ~ N andquantitiesthatcanbecalculatedby microscopictheorysuchas~ .Notethatalltheopticalconstantsdescribedherearein generalfrequencydependentprovidinginformationabouth owphotonsofparticular energy, ~ ,interactwithelectrons,phonons,andotherexcitationsint hesystem. Detailedanalysisofopticalconstantsallowsustounderstand variouspropertiesof solids.Forexample,knowledgeoftheelectronicpropertieso fsolidsisthekeyto understandingmostoftheirphysicalandchemicalproperties.

PAGE 30

15 2.4ExperimentalDeterminationofOpticalConstants Informationaboutsolidmaterialsisoftenobtainedbystudyi ngtheelectromagnetic wavesrerectedfromand/ortransmittedacrossinterfacesbet weenmaterialswithdifferentopticalproperties.Thiscanbedonebyconsideringthe boundaryconditionsof the E and H eldsandtheenergyconservation.Inexperiment,weusuallym easurethe fractionofenergyrerected[ i.e. ,rerectance, R ( )]fromand/ortransmitted[ i.e. ,transmittance, T ( )]throughaspecimen.Theformofaspecimenusuallydetermines which measurementtechniquehastobeemployed.Ourmaingoalistod educethedielectric functionaswellasotherfunctionsdirectlyrelatedtoit.I nthissection,wewilldiscussa fewexamplesofsimpleproceduresusedfordeterminingoptica lconstants. 2.4.1RerectionandTransmissionataPlaneInterface Werstconsiderthetransmissionandrerectionoflightataplane interface betweentwomediawithdierentrefractiveindices, ~ N 1 and ~ N 2 .Forsimplicity,wewill assumethelightisincidentnormaltotheinterface.Then,the boundaryconditions requirethatthetangentialcomponentsoftheelectricandm agneticeldsareconserved suchthat E i + E r = E t and H i H r = H t ; (2.46) where i r ,and t refertothecomponentsoftheincident,rerected,andtransm itted elds,respectively.Usingtherelationbetween E and H fromEq. 2.38 theboundaryconditionsyieldtheamplitudererectioncoecientand amplitudetransmission coecientas 6 ~ r = E r E i = ~ N 1 ~ N 2 ~ N 1 + ~ N 2 ; (2.47) and ~ t = E t E i =1+~ r = 2 ~ N 1 ~ N 1 + ~ N 2 : (2.48) 6 Foranarbitraryangleofincidenceamoregeneraltreatment isrequired.Thererectionandtransmissioncoecientsarethengivenbyformulaekno wnasFresnel'sequations[ 9 ].

PAGE 31

16 Thererectance(orrerectivity)istheintensityrerectionc oecient.Ifthelightis incidentonamediumfromavacuumside,thererectanceothem ediumissimply givenby R =~ r ~ r = (1 n ) 2 + 2 (1+ n ) 2 + 2 ; (2.49) wherewehaveused ~ N 1 =1and ~ N 2 = n + i .Thisisthevalidequationforthe single-bouncererectancemeasuredfromathickcrystal( i.e. ,abulkmaterial)withits thicknessmuchgreaterthanthepenetrationdepth( d ). FromEq. 2.49 ,itisobviousthatrerectancedataalonecannotdetermineb oth n and .Itisingeneralnotpossibletodeterminebothcomponentsfro mthemeasurementofjustoneopticalparameter,suchasrerectance.Theref ore,weneedseparate measurementofeither n or bysomeothermeans,ortodosomethingelseinconjunctionwithrerectancemeasurement.TheKramers-Kronigr elationsoerpractical solutiontothisproblemasdiscussedbelow.2.4.2Kramers-KronigDispersionRelations TheKramers-Kronigrelations(KK)areintegralrelationshi psbetweenrealand imaginarypartsofacomplexfunction,suchasthelinearrespo nsefunctions~ ( ), ~ ( ),and ~ N ( ),asaresultofinvokingthelawofcausalityandapplyingthec omplex analysis. 7 Oneoftherequirementsfortherelationshipstobevalidisth attheresponse functionvanishesfor !1 .TheKKrelationsforthecomplexrefractiveindexandthe complexdielectricfunctionmaybestatedasfollows: n ( ) 1= 2 P Z 1 0 0 ( 0 ) 0 2 2 d! 0 ; (2.50) ( )= 2 P Z 1 0 n ( 0 ) 1 0 2 2 d! 0 ; (2.51) 7 Inaphysicalsystem,responsefunctionsmustsatisfy G ( )= G ( ).Forthedielectricfunction,thisconditionleadsto 1 ( )= 1 ( )and 2 ( )= 2 ( ).Inother words, 1 ( )isanevenand 2 ( )isanoddfunctionofthefrequency

PAGE 32

17 and 1 ( ) 1= 2 P Z 1 0 0 2 ( 0 ) 0 2 2 d! 0 ; (2.52) 2 ( )= 2 P Z 1 0 1 ( 0 ) 1 0 2 2 d! 0 ; (2.53) where P standsfortheCauchyprincipalvalueoftheintegral.Simila rrelationsare availableforotherlinearresponsefunctions.Fromtheserelat ionsweseethatifthereal partofaresponsefunctionisknownoveranentirefrequencyra nge(0
PAGE 33

18 d Medium 1, N 1 Medium 2, N 2 Medium 3, N 3 RT Figure2{1:Rerectionandtransmissionattwoparallelinterfa ces.Thethicknessofthe secondmediumis d .Weassumethecaseofnormalincidence,butthebeamsaredrawn atanangleforaclarity.FromEq. 2.49 andEq. 2.55 ,wecandetermine n ( )and ( ),thedielectricfunction, andallotherrelatedfunctions. 8 2.4.3RerectionandTransmissionatTwoParallelInterface s Ifthelightisincidentonaplaneinterface(betweenmedium 1andmedium2), andtransmittedthroughthesecondparallelplaneinterface( betweenmedium2and medium3),theexpressionsoftransmittanceandrerectancebec omemorecomplicated sincenowwehavetoconsiderthemultiplererectionaswellasa bsorptionabsorption withinthesecondmedium.ThissituationisdepictedinFigure 2{1 .Therstandthird mediaareassumedtobenon-absorbing,andspanthesemi-innitesp acewiththeir complexrefractiveindex ~ N 1 and ~ N 3 ,respectively.Thesecondmediumhasitsthickness d withtherefractiveindex ~ N 2 .Weagainassumenormalincidenceforsimplicity.Then, thegeneralformulaefortheresultantamplitudetransmissiona ndrerectioncoecients 8 Thistechniqueisquitepractical,yettherequirementsofw iderangemeasurement canbeinconvenientinsomesituation.Oneofthetechniquecal ledellipsometrycandeterminesimultaneouslybothrealandimaginarypartsofthedi electricfunctionovera limitedfrequencyrange,andmayserveasanalternativemeth odtoconsider[ 17 ].

PAGE 34

19 includingmultiplererectionsare ~ t = ~ t 12 ~ t 23 e i ~ [1+(~ r 23 ~ r 21 e i 2 ~ )+(~ r 23 ~ r 21 e i 2 ~ ) 2 + ] = ~ t 12 ~ t 23 e i ~ 1 ~ r 23 ~ r 21 e i 2 ~ (2.58) and ~ r =~ r 12 + ~ t 12 ~ r 23 ~ t 21 e i ~ [1+(~ r 21 ~ r 23 e i 2 ~ )+(~ r 21 ~ r 23 e i 2 ~ ) 2 + ] = ~ r 12 +~ r 23 e i 2 ~ 1 ~ r 21 ~ r 23 e i 2 ~ ; (2.59) where~ r ij and ~ t ij aretheamplitudererectionandtransmissioncoecientsbetwe en mediums i and j asgivenbyEqs. 2.47 and 2.48 ,and ~ isthecomplexphasedepthof thesecondmediumwhichisdenedby ~ = c ~ N 2 d = c n 2 d + i 2 d; (2.60) where istheabsorptioncoecientdenedbyEq. 2.40 .FromEqs. 2.58 and 2.59 ,the resultanttransmittanceandrerectanceareobtained: T = n 3 n 1 j ~ t j 2 = n 3 n 1 j ~ t 12 j 2 j ~ t 23 j 2 e d 1+ j ~ r 23 j 2 j ~ r 21 j 2 e 2 d 2 j ~ r 23 jj ~ r 21 j e d cos (2.61) and R = j ~ r j 2 = j ~ r 12 j 2 + j ~ r 23 j 2 e 2 d +2 j ~ r 23 jj ~ r 12 j e d cos 1+ j ~ r 23 j 2 j ~ r 21 j 2 e 2 d 2 j ~ r 23 jj ~ r 21 j e d cos (2.62) with =2 c n 2 d + 23 + 21 ; (2.63) where ij isthephaseshiftuponrerectionateitherinterface.Thecosin etermleads tointerferencefringesinthespectrumduetomultipleinter nalrerectioninthesecond medium.Whenthesecondmediumisthick( d )orwedged,thereisnocoherence amongmultiplererections.Inalowresolutionmeasurement,th osefringesarenot resolved,andthetransmittanceorrerectanceisaveragedove rthephaseangleforthe

PAGE 35

20 partialbeamsas T ave = n 3 n 1 j ~ t 12 j 2 j ~ t 23 j 2 e d 1 j ~ r 23 j 2 j ~ r 21 j 2 e 2 d (2.64) and R ave = j ~ r 12 j 2 + j ~ r 23 j 2 e 2 d 2 j ~ r 23 j 2 j ~ r 12 j 2 e 2 d 1 j ~ r 23 j 2 j ~ r 21 j 2 e 2 d : (2.65) Whenathicksampleofthickness d withcomplexrefractiveindex~ n ismeasuredin avacuum,itisstraightforwardtondtheaveragedtransmitta nceandrerectance: T ave = (1 R s ) 2 (1+ 2 =n 2 ) e d 1 R 2 s e 2 d (2.66) and R ave = R s (1+ T ave e d ) ; (2.67) where R s isthesingle-bouncererectancegivenbyEq. 2.49 .Experimentsofthistype areveryimportantandareoftenappliedtomeasureabsorption coecientsofsolids. Whenwavelengthsofincidentlightarecomparabletothethi ckness d ,theinterferencefringesareresolvedwithsucientlyhighresolutionmeasu rements.FromEq. 2.63 itisapparentthatthespectrumexhibitsperiodicfringesof thefrequencyspacing betweentwosuccessivefringesgivenby = 1 2 nd ; (2.68) where isincm 1 and d isincm.Thisequationissometimesusefultodeterminethe thicknessofthesamplefromthefringespacing,andviceversa.F orexample,mylarlms usedasabeam-splitterinfarinfraredhavetherefractiveind exbetween1 : 64and1 : 67. Then,wecanexpectthattherstminimumfor6 mmylarbeam-splitterappearsnear 500cm 1 2.4.4OpticsinThinFilmonaSubstrate Astructureofathinlmofthickness d ( wavelengthorpenetrationdepth)laid onathickbutnon-absorbing(orweaklyabsorbing)substratewit hrefractiveindex n andthickness x isquitecommonintheopticalexperiment.Figure 2{2 showsthe schematicdiagramofthesituation.Againweonlyconsidertheno rmalincidencetoa

PAGE 36

21 n x d RT vacuumvacuum thin filmsubstrate Figure2{2:Rerectionandtransmissionwithathinlmonaweakl yabsorbingsubstrate.Thethicknessofthethinlmandthesubstrateare d and x respectively.We assumethecaseofnormalincidence,butthebeamsaredrawnatan angleforaclarity. sampleinfreespace.Itisobviouslymorecomplicatedsincenoww earedealingwitha fourlayeredstructure.Insuchcase,theKKtechniqueisinappl icable.However,itis possibletoextractlinearresponsefunctionsfrommeasurements ofbothrerectanceand transmittanceoveranitefrequencyrange. Atrstweconsiderthecasewhenmultiplererectionsinsidethesu bstratemaybe neglected.Thissimpliesthesituationsignicantlysincethe thicknessofthesubstrate x becomesunimportant,andthesystemcanbeconsideredasathree layeredstructure (vacuum-lm-substrate)justliketheonediscussedabove.Then,f romEqs. 2.58 and 2.59 withthefollowingapproximations: j ~ N 2 j ~ N 1 =1 ; j ~ N 2 j ~ N 3 n 3 n ( 3 n 3 ) ; d wavelengthorskindepth ; (2.69) itcanbeshownthatthetransmittanceacrossthelmintosubstrat eandthererectance fromthelmaregivenbytheGlover-Tinkhamequations[ 18 19 ]: T f = 1 1+ ~ y n +1 2 4 n ( y 1 + n +1) 2 + y 2 2 (2.70) and R f = ( y 1 + n 1) 2 + y 2 2 ( y 1 + n +1) 2 + y 2 2 ; (2.71)

PAGE 37

22 wherenistherefractiveindexofthesubstrate, y 1 and y 2 aretherealandcomplex partofthedimensionlesscomplexadmittanceofthelm,~ y ,respectively.~ y isrelated tothecomplexconductivity~ = 1 + i 2 ofthelmby~ y = Z 0 ~ d where Z 0 isthe impedanceoffreespace(4 =c incgs;377ninmks).Thus,theopticalbehaviorofa lmisdeterminedbyitselectricalpropertiesofthelmtha tismodiedbythesurface eects. Theactualmeasuredtransmittanceandrerectanceareinruenc edbymultiple internalrerectionswithinthesubstrateofthethickness x andtheabsorptioncoecient .Then,thesystemisafourlayeredstructurewithvacuumasthef orthmedium.Ifa substrateisthick( x )orwedged,coherenceamongmultiplererectionsarelost,th e measuredtransmittanceandrerectancearesimpliedto T = T f (1 R s ) e x 1 R s R 0 f e 2 x (2.72) and R R f + T 2 f R s e 2 x 1 R s R 0 f e 2 x ; (2.73) where R 0 f isthesubstrate-incident(backside)rerectionofthelm: R 0 f = ( y 1 n +1) 2 + y 2 2 ( y 1 + n +1) 2 + y 2 2 (2.74) and R s isthesingle-bouncererectanceofthesubstrategivenbyEq. 2.49 .Foraweakly absorbingsubstratesuchthat c= 2 n R s maybeapproximatedas R s 1 n 1+ n 2 : (2.75) Thisisusuallysatisedformeasurementsatlowtemperatureand lowfrequencies. Frommeasurementsofthetransmittanceandrerectanceoftheb aresubstrate,we canndtheindexofrefraction n andtheabsorptioncoecient ofsubstrateusing Eqs. 2.66 and 2.67 .Notethattheterm 2 =n 2 inEq. 2.66 canbeneglectedforaweakly absorbingsubstrate.

PAGE 38

23 Withtheknowledgeofsubstrate'sopticalproperties, 1 and 2 andinturnall otherresponsefunctionscanbeextractedbyinvertingEqs. 2.72 2.74 aftermeasuring bothtransmittanceandrerectanceofthelm-on-substratesyste m.Forastructure withmorelayers( e.g. ,vacuum-lm-buer-substrate-vacuum),theanalysisbecomes progressivelymorecomplicated.Amoregeneraldiscussionofthe opticalresponsefrom multi-layersisgivenin[ 15 20 ]. 2.4.5PhotoinducedAbsorption Inthephotoinducedmeasurements,weareinterestedinchanges intheoptical behaviorofasampleinphotoexcitedstatewithrespecttonon-e xcitedstate(ground state).Forasampleintheformoflmwiththickness d depositedonasubstrate,it wouldbeidealtohaveasubstratematerialthatisinsensitiveto thephotoexcitation. Insuchcase,thephotoinducedchangeinthetransmittance, T ,isduetothephotoinducedabsorptionbythelmitself.Ifthemeasurementisdonein lowresolution,the transmittancethroughthelmintosubstrateisgivenbyEq. 2.66 ,anditcanbeshown thatthenormalizedphotoinducedtransmittanceiswrittena s T T = T T 0 T 0 ( ) d; (2.76) where T and T 0 arethetransmittanceofthelminexcitedstateandgroundstat e, respectively.Notethatthenegativeofthequantity T = T iscustomaryusedasthe photoinducedsignal. 2.5MicroscopicModels Uptothispoint,wehavenotdescribedtheopticalphenomenafr omamicroscopic pointofview.Therearevariousmicroscopicmodelsthattryt oexplaintheoptical behaviorobservedexperimentally.Thesemodelsmaybeclassie daseitherclassical, semiclassical,orquantummechanical,dependingonhowwetrea tinteractionbetween lightandmatter. Intheclassicalmodel,bothlightandmatteraretreatedclassic ally.Thedipole oscillatormodel(Drude-Lorentzmodel),whichwillbediscusse dshortly,isaexample

PAGE 39

24 ofaclassicaltreatment.Thismodelhasbeenproventobeverysu ccessful,andisoften usedforunderstandingthegeneralopticalpropertiesofmedi um. Inthesemiclassicalapproach,theatomsinthemediumaretreat edquantum mechanically,whilethelightisstilltreatedasaclassicalel ectromagneticwave.The absorbtioncoecientoroscillatorstrengthduetotransitionb etweentwostatesortwo bandscanbecalculatedusingFermi'sgoldenrule,whichrequ iresknowledgeofthewave functionsofthestates. Inthecompletelyquantumapproach,thelightisalsotreated quantummechanically,namelyasphotons.Feynmandiagramscanbedrawntorep resenttheinteraction processesbetweenphotonsandatoms. Inthissection,wewilldiscussonlyafewofmicroscopicmodelst hatarecommonly usedduringanalysis.2.5.1LorentzModel Inasolid,therearevariousprocesses(orexcitations)thatcon tributetothe dielectricfunctionwhich,inturn,describesitsopticalbe haviors.Forexample,free carrierabsorptionandphonon(includingmulti-phonon)abso rptionarethetypical processesatfar-andmid-infraredfrequencies. 9 Inthespectralrangeofnear-infrared andultraviolet,processessuchasexcitonsandfundamentalab sorptionacrossthe energygap,interbandtransitions,andplasmaabsorptionmaybe seen.InthevacuumultravioletandX-rayspectralregion,thetransitionsofthec oreelectronscanbe expectedtodominatethedielectricfunction.Attheveryhi ghenergiesbeyondnuclear excitations,nothingcanrespondtothedrivingeld,andthed ielectricfunctionbecomes unitysincethemediumdoesnotpossessanypolarization.Notetha talltransitions requiretheconservationofenergyandmomentum. 9 Inprinciple,magneticexcitationscouldexistatevenlower energies.

PAGE 40

25 TheLorentzmodelisasimple,yetveryusefulclassicalmodeldie lectricfunction thatcanbederivedforasetofdampedharmonicoscillators.Whe naharmonicoscillatorwithmass m ,charge q ,dampingconstant r ,andresonantfrequency 0 isexcitedby aharmonicelectriceldoftheform E ( t )= E 0 e i!t ,theequationofmotionisgivenby m r + mr r + m! 2 0 r = q E ( t ) : (2.77) Thesecondtermmodelstheenergylossmechanismoftheoscillati ngdipole.Notethat theresonantfrequency 0 isatransverseoscillatorfrequencythatiscoupledtothe transverseelectriceld.Insertingasolutionoftheform r = r 0 e i!t intoEq. 2.77 yields r = q m 1 2 0 2 ir! E : (2.78) Ifthereare N oscillatorsperunitvolume,theresonantcontributiontothe macroscopicpolarizationis P = Nq r = Nq 2 m 1 2 0 2 ir! E : (2.79) Notethattheisotropicmediumisassumedhere.Then,thesusceptib ilityarisingfrom theoscillatoris ~ = Nq 2 m 1 2 0 2 ir! : (2.80) Thetotalpolarizationisgivenby P total =~ e E =(~ 1 ) E ; (2.81) where 1 isthebackgroundsusceptibilitythatarisesfromthepolariza tionduetoall theotheroscillatorsathigherfrequencies. ThedielectricfunctionisdeterminedfromEq. 2.10 : ~ ( )= 1 + 2 p 2 0 2 ir! ; (2.82) wherewehavedenedthehighfrequencylimitof~ ( )as 1 =1+4 1 ; (2.83)

PAGE 41

26 andtheplasmafrequency p as 2 p = 4 Nq 2 m : (2.84) Notethatthesubscript 1 shouldbeunderstoodascontributionsaboveacertain resonance.Separatingtherealandimaginaryparts,weobtain 1 ( )= 1 + 2 p ( 2 0 2 ) ( 2 0 2 ) 2 +( r! ) 2 ; (2.85) 2 ( )= 2 p r! ( 2 0 2 ) 2 +( r! ) 2 : (2.86) Fromtheseequations,itisstraightforwardtoseethat 1 graduallyincreasesfromthe value 1 + 2 p =! 2 0 asfrequenciesincreasetoward 0 ,andpeaksat 0 r= 2.Ittakes sharpnegativeslope,passingthrough 1 at 0 ,andbottomsat 0 + r= 2.Asfrequencies increasefurther,itnallyapproachesthehighfrequencyli mitof 1 .Asmentioned brieryintheearliersectionofthischapter,thefrequencyf orwhich 1 ( )=0islabelled as l atwhichelectromagneticwavesarecoupledtothelongitudi nalcomponentof theoscillator.Comparedwith 1 2 hasasimplebellshapewithastrongpeakat 0 andthefullwithathalfmaximumgivenby r .Notethatboth 1 and 2 varyonthe frequencyscaleof r ,andthedampingoftheoscillatorhastheeectofbroadening .It isingeneralthatmaterialishighlyabsorbingneartheresona nce,forobviousreason, stronglyrerectingbetween 0 and l ,andtransparentatfrequenciesfurtherawayfrom theresonancewhere 1 doesnotvarystrongly. Eq. 2.82 canbegeneralizedtoanarbitrarynumberofdierentoscilla torsas ~ ( )= 1 + X j 2 pj 2 j 2 ir j ; (2.87) where j r j ,and pj aretheresonantfrequency,dampingconstant,andplasma frequencyoftheoscillatoroftype j ,respectively.Theplasmafrequencyisdenedby 2 pj = 4 N j q 2 j m j ; (2.88) where N j q j ,and m j arethenumberdensity,eectivecharge,andeectivemassoft he oscillatoroftype j ,respectively.Thesevalesmustbeappropriatelychosentoacco unt

PAGE 42

27 forthedierentoscillators.Forexample,inthecaseofaphono n, p istheionplasma frequencywith q and m astheeectivechargeandthereducedmassoftheparticular latticevibrationmode. AcorrespondingquantummechanicalversionofEq. 2.87 canbewrittenas ~ ( )= 1 + 2 p X j f j 2 j 2 ir j ; (2.89) wherewehaveintroducedaoscillatorstrength f j inordertoaccountforthestrength oftheresponseofdierenttransitionstotheperturbingelect riceld.Inthequantum picture, j isthetransitionfrequencybetweentwostateswhicharesepara tedinenergy by ~ j ,and r j istheuncertainty(orwidth)inenergyoftheinitialandna lstates oftransition.Theoscillatorstrength f j isrelatedtotheprobabilityofaquantum mechanicaltransition,whichcanbecalculatedusingFermi's goldenrule. 10 Itsatisesa sumrule X j f j =1 : (2.90) Theoscillatorstrengthprovidesusanexplanationforthedi erentabsorptionstrength indierenttransitions.2.5.2FreeCarrierResponseandDrudeModel TheequationofmotiongiveninEq. 2.77 canalsobeusedtoderivethedielectric responseoffreecarriersofcharge q andeectivemass m bytakingtherestoringforce termzero( i.e. 0 =0): m v + m v = q E ( t ) ; (2.91) 10 Fermi'sgoldenruleshowsthatthetransitionratebetweentwo statesisproportional tothesquareofamatrixelementandalsotoadensityofstatesfor boththeinitialand nalstates.Theoscillatorstrengthandabsorptioncoecientar erelatedtothequantummechanicaltransitionrate.

PAGE 43

28 wherewehaveexpressedthedampingconstant r asareciprocalofthecollisiontime thatcharacterizeslossofmomentumofcarriersduetoscatter ing. 11 Thisisasimple equationbasedontheDrudemodel.Insertingasolutionofthefo rm v = v 0 e i!t into Eq. 2.91 yields v = q m 1 1 i! E : (2.92) For N freecarriersperunitvolume,thecurrentdensityisthen j = Nq v = Nq 2 m 1 1 i! E =~ E : (2.93) Thus,theacconductivitybasedontheDrudemodelis ~ D ( )= 0 1 i! ; (2.94) where 0 isthedcconductivitydenedas 0 = Nq 2 m : (2.95) Therealandimaginarypartsare D 1 = 0 1+ 2 2 ; (2.96) D 2 = 0 1+ 2 2 : (2.97) FromEq. 2.14 ,thedielectricfunctionforthefreecarriersisgivenby ~ D ( )=1 2 p 2 + i!= ; (2.98) 11 Atypicalvalueof forametalordopedsemiconductorisintherange 10 14 10 13 seconds,whichcorrespondto 3000cm 1 and 300cm 1

PAGE 44

29 where pD istheDrudeplasmafrequencydenedby 12 2 pD = 4 Nq 2 m : (2.99) Eq. 2.98 isobviouslythesameexpressionasEq. 2.82 with 0 =0, r = 1 ,and 1 =1. NotethatEq. 2.98 assumesthatonlyfreecarrierscontributetothedielectricf unction. Whenotherprocessesathigherfrequenciesgivecontribution s,theunityshouldbe replacedby 1 .Therealandimaginarypartsare D 1 =1 2 pD 2 1+ 2 2 ; (2.100) D 2 = 2 pD (1+ 2 2 ) : (2.101) Inthelimitoflowfrequencywhere 1 issatised,wecanobtainfollowing relations: D 1 2 pD 2 ; (2.102) D 2 2 pD =! =4 0 =! D 1 ; (2.103) n ( 2 = 2) 1 = 2 ; (2.104) R 1 2 =n 1 (2 != 0 ) 1 = 2 : (2.105) Eq. 2.105 isknownastheHagen-Rubensrelation.Fromthesecondexpressio nwecan ndtheabsorptioncoecient: = 2 c p 8 0 c (2.106) 12 TheDrudeplasmafrequency pD isrelatedtothedcconductivityandcarriermobility as 0 = 2 pD = 4 = Nq .Themobility(aratioofthecarrierdriftvelocityto theeld)isgivenby = q=m .Formetals, 0 is(nearly)independentoftemperature assumingthat doesnot(oronlyweakly)varywithtemperature,andisusedto characterizemetals.Forsemiconductors,ontheotherhand,theirc arrierdensitiescanbe variedbychangingthetemperatureorthedopantconcentrat ion.Therefore,themobility ismoreconvenientquantitytocharacterizesemiconductorsi ncethecarrierdensityis takenout.

PAGE 45

30 ortheskindepth: = 2 c p 2 0 : (2.107) Therefore,theskindepthisinverselyproportionaltothesqua rerootofdcconductivity andfrequency.Thisimpliesthatamaterialwithhigherdcco nductivityallowsshorter penetrationofaceldsforagivenfrequency. Asanotherlimitingcase,consideranundampedfreecarriersyste mlikeaperfect conductor.Inthisspecialcase,theDrudewidth 1 =0andthedielectricfunctionis realandgivenby D 1 = 1 2 pD 2 ; (2.108) D 2 = D 1 =0( 6 =0) : (2.109) Herewehaveused 1 justforthepurposeofgenerality.Thisequationtellsusthat D 0forfrequenciesbelowtheplasmaedge( ! pD = p 1 ).Then,thecomplex refractiveindex ~ N ispurelyimaginaryandthusthererectance R is1inthisfrequency rangeandthesystemsuddenlybecomestransparentabovetheplasm aedge. 13 This, so-calledaplasmarerection,happenswithoutlossofenergysin cethereisnoresistive current( i.e. D 1 =0)associatedwiththisfreecarrierresponse. Inrealmaterials,thedamping 1 hasanon-zerovaluewhichmaybededuced fromdcconductivityorothermeasurements.Theeectoftheda mpingmaybesmall butresultsinslightlylessrerectanceaswellasbroadeningof theplasmaedge.The rerectancemaybeevenlowerandhavestructuresduetoothera bsorptionprocesses suchasinterbandtransitions.Ifotherprocessesoccursnearthe plasmaedge,sharp onsetoftransmissionmaynotbeobserved. 13 Formetals, 1 1andthererectanceisveryhighforfrequenciesupto pD .For semiconductors,ontheotherhand, 1 canbelargeandasaresulttheplasmaedgeat pD = p 1 islowerthan pD

PAGE 46

31 2.5.3Drude-LorentzModel WhenboththeDrudeandtheLorentztypesofdielectricrespon seisobservedina spectrum,thetotaldielectricfunctioncanbeexpressedasthe sumofvariousdierent processesthatcauseapolarization: ~ ( )= 1 + X j 2 pj 2 j 2 ir j ! 2 p 2 + i!= : (2.110) ThisrelationiscalledtheDrude-Lorentzmodel,andcanbeu sedinttingtheexperimentalrerectancedataforextractingopticalparameters.Un liketheKK-methods,the ttingdatawiththemodelfunctioncanbeemployedinanite frequencyrangeaslong aswehaveawelldenedbackgroundcontribution 1 beyondthemeasuredfrequency range.2.5.4SumRules In x 2.5.1 ,weintroducedthenotionofoscillatorstrength f .Usingquantum mechanics,itcanbeshownthatthetotalabsorptionbyalltransi tionsforthewhole frequencyrangeisconstant,andcanbeexpressedbythe f -sumrule: Z 1 0 1 ( ) d! = X j 2 p f j 8 : (2.111) Thistellsthatthetotalareundertherealpartoftheconduc tivityisindependentof temperature,phasetransition,photo-excitations,andsoon.T hereexistseveralother sumrules,butwewillnotdiscussthemhere. Thesumruleisoftenappliedtoacertainprocess.Ifonlyfreeca rriersareconcerned,Eq. 2.111 isrewrittenas Z 1 0 1 ( ) d! = 2 pD 8 : (2.112) Thisisanexceptionallyusefulequationtoseehowthespectral weightshiftsintothe deltafunctionatzerofrequencyasasuperconductorexperie ncesphasetransition.

PAGE 47

CHAPTER3 FOURIERSPECTROSCOPY 3.1Introduction Aspectrometerisaninstrumentthatisdesignedtoyieldspectra linformation containedintheelectromagneticwavesunderstudy.Thereex istseveraltypesof spectrometersusedforanumberofresearchelds.Figure 3{1 showstheclassication ofspectrometers.Ofall,thescanningtwo-beaminterferometr ictypesareprobablythe mainstreaminstrumentnowowingtotheirvariousadvantagesw hichwillbeexplained shortly. Themonochrometerspatiallyseparatestheindividualfreque ncycomponents bymeansofadispersiveelementsuchasprismordiractiongrati ng.Anindividual frequencycomponentisselectedbyaslit,anditsintensityisse quentiallysampled.A powerspectrumisproducedaftermeasuringoverallfrequenci esofinterest.Although thistypeofinstrumentisstillusedcommonly,especiallyforne arinfraredandvisible spectroscopy,theyhavemetwithseverallimitations.Themaind icultycomesfrom theirslowscanningprocess.Becausethemonochrometermeasurese achfrequency individually,ittakesalongtime(typically10minutesorm oredependingonthe signaltonoiseaswellasresolution)tocompleteasinglescan.Th einterferometric Spectrometer Dispersingspectrometer(monochrometer)Interferencespectrometer(interferometer) Prism spectrometerDiffraction spectrometerTwin-beam interferometerMulti-beam interferometer Michelson interferometer(amplitude separation)Lamellar grating interferometer(wavefront separation)Martin-puplett interferometer(polarization separation)Fabry-Perot interferometerEtalon Figure3{1:Classicationofspectrometers. 32

PAGE 48

33 techniquesweredevelopedtoovercomesomeofthelimitation sencounteredwith dispersiveinstruments. Theinterferometerisaninstrumentthatcandividetheincom ingbeamoflight intotwopathsandthenrecombinethetwobeamsaftera(optic al)pathdierence(or retardation)hasbeenintroduced.Theserecombinedbeamspr oduceinterferenceand theresultingsignalisdetected.Themeasuredsignalasafuncti onofpathdierence, calledaninterferogram,istheFouriertransformofthepowe rspectrumoftheincident light.Thusitcanbeinverse-Fouriertransformedtoyieldthe powerspectrum.However, becauseofthefactthatthedetectedsignalmustbetreatedmath ematicallybefore obtainingmeaningfulspectrum,certaincaremustbetakentoa voidintroducingerrors intothespectrum. Interferometrictechniquehastwobasicadvantagesoverdisp ersivemethods.The factthatnearlyalwaysthetotalintensityhitsthedetector duringthewholeperiodof measurementimprovesthesignal-to-noise(S/N)ratio,particu larlyforweakradiation sources.Thisisknownasthethroughput(orJacquinot)advant age.Theinterferometer measuresallfrequencycomponentssimultaneously.Thisleads toconsiderablemultiplex (orFellgett)advantageallowingquickdataacquisitionand higherS/N. 3.2FourierTransformInterferometry 3.2.1GeneralPrinciples Thegeneralprincipleofinterferometrycanbeunderstoodby consideringasimpliedMichelsoninterferometer[ 21 22 23 ],whichisshownschematicallyinFigure 3{2 Considerthatamonochromaticplanewaveoftheform E S = E 0 e i (2 x !t ) ; (3.1)

PAGE 49

34 R Source Detector M1 M2 Beam splitter (Movable) x /2 ((w), f(w)) r 11 ((w), f(w)) r 22 ((w),(w)) rt Figure3{2:AschematicviewofasimpliedMichelsoninterfero meter.Thelighttravels tothebeam-splitterwithitsamplitudererectivity r andtransmissivity t .Thepartially rerectedbeamtravelstowardthexedmirror(M1)thathasth ererectivity r 1 and introducesphaseshift 1 .Thepartiallytransmittedbeamtravelsavariabledistance towardthemovablemirror(M2)with r 2 and 2 .Thebeamsarerecombinedatthe beam-splitterafteraopticalpathdierence x hasbeenintroduced,andhalfofthetotal beamreturnstothesource,andtheotherhalfproceedstoadet ector.Asamplecanbe placebetweeninterferometerandthedetector.isincidentonthebeam-splitterfromthesource.Here, isthewavenumber. 1 This beam-splitterpartiallyrerectsthebeamtowardthexedmir rorM1,andtransmits theresttowardthemovablemirrorM2. 2 Aftertravellingtheirrespectivepaths,the twobeamsarerecombinedatthebeam-splitter,andtheresulta ntbeamproceeds toadetector.Ifthebeam-splitterhastheamplitudererecta nce r andamplitude transmittance t 3 theresultingeldemergingfromtheinterferometertowardt he 1 Thewavenumberisdenedas =1 = =2 k = != 2 c 2 Hereforsimplicity,wewillassumethatbothM1andM2areequival entperfect rerectors.Theamplitudererectivityisacomplexnumberwhi chcanbeexpressedas r = E r =E i = j r ( ) j e i ( ) ,where E r isthererectedeld, E i istheincidenteld,and ( ) isthephaseshift.Foraperfectmirror, j r j =1and = 3 Foranidealbeam-splitter, r = t =2 1 = 2 .Theyarebothfrequencydependent.

PAGE 50

35 detectorisasuperpositionofeldsfromtwobeamswhichisgiv enby E D = rtE 0 [ e i (2 x 1 !t ) + e i (2 x 2 !t ) ] ; (3.2) where x 1 and x 2 arethetotaldistancesofrespectivebeam'sopticalpath(seeF igure 3{2 ).Sincetheenergyreachingthedetectorisproportionalto E D E D ,thetime averageddetectorsignalcanbewrittenas S ( x )= 1 2 I 0 ( )[1+cos(2 x )] ; (3.3) wherewehavedenedtheopticalpathdierence, x = x 2 x 1 ,thebeam-splitter eciency, =4 j rt j 2 ,andthesourceintensity, I 0 ( ).Thisexpressionmaybesimplied to S ( x )= f ( )[1+cos(2 x )] ; (3.4) where f ( )isanarbitraryspectralinputthatdependsonlyon S ( x )isthedetector signalforamonochromaticsource.Thecosinetermgivesthemod ulationonthe detectorsignalasafunctionof x Asmentionedearlier,withtheinterferometrictechniqueal lfrequencycomponents aremeasuredsimultaneously.Eq. 3.4 canbegeneralizedforapolychromaticsourceby integratingitoverallfrequencies: S ( x )= Z 1 0 f ( )[1+cos(2 x )] d : (3.5) At x =0,thedetectorsignalreachesitsmaximumvalueof S (0)=2 Z 1 0 f ( ) d : (3.6) Thispositioncorrespondstothezeroopticalpathdierence( orZPD)whereall frequencycomponentsinterfereconstructively.As x !1 ,ontheotherhand,the coherenceofthemodulatedlightiscompletelylost,andthec osineterminEq. 3.5 goes tozero.Therefore,thedetectorsignaloscillatesaroundana veragevalue: S ( 1 )= Z 1 0 f ( ) d = S (0) 2 : (3.7)

PAGE 51

36 Theinterferogramisthecosinemodulationpartofthedetect orsignal: F ( x )= S ( x ) S ( 1 )= Z 1 0 f ( )cos(2 x ) d : (3.8) ThisisthecosineFourierintegralofthedesiredspectrum f ( )whichcanberecovered bytakingtheinverseFouriertransform: f ( )=4 Z 1 0 F ( x )cos(2 x ) dx: (3.9) 3.2.2FiniteRetardationandApodization Sofarinourcalculation,itwasassumedthatthespectrumisobt ainedafterthe Fouriertransform(FT)oftheinterferogrammeasuredwithani nnitelylongoptical pathdierence(retardation).Inpracticetheinterferogr amcannotbemeasured toinniteretardation,anditmustbetruncated.Thistypeof truncationcanbe manipulatedmathematicallybymultiplyingthecompletein terferogrambyatruncation function G ( x )whichvanishesoutsidetherangeofthedataacquisition.Thus theactual functionwhichistransformedistheproductoftheinterfero gramandthetruncation function. Nowaccordingtotheconvolutiontheorem,theFToftheproduc toftwofunctions, say F ( x )and G ( x ),istheconvolutionoftheFTofeachfunction, f ( )and g ( ),where theconvolutionisdenedby f ( ) ?g ( )= Z 1 1 f ( 0 ) g ( 0 ) d 0 : (3.10) Hence,thecalculatedspectrumisthetruespectrumconvolvedw iththeFTofthe truncationfunction. Inordertoexaminetheeectoftruncation,considermultipl yinganinterferogram F ( x )withtheboxcarfunction G ( x )whichisdenedby G ( x )= 8><>: 1if j x j
PAGE 52

37 n cm -1 n 1 n 1 -1/2 L n 1+1/2 L 1/ L Figure3{3:Thesincfunctionconvolvedwithasinglespectrall ineofwavenumber 1 L isthemaximumretardation.where L isthemaximumretardation.TheFTof F ( x )isthetruespectrum f ( ),while theFTof G ( x )isthesincfunction: FT[ G ( x )]=2 L sin(2 L ) 2 L =2 L sinc(2 L ) : (3.12) Whenthesincfunctionisconvolvedwithasinglespectrallineo fwavenumber 1 ,theresultantspectrumisthesincfunctioncenteredabout 1 ,whichisshownin Figure 3{3 .Thustheeectofconvolutionistosmoothoutthenarrowfeat ure.The singlespectrallineshapeasaresulttruncationissometimescal ledtheinstrumentline shape(ILS)function. Itcanbeshownthattherstzerosoneithersideof 1 occurat 1 1 = 2 L .Thus, twospectrallinesseparatedby1 =L arecompletelyresolved.Thustheresolutionis limitedbythemaximumpathdierenceontheinterferogram. Thevalueof1 =L (in cm 1 )isoftenusedasaquickestimateofspectralresolution.Theful lwidthathalf maximum(FWHM)issometimesusedasanalternativeestimateofre solution.

PAGE 53

38 Thesuddencutowiththeboxcarfunctionintroducessidelobe snearsharp featuresinthespectrum. 4 Thus,itisdesirabletouseaweightedtruncationfunction thatcutsotheinterferogramingentlerfashion.Thisproce ss,knownasapodization, reducestheringingattheexpenseofafurtherreductioninre solution.Forexample,the Happ-Genzel[ 24 ]isasimpleapodizationfunctiongivenby G 1 ( x )=0 : 54+0 : 46cos( x=L ) ; (3.13) where L isstillthemaximumretardation.TheFToftheHapp-Genzelis FT[ G 1 ( x )]=2 L sinc(2 L ) 0 : 54 0 : 46(2 L ) 2 (2 L ) 2 2 : (3.14) Again,convolutionofthisfunctionwithasinglespectralline ofwavenumber 1 isthe resultantspectrumwhichisshowninFigure 3{4 togetherwiththeFToftheboxcar ( i.e. ,sincfunction).Thisgureclearlydemonstratesthattheuseo fagentlertruncation functionsuppressesthesidelobeswhiletheresolutionisreduce d.TheFWHMofthe spectrumusingtheHapp-Genzelandtheboxcarare0 : 91 =L and0 : 61 =L ,respectively. SomeofotherpopularapodizationfunctionsaretheNorton-B eer(weak,medium, strong)[ 25 ]andtheBlackman-Harris(3-term,4-term). 5 Verynicediscussionabout apodizationfunctionscanbefoundinGriths[ 22 ]. 3.2.3Sampling Intheuseofacomputerfordataacquisition,theanalogsignalm ustbeconverted todigitizeddatasets( i.e. ,A/Dconversion)beforeanysortofmanipulationcantake place.Forthisreason,theinterferogramissampledatsmall,e quallyspaceddiscrete retardation,andtheFourierintegral,Eq. 3.9 ,isapproximatedbyasum.Thisdiscrete 4 Therstminimumdropsobelowzeroby22%oftheheightatcent ralmaximum. Thesecondarymaximaarealsorelativelylarge.Thesesidelobes giverisetooscillation whichmayappearasspuriousfeaturesespeciallyintheneighb orhoodofsharpspectral features. 5 Personally,IstartwiththeNorton-Beer(medium)apodization functionrst,and tryothersifceratinimprovementhastobemadedependingon thespectralfeatures.

PAGE 54

39 n cm -1 n 1 n 1 -1/2 L n 1+1/2 L 1/ L FT[Boxcar] FT[Happ-Genzel] Figure3{4:TheFToftheHapp-Genzel(HG)apodizationfunctio nconvolvedwitha singlespectrallineofwavenumber 1 L isthemaximumretardation.Forcomparison, theFToftheboxcar(sincfunction)convolvedwiththesamesing lelineisshown.The FWHMofthespectrumfortheHGandtheboxcarcasesare0 : 91 =L and0 : 61 =L ,respectively.Notethatthesidelobesinthespectrumaresuppressedbyusi ngtheHGatthe costofresolution.naturecanbehandledmathematicallybyusingtheDiracdelta combdenedby( x )= 1 X n = 1 ( x n ) : (3.15) TheDiracdeltacombisjustaseriesof functionsattheintegers.Ithasfollowing properties:( x + m )=( x ) (periodic) ; (3.16)( ax )= 1 j a j 1 X n = 1 x n a (scaling) ; (3.17) FT[( ax )]= 1 j a j a = 1 j a j 1 X n = 1 e i 2 n=a (Fouriertransform) ; (3.18)( x ) F ( x )= 1 X n = 1 F ( n ) ( x n )(sampling) ; (3.19)( x ) ?F ( x )= 1 X n = 1 F ( x n )(replication) : (3.20)

PAGE 55

40 f '() n n cm -1 DnD =1/ x 0 n max Dn / 2 n cm -1 0 n max (A)(B) Figure3{5:Therelationbetweenspectrumreplicationandsam plingrate.(A)Proper choiceofsamplingratesuchthatthetruespectrumisconnedto one-halfofthereplicationperiod( i.e. max = 2).Inthissituation,theperiodicreplicasdonotoverlap andnoerrorisintroducedbysampling.(B)Improperchoiceof samplingrate.Overlappingwithadjacentreplicatedspectrumcausesspuriousresulti nthespectrum. Ifthecontinuous(oranalog)interferogram F ( x )issampledatintervals x ,the sampled(ordigitized)interferogram F 0 ( x )isgivenby F 0 ( x )= x x F ( x )= x 1 X n = 1 F ( n x ) ( x n x ) : (3.21) Then,thespectrumderivedfromtheFTof F 0 ( x )is f 0 ( )= 1 ?f ( )= 1 X n = 1 f ( n ) ; (3.22) where =1 = x and f ( )=FT[ F ( x )]. Eq. 3.22 isthespectrumweactuallyobtainasdatawhichiscomprisedof periodic replicasofourdesiredspectrum f ( )withperiod .Thisreplication,whichobviously arisesfromthesamplingoftheanaloginterferogram,raisesan importantissueofthe samplingfrequency,whichispeculiartodiscretesampling.Fi gure 3{5 illustratesthe relationbetweenreplicationandsamplingrate.Asinthegur e(B),ifthehighest frequency, max ,ofthetruespectrumexceedsthefoldingfrequency, = 2,thentwo adjacentreplicatedspectraoverlap,andtoo-highfrequenc iesappearfalselyatlower

PAGE 56

41 Figure3{6:Theredcurveofabove-Nyquistfrequencyappearst opossessthesamesetof datapointsastheblackcurveofbelow-Nyquistfrequency.frequenciescausingspuriousresultintheobtainedspectrum.T hisisbecausehigher frequencywavescanbedrawnadditionallythroughthesamesam plingpointstakenfor lowerfrequencywavesasillustratedinFigure 3{6 .Thiseect,knownasspectralfolding oraliasing,canbepreventedbyinsuringthecondition: max 2 (3.23) or x min 2 : (3.24) Theseconditionsstatethatthehighestfrequencyneedstobesam pledatleasttwiceper wavelength,whichisjusttheNyquistsamplingcriterion.There fore,itisexperimentally importanteithertoensuredigitizinganinterferogramatah ighenoughsamplingrate ortolimittherangeoffrequencyinputtothedetectorusingo pticaland/orelectronic lters.Theresponsivityofthedetectoroftenworksasakindof low-passlter. Followingtheabovearguments,itisquiteobviousthatmeasur ementsofnarrow frequencyrangerequiresmallernumberofsamplingpoints.Ift henumberofpoints istoosmall,thespectralshapemaynotbewelldened.Insuchcase ,wecanadd extrazero-valueddatapointsattheendoftheinterferogra mkeepingthesamesample spacing.Thistechnique,knownaszerolling,eectivelypr oduceslargernumber ofspectrumpointsperresolutionelement.Sincethepointsad dedarezero-valued, spectrumresolutionwillnotincrease.Itmerelyprovidesasmoo therspectrallineshape. 3.2.4PhaseErrorandCorrection Untilthispoint,wehaveassumedthattheinterferogramisperf ectlysymmetric abouttheZPD.Inarealexperiment,however,thereoftenexi stsaphaseerrorthat mustbeincludedtodescribetheactualmeasured( i.e. ,asymmetric)interferogram.It

PAGE 57

42 mainlyresultsfromsamplingerrors,electronicltering,and opticaleectsfromvarious partsofinstrumentopticsaswellasasample.Theeectofsuche rroristodistortthe ILSfunctionfromthesymmetricsincfunctiontoanasymmetricsh ape.Thiscouldlead tonegativespectrumorslightshiftofsharpfeatures.Therefore ,itisimportanttohave schemesthatcouldcorrectfaultyeectsfromacalculatedspe ctrum. Whenthephaseerrorisincluded,theinterferogramgivenbyE q. 3.8 ismodied to 6 F ( x )= Z 1 0 f ( ) e i (2 x ) d = Z 1 0 [ f ( ) e i ] e i 2 x d ; (3.25) where isthephaseerror(orphasespectrum)whichcanbefrequencydep endent.Note thathereweusedtheexponentialnotationforsimplicity.The n,thethecalculated spectrumthroughtheinversecomplexFTis ~ f ( ) f ( ) e i = Z 1 1 F ( x ) e i 2 x dx: (3.26) Hence,theasymmetricinterferogramyieldsacomplexspectrum .Therealpartofthe spectrum,Re[ ~ f ( )],andtheimaginarypartofthespectrum,Im[ ~ f ( )],canbecomputed bythecosineFTandthesineFToftheinterferogrammeasuredsymm etricallyoneither sideofthezeroretardationpoint(orcenterburst),respectiv ely.Ouraimistondthe phaseerror, ,fromwhichweapplysomesortofphasecorrectionschemetodeter mine thetruespectrumofinterest,whichis f ( )inEq. 3.26 Hereweexplainthesimplestwaytoachievethephasecorrection. First,wetake aninterferogrambetween L 1 x L 2 where x =0correspondstothecenterburst. Sinceitisonlyrequiredtocalculate atverylowresolution,thedistance L 1 ,which isdeterminedbythephaseresolutionsetting,canbesmallertha nthedistance, L 2 6 Thephaseerrorisaddedtothephaseangleoftheinterferogram ascos(2 x )= cos(2 x )cos +sin(2 x )sin .TheFTofatruncatedsinewaveisanoddfunction. Thus,theaddedsinecomponentisresponsiblefortheasymmetricsh apeofaninterferogram,andtheitsFTcausesdistortionoftheILSfunction.

PAGE 58

43 requiredtoattainthedesiredresolution(1 =L 2 ). 7 Fromtheshortdouble-sidedregionof theinterferogram( L 1 x L 1 ),thephasespectrumcanbefoundfrom ( )=arctan Im[ ~ f ( )] Re[ ~ f ( )] : (3.27) Havingcalculated ,thecomplexspectrum, ~ f ( )maybecorrectedbymultiplyingitby e i =cos i sin suchthat ~ f ( ) corrected = f ( ) e i e i = f ( ) : (3.28) Inthiswaytherecoveredspectrummaybecorrectedforerrors incurredasaresultof asymmetriesinthemeasuredinterferogram. Thereareseveralphasecorrectionmodesavailableamongwhic hthemethod developedbyMertzisthemostcommonlyusedone.Moredetailed discussionofphase correctionmethodscanbefoundinvariouspapers[ 26 27 28 ]. 3.2.5Step-ScanandRapid-ScanInterferometers Thereareingeneraltwodierentkindsofinterferometersd ependingonitsscanner (movablemirror)movements:step-scaninterferometersandra pid-scaninterferometers. Instep-scaninterferometers,thescannerstartsfromitsrefere nceposition,andsteps toequallyspacedsamplingpositions.Ateachsamplingposition,t hescannerisheld stationaryandthedetectoroutputsignalisintegrated.Thest eppingcontinuesuntil thedesiredresolutionhasbeenachieved.Comparedwithrapid -scaninterferometers, step-and-integratesystemshaveunavoidabledowntimewhilem ovingtothenext samplingpointandwaitingforthescannertobestablebeforeac tuallystartingdata acquisition.Inaddition,thefactthatittakeslongertimet ocompletesinglescan makesstep-and-integratesystemspronetobesensitivetoslowvar iationsinthesource intensitywhichcoulddegradespectrumespeciallyatlowfrequ ency.Further,the 7 Typicallythephaseresolutionissettohave4to8timeslowerth anthespectralresolution.Ifthedouble-sidedacquisitionmodeisused( i.e. L 1 = L 2 ),thephaseresolution settingiscompletelyignoredforobviousreason.

PAGE 59

44 systemsgenerallyrequiretouseachopper,andthusloseanother halfofthesignalafter theinterferometer.Thesecharactersmakesstep-scantechniq ueratherinecient,andin generalrapid-scanmethodissuperiorandadoptedbythemostof recentinstruments. Inrapid-scaninterferometers,thescannermovesatconstantan dsucientlyhigh velocity.Whenasignalofaparticularfrequency issentasinputtoaninterferometer, itismodulatedatafrequency 0 whichisrelatedtothemovingmirrorvelocity v as 0 = v c = v = v ; (3.29) where 0 and areinHz, incm, v incm/s,and incm 1 .Hence,inordertobe abletoanalyzethesignalatthedetectoritisnecessarytoknow thescannervelocity accurately.Itcanbecalculatedbymeasuringthemodulatedf requencyofalaser inputwithknownwavelength.IfaHelium-Neon(He-Ne)laserat632 .8nmisused,for example,itstypicalmodulatedfrequency, 8 say10kHz,correspondsto0.6328cm/sfor thescannervelocity. Now,havingacontinuoussourceasinput,allfrequencycompon entsaremodulated (typicallyinthekHzrange)accordingtoEq. 3.29 .Sincethesemodulationfrequencies areintheaudiorange,theycanbeeasilyampliedandltered electronically.Alowpassltereliminatesnoiseofmuchhigherfrequencythanthem odulationfrequency oftheshortestwavelengthinthespectrumandpreventsaliasing .Ahigh-passlter, ontheotherhand,maybeusedtoforceslowbackgroundmodulati on,suchassource ructuation,tobelowitscuto. Anotherimportantfactorinrapid-scansystemsisthedetermina tionofthecorrect timetostartdataacquisition.Thepositionofthecenterbursto fcontinuoussource canbeusedasareferencepoint.Thisinformationisessentialf ordatacollection,since themethodofanalysisreliesonthecumulativeaddition(coadding)ofanumberof 8 Someofmoderninstrument,suchasBrukerIFS66v/S,cansetthem odulatedfrequencyofHe-Nelasertoasfastas200kHz,whichcalculatesto12.6 6cm/softhescannervelocity.

PAGE 60

45 interferograms.Co-additionisatechniquewhichimprovest hesignal-to-noise(S/N) ratio.Correspondingdatapointsmustbesampledatthesamepath dierenceonevery successivescan.Thezerocrossingpointsofthelaserinterferogra mmaybeusedasa referencepointtostartandtriggerthesamplingofanalogdat afromthedetector.The signalincreaseslinearlysinceitisalwayscoherent.Noiseoccu rsrandomly,thusthe signalincreasesfasterthanthenoise.Thisprocess,calledsignal averaging,increases theS/Nratioassquarerootofthenumberofscansco-added.The refore,inorderto increasetheS/Nbyafactorof2,thenumberofscansmustbeincre asedbyafactorof 4. 3.3PolarizationModulation Uptothispointofthissection,wehavebeentalkingaboutinte rferometersof amplitudeseparationtypewhichuseapartiallytransmittinga ndpartiallyrerecting beam-splitterwithMichelsonconguration.Despiteclearadv antagesoverdispersive typeofmonochrometer,amplitudeseparationinterferomete rsalsoexhibitsomedicultiesespeciallyforveryfarinfrared.Themaindicultyofth istypeistheloweciency andlimitedspectralrangeofthin-lmdielectricbeam-split terssuchasMylarwhichis mostlyusedforfarinfrared.Inordertoovercomesuchdisadvant ages,dierenttypesof interferometersweredeveloped.Oneofthemisalamellargr atinginterferometer.Rather thanseparatingamplitudeofincidentlight,alamellargrat ingseparateswavefrontof incidentlight.Theeciencyoflamellargratingbeam-split terisnearlyindependentof frequencyandcanbeveryhigh.Althoughthelamellargrating usesdierentmethod toseparatelightfromlmbeam-splitter,botharestillintensi tymodulationtypeof interferometers.Wewillnotdiscussthelamellargratinginte rferometerfurther,but interestedreadersareencouragedtoreadseveralpapersabou tthistopic[ 22 29 ]. Thereisanothertypeofinterferometerwhichiscommercial lyavailablethesedays. ItisthepolarizinginterferometerbasedonaconceptbyMart inandPuplett[ 30 ].It hassimilarcongurationasMichelson,butusesratheruniquea pproachtoproduce modulationofincidentlight.Aschematicdiagramofpolariz ing(orMartin-Puplett) interferometerisshowninFigure 3{7 .Lightfromanunpolarized(orpolarized)sourceis

PAGE 61

46 M1 M2 P1 P2 B x Unpolarized (or polarized) source Detector Figure3{7:AschematicviewofaMartin-Puplettinterferome ter.Thecollimatedlight islinearlypolarizedatapolarizerP1andtravelstoapolar izingbeam-splitterBwhich isalignedatanangleof45 withrespecttotheplaneofpolarizationafterP1.The beam-splitterseparatestwopolarizationcomponentssending onecomponenttowarda xedrooftopmirrorM1andtheothertowardamovablerooftop mirrorM2.Onrerection,thepolarizationofeachbeamisrotatedby90 ,andtwobeamsarerecombined atthebeam-splitter.Atthebeam-splitter,theinitiallytra nsmittedbeamiscompletely rerected,andinitiallyrerectedbeamiscompletelytransmi tted.Therecombinedbeam headstothesecondanalyzingpolarizerP2andthebeamisline arlypolarizedafterP2 withanamplitudevaryingperiodicallywithpathdierence linearlypolarizedatapolarizerP1intheplaneatceratino rientation.Itisthendivided intotwopolarizationcomponentsbyapolarizingbeam-split terBwhichistypicallya free-standingnewiregrid(oragridonMylarlm).Thistype ofbeam-splitterhas beenshowntohavealmostfrequencyindependentandhighecie ncyofnearly100% fromeectivelyzerofrequencyuptoroughly1 = 2 d (cm 1 ),where d (cm)isthespacing ofthewires[ 31 ].Thegirdrerectsthecomponentoftheincidentlightparal leltothe directionofthewiresandtransmitthecomponentnormaltoth edirectionofthewires. Whenthebeam-splitterisorientedwiththewiregridsatanan gleof45 withrespectto P1,theincidentpolarizedlightisequallysplitsendingonec omponenttoaxedmirror M1andtheothertoamovablemirrorM2.BothM1andM2arethe90 rooftopmirrors whichrotatetheplaneofpolarizationby90 onrerection.Therefore,whentwobeams comebacktothebeam-splitter,theonererectedinitiallyis transmittedcompletely,and

PAGE 62

47 0 I 0 I 0 2 (a)(b)(c) Figure3{8:Interferogramsproducedbyapolarizinginterf erometer.(a)TheinterferogramforparallelP1andP2.(b)Theinvertedinterferogramf orcrossedP1andP2.(c) Thedierenceof(a)and(b),whichisobtainedbypolarizati onmodulationtechnique. Notethatthemeanleveloftheinterferogramisautomaticall yeliminated. theonetransmittedinitiallyisrerectedcompletely.Nobeam issenttothedirectionof thesource.Thecombinedbeamnallypassesthroughthesecondpo larizerP2withits polarizationaxiseitherparallelorperpendiculartothat ofP1. AsM2moves,aphasedierenceisintroducedbetweentwobeams.Fo ramonochromaticsource,theinitiallylinearlypolarizedbeamisellip ticallypolarizedafterrecombinationatthebeam-splitterwithanellipticityvaryingperi odicallywithincreasingpath dierence.AttheZPD,therecombinedbeamhasthesamepolari zationastheincident beamonthebeam-splitter.AfterP2,thebeamisplanepolarize dwithanamplitude thatvariesperiodicallywithpathdierenceinthesamewaya sinaMichelsoninterferometer.Assuminganunpolarizedsource,theintensityatthed etectorisgivenby I k ( x )= I 0 2 [1+cos(2 x )](3.30) or I ? ( x )= I 0 2 [1 cos(2 x )] ; (3.31) where I 0 istheintensityofthelinearlypolarizedbeamincidentonth ebeam-splitter. Thecase I k isforparallelP1andP2,and I ? isforcrossedP1andP2.Forasourceof continuousspectrum,theoutputintensityyieldsantypicali nterferogramexceptthatof I ? isinverted(seeFigure 3{8 ).

PAGE 63

48 Thecomplementarynatureoftheinterferogramsforthetwoo rientationsofone polarizerwithrespecttotheothercanbeutilizedtointrodu cepolarizationmodulation. ThisisusuallydonebykeepingP1xedandbydynamicallyswitc hingtheorientation ofP2usingapolarizingchopper. 9 Then,byusingstandardLock-intechnique,the detectedsignalisthedierencebetween I k and I ? ,whichisgivenforamonochromatic sourceas I ( x )= I k ( x ) I ? ( x )= I 0 cos(2 x ) : (3.32) Thus,thephasemodulationtechniqueeliminatesthemeanleve loftheinterferogram whichcouldintroduceerrorsduetospuriousructuations(see Figure 3{8 ).Thisand widerangehigheciencyofapolarizingbeam-splittermakes theMartin-Puplett interferometeradvantageousforveryfarinfraredmeasurem ents.Oneofspectrometers weusedisthepolarizationmodulationtype.Detailsofthespe cicinstrumentwillbe discussedinChapter 6 9 WecankeepP2androtateP1justaswell.Ifwehaveapolarizedi nputsource, however,P1shouldbealignedsuchthatthemostlightcangothro ugh,anduseP2for thepolarizationmodulation.Thereisalsoatechniquecalle dadoublepolarizationmodulationwhichusestwopolarizingchoppersforP1andP2[ 32 33 ].

PAGE 64

CHAPTER4 SUPERCONDUCTIVITY 4.1Introduction In1911,soonaftersuccessfullyliquifyingheliumin1908,Kamm erlinghOnnes discoveredthattheelectricalresistanceofmercurysuddenlyd ropstoanunmeasurablysmallvaluewhenitiscooledbelow4.2K[ 34 ].Thisphenomenonwasnamedas superconductivity.Insubsequentyears,manymoremetalsandme tallicalloyswere foundtobesuperconductingwhencooledtobelowacertaincri ticaltemperature T c In1933MeissnerandOchsenfelddemonstratedanotherbasicprope rtyofsuperconductor,perfectdiamagnetism,whichisknownastheMeissnere ect[ 35 ].In1935, F.LondonandH.Londondevelopedapurelyphenomenologicald escriptionthrough amodicationofanessentialequationofelectrodynamicsinsu chawaytoexplain theMeissnereect[ 36 ].Theypointedoutthatsuperconductivityisafundamentall y quantummechanicalphenomenonthatisobservedonamacroscop icscale,withan energygapbetweensuperconductingandnormalstate.Anotherp henomenological theorywasalsodevelopedbyGinzburgandLandauin1950[ 37 ].Then,nallyin1957, Bardeen,Cooper,andSchrieerproposedamicroscopictheory ofsuperconductivityas aphenomenonwhereelectronsformpairsandanenergygapdev elopsintheelectronic densityofstatesaroundFermienergy[ 38 ].Thisso-calledBCStheoryremainsasavalid microscopicexplanationformanysimplesuperconductors(BCS superconductors). Abreakthroughinsuperconductivityresearchoccurredin198 6whenBednorzand MullerfoundacopperoxidecompoundsoftheBa-La-Cu-Osyste mwhichsuperconducts atasubstantiallyhighertemperature( T c 30K)thanpreviouslyknown[ 39 ].With theirwork,aneweraofsuperconductivityopenedinthisclass ofmaterials(highT c superconductors)whichdiersfromconventionalBCSsupercon ductors.Nowweknow variousmaterialsthathave T c abovetheboilingpointofliquidnitrogen(77K). 49

PAGE 65

50 Themicroscopictheoryofsuperconductivitycannotbedescrib edinthelanguage oftheindependentelectronapproximation,andreliesonfo rmaltechniques. 1 Itisquite extensiveandhighlyspecialized.Consequently,wewilllimit oursurveyofthetheory toqualitativedescriptionsofsomeofthemajorconceptswith intheframeworkofBCS theory.Detailsofthesubjectcanbefoundinmanyplaces[ 40 41 42 43 44 ].Inthe followingsection,wewillmerelysummarizeafewbasicpropert iesofsuperconductors. InChapter 7 ,wewillprovidebrieftheoreticalbackgroundfortheinfra redproperties ofsuperconductorsandtheeectsoflocalizationonsupercon ductivity,basedonthe workbyMattisandBardeen[ 45 ],andbyMaekawaandFukuyama[ 46 ],respectively.In Chapter 8 ,wewilldiscusstheoryofnonequilibriumsuperconductivity. 4.2FundamentalsofSuperconductivity 4.2.1FundamentalPhenomenaVanishingDCResistance Ofallthecharacteristicsofsuperconductors,theabsenceofan ymeasurableDC electricalresistanceisthemoststrikingphenomenon.Aboveacr iticaltemperature T c a bulksuperconductingspecimenbehavescompletelyasnormalm etalwithDCresistivity generallygivenby ( T )= 0 + BT 5 ; (4.1) wherethersttermarisesfromimpurityanddefectscattering, andthesecondterm fromphononscattering.Below T c ,themetalbecomessuperconductingwithnodiscernibleDCresistivity(zeroDCresistivity),andcurrentrows initwithoutany 1 Thesecondquantizationdescriptionofmany-bodysystemisusedt odescribethe BCStheory,includingtheenergyoftheBCSgroundstate,givi ngtheenergygapresultingfromtheelectronpairing.

PAGE 66

51 Table4{1:Transitiontemperaturesforseveralsuperconducto rs.SomeofhighT c materialsarealsolisted. Element T c (K) Compound T c (K) High-T c T c (K) Mo0.92 NiTi10 Ba 0 : 75 La 4 : 25 Cu 5 O 5(3 y ) 30 Al1.2 NbN15.2 La 2 x Sr x CuO 4 38 In3.4 Nb 3 Sn18.1 YB 2 C 3 O 7 92 Hg4.1 Nb 3 Ga20.3 Bi 2 Sr 2 CaCu 2 O 2 85 Pb7.2 Nb 3 Ge23.2 Bi 2 Sr 2 Ca 2 Cu 3 O 10 110 Nb9.2 MgB 2 39 HgBa 2 Ca 2 Cu 3 O 8 133 dissipationofenergy.Thetransitionofabulkmaterialisusual lyabrupt,andhappensatverylowtemperature. 2 Table 4{1 liststhetransitiontemperaturesofseveral superconductors.Thefactthatthereisnomeasurableresistivit yallowsustopasslarge currentthroughasuperconductor,andinturn,tocreatelarg emagneticeld.However, ifthecurrentdensityexceedsacriticalcurrent J c ,asuperconductorrevertstoanormal conductor(Silsbeeeect). J c isrelatedtowhetherthemagneticeldcreatedbythe currentexceedsthecriticaleld H c abovewhichsuperconductivityisdestroyed.Inan ACelectriceld,superconductorsatnitetemperaturenolo ngerexhibitzeroresistivity. Theresistivityincreaseswithfrequency.However,attemperat ureswellbelow T c ,the resistivityisstillnegligibleprovidedthatthefrequencyis nottoolarge( = ~ ,where istheenergygap.). x 7.2.1 describestheresponseofsuperconductorsinACelds. MeissnerEect Asuperconductorexpelsmagneticrux,andhenceactslikeape rfectdiamagnet. Thisisanotherpeculiarphenomenonofsuperconductivitykn ownastheMeissnereect (orMeissner-Ochsenfeldeect).Having =0intheMaxwellequationsforaperfect conductor,wend @ B =@t =0,andthusthemagneticruxisexpectedtoremain unchangedwithinthespecimen.Insuperconductingstate,howe ver,wendnotonly B =constant,butalso B =0,andtheeldpenetratingthespecimen(providedthat 2 Thethermalenergy k B T c correspondingtothetransitiontemperatureisontheorderofafewmeVorless.Thisismuchsmallerthantheenergyscalesu chastheFermi energy E F ( 10eV)andtheDebyeenergy ~ D ( 0 : 1eV)ofthemostofmetals.

PAGE 67

52 itisnottoostrong)priortomakingthetransitiontosupercond uctingstatewillbe expelledfromtheinterior.Asimpleexplanationforthisee ctisthattheimpinging magneticeldinducesshieldingcurrentsonthesurfaceofasup erconductor,which arejustenoughtocanceltheeldintheinterior.Sincethesup erconductorhaszero resistivity,thecurrents( i.e. ,supercurrents)willpersistevenaftertheeldstopped changing.Thedistancewhichthesupercurrentsformaniteshe athintothespecimen iscalledtheLondonpenetrationdepth L .Magneticruxcanalsopenetratethesame distanceintothematerial.Formanysimple,puremetals,thisp enetrationdepthison theorderof500 A.Asmentionedabove,iftheeldgetstoolarge,however,them aterial willeventuallyloseitssuperconductingstate.MagneticFluxQuantization Itisanotherpropertyofsuperconductorsthatthemagneticr uxpassingthrough anyareaenclosedbyasupercurrentinaclosedloopcanonlytake onvaluesofintegral multiplesoftheso-calledruxquantum(orruxoid): 0 = hc 2 e =2 : 0679 10 7 Gcm 2 ; (4.2) where h isPlanck'sconstant, c isthespeedoflight,and e istheelementarycharge. Thisruxquantizationisaconsequenceofthatthecomplexord erparameter ( r )= j j e i (introducedintheGinzburg-Landautheory)isasingle-valu edfunction,andthus itsphasemustchangeby2 timesaninteger. AsimilareectoccurswhenatypeIIsuperconductor(referto x 4.2.3 )isplaced inamagneticeld.Atsucientlyhigheldstrengths,someofthe magneticeldmay penetratethesuperconductorintheformofthinthreadsofma terialthathaveturned normal.Eachthreadisinfactthecentralregion(\core")of vortexofthesupercurrent, andcarriesasingleruxquantum.JosephsonEects Whentwosuperconductorsareinweakcontact( e.g. ,separatedbyathininsulating oxidebarrier(10 20 A),anormalconductinglayer(100 1000 A),oraconstriction),

PAGE 68

53 Cooperpairscouldtunnelfromonetotheother,givingriseto acharacteristiccurrent throughtheso-calledJosephsonjunction. Whenthereisnovoltagedropacrossthejunction,aDCcurrent willbegenerated, givenby I = I c sin '; (4.3) where isaconstantphasedierence( i.e. ,relativephase)oftheBCSmany-body statesintwosuperconductors,and I c isthemaximumcurrentthatcanpassthroughthe junctionbeforedrivingittoaresistivestate.Thisiscalledt heDCJosephsoneect. WhenaDCvoltage U isappliedbetweenthejunction,therelativephase evolves withtimeas ( t )= (0) 2 eU ~ t: (4.4) ThisgivesrisetoanACcurrentgivenby I = I c sin[ (0) !t ] ; (4.5) with = 2 eU ~ : (4.6) ThisiscalledtheACJosephsoneect.Interestinginterferenc ephenomenaarisewhen twoJosephsonjunctionsareconnectedinparallel.Thesecanbe usedforaverysensitive magneticeldsenor,knownastheSQUID. Thesearetheeectswherethecharacteristichighcoherenceo ftheCooperpairs becomesparticularlyevident.IsotopeEect Whenaconstituentatomofasuperconductingmaterialisrepla cedbyitsisotope, thecriticaltemperatureoftenchangeswithatomicmass M inaccordancewiththe relation M T c =constant ; (4.7)

PAGE 69

54 where =1 = 2forthesimpliedBCSmodel.Aswillbeshownlater,thesimpleBC S theorypredictsthat T c isproportionaltotheDebyefrequency D ( ~ D isameasure ofthetypicalphononenergy),andthusthisisexpectedsince theDebyefrequencyis proportionaltothesquarerootoftheatomicmassforasimpleme tal. 4.2.2ThermodynamicProperties Thetransitionofametalfromitsnormalstatetoitssupercondu ctingstateisa thermodynamicphasetransition.Therefore,somesortofchange smaybeexpectedin thermodynamicquantitiesasaspecimenmakesitstransition. Theelectronicpartof specicheat,forexample,increasesdiscontinuouslyat T c fromthelineartemperature dependenceobservedinnormalstate( T>T c ),andthenatverylowtemperaturessinks tobelowthevalueofthenormalphase.Attemperatureswellbe low T c ,thespecicheat decreasesexponentially. Inthermodynamics,wecanuseafreeenergy F ( T )todescribethestabilityofa systematagiventemperature.Naturally,thesystemtendstochan geitsstatetoward thelowerfreeenergy,andbecomesstableataminimumofthefr eeenergy.Belowthe transitiontemperature,thefreeenergyinthesuperconducti ngphase F s isreduced belowthatinthenormalphase F n ( i.e. F s
PAGE 70

55 Thus,from H c ,wecancalculatethefreeenergydierence.ThenusingEq. 4.8 ,we candeduceaseriesofthermodynamicalpropertiesincluding thedierenceinentropy betweentwophases,thelatentheatofthetransition,andthedi scontinuityinthe electronicspecicheat.Thelatentheatofthetransition L vanishesforthetransition inzeroeld,andthusthesuperconductingtransitioninzero eldisofthesecond order.Whenamagneticeldispresent,however,thereisalat entheat,andthenature ofthetransitionchangestotherstorder.Thedierence( F s F n ) T =0 iscalledthe condensationenergy.4.2.3TypesofSuperconductor Superconductorsarecategorizedasbeingoneoftwotypes:ty peIandtypeII.Type Isuperconductorsaremostlythesimple(nontransition)metals andmetalloidswithlow T c .TheBCStheoryexplainsthesesuperconductorsquitewell.Ty peIIsuperconductors, incontrast,aremorecomplex(transitionmetals,intermetall iccompounds,highT c andetc.),andoftenhaveahigher T c .Oneofthemaindierencebetweentwotypes ofsuperconductorsisthemannerinwhichpenetrationoccurs withincreasingexternal magneticeldstrength.Itgenerallydependsalsoontheshapeo fthespecimen,but thecleardistinctioncanbedemonstratedwiththesimplestgeom etryofalongcylinder (diameter > penetrationdepth)withitsaxisparalleltotheappliedel d. TypeI Withtheappliedeldbelowacriticaleld[ H
PAGE 71

56 Withmorecomplexgeometries,theeldsatsomemacroscopicpor tionsofspecimen necessarilyexceed H c ,andtherefore,thesampleexhibitsanintermediatestatewit h somepartsbeingnormalwhilethereststayingsuperconducting.TypeII FortypeIIsuperconductors,therearethreedistinctphasesdep endingonthe strengthoftheappliedeld.Belowalowercriticaleld H c 1 ( T ),thereisnoruxpenetrationjustasfortypeImaterial.Whentheappliedeldexce edsanuppercriticaleld H c 2 ( T ),thereiscompleteruxpenetration,andthespecimenbecome stotallynormal. However,whentheappliedeldisinbetween H c 1 ( T )and H c 2 ( T ),thereisapartialpenetrationofruxintothespecimendevelopingarathercomplic atedmicroscopicstructure ofbothsuperconductingandnormallyconductingregions.Thi sphaseisknownasthe mixedstate(orShubnikovphase).Theruxpenetratesinthefor mofthinlaments (referredasvortexlines).Inthecoreofalament,theeldi shighandthematerialis normal.Eachlamentissurroundedbyasuperconductingscreen ingcurrentandenclosesexactlyoneruxquantum 0 .Currentrowsthroughthesuperconductingregions andthusthematerialstillhaszeroresistance.Thevortexline srepeloneanotherdue tothemagneticforcebetweenthem,andthustheyarrangethe mselvesintoanordered arrayofatriangularlattice.Withincreasingexternaleld ,thedistancebetweenthe vortexlinesbecomessmaller,andat H c 2 theyoverlapcompletely.Themagnetization curveoftypeIIsuperconductorsisquitedierentfromthato ftypeI.Upto H c 1 4 M riseslinearlywiththeappliedeld H justliketypeI.At H c 1 partialpenetrationbegins, andthemagnetizationdecreasesmonotonicallywithincreasi ngelduntilitvanishes completelyat H c 2 .IncontrasttothebehavioroftypeI,thetransitionisnotabr upt. 4.2.4LengthScalesLondonEquationandPenetrationDepth InaneorttodescribetheobservedbehavioroftheMeissnereec tcorrectly,F. andH.Londonsuggestedacondition(knownastheLondonequatio n)thatthelocal magneticeld h ( r )andthecurrentdensitycarriedbysuperconductingelectron s j s ( r )

PAGE 72

57 satisfy 3 r j s = N s e 2 mc h ; (4.9) where m istheeectivemassofthesuperconductingelectrons,and N s isthesuperconductingelectrondensity(orsuperruiddensity). 4 Thispurelyphenomenological equation,togetherwiththeMaxwellequation r h =4 j s =c yields r 2 h = h 2L ; (4.10) r 2 j s = j s 2L ; (4.11) wherethelengthscale L ,knownastheLondonpenetrationdepth,isdenedby L ( T )= mc 2 4 N s ( T ) e 2 1 = 2 : (4.12) Eqs. 4.10 and 4.11 allowustocalculatethedistributionofeldsandcurrentsw ithina superconductor.Forthesimplestgeometryofasemi-innitesupe rconductorsoccupying thehalfspace z> 0,thesolutionsoftheseequationsdecayexponentiallyshowin g thatbothmagneticeldsandcurrentsinsuperconductorscan existonlywithinalayer ofthickness L ofthesurface.Therefore,theLondonequationimpliesthatw hena superconductorisinanexternalmagneticeld,thesurfacecu rrentrowsinathinlayer andkeepstheinterioreld-free; i.e. ,theMeissnereect. CoherenceLength TheLondonequation(Eq. 4.9 )assumesthatthecurrentdensity j s ( r )atone point r isrelatedtotheeld h ( r )(orthevectorpotential A ( r ))atthesamepoint. 3 Fieldsandcurrentsareassumedtobeweakandslowlyvaryingont helengthscale ofthecoherencelengthofthesuperconductor. 4 TheLondonbrothersincorporatedthetwo-ruidmodelofGort erandCasimir[ 47 ]. Themodelseparatesthetotaldensityofconductionelectrons N intoadensityofsuperconductingelectrons N s (superruiddensity)andadensityofnormalelectrons N n (normalruiddensity)suchthat N = N s + N n N s N as T 0,and N n = N when T>T c .Theyassumedthatonlythesuperruidparticipatesinasupercur rentwhilethe normalruidremaininertat T
PAGE 73

58 Thus,theLondonequationisalocalequation.However,itismo regeneraltoassume that j s ( r )atonepoint r willdependonthevectorpotential A ( r 0 )atallneighboring points r 0 .Inordertodescribethisnon-localeects,Pippardmodiedt heLondon equation,andintroducedalengthscale 0 ,suchthat j r r 0 j 0 [ 48 ].Thisdistance 0 isoneoffundamentallengthscharacterizingasuperconduct or,andisreferred toasthecoherencelength.Inonecontext,itisusedforthedi stanceoverwhich thedensityofsuperconductingelectrons N s variessignicantly(fromzerotofull thermodynamicvalue).Inanothercontext,itisusedasthespa tialextentofthepair wavefunction( i.e. ,thesizeofaCooperpair).Inpurematerialswellbelow T c ,however, bothcoherencelengthdenitionshavethesamevalue;usingth euncertaintyprinciple, Pippardestimatedthecoherencelengthtobe 0 = ~ v F 0 ; (4.13) where v F istheFermivelocity,and 0 istheenergygaparoundtheFermisurfacein thesuperconductingstateatabsolutezero.NotethatthePippar d'scoherencelengthis independentoftemperature. IntheLondonmodel,itwasassumedthatthedensityofsupercondu ctingelectrons N s wouldhavethefullthermodynamicvaluerightfromthesurfac e( i.e. 0 =0).Since j s and h varyonascale L ,wemightexpectthattheLondon'smodelisvalidonlyfor L 0 .Infact,thisisthecase,andPippard'snon-localmodelredu cestotheLondon modelinsuchalimit.Thematerialsthatsatisfythiscondition ( L 0 )arethetype IIsuperconductors,andEq. 4.12 accuratelycalculatethepenetrationdepthforthetype II. IntypeImaterials,ontheotherhand,thepenetrationdepthi smuchshorter thanthecoherencelength( L 0 ).Thus, N s doesnotreachitsfullvalueoverthe penetrationdepth.Thisimpliesthatnotalloftheelectron swithinthethickness 0 fromthesurfacecontributetothescreeningcurrents.Forthese materialstheLondon equationisinadequate.Inordertocalculatethepenetrati ondepthinthetypeI materialsmoreaccurately,thePippard'snon-localmodelh astobeused,andarigorous

PAGE 74

59 calculationgives 3 =0 : 62 2L 0 : (4.14) Consequently,theeldpenetratestypeImaterialsdeeperth antheLondonvalue. Ginzburg-LandauTheory AnotherphenomenologicalapproachproposedbyGinzburgandL andau(GL) describessuperconductivityintermsofacomplexorderparam eter ( r )= j ( r ) j e i whosemagnitude j ( r ) j isameasureofthesuperconductingorderatposition r below T c [ 37 49 ].Theorderparameter iszeroabove T c andincreasescontinuouslyasthe temperaturefallsbelow T c .Thephysicalsignicanceof ( r )wasnotclearatthetime theGLtheorywasdeveloped,butnowwecaninterpretitasawa vefunctionofa particleofmass m ,charge q ,anddensity N ,whicharegivenby m =2 m; (4.15) q =2 e; (4.16) N = j j 2 = N s = 2 ; (4.17) where m e ,and N s aretheeectiveelectronmass,electroncharge,andsuperruid density,respectively. IntheGLformalism,twotemperaturedependentcharacteristi clengthsareintroduced:thecoherencelength ( T )andthepenetrationdepth ( T ).TheGLcoherence lengthdenesthelengthscaleoverwhich ( r )varies,andisgivenby ( T )= ~ 2 2 m j j 1 = 2 ; (4.18) where isatemperaturedependentcoecientinthe j j 2 termofthefreeenergy (See[ 40 ]).ItiscloselyrelatedtothePippardcoherencelength 0 denedinEq. 4.13 .In weakelds,theGLpenetrationdepthisgivenby ( T )= m c 2 4 q 2 j 2 0 j 1 = 2 ; (4.19) where 0 istheequilibriumorderparameterwellinsidethematerial.

PAGE 75

60 Forapurematerialnear T c ,themicroscopiccalculationintheBCSapproximation gives ( T )=0 : 74 0 1 T T c 1 = 2 ; (4.20) ( T )= 1 p 2 L (0) 1 T T c 1 = 2 : (4.21) Sincebothdivergesinthesamewayas T T 0 ,itispracticaltoformtheirratio = ( T ) ( T ) : (4.22) Theratio isknownastheGinzburg-Landauparameterofthematerial.F orapure material,thisisgivenby =0 : 96 L (0) 0 : (4.23) Thedierenceinthebehavioroftwotypesofsuperconductors inamagneticeld dependsonwhetherthecreationofinterfacesbetweennorma landsuperconducting regionsisenergeticallyfavorable,ornot.Penetrationof magneticeldreducestheeld energypenaltyimplicitintheMeissnereect.Thus,amaterial withlarge favors interfaces.Largecoherencelengthmeansagreaterextentof thesuperconductingstate. Therefore,withtheassociatedenergygainfromthesupercondu ctingcondensation energy,alarge opposesinterfaces.Interfacialenergychangessignat =1 = p 2.When < 1 = p 2,thematerialisthetypeI,while > 1 = p 2,thematerialisthetypeII.Inthe limitof 1,theGLtheoryreducestotheLondontheory. ElectronMeanFreePath Anotherimportantlengthscalecharacterizingasuperconduct oristheelectron meanfreepath l inthenormalstateduetoelasticscatteringbydisorder.Inthe presenceofdisorder,wecandeneaneectivecoherencelengt h ( l ),whichisvalidat absolutezero, 1 ( l ) = 1 0 + 1 l : (4.24) Dependingofthesizeof l relativeto 0 ,wecanthinkoftwolimitingcasesconcerning thepurityofasuperconductor:cleanlimitanddirtylimit[ 44 ].Uptothispoint,we

PAGE 76

61 haveconcernedonlypurematerials,andthemeanfreepathhas playednoroleon determiningthecharacteristiclengthscales.Inreality,how ever,theactualvaluesof bothcoherencelengthandpenetrationdeptharesomewhatmod iedfromthevalues denedabovebymeanfreepatheects. Inthecleanlimit( l 0 ),Eq. 4.24 gives ( l )= 0 : (4.25) Thus,thecoherencelengthandthepenetrationdepthwediscusse dabovecanbeused withoutanymodication. Incontrast,Eq. 4.24 givesforthedirtylimit( l 0 ), ( l )= l: (4.26) Thus,thecoherencelengthatabsolutezeroiscompletelydete rminedbythemeanfree path,thelengththatgovernsthetransportpropertiesofthe materialinthenormal state.Inthislimit,therelationshipbetweencurrentandmag neticeld( i.e. ,vector potential),andinturn,magneticpenetrationdeptharemod ied.NotethattheLondon penetrationdepth L giveninEq. 4.12 isanexpressionforpuremetals.Thedirtylimit expressionofthemagneticpenetrationdepthis[ 40 ] = L 0 l 1 = 2 ( l 0 ) : (4.27) Thus, increasesas l becomesshorter.Attemperaturesnear T c ,thecoherencelength andthepenetrationdepthinthedirtylimitaregivenby[ 40 ] ( T )=0 : 85( 0 l ) 1 = 2 1 T T c 1 = 2 ; (4.28) ( T )=0 : 62 L 0 l 1 = 2 1 T T c 1 = 2 : (4.29) Thus,theGLparameterforadirtymaterialisgivenby =0 : 75 L (0) l : (4.30)

PAGE 77

62 Consequently,asthemeanfreepathbecomesshorter,thecoher encelengthbecomes smallerthanthatgiveninEq. 4.13 andpenetrationdepthbecomeslongerthanthe London'sdenedinEq. 4.12 .Infact,itfrequentlyhappensthatalloyingapuretypeI superconductortransformsitintoatypeIIsuperconductor.Ma nyofsuperconductorsin theformofthinlms,nottomentionthoseinamorphousform,ar einthedirtylimit. 4.2.5BCSTheory In1957,Bardeen,Cooper,andSchrieer(BCS)proposedamicr oscopictheory ofsuperconductivity(nowknownastheBCStheory)[ 38 ].Acentralresultofthe BCStheoryistheexistenceofanenergygapbetweentheelectr onsysteminthe superconductinggroundstateandtheexcitedstates.Here,wewil lonlydescribethe underlyingideas,assumptions,andmajorpredictionsassociated withthetheory, withoutanyrigorousmathematicaldetails.CooperPairs Thegroundstate( T =0K)ofanon-interactingFermigasofelectronscorresponds tothesituationwhereallelectronstateswithwavevector k withintheFermisphere (with E F = ~ 2 k 2 F = 2 m )arelledandallstatesoutsideareempty.Ifapairofelectro ns isaddedinstatesjustabove E F ,thetotalenergyofthesystemshouldincreasebythe kineticenergyofthepair.However,Cooperrecognizedthati fthereisanattractive interactionbetweentheelectrons,nomatterhowweakitis,th eywillformabound state,andaddingapairofelectronsmayreducethetotalener gy(kineticpluspotential energy). 5 Thus,thenormalstatebecomesunstabletotheformationofthese paired boundstates[ 50 ]. 5 Notethatthesetwoadditionalelectronsarepreventedfromin dividuallyhaving energylessthan E F bythePauliexclusionprinciple.

PAGE 78

63 SinceelectronshavearepulsiveCoulombinteraction, 6 theattractiveforcemust, intheory,comefromsomeinteractionbetweentheelectronst hatismediatedbysome othermechanisminherentinthematerial.Cooperarguedthat continuousexchangeofa virtualphononbetweenelectronsoccupyingstates k 1 and k 2 providesamechanismfor aweakattractionthatresultsinthereductionoftotalenerg y. 7 Theprobabilityofthe energy-reducingphononexchangeprocessesismaximumforthe case k 1 = k 2 = k .It isthereforesucienttothinkthatelectronswithequalando ppositewavevectorsform apair.Thisso-calledCooperpaircanberepresentedbyatwo-p articlewavefunction givenby ( r 1 ; r 2 )= X k a k e i k ( r 1 r 2 ) ; (4.31) whichissymmetricinspatialcoordinates( r 1 ; r 2 )uponexchangeofelectrons1and2. Therangeofsummationisconnedto E F < ~ 2 k 2 2 m
PAGE 79

64 BCSGroundState TheformationofaCooperpairleadstoanenergyreduction.I narealmaterial, manymoreelectronsparticipateintheCooperpairingtoach ieveanewlower-energy groundstate.BecauseaCooperpairiscomposedoftwofermionsw ithoppositespin, itmaybeconsideredasasingleentitythatobeysBose-Einsteinst atistics.Thus,at T =0K,allCooperpairscondenseintoanidenticaltwo-electro nstateeventhoughthe individualelectronsarebeingscatteredcontinuallybetwe ensingleelectronstates.The Pauliprinciplelimitsthestatesintowhichthetwointeract ingelectrons,whichmakeup thepair,maybescattered. Inordertocalculatethegroundstate( T =0K),BCSmadeseveralassumptions forsimplicity.Firstofall,justlikeCooperdid,theBCStheor yisbasedonthefree electronapproximation.Thus,theFermisurfaceisspherical. Theyalsosimpliedthe netattractiveinteractionbetweenelectronsbyexpressingt hematrixelementthat describesscatteringoftheelectronpairfrom( k ; k # )to( k 0 ; k 0 # )andviceversa as 9 V kk 0 = 8><>: V=L 3 for j k j ; j k 0 j < ~ D 0otherwise ; (4.33) where V isapositiveconstant, L 3 isthevolumeofthesystem, ~ D istheDebyeenergy, and isthekineticenergyrelativetotheFermilevel,whichisde nedas = ~ 2 k 2 2 m E F : (4.34) Further,theyapproximatedtheBCSgroundstatevectorofthe many-bodysystem ofallCooperpairsbytheproductoftheidenticalpairstatev ectors.Withallthe assumptions,theydeducedthegroundstateenergyofthesupercon ductor,andshowed 9 Insomematerials( e.g. ,HgandPb),theelectron-phononinteractionisverystrong. Insuchcase,thenetinteractionbetweenelectronsisquiteco mplexandevenretarded. Sincephononsaretheoriginofthecoupling,thephononstruc tureofeachmaterialwill alsoinruencethematrixelement.TheextensionoftheBCStheo rytostrong-coupling superconductorsisknownasthestrong-couplingtheory[ 44 ].

PAGE 80

65 NE ()/ N (0) EE F E F + D 0 E F + D 0 1 NE ()/ N (0) EE F 1 E+(T) F D E-(T) F D(a) (b)electron-likethermalquasiparticles hole-likethermallquasiparticles NTkT qB ()~exp(-2/) D 0 Figure4{1:(a)DensityofstatesinBCSgroundstate(at T =0K)relativetothatin normalstate.Agapof2 0 isdevelopedaroundtheFermilevel.Theshadedregionare thestatesoccupiedbysuperconductingelectrons.Notethatnost atesarelostinthe phasetransition.(b)Correspondingdensityofstatesatnitete mperature( T
PAGE 81

66 0.00.20.40.60.81.0 0.0 0.2 0.4 0.6 0.8 1.0 D ( T )/ D (0)T / T c Figure4{2:Temperaturedependenceofthegapasafunctiono ftemperatureinthe BCSapproximation.BCSPredictions Attemperaturesabove T =0K,thermallyexcitedphononsbecomeavailableto scatterelectronsinaCooperpair.Thus,thereisaniteproba bilityofndingelectrons inthestatesabovethegap2(seeFigure 4{1 ).Theseexcitedelectronsarecalled quasiparticles.Asthetemperatureincreases,pair-breakingis progressivelyenhanced, andnallyCooperpairsceasetoexistat T c .Inameantime,thegap2shrinksas T increases,andcompletelyclosesat T c .IntheframeworkoftheBCStheory,onecan deducethetemperaturedependenceofthegap( T )asthesolutionto 1 N (0) V = Z ~ D 0 d p 2 + 2 [1 2 f ( p 2 + 2 )] ; (4.37) where f ( E )istheFermifunction.Notethatfor T =0, f ( E )iszero( E beingpositive), andonerecoversEq. 4.35 .Thisequationdenesanimplicitrelationbetweenand T andnumericalanalysisyields( T )asshowninFigure 4{2 .Asthegureshows,thegap developsquicklyasthetemperatureisloweredbelow T c ,andopensupalmostfullybya halfof T c .Itisalsoconvenienttorememberthattheresultofnumerical analysiscanbe

PAGE 82

67 approximatedby ( T ) (0) = vuut cos 2 T T c 2 # : (4.38) Attemperaturesnear T c ,thevalueofthegapcanbeapproximatedby ( T ) (0) 1 : 74 1 T T c 1 = 2 : (4.39) Bysetting=0inEq. 4.37 ,anequationfor T c isdeterminedby 1 N (0) V = Z ~ D 0 d tanh 2 k B T c : (4.40) For ~ D k B T c ,numericalcalculationyields k B T c =1 : 14 ~ D e 1 =N (0) V : (4.41) Then,bycomparingEq. 4.36 withEq. 4.41 ,onecanndtherelationshipbetweenthe groundstategap 0 [ (0)]and T c intheweak-couplinglimitas 2 0 k B T c =3 : 52 ; (4.42) whichisfreefromparameterssuchas V and D 11 Thisrelationshipagreesquitewell (withinabout10percentwithtunnellingexperiments[ 52 ])fortheweaklycoupled superconductors.Forthosestrong-couplingsuperconductors( e.g. ,HgandPb),theratio islargerthan3.52.Forexample,theratioforHgandPbwereex perimentallyfoundto be4.6and4.3,respectively.Thestrong-couplingtheory[ 44 ]providesbetteragreement. Atnitetemperature,thequasiparticle-occupationofthee xcitedone-electronstates E =( 2 + 2 ) 1 = 2 obeysFermistatistics.Therefore,thedensityofquasiparticle sata 11 TheDebyetemperature D (hence,Debyefrequency D )maybededucedfrom specicheatmeasurement,butthematrixelement V isdiculttocalculateprecisely. Therefore,parameter-freeexpressionaredesired.

PAGE 83

68 functionoftemperatureisgivenby N q = X k f k = Z 1 1 f ( E ) N ( ) d 2 N (0) Z 1 0 d 1+exp( p 2 + 2 =k B T ) : (4.43) 4.2.6EliashbergFormalism IntheBCStheory,thedynamicinteractioninducedamongele ctronsbyphonon wascrudelyrepresentedbyusingadimensionlessconstant N (0) V asthestrengthof electron-electroninteractionandtheDebyeenergy ~ D asthemaximumphononenergy; thedetailsoftheelectron-phononcouplingwasnotconsider edatall.Eventhough thetheorywasquitesuccessfulforweak-couplingsuperconduct ors,itfailedtotreat strong-couplingsuperconductorsaccurately.Eliashbergtoo kamoregeneralapproachto theelectron-phononcouplingbytakingintoaccounttheret ardednatureofthephononinducedinteractionandbyproperlytreatingthedampingof theexcitations[ 44 53 54 55 ]. TheEliashbergtheorystartswithtwononlinearcoupledequat ionsforthegap andtherenormalizationfactor Z ,whichreplacetheBCSgapequation.IntheEliashbergequations,twoparameters, and ,areintroduced,where isknownasthe Coulombpseudopotential(ortherenormalizedCoulombinter actionparameter)which describesaresidualrepulsivescreenedCoulombinteraction[ 56 ],and isknownasthe electron-phononcouplingconstant 12 whichisrelatedtotheattractiveinteraction.The constant isdenedby 2 Z 1 0 2 (n) F (n) n d n ; (4.44) where 2 (n)istheeectiveelectron-phononinteraction,and F (n)isthephonondensity ofstateswithnthefrequencyoftheexchangedphonon.IntheE liashbergtheory, 12 Theparameter isalsoknownasmass-renormalization(ormass-enhancement) parameterbecausetheeectiveelectronmassismodiedbythe electron-phononinteractionas Z =1+ = m =m .Superconductorsarecharacterizedaccordingtothe magnitudeof ,weak-coupling( 1),intermediatecoupling( 1),strongcoupling ( > 1).

PAGE 84

69 2 (n) F (n)(theelectron-phononspectraldensity)isanimportantfu nctionthatcontains alltherelevantinformationabouttheelectron-phononint eractionthatgivesrisetothe eectiveattractiveinteractionbetweenelectronsaround theFermienergy.Inprinciple, superconductingtunnellingmeasurementsprovidedirectinf ormationon 2 (n) F (n). Forasimplemodelofametal, 2 (n) F (n)canbeapproximatedatlowfrequenciesby thequadraticform b n 2 ,where b isaconstantcharacteristicofagivenmaterial.Forthe strong-couplingsuperconductors, 2 (n) F (n)showssignicantlowfrequencystructure. FromtheEliashbergequations,McMillandevelopedamuchmore quantitative equationfor T c thantheBCSresult(Eq. 4.41 )[ 57 ].TheMcMillanformulaimproved laterbyAllenandDynesisgivenby[ 58 ] k B T c = ~ n ln 1 : 2 exp 1 : 04(1+ ) (1+0 : 62 ) ; (4.45) wheren ln isacharacteristicphononfrequencydenedby[ 58 ] n ln exp + 2 Z 1 0 ln(n) 2 (n) F (n) n d n : (4.46) AlsofromtheEliashbergequations,theratio2 0 =k B T c isexpressedapproximately by[ 55 ] 2 0 k B T c =3 : 53 1+12 : 5 T c ln 2 ln ln 2 T c # ; (4.47) where ln = ~ n ln =k B .Thisequationincludesstrong-couplingcorrectionsinter msofthe parameter T c = ln ,andtheuniversalBCSvalueisrecoveredfor T c = ln 0.Itshows excellentagreementwithexperiment.

PAGE 85

CHAPTER5 SYNCHROTRONRADIATIONANDPUMP-PROBETECHNIQUE 5.1SynchrotronRadiation 5.1.1Introduction Itiswellknownthatanacceleratedchargedparticleemitse lectromagneticradiation[ 9 ].Synchrotronradiationisradiationemittedbyachargemo vingatrelativistic speed.Itisaverystable,highrux,broadbandlightsource.Ina ddition,ithaspeculiar propertiessuchaspolarization,pulsedtimestructure,angul arcollimation,andsmall sourcesize.Itwasrstidentiedasatechnicalprobleminacce leratorphysics,butits propertiesmakesynchrotronvitalforvariouseldsofscienc e. Synchrotronfacilitiesavailablearoundtheworldarebased ontheuseofan electronstoragering,aclosed,high-vacuumchamberwithanu mberofcirculararc andstraightsegments.Inthissectionthetheoryandproperties ofsynchrotronradiation aresummarizedinparticularforanelectronmakingacircula rtrajectoryatadipole bendingmagnetsectionofastoragering.Synchrotronradiati onfromso-calledinsertion devices,suchaswigglersandundulatorsplacedatstraightsegm ents,willnotbe discussedhere[ 59 60 ]. 5.1.2RadiatedPowerfromaBendingMagnet Forasinglenonrelativistic( v c )acceleratedparticlewithcharge e ,thetotal instantaneousradiatedpowerisgivenbyLarmorformula: P = 2 3 e 2 c 3 j v j 2 ; (5.1) where v istheaccelerationofelectron. Larmorformulacanbegeneralizedforarbitraryvelocities byaseriesofLorentz transformations.Foraparticleofmass m incircularmotionwithvelocity = v=c energy E ,andradiusofcurvature(thebendingradius) ,therelativistic( v c ) 70

PAGE 86

71 generalizationoftheformulais[ 9 59 60 61 ] P = 2 3 e 2 c 2 4 r 4 (5.2) where r = E=mc 2 .Theemittedpowerisproportionaltothefourthpowerofthe energy andinverselyproportionaltotherestmass.Thispropertyexpla inswhyelectronsare usedratherthanotherheavierchargedparticlessuchasproto ns.Whenelectrontravels aroundastoragering,itmakesacirculartrajectoryandemit sradiationonlywhileit experiencesmagneticeldateachbendingmagnet. 1 Thus,thetotaltimeforittohave radiative-energylossperrevolutionis2 =c .Therefore,theradiative-lossperturnby oneelectronis E = 4 3 e 2 3 r 4 : (5.3) Forahighlyrelativisticelectrons( 1)Eq. 5.3 isexpressedinpracticalunitsas 2 E (keV) 88 : 5 [ E (GeV)] 4 (m) : (5.4) Thesynchrotronradiationspontaneouslyemittedfrommanyele ctronsinrandom distribution(asfromastoragering)isgenerallyincoherent .Figure 5{1 schematically showsthissituationaswellascoherentradiationwhichcanbe foundforexampleinthe coherenttelahertzemissionfrommicro-bunchedelectronsor inthefreeelectronlasers (FEL).Inincoherentcase,thetotalradiatedpowerby N electronsintheringissimply NE=T where T istheperiodofelectroncirculationaroundthering.There fore,the totalpowerradiatedbyringwithringcurrent i isgivenby 3 P ring (kW) 88 : 5 [ E (GeV)] 4 (m) i (A) 26 : 5[ E (GeV)] 3 B (T) i (A) : (5.5) 1 Thebendingradius isrelatedtothemagneticeld B ofthebendingmagnet, whichisgiveninpracticalunitsas (m) 3 : 336 E (GeV) =B (T).FortheVUVringwith E =0 : 808GeVand B =1 : 41T,thebendingradius is1.91m. 2 FortheVUVring, E 20keVperelectronperrevolution. 3 FortheVUVring, P ring 20kW/ampofbeam.

PAGE 87

72 (a) Incoherent ENEPNP incoherentsingleincoherentsingle ~~ 1/2 (b) Coherent ENEPNP coherentsinglecoherentsingle ~~ 2 Figure5{1:(a)Incoherentradiationfrom N -electronsinrandomdistribution,and(b) coherentradiationfrommicro-bunched N -electrons. Acceleration Electron orbit (a)<<1 b (b)~1 b q y Bending radius q Figure5{2:Angulardistributionofradiationemittedfroman electronmovingalonga circularorbit.Thisequationtellsusthatthetotalintensitydeliveredtoe achbeamlineisproportional tothebeamcurrent,thusthecurrentsignalcanbeusedtonorma lizemeasuredspectra inordertocompensatetimevaryingintensityduetodecayofbe amcurrent. 5.1.3AngularCollimationandPolarization Foranelectroncirculatingatnonrelativisticspeed,theang ulardistributionof emissionisadipolepatternwhichextendstoalargerangeofan gles(seeFigure 5{2 ). Forarelativisticelectron,however,theradiationisstrong lyconcentratedtoanarrow angularrangearoundadirectiontangentialtotheorbitassh owninFigure 5{2 .The divergenceoftheverticalangle isroughlyestimatedfrom r 1

PAGE 88

73 Theinstantaneouspower(incgsunitsoferg/[secradcm])radi atedperunit wavelengthandperunitverticalangleaccordingtotheSchw ingertheory[ 61 ]isgivenby d 2 P ( ; ;t ) dd = 27 32 3 e 2 c 3 c 4 r 8 (1+ X 2 ) 2 K 2 2 = 3 ( )+ X 2 1+ X 2 K 2 1 = 3 ( ) ; (5.6) where X = r ; = c (1+ X 2 ) 3 = 2 = 2 ; andthesubscripted K 'saremodiedBessel functionsofthesecondkind.Theparameter c iscalledcriticalwavelengththat characterizesthespectraloutputofparticularstoragering whichisgivenby 4 c =4 = 3 r 3 : (5.7) Halfthetotalpowerisemittedasphotonsofwavelengthshorte randhalflongerthan c Eq. 5.6 isthebasicformulaforthecalculationofthecharacteristic softhesynchrotron radiation. Thebendingmagnetradiationhasapeculiarpolarizationpr operty.Thetwoterms inthesquarebracketsofEq. 5.6 areassociatedwiththeparallelandperpendicular componentsoftheemittedpower,respectively.Atsmallverti calangles theradiation ispredominantlypolarizedinthedirectionparalleltothe electron'sorbitalplane,andat =0,itiscompletelylinearlypolarized.Astheverticalangl eincreases,perpendicular componentstartsshowingup,buttheparallelcomponentisalw aysthelargeroftwo. Bothcomponentsarephasecorrelated,andasaconsequence,th eemissionobserved aboveandbelowtheelectron'sorbitalplane( i.e. 6 =0)isellipticallypolarized.In Figure 5{3 thenormalizedintensitiesoftheparallelandperpendicula rcomponentsare plottedasafunctionof fortheVUVringofNSLSatthreedierentphotonenergies. Thisgureshowsthattheradiationisstronglyconcentrateda tthecriticalwavelength, buttheverticalspreadincreasesatlongerwavelengths. 4 Alternativeparameterusedforthesamepurposeisthecriticalp hotonenergywhich isgivenby h c = hc= c =3 hcr 3 = 4

PAGE 89

74 010203040 0.0 0.2 0.4 0.6 0.8 1.0 dash://solid: ^ blue:100cm-1green:1000cm-1red: lcNormarizedIntensityy [mrad] Figure5{3:Angulardistributionofparallelandperpendicul arpolarizationcomponentsatthreedierentphotonenergies.Thecriticalwavele ngthoftheVUVringis19 : 9 A( 5 ; 000 ; 000cm 1 ). 5.1.4RFCavityandPulsedNature TheacceleratingeldsinsidetheRFcavitysystemperiodicall yactsonthecirculatingelectronstorestoretheenergylostduetoemission.Becauset heRFeldoscillates, onlyelectronsarrivingataparticulartimereceivethepro peracceleration.Thisleads toformelectronbuncheswhicharecontainedinregularlyspa ced,imaginarycontainersso-called\RFbuckets"[ 21 ].Therefore,thelightproducedbythesynchrotronis pulsed.Thispulsedtimestructureofthesynchrotronradiation wasexploitedinour time-resolvedmeasurements.Fortheordinarylinearspectrosco picexperiments,thetime constantofcommondetectorsaremuchlongerthanthepulserep etitionperiodofthe radiation.Forexample,themostcommonlyusedfarinfraredde tectorsisabolometer. Itisathermaldetectorwithatypicaltimeconstantontheord erofmilliseconds.Thus suchadetectorseespulsesjustassteady-statesourceoflight. ThemaximumnumberofbucketsisdeterminedbytheRFfrequen cy rf ofthe cavityandthetime T 0 (orcircumference D )foranelectrontomakeonerevolution

PAGE 90

75 aroundthering,whichisgivenby N max b = rf T 0 = rf D v ; (5.8) where v isthevelocityoftheelectron.Anyintegralnumberofbucket ssmallerthan N max b canbelledwithelectronsarbitrarily. 5 Withinabunch,electronsaredistributedrandomly,andther eisaslightspreadin energyfromthatoftheaverageelectronwhichistravelling aroundtheidealelectron pathatthereferencecenterofthebunch.Allelectronsinabu ncharemovingatthe samespeed( v c )andsubjecttothesameLorentzforcewhilepassingthrougha bendingmagnet.However,theelectronwithslightlyhigher(l ower)energyhaslarger (smaller)mass.Asaconsequence,ithasslightlylonger(shorter)o rbitallengththan thereferenceorbit,andthusarriveslater(earlier)thant hereferenceelectron.The acceleratingeldactstoelectronsinsuchawaytobringthee nergyofallelectrons closertothatofreferenceeverytimeabunchentersthecavit y.Figure 5{4 schematically illustratestheeldfoundbyelectronsarrivingatcavityat dierenttimes. TheRFsystemisdesignedtoregainonlytheenergylostbyradiati onforthe referenceelectron,butmore(less)energyforelectronsarri vingearlier(later).This causeslongitudinaloscillationsaboutthecenterofthebunc h,whichisreferredas synchrotronoscillations. 6 5.1.5BeamLifetime EventhoughtheelectronenergyismaintainedbytheRFsystem, theelectrons haveanitelifetimeduetotwomajormechanisms[ 59 ]:thescatteringofelectrons byresidualgasparticlesinthevacuumchamberandTouscheke ect(discussedbelow).Therefore,rellingofelectronsareregularlyschedu ledeveryafewhours.As 5 FortheVUVring, N max b =9. 6 Besidesthesynchrotronoscillations,electronsinabunchmake transverse(bothhorizontalandvertical)oscillatorymotion,whicharecalledt hebetatronoscillations.Pairs ofquadrupolemagnetsareusedtofocuselectronstowardther eferenceorbital.

PAGE 91

76 RFsystem 4thharmonicsystem RF+4thharmonic RF voltage Time RF voltage Time Accelerating voltagefound by referenceelectron 0 0 Figure5{4:Theacceleratingvoltageasafunctionoftime.T hetime=0correspondsto thearrivalofthereferenceelectron.TheRFsystemisdesigned toregainonlytheenergylostbyradiationforthereferenceelectron,butmore(l ess)energyforelectronsarrivingearlier(later).Therighthandsideshowstheeectofu singthehigherharmonic cavitysystemusedinconjunctionwiththemainRFsystemintheeo rttoincreasethe lifetime.The4thharmonicsystemisshownhere.Eachbunchseesa ratvoltagewhich stretchesthebunchlength.explainedintheprevioussubsection,theelectronsoscillate aroundthereferenceorbitwhileorbitingaroundthering:betatronoscillations(t ransverseoscillations)and synchrotronoscillations(longitudinaloscillations).TheTo uschekeectiscausedby thescatteringbetweentransverselyoscillatingelectronsinsi deeachbunch.Thistype ofelectron-electronscatteringconvertspartofthetransve rsemomentumintolongitudinalmomentumthatmodiesthetimeatwhichtheelectron enterstheRFcavity. Then,thoseelectronswhichgainedlargeenoughlongitudina lmomentumarenolonger properlyaccelerated,andcanbelostfromthebunch.Theeec tismoreseverewhen electronsarepackedtighter.Rightafterelectroninjecti on,electrondensityisthehighest.Therefore,theTouschekeectisthedominantlifetimeli mitingmechanismatthe earlystageofbeamcurrentdecaywithtime-dependentdecayt ime.Astheelectron densitydecreases,thescatteringbyresidualgasparticlesstart stotakeover,andatthis time,thedecaybecomesexponentialthatisrepresentedbyasi nglecharacteristicdecay time. AhigherharmonicRFcavitycanbeusedtorattenthepotential inthemain RFbucketcausinganincreaseinthebunchlengthwithaconseque ntreductionof

PAGE 92

77 intrabeamscatteringandanimprovementintheTouscheklifet ime.Figure 5{4 shows theeectofusingthehigherharmoniccavitysystemusedinconju nctionwiththemain RFsystemintheeorttoincreasethelifetime.5.1.6InfraredSynchrotronRadiation TheEq. 5.6 canbeconsiderablysimpliedinthespectralrangewherewavel engths aremuchlongerthanthecriticalwavelength c .Thiscondition( c = 1)isusually satisedintheentireinfraredwavelengthsforthemoststorage rings,andwecanobtain usefulexpressionsvalidfortheinfraredsynchrotronradiatio n(IRSR)suchas[ 62 ] dP ( ;t ) d =8 : 6416 10 10 i 1 = 3 7 = 3 G W cm ; (5.9) d 2 P ( ; ;t ) d =0 =5 : 2 10 10 i 2 = 3 8 = 3 H W radcm ; (5.10) where and arebothincm, i (theringcurrent)inA,and inmrad.Thefunctions G and H aredenedas G = 1 2 : 193 1 r 2 2 = 3 ; (5.11) H = 1 6 : 312 1 r 4 4 = 3 : (5.12) For c = 1, G and H canbetakentobeunity. Theverticalopeningangleasafunctionofwavelengthisgiv enby ( )=1 : 66188 1 = 3 G [rad] : (5.13) Notethatistwiceoftheangledenedfortheangulardiverge nce (seeFigure 5{2 ). Thisisausefulexpressionwhenwedeterminethenaturalopenin ganglethatisnecessarytocollectthefull-widthathalf-maximumofthepowerp roleatagivenwavelength.Figure 5{5 showsintheinfraredspectralrangeasafunctionofwavenumb er usingtheVUVringparameters. 7 7 TheU12IR'srstmirroriscapableofcorrectinglightwith90m radofthevertical openingangle.

PAGE 93

78 110100100010000 10 100 1000 Y [mrad]Frequency[cm -1 ] Figure5{5:ThenaturalopeningangleofIRSRusingtheVUVringp arameters. 5.1.7SourceComparison TheEq. 5.5 givesthetotalradiatedpowerfromastorageringinalldirec tions integratedoverentirespectralrange.Althoughthetotalpow ercertainlyindicates certainaspectoftheoutputcapability,itdoesnotdescribes superioritiesofsynchrotron radiationoverconventionalthermalsources.Forapractical pointofview,thespectral brightness b isamoreusefulsourcequalityparametersinceittakesintoacc ountthe sourcesizeaswellastheangulardistributionofsynchrotronra diation.Thebrightness ofalightsourceisdenedas b ( )= C F ( ) S n ; (5.14) where C isaconstant, F ( )istheruxofphotons, S isthesourcearea,andnisthe solidangleofemission.Itisintuitivelyobviousthatasourcew ithsmallersizeand divergencehashigherbrightnessjustlikealightbeamfromal aserisbrighterthan thatfromarameofcandle.Asmallsourcesizeallowsopticstofo cusphotonstoa diraction-limitedsize,andsmalldivergenceminimizesthe lossofphotonsevenwith reasonablysmallopticalcomponents.Therefore,abrightersou rcehasamarkedeect

PAGE 94

79 110100100010000 10 -8 10 -7 10 -6 1x10 -5 1x10 -4 10 -3 SpectralPower[W/cm -1 ]Frequency[cm -1 ] Synchrotron Blackbody Figure5{6:Spectralpowercalculatedfora2000Kblackbody sourceandsynchrotron radiation.Forthesynchrotronradiation,parametersforth eVUVringisused.This showsthepoweradvantageofthesynchrotronradiationoverth ethermalsourceonlyin thefarinfraredregion.onimprovingsignaltonoiseratioforvarioustypesofexperim entssuchasmicroscopy andsurfacescience. Figures 5{6 and 5{7 showcalculatedspectralpowerandbrightnesscomparisons betweenconventionalthermalsourceandsynchrotronradiati on,respectively[ 21 ].Inthe plots,ablackbodysourceattemperatureof2000Kwithitssourc esizeof0 : 4cm 2 and solidangleof0.02sr(f/3.5)isused.Forthesynchrotronradiat ion,theparametersof theNSLSVUVringareused. Notethatthesynchrotronshowssignicantlyloweroutputpower thanthethermal sourceovermostofthespectralrange(betweenmid-IRandvisibl e)wheretheglobaris commonlyused(seeFigure 5{6 ).Thesynchrotronhasapoweradvantageonlyinthe veryfarinfrared( 100cm 1 ).Intermsofbrightness,thesynchrotronsourcehasan advantageoverentirespectralrangeshowninFigure 5{7 overthethermalsource,which isobviouslyattributedtoitssmallsourcesizeandangularcoll imation.

PAGE 95

80 110100100010000 10 -9 10 -8 10 -7 10 -6 1x10 -5 1x10 -4 10 -3 10 -2 10 -1 SpectralBrightness[W/(srcm -1 )]Frequency[cm-1] Synchrotron Blackbody Figure5{7:Spectralbrightnesscalculatedfora2000Kblack bodysourceandsynchrotronradiation.Forthesynchrotronradiation,paramet ersfortheVUVringisused. Thisshowsthebrightnessadvantageofthesynchrotronradiati onoverthethermal sourceintheentirespectralrange. 5.2PrincipleofPump-ProbeStudies Thepump-probemeasurementisavaluabletechniquethatdete rminesthenonequilibriumstateofasystematvariousinstantsoftimeaftersomesort ofstimulushasbeen applied.Theprocessisrepeatedforawiderangeoftimevalue stobuildupacomplete historyofthesample'srelaxationprocesses,namelythedynamic softhesystem.There areavarietyofexcitation(pumping)methodscommonlyusedt hatprovideadequateenergydensitytocreatethedesireddensityofexcitationsinthe sample.Examplesinclude electricalcurrent,electriceld,magneticeld,orlight pulses.Herewewilldiscussthe principleofthetechniquethatusesnearIR/visiblelaserpulse sasexcitationsourceand synchrotronpulsesasprobe. Thepurposeofthissectionistoprovideaverysimpleideaofthe technique thatwouldbehelpfultoknowbeforegoingtothenextchapter .Thedetailsofthe experimentaltechniquearedescribedin x 6.6

PAGE 96

81 Probe (IRSR) Pump (Laser) Sample Spectrometer 1 2 3 Figure5{8:Principleofthepump-probeexperiment.(1)Lase rpulsecreatesphotoexcitationsinsample,whichsubsequentlyevolvewithtime.(2)Afte rtime 4 t ,broadband IRpulsearrivesandispartiallyabsorbed(orrerected)byexc itations.(3)IRpulseanalyzedwithorwithoutaspectrometer,extractingdetailsofe xcitationsatatime 4 t after theircreation.5.2.1Laser-SynchrotronPump-ProbeMeasurement Synchrotronradiationisabroadbandbrightsourceoflight. Mostpeopleexploit itsbrightnessandoverlookitstemporalstructureoftheligh tpulses.Thepump-probe techniquedevelopedattheNationalSynchrotronLightSourc e(NSLS)ofBrookhaven NationalLaboratoryutilizesthepulsednatureofsynchrotron sourceespeciallyatfar infraredwhereitoersbothbrightnessandpoweradvantageo verconventionalthermal sources[ 1 ].Theshortpulsesoflaserlightareusedtoilluminateasample,a ndcreate photoexcitations.Theseexcitationsinthesamplebegintorel aximmediatelyafterthe arrivaloflaserpulse,andcanappearaschangesinthesample's opticalproperties.The synchrotronpulsearrivesatthesampleatsomepointintime t afterthepump,and analyzesthesample'sresponse( e.g. ,transmissionorrerection)atatime t intoits relaxationprocess.Theexperimentsareperformedbyxingth etimedierencebetween thelaser(pump)andthesynchrotron(probe)pulses,andthenmea suringaspectrum inthenormalway.Afastdetectorisnotrequired.Theentirep rocessrepeatsatahigh repetitionrate(10'sofMHz)inamannersimilartousingasynchr onizedstrobelightto freezeaparticularmomentofarepetitiveprocess,allowingt heslowlyrespondinghuman eyetoviewit.Thiswayacompletespectrumthatrepresentsamo mentarysnapshotof thesample'sstateforaparticular t canbemeasured.Varioustimedierencesbetween pumpandprobethusproduceasetofdataasafunctionoftimean denergyproviding greaterinsightintotherelaxationprocessofthesystem.Figur e 5{8 showstheprinciple oftheexperiment.

PAGE 97

82 Themeasuredtemporalresponse S ( t )inapump-probeexperimentisdetermined bythesample'simpulseresponsefunction(thequantityofinter est)aswellasthe durationofthepumpandprobepulses.Whenthesamplehasalinea rresponse, S ( t ) isgivenas S ( t )= Z + 1 1 dt 0 Z t 0 1 dt 00 I probe ( t 0 + t ) I pump ( t 00 ) G ( t 00 ) ; (5.15) where I probe ( t )and I pump ( t )aretemporalintensityprolesoftheprobeandpumppulses, respectively,and G ( t )istheimpulseresponsefunctionofthesample.Notethatthe expressionassumesthatthereisnoself-excitationbyprobepulse s.Thisconditionis easytoachieveinpractice.Wecaneitherusemuchlessintensepr obepulsesthanthe pumppulseorlimitthespectralrangeoftheprobebelowsomepho tonenergythreshold usinganopticallter.For G ( t )= ( t ),theexpressionbecomesacrosscorrelation oftheprobeandpumppulsesthatdenestheminimumtemporalr esolution.Note thatthetemporalresolutionisindependentofthesensitivity andresponsetimeofthe spectrometeranddetector. Inourpump-probeexperiment,weusedpicosecondpumppulsetha thassignicantlyshortertemporalprolethanthesynchrotronprobepul seofthepulsewidthon theorderof1ns.Hencewecantake I pump ( t )= I 0 ( t ),andEq. 5.15 canberewrittenas S ( t )= I 0 Z + 1 1 dt 0 I probe ( t 0 + t ) G ( t 0 ) : (5.16) Thisshowsthatthemeasuredresponseisaconvolutionofthesynch rotronpulseshape withthesample'sresponse.Thenatureofdampinginastoragerin gleadstoaGaussian likeelectrondistributionwithinabunchandthusaGaussiansha pedprobeintensity prole.5.2.2InterferometryUsingPulsedSource Whenpulsedlightsourceisusedforaninterferometer,abeam-sp litterdividesevery pulseintotwopulses.Asascannermirrormoves,oneofthepulseisde layedintime relativetotheother,sothatthelighttravellingtowardsamp leanddetectorconsists oftwopulsesforeverypulseincidentofthebeam-splitter.Whe nthedelayisshorter

PAGE 98

83 thanthepulseduration,thetwopulsesoverlaptemporally,an dcauseinterference.This situationisclearlythesameasthecaseofacontinuoussource.No w,ifwerunhighresolutionmeasurementstoresolveanarrowspectralfeature,o nemaythinkthatwe mayencounterasituationwherethescannermovesfarenoughth atthedelayexceeds thepulsedurationandtwopulsesnolongeroverlap.However,th isisnotthecase[ 1 21 ]. Asamplewithanarrowabsorptionfeaturewillautomaticallyl engthenashort pulse.Thelengthenedpulseswilloverlaptocauseinterferenc e.Theamountoflengtheningisequivalenttothepathdierencenecessarytoresolvet hefeature'sabsorption width.AFabry-Perotinterferometerisasimplewaytopictur ehowashortpulsecanbe lengthenedbyaresonance.Therefore,regardlessofthesharpn essofafeature,thereis nolimittothespectralresolutionusingshortpulsedsource. Wecanalsothinkofitinthefollowingway.Therstpulseisinci dentonthe sample.Ifthereisanarrowabsorptionfeature,thesampleabsor bsthatparticular fouriercomponentfromthepulse,andtheabsorptionmode\rin gs"forawhile(ring downtimedeterminedbythenarrownessoftheabsorptionmode) .Thesecondpulseis thenincidentonthespecimen,andthesamefouriercomponenti sabsorbed.Butifthe modeisalready\ringing"(fromtherstpulse),thentheparti cularfouriercomponent ofthesecondpulsemaybeatthewrongphase(thesecondpulsetries todriveatoms inonedirection,buttheyarealreadymovingintheopposited irectionduetotherst pulse).Varyingthetime-delayoftheinterferometerwillbr ingthepropermodeinand outofphase.Sointerferenceisobserved.Observableinterfer encewilloccuraslongas themodekeepsringing.Thisisconsistentwiththelongerpath dierencenecessary toachieveahigherspectralresolution.Thispathdierencec anbemuchlongerthan theoriginalpulse.Inthispicture,thesamplehasa\memory"d eterminedbythe narrownessoftherelevantabsorptionfeatures.Itremembersf oratimelongenoughto

PAGE 99

84 spanthetimebetweenthetwooriginalpulses.Thereareotherwa ystopicturethis,but theresultisthesame. 8 5.2.3AdvantageofLaser-SynchrotronTechnique Thereareothersourcesoflightthatmaybeusefulasaprobe.Fo rexample, tunablepulsedlasers,free-electronlasers(FELs),opticalpar ametricoscillators(OPOs), coherentTHzpulsesfromabiasedsemiconductorsilluminatedby afemtosecondlaser arepossibleprobesources.Eventhoughthesecanhavehighertemp oralresolution thanthesynchrotron,theyhaveeitherrestrictedspectralran georstabilityissues. Asynchrotron,ontheotherhand,isabroadband,bright,andst ablesource.These propertiesmakethesynchrotronsuitableforordinaryspectro scopyoverabroadspectral range.Forthetime-resolvedstudy,thesynchrotroncanfollow thesystemthatrelaxes throughawiderangeofenergies.Aswillbedescribedinthefoll owingchapter,pulse widthandrepetitionfrequencies(PRF)aresomewhatadjustab leforvariousrelaxation timescales.Allofthesepropertiesactasadvantagesofusingsync hrotronasaprobing sourceevenattheexpenseoftemporalresolution.Thefactthat ourpumplaser (Ti:Sapphire)istunableinwavelength,PRF,andpower,add srexibilitytoourpumpprobesystemthatcanbeveryusefultoinvestigatethedynamicso fsystemswithtime scalesfrom 100psto 100ns. 8 TheexplanationgivenhereisbasedonaconversationwithG.L. Carr.

PAGE 100

CHAPTER6 EXPERIMENT 6.1Introduction Pump-probetimingexperimentswereperformedattheNationa lSynchrotronLight Source(NSLS)tostudylow-frequencydynamicsinsolids.Synchr otronradiationisa broadbandpulsedsource.Wetookadvantageofthispulsednatur etoobservethestate ofmaterialsexcitedbyalaserwhichisalsopulsedandsynchroni zedtothesynchrotron radiation.TheVacuumUltraviolet(VUV)ringattheNSLShastwoin fraredbeamlines, U10AandU12IR,dedicatedforsolidstatephysicsstudy.Thesearetw obeamlines usedforbothtime-resolvedandlinearspectroscopy,describedi nthisdissertation.This chapterwillstartwithadescriptionoftheNSLSfacilityfocusi ngontheproperties oftheVUVringandbeamlines.SpectrometersatU10AandU12IRandp umplaser systemarethreeprincipalpiecesofinstrumentation,andwill bedescribedseparately indetailfollowedbybriefdescriptionsoftheotherapparat ussuchasthecryostat,our home-madesamplechamber,superconductingmagnet,detector s,andberoptics.The experimentalsetupandtechniqueswillbediscussedtowardthee ndofthechapter. 6.2NationalSynchrotronLightSource 6.2.1General TheNSLSisauserfacilityfundedbytheU.S.DepartmentofEnerg y.Two separateelectronstoragerings,anX-Rayring(2.8GeV,300mA)and aVUVring (800MeV,1.0A),provideintenselightspanningtheelectromagn eticspectrumfrom theinfraredthroughx-rays.Thepropertiesofthislight,an dthespeciallydesigned experimentalstations,calledbeamlines,allowscientistsinma nyeldsofresearch toperformexperimentsnototherwisepossibleattheirownlabo ratories.TheNSLS currentlyhas56X-Rayand23VUVoperationalbeamlinesforperf ormingawiderange 85

PAGE 101

86 ofexperiments[ 63 ].Thepropertiesofsynchrotronradiationanditsadvantage sover othersourcesoflightaredescribedinthepreviouschapter. ElectronsareinjectedintotheNSLSstorageringsfroma750Me Vboostersynchrotronfedbya120MeVlinac.Theelectronsarerstproduce dina100keVtriode electrongun.Thegunispulsedattheboosterrevolutionperio d,94.6ns,seventimes perboostercycle.Eachpulseis5nslongandsuppliesabout17mi crobunchesinthe linac.Afteraccelerationinthelinac,thebeamisinjectedi ntotheboosteronseven successiveturns.Multi-turninjectionintheboosterisaccompl ishedinthefollowing way:Thebeamisderectedintotheboosterbyaseptummagnet.Th erstlinacpulse goesaroundtheboosterandreturnstotheinjectionpointjust asthesecondpulseis comingoutoftheseptum.Thetwopulsesmergeintoaboosterbunc handcontinueto circulate.Thisprocessisrepeateduntilallsevenlinacpulse sareinjected.Duringthe injectionprocess,theeldofapulsedmagnetpreventsthecirc ulatingbeamfromstrikingtheseptum.Theeldofthemainboostermagnetsisalsoincre asingslightlyduring injectiontoplaceeachlinacpulseonaslightlydierentorbi tfromitspredecessors. Afterinjection,themagneticeldoftheboosterincreasestom aintainaconstantorbit radiusastheradiofrequency(RF)acceleratingcavityboost stheelectronenergyto750 MeV.Atmaximumenergy,akickermagnetispulsedtosendthebeam pastaseptum andintotheX-RayorVUVstoragering.Afterextraction,thebooste rmagnetsramp downtotheirinjectionsettings.Theboostercycletakes1.2sec ondsfromoneinjection tothenext.Inthefuture,theinjectioncyclewillbedecrea sedto0.5secondsandthe maximumenergywillberaisedto800MeVforimprovedstorageri nginjection. 6.2.2VacuumUltravioletRing TheVUVringisthesmallerofthetwostorageringswithacircumfe renceof51.0 meters.Itcontains8dipolebendingmagnetsforforcingelec tronstotravelinaclosed orbitalongwith24quadrupoleand12sextupolefocusingmagne tsforthepractical operation.SeeAppendix A forparametersoftheVUVringaswellastheinjection system.Eachbendingmagnetallowstwobeamextractionportso neachofwhich singlebeamlineisattachedinordertodeliverthelighttoit sexperimentalendstation.

PAGE 102

87 Someofbeamlines,suchasU10,aresplitintomultiplebeamlines. Therearealsotwo insertiondevicesinastraightportionofthestoragering.The ringisnormallyoperated atanenergyof0.808GeVwithamaximumcurrent(averagedove rbunches)of1.0 A(1 : 06 10 12 electrons)atinjection.Electronscirculatetheringevery 170.2nsat relativisticspeed,andemitsynchrotronradiationateachben dingmagnet;thesource sizeinroutineoperationis536to568 mhorizontallyand170to200 mvertically. TheRFcavityoftheVUVringrunsatthefrequencyof52.887MHz,a ndit supports9RFbuckets,whicharedeterminedbytheringcircumf erenceandtheRF periodasdiscussedin x 5.1.4 ;anarbitrarynumberofbucketscanbelledwithelectron bunches.Thisleadstoavarietyofoperationmodestheringca noperate.Table 6{1 liststhemodescurrentlyavailablewiththeirparameters.In so-called9-bunchmode, allofthe9bucketsarelledproducing52.9MHzofthepulserep etitionfrequency (PRF),whichisthesameastheRFcavityfrequency.Thismode, however,isnotthe onecommonlyusedbecauseoftheinstabilitiesintheelectrono rbitcausedbyllingall buckets.Forday-to-dayoperation,7-bunchmodeisused.Itru nsatthesamemaximum averagecurrent(1000mA)asthe9-bunchmodeprovidinghighe stintensityoflight pulseat52.9MHztouserswithmaximumstabilityandreliability .The7-bunchmode hasseveraldierenttypes(stretched,detuned,compressed,an dwiggled)depending ontheshapeandmotionofelectronbunches,andthedetailsoft hesetypesaregiven below.Whenwesayroutineoperation(ornormalmode),itisth e7-bunchstretched mode.In3-bunchsymmetricmode,everythirdbucketislledp roducingthePRF of17.6MHz.Insingle-bunchmode,onlyasinglebucketislled, andthePRFisthe sameastherateatwhichsingleelectronbunchgoesaroundonec ycleofitsclosed orbit.Boththe3-bunchandsingle-bunchmodesrunatlowerav eragecurrentthanthe onefornormaloperationbecauseofbunchinstabilitycausedby llingmoreelectrons ( i.e. ,increasingCoulombinteractionbetweenelectrons)inagive nbucket.Runningthe ringatloweraveragecurrentcausestheloweroutputintensit yofemittedlight,and manyoftheotheruserswhodependdeeplyontheoutputintensit yofthebeamsuer fromthelowersignaltonoiseratiointheirdata.However,these modesareusefulto

PAGE 103

88 Table6{1:OperationmodesoftheVUVring.Inthellpattern,1 and0indicatelled andemptybucket,respectively. I max isamaximumcurrentatinjectionforeachmode, l b arangeofelectronbunchlength,PRFthepulsedradiationfre quency, T PRF thetime betweenpulses,and pw arangeofpulsewidth.Themodessuitedforthetimingexperimentsareindicatedbytheasterisk. Mode FillPattern I max (mA) l b (cm) PRF(MHz) T PRF (ns) pw (ns) 9b 111111111 1000 72-36 52.9 18.9 2.4-1.2 7b-stretched 111111100 1000 72-36 52.9 18.9 2.4-1.2 7b-detuned* 111111100 800 30-18 52.9 18.9 1.0-0.6 7b-compressed* 111111100 200 15-9 52.9 18.9 0.5-0.3 7b-wiggled 111111100 1000 72-36 52.9 18.9 2.4-1.2 3b-symmetric* 100100100 600 40-20 17.6 56.7 1.4-0.7 1b* 100000000 400 60-30 5.9 170.2 2.0-1.0 studythetransientphenomenaofthetimescalelongerthantheP RFperiodofnormal operation.Inordertominimizetheimpactontheotherusers,o perationmodesdierent fromthenormalonemustberequestedattheweeklyuser'smeetin g.Thetiming operation,whichusestypicallyeither7-bunchdetunedorco mpressedbyrequest,are scheduledaheadfortwodaysineverymonthfortheuserswhoper formtime-resolved experiments.Weutilizedthemostofthebeamtimesscheduledfo rthetimingandthe nightshiftsduringstudy,maintenance,andweekendsforthew orkdescribedonthis dissertation. Duringroutineoperation,anotherRFsystemcalledthe\4thha rmoniccavity"(a RFcavitywithitsresonantfrequency4timesthatoftheRF,52 .9MHz)isturnedon tostretchanelectronbunchinthelongitudinaldirectionof itsorbit.This,inturn,diminishesTouschekeect,andincreasesthelifetimeofelectro nsallowinghigheraverage beamcurrentandfewerlls.Abroaderelectronbunch,howeve r,implieslongerpulse widththatresultsinlowertimeresolutionsincethedurationo fthesynchrotronpulses determinesthetemporalresolutionofthetime-resolvedmeasu rementsasdescribedin thepreviouschapter.Forthe7-bunchstretchedmode,arange ofthepulsewidthis between2.0and1.0nsdependingonthebeamcurrentoftherin g.Thepulsewidth hereisdenedasthefullwidthathalfmaximum(FWHM)ofthepu lseintensity.See Table 6{1 forthepulsewidthoftheothermodes,too.

PAGE 104

89 192021222324 600 700 800 900 1000 1100 PulseWidth[ps]Time[hours] Figure6{1:Changeofthepulsewidthemittedfromall7bunche sduringdetunedmode. Asthecurrentdecays,electronsarere-injectedinthestorage ringat10:30PM. Inordertoprovidebettertemporalresolutionforthetime-r esolvedexperiments, theRFgroupattheNSLShasdevelopedtwospecial7-bunchmodes otherthanthe stretchedmode;detunedandcompressed.Inthe7-bunchdetuned mode,the4th harmoniccavityisturnedoleavingthebunchesunstretched providingthepulse widthofbetween1.0and0.6ns.Figure 6{1 showsthetimedependentpulsewidth, emittedfromall7bunchesduringthedetunedmode.Thismode canberunatafull current,buthasapproximatelyhalfthelifetimeofthatach ievedinnormal7-bunch stretchedmode.Inthe7-bunchcompressedmode,the4thharmoni ccavityisturned on,butruns180degreesoutofphasewithrespecttothephaseused forthestretched mode.Thiscompressesthebunches,andmakesthepulsewidthofbe tween0.5and 0.3ns;thebesttemporalresolutionachievableattheNSLS.Adra wbackofusingthe compressedmodeisthatitmustberunatconsiderablylowercurre ntcausingworse signaltonoiseratio(S/N).Hence,anappropriatemodemustbesele ctedforthetimeresolvedmeasurements,negotiatingtherequiredtemporalreso lutionandenoughS/N forthesystemunderinvestigation.The7-bunchwiggledmodeis understudy(atthe timeofwritingthisdissertation)forfutureoperations.This modeshakestheelectron

PAGE 105

90 buncheshorizontallyatacertainfrequency,andeectivel yremovestheringintrinsic interferencefringesthatshowupintheveryfarendofinfrar edspectrum(2to20cm 1 ) takenathighresolution( < 1cm 1 ).SeeFigure B{1 inAppendix B.2 .Thedetailofthe techniqueremainstobestudiedfurther.Inalltypesofthe7bunchmode,therearetwo emptybuckets,butthiswillnotcauseanyproblemtobothspectr oscopicandtiming measurements.Duringmeasurements,thestateofasystemisprobedb ycollecting thesynchrotronpulsesthathadinteractionwiththesampleatt hedetector.Since thedetectordoesnotseethepulseduringtwomissingpulses,there isnoeectonthe spectra. TheVUVringistheworld'sbrightestsourceofinfraredbecauseof itshighstored beamcurrent.Inaddition,thereal-timeglobalorbitfeedb acksystemimprovesthe stabilityoftheclosedorbit,byimplementingafeedbacksystem baseduponharmonic analysisoftheorbitmovementsandthecorrectionmagnetic elds.Thestablebeam iscrucialfortheacceleratorbasedFourier-Transformspectr oscopy.Thesetwofactors, brightnessandstability,alongwithitsrexibilityofoperat ionmodesmaketheNSLS VUVringauniquefacilityprovidingsolutionstomanyscientists forcertaintypesof experimentsotherwiseimpossibleinthelowendofthespectralr ange. 6.2.3BeamlinesU12IRandU10A Forthestudiesdescribedinthisdissertation(bothlinearandt ime-resolved measurements),twoofsixinfraredbeamlines(U12IRandU10A)that arededicated tosolidstatephysicsinvestigationswereused.RefertoAppendix B foradditional informationaboutotherNSLSinfraredprograms. U12IRwasdesignedspecicallyforoptimalperformanceinthef arinfrared[ 64 ]. Asexplainedinthepreviouschapter,synchrotronradiationi semittedintoincreasinglylargerangleasthewavelengthbecomeslonger.This,as aresult,requireslarger extractionopticsforecientlycollectingthefarinfrare d.U12IRhasagold-coated, 1 1 RerectorswithgoldcoatingareusedforexcellentIRrerecta ncewithUVrejection.

PAGE 106

91 Diamond window 1.1 cm aperture Collimating Box Light coneSpectrometerFar-infrared detector Mirror M2 & M315 cm aperture Rough vacuum UHV Mirror M1 6 cm aperture Orbit plane Ring chamber Figure6{2:TheelevationviewofU12IRbeamlinewiththeSPS200spectrometerattached.ThediamondwindowseparatesanUHVsectionandaroughva cuumsection. water-cooled,SiCextractionmirrorthathasanangularacc eptanceof90H 90Vmrad. Itcollects100%ofverticallyspreadinglightdowntoapprox imately30cm 1 ,butfalling to40%at2cm 1 .InFigure 6{2 ,M1correspondstothismirror.Thecombinationof M1andtwoaluminum-coatedPyrexmirror,M2andM3,directst hebeamtowardan 11mmaperture,wedgedCVDdiamondwindow 2 (17.7mmdiameter,0.5 wedgeangle, 0.35mmthick)thatseparatestheultrahighvacuum(UHV)oftheri ngside( 10 9 Torr)andaroughvacuumofthecollimatingopticsandendstat ion( 20mTorrbase). M1andM2areplanemirrors,whileM3isanellipsoidalmirrorth atfocusesthesource toapointjustbeyondthediamondwindow. 2 Polycrystallinediamondsynthesizedbychemicalvapordeposit ion(CVD)isa uniquematerialforopticalexperimentsbecauseofitsextre melygoodtransparency overawidespectralrange.Thisiscausedbythefactthatdiamo ndisapurelycovalent crystal,whichmeansthatitsopticalphononscannotinterac tdirectlywithlightwaves. Dependingonthelevelofpurity,diamondistransparentfrom itsfundamentalcut-oat 220nmtothefarinfrared.Thereisalsoanintrinsicmulti-pho nonabsorptionbandin thewavelengthrangeof2.5 mto6.7 m[ 65 ].

PAGE 107

92 110100100010000 Power/BW[ m W/cm -1 ]Frequency[cm-1] 0.0010.0100.1001.000 Energy[eV] 0.001 0.01 0.1 1 10Far-IR 1 mW Mid-IR 17 mW Near-IR 52 mW Vis-UV 87 mW Without light cone With light cone Figure6{3:Powertransmittedthroughthediamondwindowatt heU12IRbeamline withandwithoutthelightcone.Theabsorptionaround2600cm 1 isduetotwophononabsorptioninthediamondwindow.Thebandat12500cm 1 isduetoelectronic transitionsontheAlmirrors.Theedgeat 15000cm 1 isduetoabsorptioninthegold coatingoftherstmirror.Thebandgapofthediamondwindowi sresponsiblefora cutoat 40000cm 1 Atthelongestwavelengths,diractioncausesappreciableloss. Alargelightcone justupstreamofthediamondwindowhelpscollectingthelonge stwavelengthsand guidethemintothecollimatingmirrorbox.Theconeistaper edfroma62mmdiameter entranceaperturedowntothe11mmapertureofthediamondwi ndow,anditsinterior wallisgold-coatedforimprovedIReciency.Powerdeliver edthroughthediamond windowwithandwithoutthelightconeisshowninFigure 6{3 Thebeamthroughthediamondwindowiscollimatedbyaspheric almirror(8-inch focallength)inthecollimatingbox,andre-focusedbyanoaxisparaboloidrerector (6-inchfocallength)attheveryendoftheU12IRbeamlinejust infrontofendstation's entrance.Dependingonexperimentalrequirementsofeache xperiment,aparticulartype

PAGE 108

93 ofspectrometerordirectconnectionofourcustommadesamplec hamberisselected asanendstation.Detailsofspectrometersandthesamplechamb erwillbedescribed shortly. U10AisanotherinfraredportlocatedadjacenttotheU12IR,an dmayalsobeused forpump-probestudies.IthasaBrukerIFS66v/Sspectrometer. Bycombiningsynchrotronandspectrometer'sinternalsource,widerange,hig hbrightnessIRspectroscopy ispossibleatthisbeamline. TheOpticalcongurationoftheU10beamlineisfollowing.At wo-mirrorsystem (M1andM2)collectsandre-imagesthesynchrotroninfraredso urceatapointjust beyondasimilardiamondwindowastheU12IRwhichseparatesthe UHVofthering sideandaroughvacuumofamirrorbox.M1isagold-coated,wat er-cooled,plane extractionmirrormadefromsiliconwithanangularacceptan ceof40H 40Vmrad (100%verticalcollectiondownto240cm 1 ).M2isaglassellipsoidwithanaluminum rerectivecoating.Thedeliveredspectralrangeextendsfro mapproximately10cm 1 tobeyond40,000cm 1 .Atthemirrorboxtheinfraredbeamissplitintotwo(onefor U10AandanotherforU10B),thenthebeamsenttowardU10Aiscolli matedwithan aluminizedo-axisparaboloidtoadiameterofeither14mmo r8mmandtransported underroughvacuumthroughaKBr(orpolyethylene)window.T hecollimatedbeamis thenrefocusedintothespectrometerusingano-axisparaboli cmirror;thismirroris identicaltothemirrorusedtocollimatethelightfromthein ternalsourcesresultingin asymmetricarrangement,allowingtheusertochangebackandf orthbetweensources whiletheinstrumentisundervacuumwithoutanylossinalignm ent. 6.3Spectrometers In x 3.1 ,theclassicationofcommonlyusedspectrometerswaslisted(see Figure 3{1 ).TheNSLShasmanyspectrometers,includingallthreetypesof two-beam interferometer(Michelson,Lamellar,andMartin-Puplett) .Inthissectiononlythe specicinstrumentusedforourexperimentswillbedescribedin detail.

PAGE 109

94 6.3.1BrukerIFS66v/S TheBrukerIFS66v/S(Bruker66)isaFouriertransforminterf erometerwithrapid andstep-scanoptions.Withproperchoiceofthesource,beam-spl itter,anddetector, itcancoverthefullspectralrangefromtheveryfarinfrared ( > 5cm 1 )uptothe vacuumUV( < 55,000cm 1 )withspectralresolutionof 0.1cm 1 .Thefriction-free airbearingscannermakesitpossibletoachieveverystablerapi dscanattherate greaterthan100spectra/sec.DigitalSignalProcessing(DSP)e lectronicsprovide precisescannercontrolandinstrumentautomationforsource,a perture,anddetector selections.Beam-splittersarechangedmanually.Combiningt heveryfastscanrate capabilitywithsuperiorprecision,spectroscopywithhighsign altonoiseratio(S/N)is possibleeveninthefarinfrared.Theinstrumentoperatesunde rvacuum( < 3mbar) torecordspectrafreefromabsorptionfromH 2 OandCO 2 vaporinthefarandmid infrared.SeeAppendix D formoreinformationaboutthisgas-phasecontamination. Thespectrometerhasanexternalporttoextractcollimatedl ight,whichallowsusers toattachspecializedexperimentalsetup;suchasacustommadesa mplechamberora magnet. AHe-Nelaser(633nm,nominal1mW)isusedtocontrolthepositiono fthe movingmirror(thescanner)andtocontrolthedataacquisitio nprocess.ThemonochromaticbeamproducedbythisHe-Nelaserismodulatedbytheinter ferometertoproduce asinusoidalsignal.Aphotodiodedetectorisplacedatbothout putsoftheinterferometer:laserdetectorAandB.Signalsfromthesetwodetector saremonitoredwith anoscilloscope,andthetheamplitudeofsignalsareusedtoopti mizethealignmentof thebeam-splitter.Whenthebeam-splitterisnotalignedprop erly,theamplitudecan becometoosmalltocontrolthescanner,andthendataacquisiti onwillbeinterrupted. Therearethreeinternalsources(Hgarclamp,SiCglobar,andT ungstenlampfor thefarinfrared,midinfrared,andvisibleregions),aswella sthebroad-bandexternal synchrotronsource.Figure 6{4 andTable 6{2 showthefrequencyrangesofthevarious sources.

PAGE 110

95 104 40 100 1000 10000 40000 13000 250004000400 UV VISNIRMIRFIR WAVENUMBER (cm) -1EMISSION 1m m 250nm 10m m 100m m 1mm WAVELENGTH (HeNe)LASER =0.6328m lm Tungsten Globar Hg-Arc Figure6{4:EmissionspectraofthreeinternalsourcesoftheBru ker66. Table6{2:FrequencyrangesoflightsourcesusedfortheBruke r66. Source Range(cm 1 ) PrimaryApplication Mercury-arclamp 10-700 FarIR SiCglobar 100-6000 MidIR Tungstenlamp 4000-40000 VIS Synchrotron(U10A) 2-40000 IRtoVIS Avarietyofbeam-splittersanddetectorscancoverwholeran geofspectrum. Tables 6{3 and 6{4 showsthefrequencyrangesofsetsofbeam-splittersanddetect ors, respectively,availableforthebenchweused.Detailsofvari ousdetectorswillbe describedin x 6.5.4 TheBruker66isaveryreliablespectrometerforwiderangeof spectrum,and thusitisthemainspectrometerusedinourworkatthebeamline sU10AandU12IR. However,thebeam-splittereciencyaswellasdiractionloss duetospectrometer's smallopticssetthelimittothelongestwavelengthofspectrumt hatwecanmeasure condentlywiththisspectrometer.Withthethickest(50 m)Mylarbeam-splitter availableathandandverysensitive1.5Kbolometer,theBruke r66attachedonthe U12IRbeamline,whichisthebetteroftwobeamlinesforthefa rinfrared,iscapableof

PAGE 111

96 Table6{3:Frequencyrangesofbeam-splittersusedfortheBru ker66. Beam-splitter Type Range(cm 1 ) PrimaryApplication Mylar3.5 m T201 125-750 FarIR Mylar6 m T202 80-450 FarIR Mylar12 m T203 40-220 FarIR Mylar23 m T204 20-110 FarIR Mylar50 m T205 10-50 FarIR Ge/Mylar T222 30-680 FarIR Ge/KBr T303 370-7800 MidIR Ge/KBr(WideRange) T304 400-10000 MidIR QuartzVIS T501 9000-25000 VIS Table6{4:FrequencyrangesofdetectorsusedfortheBruker6 6.PEinthewindow collumstandsforpolyethylene. Detector Window Temperature(K) Range(cm 1 ) PrimaryApplication SiBolometer Quartz+scatterlayer 1.8(LHe-pumped) 2-100 FarIR Si:BBolometer PE 4.2(LHe) 10-600 FarIR DTGS PE 300(ambient) 10-600 FarIR DTGS KBr 300(ambient) 400-7000 MidIR Si:B KRS-5 4.2(LHe) 350-4000 MidIR Ge:Cu KRS-5 4.2(LHe) 350-4000 MidIR MCT 77(LN 2 ) MidIR InSb Sapphire 77(LN 2 ) 1850-15000 NearIR SiPhotodiode 300(ambient) 9000-28000 VISandUV GaPPhotodiode 300(ambient) 18000-33000 VISandUV producingacceptablespectrumdownto 20cm 1 .Theuseoffar-IRlowpasslter suchasFluorogold(thecut-ofrequencydependsofthethick nessofthelter)pushes thelimitdownbyimprovingtheS/Neventhoughtheoverallen ergygoingintothe detectordecreases.Witha50cm 1 cut-olter,areasonablespectrumdownto 12cm 1 wascondentlyobtained.ThereisathickerMylarbeam-split ter(125 m) availableonthemarket.Thismayimprovetheperformanceat evenlongerwavelengths. TheVUVringisrigidlyattachedontheexperimentalroorwhere therearemany sourcesoflowfrequencynoises(mostnotably,mechanicalnoise duetothepumps). Thesecouldcausemodulationoflightatthosefrequencies,anda retranslatedinto noiseinthespectrum.Thismayposesomeproblemswhiletakingda taespecially inthefarinfrared.Asmentionedabove,theBruker66isabenc hthatiscapableof scanningatexceptionallyfastspeed.Bychoosingthescanspeedfa stenough,wecan pushtheseundesirablelowfrequencynoisesbelowthespectralra ngeofinterest.For example,ifweuse200kHzofthescanvelocity,60Hznoiseshowsupat 4.74cm 1 in

PAGE 112

97 thespectrum,andinfactthistechniquewasusedwhenwewerefo cusingonthespectral rangebetween10and20cm 1 usingtheBruker66. Foreachmeasurement,oneneedtospecifyascanvelocity.Hereis atechniqueI personallyusetodetermineanoptimalscanvelocity.Iwoulduse thefastestvelocity thatdoesnotsignicantlyreducethesignalattheupperfrequ encyrange.Onewayto determinethisistostartatamodestscanvelocity,say20kHzfort hefarinfrared,and increasethisinmultiplesoftwo.Whenthesignalintheupperh alfofthespectralrange fallsbyafactorof1.4( i.e. ,dropsto70%ofthepreviousscanathalfthevelocity),then wehavejustfoundtheoptimalvelocity.Wecanestimateitbased onthemodulation frequencyoftheupperspectralendandcompareittothedetec tor'stimeconstant.At fasterspeeds,thelossinsignalexceedstheincreasednumberofsca nssothattheS/N pertimeisnowfalling.Atslowerspeeds,thesignaldoesnotincr easeverymuch,butwe getfewerscanspertime,sothenoisestartstoincrease(assumingit israndomnoise). 6.3.2BrukerIFS125HR TheBrukerIFS125HR(Bruker125)isanotherFouriertransform interferometer thatwasattachedontheU12IRbeamlineduringthemaintenanc eperiodinDecember 2003.Thisinstrumentoerstheultimatelyhighresolution(r esolvedlinewidthsof < 0.001cm 1 )acrossentirespectrumfrom5cm 1 inthefar-IRto50,000cm 1 inthe UV.Thehighresolutionisachievedbyitsextraordinarylongsca nner( 5m)armthat createslongpathdierence(retardation).Itsglide-bear inginterferometerwithhybrid scannerconstructionenhancesvelocitystability.Thesourcec hambercanaccommodate upto4internalsourcesaswellastheexternalsynchrotronsour cethroughasource inputport.Thereare4internaland2externaldetectorsacc essiblethrougheachoftwo dierentsamplecompartmentswithoutbreakingvacuum.Itha smodularconstruction justlikeolderBrukerIFS113vsothatuserscanremovewholesamp leanddetector compartmentstosetuptheirownexperiment.Thereareafewex tractionportsthrough whichthebeamcanbebroughtintoothercompartmentssuchasa custommadesample chamber,microscope,andmagnet.Withalltheadvantagestha tU12IRoers,this rexibilityaswellasitscapabilitytoresolvehighlycomple xspectraintodiscretelines

PAGE 113

98 5.7m 2.22m Sources Spectometer Sample Detectors Scanner arm SynchrotronFigure6{5:DiagramoftheBruker125. makesU12IRtheuniqueplacethatcouldattractmanyuser'scon siderationfortheyears tocome.Figure 6{5 showsthediagramoftheBruker125. Thisspectrometeruses80mmoptics,approximatelytwiceaslar geasthosein theBruker66(40mm)collectingmorelightoflongwavelengt hs.Thescannerand xedmirrorarethefullcubiccornermirror.Wealsohave125 mMylarbeamsplitter(usefulrangefrom5to22cm 1 )fortheBruker125.Useofthisbeam-splitter, synchrotronsource,andlargeopticscertainlyimproveperfo rmanceatlowfrequency achievingreasonablespectrumdownto 5cm 1 6.3.3SciencetechSPS-200 TheSciencetechSPS-200isaMartin-Puplett(roofmirrorpo larizing)interferometerthatcanoperateinthreemodes:Michelson(amplitudemod ulation),Polarizing (polarizationmodulation),orMixed.Inmostcase,weoptedto usethePolarizing modeforitsbetterperformanceatthelongestwavelength.Re ferto x 3.3 fortheprincipleofpolarizationmodulationtechnique.Figure 6{6 showstheopticallayoutofthe spectrometer.IntheMichelsonmode,thepolarizingchopperC 2andpolarizerP1are removed,andintensitybeam-splitterisused.ThereareMylarb eam-splittersofseveral

PAGE 114

99 S1 M1 C1 I1 M2 M3 P1 BS1 M4 TRAVEL400mm M5 M7 C2 M6 Tilt Rotary Shear Lateral Shear ExternalAdjustments S2 Sample and detector Beamline Figure6{6:SchematicofopticallayoutoftheSciencetechS PS-200.BS1polarizingor intensitybeam-splitter;C1intensitychopper;C2polarizing chopper;I1iris;M1concave mirror;M2andM6ratmirrors;M3andM7paraboloidalmirrors;M 4andM5rooftop mirrors;P1xedpolarizer;S1Hg-Xelamp;S2synchrotronlightso urce. dierentthicknessavailable.Theoperationislikethatofa standardMichelsonasin Bruker66.Thelowestfrequencyobtainablewiththismodeisl imitedmainelybythe beam-splittereciency,butitcouldmeasureupto1250cm 1 thatisdeterminedby thesamplingfrequencyaccordingtotheNyquisttheorem.Inthe polarizingmode,the intensitybeam-splitterisreplacedbyapolarizingbeam-spli ttermadeofanaluminum gridof2500lines/cm(4 mpitch)onathinMylarsubstrate.Atlowfrequency,the beam-splittereciencyisalmost100%:theonlylimitingfact orsarethesizeofthe mirrorsandthesource'spowerspectrum.Usingasensitivedetecto rlike1.5KSi:B bolometerandlteringouthighfrequencies,thelowestfrequ encyof2cm 1 areachievableforthisinstrument.Synchrotronbrightnessispreserved bythelargeinputoptics(9 cmdiameter f= 2).Athighfrequenciestheeciencyofthebeam-splitterand polarizers fallstozeroatthemaximumfrequencyproportionaltothespa cing.TheSPS-200can takespectraupto600cm 1 ,butatthatfrequency,theBruker66outperformsthe SPS-200,andthusweusedthisinstrumentmainlybelow100cm 1 .Aninputpolarizer

PAGE 115

100 P1andapolarizingchopperC2areadded.Theinputintensityc hopperC1isremoved. Mixedmodeisbarelyused.Itusesamplitudemodulationwithpo larizers(including beam-splitter)inplace.Itpasseslowersignalattheexitthane itherpuremode,butthe spectralrangeisthecombinationofbothmodes. Inthegure,M4andM5aretheroofmirrors.M4cantravelupto4 00mm ( i.e. ,80cmofretardation)achievingamaximumresolutionof0.00 6cm 1 .Thishigh resolutioncapabilityrevealedverynespectralcontentsin trinsictothesynchrotron radiationatU12IR.Thescannercanoperateineitherthestep-sc anorquasi-rapid-scan mode.TheSciencetechMD500electronicsboxcontrolsthech opperandscanner.The instrumenthasasingleinternalsource(Highpressure100WHg-Xelam p),andthe externalinputportisconnectedtotheU12IRbeamlineforthe synchrotronradiation. Modulatedlightgoesthroughtheexternaloutputportontow hichvariousexperimental setups( e.g. ,samplechamberormagnet)canbeattached.Thespectrometer' svacuum boxhasthreeexternaladjustmentknobsinordertoalignthe xedmirrorM5whileit isinvacuum.Althoughtheplanemirrorneedsonlytwotiltadj ustments,therooftop mirrorrequiresthree:tiltintheaxisperpendiculartothe mirroropticalaxisandthe roofedge,lateralshear,androtaryshear.Oncealignedoptim ally,theSPS-200works betterthanBrukerbenchesespeciallybelow20cm 1 owingtoitsusebiggeroptics(90 mm)combinedwithhighereciencyofthepolarizingbeam-spl itter.SeeTable 6{5 for thespecicationoftheSPS-200. 6.4PumpLaserSystem 6.4.1SystemOverview ThepumplasersystemislocatedinsidetheU6beamlinehutchonthe VUVroor alongwithothercomponentsthatarenecessaryfortime-resolv edexperiments.The titanium-dopedsapphire(Ti:Sapphire)solid-statelaserprod uceslightpulsesofshort durationthatcanbesynchronizedwiththatofthesynchrotron .Theprimarypurposeof wholelasersystemistophotoexcitematerials,andtointroduce anarbitrarytime-delay betweenlaserandthesynchrotronprobepulsesusedtoinvestigat ethetransientstate ofsamples.Ourgoalistoobtaincompleteinfraredspectraduri ngthevariousphases

PAGE 116

101 Table6{5:SpecicationsoftheSPS-200. OPERATINGMODES Michelson amplitudemodulation Polarizing polarizationmodulation Mixed amplitudemodulationwithpolarizers SOURCES Internal Highpressure100WHg-Xelamp(arcsize:1.3mm) External Synchrotronradiation Chopperfrequency 20-175Hz SCANNER Stepscanandquasi-rapidscan Max.travel 40cm(80cmretardation) Min.scanstep 2.54 m Max.unapodizedresolution 0.006cm 1 Spectralrange 2-600cm 1 inpolarizingmode OPTICS f/ 2.5 Beamsize 60cm 2 Roofmirrorsangle 90 2arcsec. POLARIZERS Beam-splitter,polarizerandpolarizingchopper Gridmaterial Aluminum Conductorscrosssection 2 mwide,0.4 mthick Linepitch 4 m Substrate Mylar,12 m MichelsonmodeBeam-splitter 3 mMylar oftherelaxationprocessthatfollowsimmediatelyafterthe laserpulse.Theprinciple oflaser-synchrotron(pump-probe)experimentsaredescribed inthepreviouschapter (see x 5.2 ).ThelaserpulsesarecoupledintoopticalberattheU6hutch, anddelivered totheendstationsatbeamlines(mainlyU10AandU12IR)whereac tualexperiments areperformed.Detailsofeachcomponentoflasersystemaredesc ribedinthefollowing subsections.Inaddition,becauseofthenatureofdangerinvolv edinusingtheclass 4laserssuchasTi:SapphireandNd:YVO 4 lasers,theissuesoflasersafetyandthe operatingproceduresarealsodescribedinAppendix C 6.4.2Mode-locked,Solid-StateTi:SapphireLaser TheCoherentMiraModel900-Pisamode-lockedultrafastlaser thatusestitaniumdopedsapphireasagainmedium.AnopticalschematicoftheMira isshownin Figure 6{7 .Itproducesapproximately2to3psdurationpulesofnearin fraredlight. Apulserepetitionrate(PRF)ofacommercialMiraunitis76MHz ,buttheoneinthe U6hutchismodiedtooperatewithaPRFof105.8MHz,twicetheVUV RFsystem fundamentalfrequency(52.9MHz).Attemptwasmadetoproduc ealongercavityfor

PAGE 117

102 Pump Beam M8 M9 GTI M5 L1 M4 M3 M2 Slit M1 output coupler Ti:S BRF StarterFigure6{7:TheopticalschematicoftheMiralaserhead. producingstablepulsesat52.9MHzwithoutsuccess.Thewavelengt histunablefrom approximately700to1000nm.Aparticularsetofoptics(S-,M -,L-,andX-Wave optics)determinesitstuningrange.Themaximumaveragepow eroutputisnearly1 Watt(or10nJperpulse).TheMiraisopticallypumpedwithaCo herentVerdipump laser.TheVerdiisacompactsolid-statediode-pumped,freque ncy-doubledNd:Vanadate (Nd:YVO 4 )laserthatprovidessingle-frequencyCWgreen(532nm)outpu tatpower levelupto5.5Watts. 3 TheVerdiisequippedwithPowerTrack TM softwaretoinsure stableoperation.SeeTable 6{6 fortheMiralaserspecication. Pulsesinthepicosecondregimecanbegeneratedbymode-locki ng[ 66 ].The simplestwaytovisualizemode-lockedpulsesisagroupofphoton sclumpedtogether andalignedinphaseastheyoscillatethroughthelasercavity. Thebasicideaisthe following.Emissionspectraofthemode-lockedlaser( e.g. ,Miralaser)aregenerally composedofmanydierentlongitudinalmodescausedbymodula tionoftheloss orphaseofanopticalelementinthelasercavity.Whenthesereso nantmodesare coupledinphase,thelaseryieldatrainofveryshortpulses,othe rwisecontinuouswith 3 TheVerdiusesaLBOnon-linearcrystalforthesecondharmonicg eneration.Since therefractiveindexistemperaturedependent,thetempera tureofthecrystaliselevated fortheoptimalphasematching( 150 C).

PAGE 118

103 Table6{6:ThespecicationoftheMiralasersystemontheVUVexper imentalroor. Pumplaser CWNd:YVO 4 laser(532nm) Pumppower < 6Watts Pulserepetitionfrequency 105.8MHz Pulseduration < 3ps Averagemaximumpower < 1Watt Peakenergyperpulse 10nJ Spectralrange: SWopticsset 720to810nm MWopticsset 800to910nm LWopticsset 900to980nm XWopticsset 710to900nm ructuatingamplitude.Thecouplingofthemodesisobtained bymodulationofthe gainintheresonator,andcanbeactive(electro-opticmodul ationofthelossesorofthe pumpintensity),orpassive(withasaturableabsorber).Thetech niqueusedtomodelocktheMiralaserisreferredtoasKerrLensMode-locking(K LM).Theopticalcavity isspecicallydesignedtoutilizechangesinthespatialprol eofthebeamproducedby self-focusingfromtheopticalKerreect 4 inthetitanium:sapphirecrystal.Thisselffocusingresultsinhigherroundtripgaininthemode-locked( highpeakpower)versus CW(lowpeakpower)operationduetoanincreasedoverlapbetw eenthepumpedgain proleandthecirculatingcavitymode.Inaddition,anaper tureisplacedataposition withinthecavitytoproducelowerroundtriplossinmode-loc kedversusCWoperation ( i.e. ,alocationwherethemode-lockedbeamdiameterissmallerth anthatoftheCW beam). Titanium-dopedsapphire(Al 2 O 3 :Ti)hasthebroadesttuningrangeofanyconventionallaser[ 67 ].Themediumcontainsontheorderof0.1%titanium,addedin theform ofTi 2 O 3 toproducethedesiredTi 3+ ion,whichreplacesaluminuminthecrystallattice. OpticalpumpingexcitesTi 3+ fromgroundstatetoavibrationallyexcitedsublevelof 4 TheKerreectisoneoftheelectro-opticeectsthatinduce sbirefringenceinan isotropictransparentsubstancewhenplacedinanelectriceld .Itisoftenreferredtoas thequadraticelectro-opticeectsincetheinducedbirefri ngenceisproportionaltothe squareoftheeld[ 10 ].

PAGE 119

104 theupperlaserlevel.Theionthendropstoalowersubleveloft heupperlaserlevel beforemakingthelasertransitiontoavibrationallyexcited sublevelofthegroundstate. Vibrationalrelaxationreturnstheiontothegroundstate.Th estronginteractionbetweenthetitaniumatomandhostcrystal,combinedwiththelar gedierenceinelectron distributionbetweenthetwoenergylevels,leadstoabroadtr ansitionlinewidth. TheMiralasercanbeoperatedinoneofthreemodes;continuous wave(CW), mode-locked(ML),or -locked( L)modes.CWmodeisusedatstartupofdailyoperation,andtheinternalpowermeterreadingallowsaquickal ignmentofthelasercavity. Thismodecanbeusefulforsteadystatephotoinducedexperimen ts.Whenmirrors aresucientlyaligned,theMiraisputinMLmode,andsynchron izedtotheringRF forpump-probeexperiments.Detailsofthesynchronizationsc hemewillbedescribed shortly.Inordertomode-lockthesystem,theeectivecavityl engthshouldbeadjusted toanintegermultipleofthelaserwavelength( i.e. ,theresonantwavelength).This canbeachievedbyeitherchangingmicrometersettingofabir efringentlter(BRF)or movingtheratcavitymirror(M3)mountedonthePZTactuator .TheBRFprovides smoothlasercavitytuning,andallowstheusertoselectasingler esonantmode.For picosecondpulses,theintracavitygroupvelocitydispersion(G VD)compensationisrequired.ThismodeisgeneratedviaaGries-TournoisInterfer ometer(GTI)endmirrorin thecavity. Lmodeusesaproprietaryservolooptomonitorandadjusttothec orrect valueoftheGVD.ItcanbeimaginedasanautomatedversionofML mode. 6.4.3OpticsandLightDistribution Figure 6{8 showstheopticallayoutoftheU6lasersystem.Aninterlocksystem onthehutchdoorwayentranceisinterfacedtoashutterdirec tlyattheexitaperture ofthelaser.Ifanunauthorizedpersonentersthehutchwithou tproperlytriggering theinterlockbypasselectronics,theshutterwillcloseforthe beamtobecontained insidethelaser'sownenclosure,andreducethepossibilityofin jurytotheunprotected eyes.Whenthesafetyshutterisopened,thebeamgoesthroughaF aradayisolator.A Faradayisolatorisaunidirectionalopticaldevicebasedont heFaradayeect.Atthe heartofaFaradayisolatorisaFaradayrotator.Faradayrota torsutilizehighstrength,

PAGE 120

105 1 2 3 4 5 6 7 8 9 10 11 Optical Delay 12 Figure6{8:TheopticallayoutoftheU6lasersystem.(1)Nd:YVO 4 laser(Verdi), (2)Ti:Sapphirelaser(Mira),(3)Photodiode,(4)SafetyShu tter,(5)Faradayisolator, (6)Cylindricallenses,(7)EOM/2pulsepicker,(8)EOM/Npulsep icker,(9)Photodiode,(10)Fibercoupler,(11)1/2waveplate,(12)Opticalb ercable. rareearthpermanentmagnetsinconjunctionwithasingle,hi ghdamagethreshold opticalelementtoproduceauniform45 polarizationrotation.WhenaFaradayrotator isplacedbetweenalignedpolarizers,itbecomesaFaradayiso lator.Faradayisolatorsare usedtopreventdestabilizingback-rerectionsofdownstreamo pticsfromreenteringthe lasercavity.Followingtheisolatorisapairofcylindricall ensesthatareusedtocorrect foranastigmatisminthehorizontaldirection.Thecauseofthi sastigmatismisnot known,butitisprobablyduetoaslightdivergencecreatedin thecustommadecavity. Allmirrorsontheopticalbencharebroadbandrerectorswith amulti-layerdielectric coatingforanenhancedrerectanceinthenearinfrared. Thepulserepetitionfrequency(PRF)ofthelaser,105.8MHz,is reducedtothat ofthesynchrotronbyselectivelypassingeverytwopulsesthroug hadevice,whichis whatwecallthe\divide-by-twopulsepicker"(orEOM/2,ConO pticsmodel360-40),

PAGE 121

106 madebyConopticsInc.ItcontainsaPockelscell 5 andapolarizingbeam-splitter. ThePockelscellcausespolarizationofeveryotherpulsetobe rotatedby90 ,andthe subsequentpolarizingbeam-splittertransmitspulsesincertai npolarizationdirection, andrerectsonesinorthogonaldirection.Whenthemodulato risproperlytriggered, everyotherpulseisselected(orrejected)producing52.9MHzP RFthatmatcheswith thesynchrotronPRF.Ratherthanwastingrejectedpulses,theya rerecycledtorecover someofthelostpower.Thisisachievedbyintroducinganoptic aldelay(of9.45ns)so thattherecycledpulseisrejoinedtotheonesrightbehindit selfafterthepolarization hasbeenproperlyrotatedbackbyahalf-waveplate.Thewell stackedpulseshaveas highas80%additionalpowercomparedtonon-recycledsingle pulse. Asecondpulseselectionsystem,the\divide-by-Npulsepicker"(o rEOM/N, ConOpticsmodel350-60),isusedtomatchthevariousbunchpa tternssuchassymmetric3-bunchoperation(17.6MHz)andsinglebunchoperation(5 .9MHz).Figure 6{9 showstheeectsofpulseselection.ThesecondEOMhasthesameope ratingprinciple asthe\divide-by-twopulsepicker",buttheelectronicshas asixdecadethumbwheel switchtoprovidealltherequiredtiming.Rejectedpulsesfro mthismodulatoraresent toabeamdump,andarenotrecycled. Thelaserpulsesarecoupledintoanopticalbercableusingasta ndardber coupler,andaretransportedtoaparticularbeamlineendstat ionoveradistanceof approximately30m.Becauseopticalbercableisanimportan tcomponentofour experiment,thesomedetailsaredescribedin x 6.5.6 AlthoughnotshownontheFigure 6{8 ,anINRADM/N5-505UltrafastHarmonic GenerationSystemcanbeinsertedinfrontofthebercouplert oextendsthefundamentaltuningrangeofTi:Sapphirelasertoshorterwavelengt hsthroughtheuseof 5 APockelscellisanelectro-opticalmodulator(EOM)whiche xploitsanothervery importantelectro-opticaleectknownasthePockelseect .ThePockelseectisalinearelectro-opticaleect,inasmuchastheinducedbirefrin genceisproportionaltothe rstpoweroftheappliedelectriceldandthereforetheappl iedvoltage.Theeectexistsonlyincertaincrystalsthatlackacenterofsymmetry[ 10 ].

PAGE 122

107 050100150200 0.0 0.1 0.2 0.3 0.4 0.5 0.6 (D)(C) (B) (A)PhotodiodeSignal[a.u.]Time[ns] Figure6{9:Eectsofthepulsepickingonthe105.8MHzlaserpul setrain.Thecurve (A)showsthecasewithoutanypulsepicker,thatis105.8MHzpulset rain.(B)shows thepulseswiththe\divide-by-twopulsepicker"inuse.(C)and (D)arethecaseofusingthe\divided-by-Npulsepicker"for3bunchsymmetricandsi nglebunchmode.Note thatvariationsinpeakheightareduetoundersamplingbythe digitaloscilloscopeand donotrerectpowerructuationsinthelaser.nonlinearmixingcrystals.Fromafundamentalrangeof700nmt o900nm,forexample,secondharmonicwavelengthscanbegeneratedfrom350nm to450nm,andthird harmonicwavelengthsfrom233nmto300nmcanbeproduced.6.4.4Laser-SynchrotronSynchronization TheSynchro-lock900isanaccessorytotheMira900unit.Itisd esignedtoallow thesynchronizationofthelaserpulsesfromaMirawithastablee xternalfrequency sourceorwithastableinternalcrystaloscillator.Thesystemuses threecavitylength actuatorsintheMiraheadtocontrolthelaserfrequency:ahi gh-frequencypiezo-electric transducer(PZT),alowfrequencygalvonometerdrivendelay lineandadiscretestepmotordrive.Thesystemmonitorsthelaseroutputwithapickoa ndphotodiode mountedontheopticaltabledirectlybeyondtheMiraoutput bezel.TheSynchro-lock systemmixesthepulsedlasersignalwiththereferencesignal,and anerrorsignalis

PAGE 123

108 HPPulse Generator (Delay) Phase Shifter (Delay) Function Generator (Phase Modulation) Synchro-Lock 900 Control Box Mira 900 /2 Pulse Picker /N Pulse Picker Conoptics Model 305 Electronics (Delay) Conoptics Model 10 Electronics (Delay) 53 MHz RF DC Power Supply Beamline U6 hutch Figure6{10:Blockdiagramofthetimingscheme.Althoughnotsh own,coaxialcables arealsodelayelements.usedtocorrectthecavitylength.Whentheerrorsignalisdriv entozero,thelaseris synchronizedtothereference.Theelectronicsarecontaine dinacontrollerboxwhich ismonitoredandcompletelycontrolledbyacomputer.Theco mputercontinuously measuresanddisplaysthelaserfrequencyandhasafullyautoma tic\one-touch"lock acquisitionoperationmode. Inthecaseof7-bunchoperation,the52.9MHzsignalfromtheRFc avityofthe VUVringservesastheexternalfrequencysourcefortheSynchrolock900.Forthe time-resolvedmeasurements,aspecicphaserelation(delay)be tweenthelaserand synchrotronpulsesatthesamplelocationmustbeestablishedinac ontrolledway. Figure 6{10 showsthetiming( i.e. ,bothsynchronizationanddelay)schemewehave optedtouse.SeealsoFigure 6{20 formorevisualizedversionofthisdiagram.There areseveralwaystointroducetimedelay.Dierentlengthsof coaxialcable 6 canbe 6 Signalsthroughthetransmissionlinetravelsatarate(charac teristicdelaytime) givenby t d = p LC ,where L isaseriesinductanceperunitlengthand C isaparallel

PAGE 124

109 usedasdelayelements.Finecontrolofdelaytimeisachieveda sfollowing.TheRF ringsignalisfedintoapulsegenerator(HP81101A)atthebeamli ne(U10A/U12IR), andtriggersitsoastogeneratevoltagepulsesofthesame52.9M Hzfrequencywitha variabledelay-settinginincrementsaslowas0.01ns.Thedel ayedRFsignalfromthe generatoroutputistransmittedtotheSynchro-Lockcontrol boxthroughcoaxialcables fordesiredtiming.Wecanalsouseavoltagecontrolledphaseshif terbetweenthepulse generatorandtheSynchro-Lockcontrolboxforanadditiona ldelaythatcanbeutilized indierencespectrameasurementsaswillbediscussedin x 6.6 Inordertosetaccuratelythepump-to-probedelaytime,thec oincidencebetween thelaserandsynchrotronpulsesmustbemeasuredatthesampleloca tion.Thedelaysettingofthepulsegeneratorisadjusteduntilthepeaksofbot hpulsesdetectedby aGeavalanchephotodiode(APD;nearinfraredfastdetectorof 150psrisetime) overlapcompletelyonthedisplayofa1GHzdigital(electroni csrise/falltimeof400ps) fastoscilloscope.Becausethesynchrotronradiationisabroadb andsourcecontaining spectrumbeyondnearinfrared,asingledetectorcanbeusedtod etectbothlaserand synchrotronpulses.Wedenethiscoincidenceasthe\zero"del aypoint( t d =0),and canintroduceanarbitrarytimedelaywithrespecttothecoin cidence.Figure 6{11 showseachsynchrotronpulsearrivingatthesamplelocation4ns afterlaserpulse ( i.e. t d =+4.0ns). Thereisasignicantmodicationthatwasmadefromtheiniti aldesignofsynchronizationmethod.Sincethelaserrunsat105.8MHzwhichisexac tlytwiceasfastasthe PRFofsynchrotron,everyotherpulseshadtobeselectedbytheE OM/2pulsepicker asdiscussedearlier.Acorrectsetoftwopossiblepulsetrains(one spassedandothers rejected)shouldbechosenforapropertiming.TheConOpticsM odel10electronics forEOM/2pulsepickerprovidesabiasadjustknobforaneasysele ctionofapulse capacitanceperlength.Forexample,thepopular50ncoaxia lcablehasadelaytimeof 4.2ns/m.

PAGE 125

110 140160180200220 -2 0 2 4 6 8 10 DetectorsignalTime[ns] Synchrotron Laser 4 nsFigure6{11:Synchronizedlaserandstorageringpulses.Itshows thesynchrotronpulse arriving4nsafterthelaserpulseatthesamplelocation.train.Ifthewrongsetisselected,laserpulsesarrive9.45nso thecoincidence.When thesynchronizationschemewasdesignedinitially,thephotod iodesignalfromthelaser outputdividedby2wasusedtodrivethepulsepicker,anddelay wascontrolledfrom theSynchro-lock900program.Inthisconguration,althou ghthepulsepickerwas operatinginphasewiththelasernomatterwhattimedelaywasse t,thecorrectsetof pulsetrainhadtobeconrmedeverytimethelaserloosemode-lo ckduetoinstabilities. Withthenewconguration,thedelayedRFsignalfromtheHP811 01Adrivesthe Synchro-lock900andthepulsepickertogether,eliminating thepossibilityofhoppingto thewrongsetofpulses. Whenthesynchrotronisoperatingineitherthesingle-buncho r3-bunchsymmetric operation,the5.9MHzRF/9signalavailableatbeamlinecanbe usedinplaceofthe RFsignalforthe7-bunchoperation.DelayedRF/9signaloutof theHP81101Acanbe decomposedintoitsharmonics,thenwithahelpofbandpasslte r,the9thharmonics canserveasanexternalfrequencysourcefortheSynchro-lock 900,andthefundamental orthe3rdharmonicscanbeusedtodrivetheEOM/Npulsepicker.

PAGE 126

111 Nitroogen fill/exhaust Needle valve OVC valve Sample space Wiring connections Helium transfer tube entry Helium reservoir exhaust Level probeentry Sample spacepumping line Sample space 77K radiationshield Heat exchanger Figure6{12:SchematicoftheOxfordOptistatbathcryostat.T opofthecryostatis ttedwithservicesnecessarytorunthecryostat. ThefunctiongeneratorshowninFigure 6{10 allowslaserpulsestobeditheredwith respecttothesynchrotronpulses,makingquasi-dierentialmea surementspossible.See x 6.6 forthedetailofthistechnique. 6.5OtherExperimentalComponents 6.5.1OxfordOptistatBathCryostat TheOxfordOptistatcryostatisaveryimportantcomponentofo urpump-probe measurement.Itisabathcryostatwithabuiltinvariabletemp eraturefacility.The sample,mountedonasamplerod(insert),isloadedthroughthet opofthecryostat, andcanbecooleddirectlybythecryogen(dynamicsystem).The sampletemperature iscontinuouslyvariablebetween1.5and320K.Figure 6{12 showsaschematicofthe Optistat.

PAGE 127

112 Thecryostatcontainsa2.5-litterliquidheliumreservoiras wellasaliquidnitrogen reservoir.Thereisnoneedtorellthecryostatcontinuouslyf romastoragedewar foraconvenientperiodofoperation.Liquidheliumissuppli edfromthereservoirto thesamplespace(20mmdiameter)throughaneedlevalve,regul atingtherowtobe optimizedtosuittheoperatingrequirements.Theheliumreser voirhastwonecks,used fordierentservices.Oneisusedfortheneedlevalvedriverod .Theotheracceptsa9.6 mmdiameterliquidheliumtransfertubeusedtolltheheliumr eservoiranda4.8mm diameterheliumlevelprobe(dipstick).Anon-return(one-w ay)valveisconnectedto theexhaustportoftheheliumreservoir.Aliquidnitrogenrese rvoirisusedtocoolthe radiationshieldaroundtheliquidheliumreservoirandsample space.Thisshieldsthe lowtemperaturepartsofthesystemfromroom-temperaturethe rmalradiation.Italso shieldsthesamplespacefromtheliquidheliumreservoirsothatt heheliumevaporation rate(boilo)isnotaectedbyhighsampletemperatures.Then itrogenreservoir hasthreevents.Oneofthenecksisttedwithanon-returnval ve.Thisensuresthat evaporatingnitrogengascanbereleasedsafelyfromthereserv oireveniftheothernecks areaccidentallyblockedbyicecondensedfromtheatmosphere Thesamplespaceisbuiltintothecryostat.Itusesacontinuousr owofliquid heliumfromthereservoirtoprovidecoolingpower.Thus,thesa mpleisindirectcontact withthecryogeneitheringasorliquidphase,providingmuch fastercoolingrateto thesampleandsampleholderblockthanthetypeofcryostatthat reliescoolingon heatconductionthroughacoldnger( e.g. ,theAPDHelitran).Inourpump-probe experiment,thebathcryostatsuitedthebetteroftwotypessin ceitcouldminimizethe thermalexcitationduetothelocalheatingbythepumplaser. Aheatexchangeratthe bottomofthesamplespaceisttedwithaheaterandRhFetemper aturesensor,sothat thetemperatureoftheheliumrowingthroughthesamplespacec anbecontrolledby atemperaturecontroller.TheITC502temperaturecontroll erisusedtooptimizethe heliumrowrateandheaterpowerautomaticallyovermostofth eoperatingtemperature range.TheneckofthesamplespaceisttedwithanNW25rangethr oughwhich theheliumispumped.Byreducingthepressureinthesamplespace temperatures

PAGE 128

113 downto1.5Kcanbeobtained.Apumpingmanifoldcontrolsthe pumprate,and thus,thepressureinsidethesamplespace.Theenvironmentaround thesampleaects theparametersuchasphononescaperate(themeaningofwhichw illbeclearlater) obtainedfromtheexperiment.Insteadofpumpinghard,weused thehighestheliumgas pressurepossible(justbelowambientpressureifpossible)forthede siredtemperature. Thisensuresthatasmanyheliumatomsrowbythesampleaspossibl ehelpingecient heattransfer. Thetopofthecryostatisttedwithotherservicesincludinga nelectricalaccess totheheatexchangerandavacuumvalvewithapressurerelieff ortheoutervacuum chamber(OVC). Thesampleholderisattachedatthetipoftheinsert.Wemadesev eralsample holderswithvarioussizedapertures.Oneholderweusedmostacc ommodatesthree samplesverticallyinseries;eachparticularsamplecanbeselec tedbymovingtheinsert upordown.Theinsertcanberotatedabouttheverticalaxis(t heshaft)providing anotherdegreeoffreedomforthealignmentofthesample.The rearetwomulti-pin electricalfeedthroughesattheotherendoftheinsert.Onei sconnectedtoanother temperaturecontroller(ScienticInstrumentsModel9650) thatmeasuresthetemperaturenearthesampleviaadiodethermometerembeddedinthesa mpleholderand appliesvoltagetoaheater(Teroninsulatedconstantanwire, 0.005"diameter)whichis wrappedaroundthesampleholder.Oncethetemperaturesetpoi ntontheITC502are changed,thetemperaturereadingontheSIModel9650quickl yandcloselyfollowsthat oftheITC502.Thisimplieshowecientlydynamicsystemcanad justthetemperature ofthesample.Theheaterontheinsertservesanotherusefulpurp ose.Sincewecan warmthesampleandholderto300Kindependentlyfromthesampl espace,samplescan bechangedtoanothersetofthreesampleswithoutwarmingenti resamplespace. Therearethreepairsofwindows:theoutervacuumwindows,mid dle77Kradiationshieldwindows,andinnersamplespacewindows.SeeFigur e 6{12 fortheir locations.Thecryostathastwomutuallyperpendiculardirec tionsinwhichexperiment canbeperformed.Wecan,thus,putonesetofwindows(totalof6 windows)inone

PAGE 129

114 Table6{7:PropertiesofwindowsfortheOxfordOptistatcryo stat. location material dimensions range(cm 1 ) Outervacuum Quartz 42mmdiameter,1mmthick 0-250 and2700-65000 KBr 42mmdiameter,3mmthick,wedged30mins. 400-40000 Polyethylene 42mmdiameter,variousthickness 0-700 Middleshield Sapphire 26mmdiameter,1mmthick 0-350(below50K) and2000-65000 KBr 26mmdiameter,1mmthick,wedged30mins. 400-40000 Innersample Sapphire 0-350(below50K) and2000-65000 ZnSe 720-17000 directionanddierentsetinanotherdirectionsothatwidespe ctralrangeofoptical measurementscanbedonejustbyrotatingthecryostatby90degr ees.Theouter vacuumwindowssealtheOVCbyO-rings,andareretainedbyfour screws.Wehave Quartzwindows,KBrwindows,andpolymer(polyethyleneandpo lypropylene)windows. Theradiationshieldwindowsareheldinplacebywireclips.Th epressurefromthe wireclipshouldbesucienttomakesurethatthewindowiscoole dproperly. 7 These middlewindows,however,donotserveasvacuumwindow,andare optional.Wehave sapphireandKBrwindows,butchoosenottousethemiddlewindows inordertodeliverasmuchlightaspossibletothesample.This,ofcourse,cause smoreheatloadthat limitsthelowesttemperatureaccessiblefortheexperiment. 8 Theinnersamplespace windowsareindiumsealed.WehaveapairofsapphireandZnSewi ndowsattachedon theblockofsamplespace.Table 6{7 summarizespropertiesofwindowsfortheOptistat. Forthefarinfraredmeasurements(below250cm 1 ),apairofquartzvacuumwindows, sapphireradiationshieldwindows(optional),andsapphiresam plespacewindowscanbe used.Atroomtemperature,themulti-phononprocessesinsapphi relimitthespectral range.Asthetemperatureislowered,theacousticphononsstar tfreezingoutand,asa result,thespectralrangestartsopeningup.Below100K,sapphi reopensitsrangeup 7 Lightlygreasingthewindowmountwithvacuumgrease,suchasApi ezon`N'will improvesthethermalcontactbetweentheshieldandthewindo w.Thiscandecreasethe liquidheliumconsumptionsignicantly. 8 Theamountofheatradiatedfromonebodytoanotheratadier enttemperatureis proportionaltothedierencebetweenthefourthpowerofth eirtemperatures.

PAGE 130

115 to350cm 1 ,buttheabsorptionduetophononsinquartzlimitstheupperl imitofthe rangewiththissetofwindows. PreparationofthecryostatstartsbypumpingtheOVC.Ithasto bepumped tohighvacuum(typically10 4 or10 5 Torr).Weusedaturbo-molecularpump backedbyarotarypump.Incasethatthesystemisbadlycontamin atedwithwater vapor,therotarypump(ideallywithagasballastfacility)sh ouldbeusedrstto roughout.Beforewecooldownthesystem,itisveryimportantt oremoveairfrom theheliumreservoirandsamplespaceinordertoreducethechan ceoffreezingand blockingthenarrowcapillarytubeandneedlevalve.Thisis donebyopeningthe needlevalvewidefollowedbypumpingthereservoirandsample spaceandrushing heliumgasfromsamplespacepumpingline(orthereservoirexha ust).Oncethisis done,thecryostatcanbepre-cooledbyllingtheliquidnitr ogenreservoirwithliquid nitrogen.Wenormallywaitatleast12hoursbeforeliquidhel iumistransferredinto thesystem.Duringthepre-coolingprocess,thepumpcanbeeithe rleftonorturned o.Ipersonallyoptedtoturnitobecausethenliquidnitroge nevaporatesquicker resultinginfastercoolingrateforthesystem. 9 Justbeforestartllingliquidhelium,I lltheheliumreservoirandsamplespacewithheliumgasonemor etimetoatmospheric pressure,closethevalveforthepumpingline,andsettheneedle valvetothe30%of maximumopenedstate.Nowwecanlltheliquidfromastoragedew arthrougha transfertube.Thenon-returnvalveonthereservoirexhaustsho uldberemovedbefore insertingtransfertubeintothetubeentry.Atthebeginning, theboiledheliumcreates aplumeofexhaustgas,butwhenliquidstartstocollect,thegas rowratewilldrop noticeably.Whenthereservoirislledcompletely,thereis suddenexcessivecoldgas 9 Liquidnitrogenhasahighlatentheatofevaporation:thati s,averylargeamount ofheatisrequiredtoevaporateit.Thus,fastercoolingisach ievedbyevaporatingthe liquidnitrogen.Liquidhelium,ontheotherhand,hasavery lowlatentheat.However,heliumgashasaveryhighenthalpy.Itmeansitisverye asytogenerategas,but itismuchmorediculttowarmthatgasup,andthecoldgaspro videsahighcooling power.

PAGE 131

116 (noticeablydenserexhaustgas),andthentheheliumtransfersho uldbestopped.The dipstick 10 shouldindicatealevelof 10cm.Thesoundfromtheexhaustalsochanges slightly.Therearetwowaysofcoolingthesample:pumpfastwit hnarrowneedlevalve openingorpumpslowwithwideneedlevalveopening.Therowra teshouldbeadjusted manuallytogetasuitablecoolingrate(typically2to3Kperm inute).Ittypically takes60to90minutestocoolthesamplespaceto10Korbelow.On cethetemperature approachesthedesiredsetpoint,wecanswitchtotheautomatic temperaturecontrol. TheITC502isathree-termcontroller.Automatictemperatur econtrolisoptimizedby settingthebestvaluesforproportional(P),integral(I),an dderivative(D)constants. Fortheexperimentatthelowestpossibletemperature,thesampl espacecanbelled withliquidheliumbyopeningtheneedlevalvewideopen.The n,byclosingtheneedle valveandbypumpingasfastaspossible,wemanagedtocoolthesam pledownaslow as1.8K. 11 Thisisasingleshotmethod.Oncetheliquidispumpedoutcompl etely fromthesamplespace,thetemperaturestartsgoesupsuddenly,a ndthentheprocess hastoberepeated.6.5.2Ox-BoxCustom-madeSampleChamber Inordertoaddrexibilitytoourexperimentalsetup,wedesign edacustommade samplecompartment(wehavebeencallingitasthe\Ox-Box".) thatbecameanother keycomponentofourexperiment.TheOx-Boxhasansourceinpu tportandan externaldetectorport.Wemadeseveralrangesthatconnectt hesourceinputport totheBruker66'sexternalport,theSPS-200'sexternalpor t,ordirectlytheU12IR beamline.Theexternaldetectorportisdesignedtosupportva rioustypesofbolometers. 10 Narrowtubewiththinmembraneoverahousingatthetopend,used asasimple levelprobeforliquidhelium.Thethermalgradientsetupint hetubeleadstothermal oscillationswhicharefeltbythevibrationofthemembrane. Thefrequencyoftheoscillationwiththelowerendinliquidheliumisnoticeablyl owerthanthatwhenitisin coldgas,allowingtheliquidleveltobedeterminedeasily. 11 Thesuperruidtransitionofheliumoccursatthe point(2.2K)belowwhichthe liquidbecomescalmandhardlydistinguishablefromvacuum.

PAGE 132

117 M1 M2 M3 M4 M5 M6 M7 M8 Bolometer Input port M3M4 (A)Top (B) Side Figure6{13:Diagramofourcustommadesamplecompartment,th eOx-Box.(A)Top viewoftheOx-Boxshowingitsopticallayout.(B)Sideviewwi ththeOptistatmounted onthebox.OnlyM3andM4areshown.Therearetwowidesideopeningsthroughwhichwecanaccessthe insideforminor adjustmentofopticswithoutremovingthetopcoverofthebox .Theseopeningsare coveredbyacrylicwindowsthatsometimeshelpalignmentwhi letheboxisevacuated. Duringthepump-probeexperiments,thesewindowsmustbecover edbymetallicplates inordertoavoidanypotentialleakofhazardousclass4laserl ightfromthebox.An opticalbercableisinsertedthroughaholeonthesidettedw ithanNW25range. ThereisanotherutilityholewithanNW25rangetowhichwecan connectavacuum pump,drynitrogenline,pressuregauge,ventvalve,and/orel ectricalfeedthroughfora chopper.Figure 6{13 showsthediagramoftheOx-Box. MirrorsM2,M7,andM8aregoldcoatedplanemirrors.MirrorM1 ,M3,M4,M5, andM6areallo-axisparaboloidwhicharecutfromalargepa raboloidalrerector (RhodiumcoatedonanelectroformedNickelfromOpti-forms,I NC.)withfocallength f =2 : 35inches.SeeFigure 6{14 .MirrorsM1andM5arethetrue90 paraboloid thatrerectsthecenterofincomingrayat90 towarditsfocus.Ascanbeseenfrom Figure 6{14 (B),thesemirrorshaveaneectivefocallengthof2 f (4.7inches).Mirrors M3,M4,andM6,arecutsuchthattheireectivefocallengthar elongerthan2 f

PAGE 133

118 f y x y = x/4f 2 f 2f Focus OpticalAxis 90 f 2f Focus OpticalAxis 90 (A)(B) (C) Figure6{14:(A)Crosssectionofaparaboloid.(B)O-axispara boloidalrerectorwith thecenterofrayrerectedat90 .(C)O-axisparaboloidalrerectorwiththecenterof rayrerectedatgreaterthan90 asshowninFigure 6{14 (C).Theyaresittingonthestagethatcanbemovedby micrometerinonedirectionforanalignmentpurpose. TheOx-Boxisdesignedtodobothtransmittanceandrerectance measurements insequencewithoutbreakingvacuumifitisdesired.MirrorM8 canbesledinto thepositionsothatitdeliversrerectedlightoasampletodet ectorblockingthe transmittedlightoM4.Forthetransmittancemeasurement,M8 isjustremovedso thatonlytransmittedlightgoesintodetector.Theboxisalso designedtoacceptboth theOxfordOptistatandAPDHelitrancryostats.6.5.3OxfordInstrumentsVertical-boreSuperconductingM agnet Opticalmeasurementscanbeperformedinmagneticeldofupt o16Teslawithan Oxfordinstrumentsvertical-boresuperconductingmagnet.T hecollimatedlightfromthe extractionportoftheBruker125spectrometer 12 isdeliveredtoaparaboloidrerector atthebottomofthemagnet.Then,afterpassingaseriesofwedge dquartzwindows,the lightisfocusedatasamplemountedatthetipofavariabletemp eratureinsert(VTI), 12 TheBruker125usesHe-Nelaser.SinceHe-Nelaseroperateswithanel ectricaldischargeinaplasmatubecontainingamixtureofheliumandneon gases,strongmagnetic eldcouldcauseinstabilityofthelaser,andspectrometerstops scanning.Thus,the magnetshouldbeplacedatcertaindistancefromthespectromet er.

PAGE 134

119 SpectrometerBruker 125 Bolometer Brass elbow Paraboloid VTI Superconducting magnet Polyethylene window Quartz window Stainless steellight-pipe (A) VTIHeaterTemperaturesensorLight-conesSample Wedged quartzwindow Teflon centeringring (B) H Figure6{15:(A)AschematicoftheOxfordinstrumentsvertical -boresuperconductingmagnetconnectedtotheBruker125atU12IR.(B)Moredetai ledviewofthe sample-space.Asampleissandwichedbetweentwolight-cornsin Faradaygeometry formagneto-opticalmeasurement,andplacedatthecenterof themagnet. andnallyguidedtoadetectorthroughlight-pipes(14mmin nerdiameter)witha polyethylenewindowattheveryend.Figure 6{15 (A)showsaschematicofthesetup. Copperisoneofcommonlyusedmaterialforlight-pipesbecau seofitshigh conductivitytominimizethererectionlossinthepipe.Howev er,thehighconductivity ofcopperalsoresultsinhighthermalconductivity.Inordert oreduceheatload,a stainlesssteellight-pipeisusedforthesectionthatgoesintot hecoldenvironmentof themagneteventhoughrerectionlossinastainless-steelpipeis higherthanthatina copperpipe. ThesampleismountedattheendoftheVTIsuchthatstaticeldise itherparallel (Faradaygeometry)orperpendicular(Voigtgeometry)toth epropagationofthe electromagneticwaves.IntheFaradaygeometry,thesampleis sandwichedbetweentwo light-cones,andplacedatthecenterofthemagnet.Thisisth eonlygeometryweused forourmeasurements.Figure 6{15 (B)showsadetailedviewofthesample-spaceofthe VTI.

PAGE 135

120 6.5.4Detectors Opticaldetectorsaretheradiationtransducersthatconver tradiationpowerinto anelectricalsignalortoanotherphysicalquantity( e.g. ,heatorresistance)thatcanbe convertedtoanelectricalsignal.Inthissubsection,someofth egeneralcharacteristics ofdetectors(sensitivity,linearity, etc .)thatplayanimportantroleindeterminingthe accuracyandprecisionattainableinspectroscopicmethodsar epresentedrst[ 68 ]. Then,theoperatingprinciplesofseveraltypesofthemostcom monlyuseddetectorsare discussed.Wewill,nally,describethedetailofthe1.8KSibol ometer,whichisour principalfar-infrareddetectorforourtime-resolvedexpe riments. DetectorCharacteristics Opticaldetectorsvarywidelyincharacteristicssuchassensit ivity,linearity,spectral response,responsespeed,noisegure,andsoon.Beforewegoontode scribevarious typesofdetectorsandtheiroperatingprinciples,itmaybew orthmentioningsome termsthatcharacterizeopticaldetectors. Thesensitivityofadetectorcanbedescribedinseveralways.The responsivity R ( )istheratioofthermssignaloutput X (voltage,current,etc)tothermsincident radiantpowerevaluatedataparticularwavelengthandinc identpower: R ( )= X= : (6.1) Thesensitivity Q ( )istheslopeofaplotof X vs.: Q ( )= dX=d : (6.2) Aplotof R vs. or Q vs. iscalledthespectralresponseofthedetector.The functionalrelationshipbetween X andisknownasthetransferfunction.If Q is constantandindependentof,thedetectorissaidtobelinear ( i.e. ,theoutput electricalsignalislinearlyproportionaltotheinputopti calpower).Figure 6{16 illustratesthesimpliedtransferfunction.Nodetectorhasac onstantsensitivityunder allconditionsofuse.Forinstance,thesensitivityofphotodio dedetectorsfallsoabove acertainincidentpowerlevelduetosaturationeects.Thus,d etectorsexhibitlinearity

PAGE 136

121 X () l Fl () Slope = sensitivity (/) dXd F Responsivity (/) at given incident power X F Linearity :() constant, independent of Q lF Linear dynamic Range Figure6{16:Simpliedtransferfunction. overalimitedrangeofincidentradiantpower.Lineardyna micrange(orlinearity range)referstothetotalrangeofincidentopticalpowerle velsoverwhichthedetector outputvarieslinearlywithincidentpower. Detectorsalsovarywidelyintheirabilitytodetectrapidch angesinincident radiantpower.Quantitatively,theresponsetimeisdenedas: =1 = 2 c ; (6.3) where c istherollofrequencyatwhich R ( )hasfallento0.707ofitsmaximumvalue (3-dBpoint)whenasinusoidalinputoffrequency c isincidentonthedetector. Thenoiseequivalentpower(NEP)andthedetectivityareother importantquantitiesthatcharacterizethedetectorperformance.NEP(inw atts)isdenedasthe incidentradiantpower,ataspeciedwavelengthandbandpass thatwillproducea anoutputsignalfromadetectorthatisequivalenttotheinhe rent(background)noise inthatdetector.TheNEPdependsonthetypeofdetector,surfa ceareaofdetector, andwavelength.Thedetectivity(incmHz 1 = 2 W 1 )denotedas D (termedDstar)isa measureofminimumdetectabilityusedforcomparisonbetweend ierentdetectors. D

PAGE 137

122 isinverselyproportionaltoNEP,andisgivenas: D =( A ) 1 = 2 = NEP : (6.4) whereAisthesurfaceareaofdetector(incm 2 )and isthenoiseequivalentbandwidth(inHz).DetectorTypes Generally,detectorsfallintotwomajorcategories:therma ldetectorsandphoton detectors.Figure 6{17 showstheclassicationofcommonlyuseddetectors. Thermaldetectorssensethechangeintemperaturethatisprod ucedbythe absorptionofincidentradiation( i.e. ,photonenergy).Thetemperaturechangeis convertedintoanelectricalsignalbymethodsthatdependon thespecictransducer. Thermaldetectorshaveanearlyuniformspectralresponsethat isdeterminedbythe absorptioncharacteristicsoftheirresponsiveelementsandwi ndowmaterials.Photon detectors,ontheotherhand,respondtoincidentphotonarriv alratesratherthanto photonenergies.Thespectralresponseofthesedetectorswithwa velength,buttheir majoradvantageoverthermaldetectorsistheirfasterrespon setime.Photondetectors canalsodetectlowerradiantpowersthanthermaldetectorsi nmanycases. Abolometerisoneofthemostwidelyusedthermaldetectorfort hefarinfrared region.Itisarelativelyslowdetector(thermaltimeconstan tontheorderof1ms),and exhibitsawidelinearityrange.Itisatypeofresistancether mometerconstructedfroma Optical Detector Thermal DetectorPhoton Detector Optical ExcitationPhotoemission Thermal Effect BolometerPyroelectricPneumaticThermocouplePhotodiodePhototransisterPhotoconductorLinearArray SensorPhotoTubePhoto MultiplierTube Figure6{17:Classicationofopticaldetectors.

PAGE 138

123 dopedsemiconducting(germaniumorsilicon)sensingelementsup portedinavacuumby leadwiresattachedtothecooledsubstrate.Adopedsiliconist hemostcommonlyused materialsthesedays,andexhibitarelativelylargechangein resistanceasafunction oftemperature.Theresponsiveelementiskeptsmall( i.e. ,smallerheatcapacity)for highersensitivity.Inmanyapplicationsitisnecessarytoincr easetheeectiveareaof abolometerwithoutincreasingthethermaltimeconstant.Thi sisaccomplishedby bondingthesiliconsensingelementtoalarge,thinplateofeit hersilicon,sapphire, ordiamond.Thesematerialshaveexceptionallylowheatcapa cityandhighthermal conductivityatlowtemperatures.Athinconductinglayerof NichromeorBismuthis vacuumdepositedontoonefaceofthethinsubstrateinordertoi ncreaseabsorption ofinfraredradiation.Thistypeofbolometerisknownascom positebolometer(See Figure 6{18 ).Astheoperatingtemperatureislowered( 4.2K),thesensingelement approachesclosertothesensitivitylimitsofthermaldetecto rssetbyfundamental thermalructuations,anddetectorperformancebecomesbett er. 13 Theoperating temperatureisdeterminedbydewarbathtemperature.Arstst ageJ-FETpreamplier isplacednearthesensingelementmountedonthecoldplateofd ewar.Itrequiresan operatingtemperatureof60Kormore.Thisisaccomplishedby maintainingasmall currentrowthroughaheaterresistor.Thereisusuallyaserieso fwedgedopticallters infrontofthesensingelement. Apyroelectricdetectorisanotherexampleofathermaldete ctor.Deuterated triglycinesulfate[DTGS:(NH 2 CH 2 COOH) 3 H 2 SO 4 ]crystalhasgoodpyroelectric 13 Wecancheckifthebolometerisstillcold(inotherword,ifth ereisstillLHeleft inthedewar)bymeasuringtheresistanceattheBIASTESTBNCconne ctorwiththe BIASswitchturnedo.Thismeasurestheresistanceofthebolomet erandloadresistorconnectedinseries.Obviously,theseresistancesdependonap articularsystem,but bolometerresistanceisusuallyontheorderof k natroomtemperatureandloadresistanceisnear10Mn.Whenbolometerisatitsoperatingtemper ature,themeasured resistanceshouldreadhigherthanloadresistance.Asbolometerst artswarmingup, thebolometer'sresistancebecomessmaller,andthemeasuredre sistanceapproachesthe valueofloadresistance.

PAGE 139

124 MetalAbsorber Si:B thermometer bonded to substrate Diamond or sapphire substrate Lead Wire Support if needed Figure6{18:Aschematicofcompositebolometer. properties.Whenplacedinanelectriceld,asurfacecharger esultsfromalignment ofelectricdipoles.WhenincidentradiationheatstheDTGS, achangeinsurface chargeresults(pyroelectriceect),whichisrelatedtothe incidentradiantpower.The outputcurrentisproportionaltotherateoftemperaturech angeofthematerial;the detectordoesnotrespondtoconstantradiantenergylevels.Th epyroelectricdetector isfasterthanbolometerbecauseonlycharge-reorientationl imitstheresponsespeedfor modulatedinputs.Thecrystalexhibitsstrongabilityinthemo stpartofinfraredregion. WehavetwoDTGSdetectors:farandmidinfraredDTGSs.Thedie rencebetween thesetwodetectorsarethewindowmaterials(Polyethylenea ndKBr,respectively).See Table 6{4 fortheirspectralranges.Thecrystalhasthehighestpyroelect riccoecient valueatroomtemperature,andthusthedetectorisusedatamb ienttemperature. Thereareotherexamplesofthermaldetectorssuchasthermoc oupleandpneumatic (Golay)detectors,butsincewedidnotencountertousethesedet ectors,wewillnot discussaboutthemfurther. Photondetectorscanbebroadlyclassiedasphotoemissivetype andopticalexcitationtype.Photomultipliertubeisanexampleofthephoto emissiontypewhichhas sensitivityintheregionfromultraviolettovisiblelight.Ph otodiode,phototransistor, photoconductivedetectors,andlineararraysensorsareexamp lesofopticalexcitation types.Ofthesedetectors,photodiodesandphotoconductorsar eprobablythemost commonlyadopteddetectorsinopticalmeasurements.Theoper atingprinciplesofthese twodetectorsarediscussedbelow.

PAGE 140

125 Inaphotodiode,absorptionofelectromagneticradiationby ap(i)n-junctiondiode exciteselectronsfromthevalencebandtotheconductionba nd.Thusasingleelectronholepairperphotonarecreatedinthedepletionregion.Ift herateofphotoinduced chargecarriercreationgreatlyexceedsthatduetothermal excitation,thelimiting currentunderreversebiasisdirectlyproportionaltothein cidentradiantpower. Therefore,thephotodiodeactsasacurrentsource,andthevo ltagedropacrossaload resistorismeasured.Thistypeofdetectorshowsexcellentline arityoverwiderange ofincidentradiantpower.Itisaroomtemperaturedetector thatisusedforthenear infraredandUV-Visspectralrange.Itisalsoaveryfastdetector, andthusoftenused todetectveryshortpulses.Theavalanchephotodiode(APD)isuse dwherebothfast responseandhighsensitivityarerequired.APDisoperatedinthe reversebreakdown regionofthepnjunction.WehaveSiphotodiodedetectorand GeAPD. Aphotoconductivedetectorismadeofanintrinsicsemiconduc tormaterial ( e.g. ,CdS,PbS,PbSe,InAs,InSb,Hg-Cd-Te(MCT),Pb-Sn-Te,etc.)or anextrinsicsemiconductormaterial( e.g. ,Si:B,Ge:Cu,Ge:Au,Ge:Hg,Ge:Cd,Ge:Zn,etc).When incidentphotonsareabsorbed,electron-holepairsarecrea tedandincreaseconductivity.Thusitactslikeavariableresistorasafunctionofradia ntpower.Typically,the detectorisputinserieswithavoltagesourceandloadresistor, andthevoltagedrop acrosstheloadresistorismeasured.Wehavea77KInSb,77KMCT,4 .2KSi:B, and4.2KGe:Cu.SeeTable 6{4 fortheirspectralrange.Coolingisnecessarytoavoid thermalexcitationofelectronsintotheconductionband.T histypeofdetectortendsto benonlinear.MCT'snonlinearityiswellknown.1.8KSiBolometer The1.8KSibolometer(pumpedLHe 4 )isaverysensitivedetectorusedprincipally forthetime-resolvedexperimentsintheveryfarinfrared.T herefore,wewilldescribe thisparticulardetectoralittlemoredetail.Thesensingele mentismountedonanL shapedblockwhichisxedonagoldplatedcoppercoldworksurf aceofthedewar (InfraredLaboratoriesInc.,ModelHDL-8Dewar).ThemodelHD L-8dewarisascaledupversionofthecommonlyusedInfraredLaboratories'HD-3andHD L-5units,and

PAGE 141

126 feature8.12inchdiametercoldworksurfacewithincreasedli quidheliumandnitrogen capacity(2.8and2.5liters,respectively).Theheliumdewar canbepumpedtoreduce theoperatingtemperaturedownto1.8Kforhighersensitivity .Whenitispumped, theholdtimeforLHeisabout50hours.Thedewarhasawedgedwhi tepolyethylene withadiamondscatterlayerasthevacuumlteraswellasafar infraredlowpass lterthatismadeofaquartzcrystallaminatedwithcombinat ionsofantirerection (AR)coatingandGarnetpowderscatteringlayerthatlimitsth espectralrangeforthis detector( < 100cm 1 ). 14 Thefarinfraredlterisacooledtocryogenictemperature. Thetransmissioncharacteristicsofalayerofdielectricpowde risdeterminedbythe size,distribution,refractiveindex,andthickness.Thedewar alsohasaWinstoncone condenserformaximumconcentrationandecientreceptiono ffarinfraredandsubmillimeterradiation.Thedetectorisplacedinacavityatt herearofthecondenser. Theconeisconstructedfromnickelandisthengoldplatedtoe nhancererectivityand thermalcooling. Otherthanthe1.8KSibolometer,wehaveSibolometerandSi: B/Sisubstrate compositebolometersoperatingat4.2(LHe 4 ),andSibolometerat0.3K(LHe 3 ).The LHe 3 systemisthemostsensitiveofall,butitrequiresarepairatthis moment. 6.5.5RatioBox Thenumberofelectronsinthestorageringcontinuouslydecay swithtime.Since theintensityofthesynchrotronlightisproportionaltother ingcurrent,theintensity goesdownwithtimeaswell.Unlesswerecordtheringcurrentev erysooften,this couldbetroublesomeforameasurementthattakeslongtimeorr equiresmanyscans foraveraging.Inordertoavoidthiscomplication,weusedaso -calledtheratioboxthat normalizesthedetectorsignalwiththeringcurrent.Therin gcurrentof1000mAis convertedto10V,anddeliveredtothebeamlineareathrougha BNCcable.Theratio 14 Weoftenusedaruorogold(aglass-lledTeron)lowpassltertof urtherincrease sensitivityatlowfrequencyend.Thecut-ofrequencydepend sonthickness,butitit typicallyaround60cm 1

PAGE 142

127 Table6{8:Characteristicsoftheberopticcable(SpecTran SpecialtyOpticsCo.Model F-MFD)usedtotransferlaserpulsestobeamlines. Attenuation 3.2dB/kmat850nm 0.9dB/kmat1300nm Bandwidth 160MHz-kmat850nm 500MHz-kmat1300nm CoreDiameter 62.5 3 m CladdingDiameter 125 2 m CoatingDiameter 250 15 m Numericalaperture 0.275 IndexProle Graded boxtakesthedetectorsignalasanumeratorandthecurrentsig nalasadenominator. Thedenominatorsignalisampliedbyagainof10withanopera tionalamplier.The divisionisdonebyananalogmultiplierchipindividermode, anditsoutputsignal becomesindependentoftime.Theratioboxwasanecessarycomp onentforournotonly thetime-resolvedmeasurements,butalsotheordinarylinearme asurements. 6.5.6FiberOpticCableandPulseDelivery Theparticularopticalberweused(SpecTranSpecialtyOpti csCo.ModelFMFD)isastandardcommunicationgrade,multi-modetypewith agradedrefractive indexprole.Itisoptimizedfortransmissionat850and1300nm .Table 6{8 showsthe specicationsofthisberopticcable.Thebareopticalber consistsofacentralcore (madeofsilica, n 1 : 45),acladdingwithslightlylowerrefractiveindex,andala yerof acrylicbuer.Thelargecore(62.5 mdiameter)hasagraded-indexprole(asopposed toastep-index)inordertosupportspropagationofanumberof modes( e.g. ,linear, sinusoidal,helical,andcombinationsofthese).Ingraded-in dexbers,therefractive indexofthecorevariesgraduallyasafunctionofradialdist ancefromthebercenter. Eachmodecarriesonlyafractionofthetotalopticalpower. Thegraded-indexproleis achievedwithindex-modifyingdopantssuchasGeO 2 .Forgreaterprotection,theberis incorporatedintocablethathasapolyethyleneinnersheath (900 mdiameter),Kevlar reinforcingstrands,andanopaquePVCouterjacket(3mmdiame ter).Thelightexiting theberexpandsintoaconewitha30 vertex.SMAtypeopticalberconnectorsare axedtotheendofthebercable.Cablescanthenbeconnecte dwithascrew-type

PAGE 143

128 CoreCladding Acrylate Coating (250m dia.) m Bare Cabled Bare Fiber PE inner sheath (900m dia.) m Kevlar Strands PVC Outer Jacket (3 mm) n1n2a b Graded-IndexFigure6{19:Structureoftypicalopticalbercableandgra ded-indexprole. union.Figure 6{19 showsthestructureofthetypicalopticalbercableaswellas the graded-indexprole. NotallthelaserpowerinjectedintotheopticalberattheU6la serhutchis deliveredtothesample.Dispersion,absorption,andscattering arethethreeproperties ofopticalbersthatcauseattenuation,oramarkeddecreasei ntransmittedpower[ 69 ]. Absorptionandscatteringareobviouscausesofattenuationtha tneednoexplanation. Therearethreemaintypesofdispersion:chromaticdispersion( alsoknownasmaterial dispersion),wave-guidedispersion,andmodaldispersion.Thech romaticdispersion resultsfromthefactthattherefractiveindexofthebermed iumvariesasafunctionof wavelength.Inordertosatisfytheuncertaintyprinciple,ap ulseoflightofduration t p mustnecessarilycontainaspreadoffrequencygivenapproximat elyby: 1 t p : (6.5) Hencethepulsesarebroadenedintimeastheypropagatethroug hthemedium.This canbecomeaseriousproblemwhenattemptingtotransmitverysh ortpulsesover

PAGE 144

129 alongdistancewithoutsomesortofdispersioncompensation.Inou rsystemwith 2pspulsesat 800nm,theintrinsicdispersionis0.12ps/mresultinginapulse broadeningofnearly4psasthepulsetravelsapproximately3 0mfromtheU6hutch totheU12IRorU10Abeamline[ 1 ].However,sincethisbroadeningismuchsmaller thanthesubnanosecondsynchrotronpulses,wearesafeinneglecti ngthiseectinour time-resolvedexperiment. Wave-guidedispersionalsocausessignalsofdierentwavelengt hstospread,similar tochromaticdispersion.Itresultsfromthefactthatnotallof thelightareconned tothecore.Somefractionofthelightactuallypropagatest hroughtheinnerlayerof thecladding.Becausetherefractiveindexofthecladdingis lowerthanthatofthe core,thesmallfractionoflighttravelsfastercausingspreadi ngofsignalswithdierent frequencies. Modaldispersionisrelatedtothefactthatapulseoflighttran smittedthrougha multi-modeberopticcableiscomposedofseveralmodesoflig ht.Sincetheraysofthe lightpulsearenotperfectlyfocusedtogetherintoonebeam,e achmodeoflighttravelsa dierentpath,someshortandsomelong.Asaresult,themodeswill notbereceivedat thesametime,andthesignalwillbedistortedorevenlostoverlo ngdistances. Thereareotherplacesthatcouldcauselossofphotons.Forinsta nce,inecient couplingofbeamandber,andkinksandsharpbendoftheberc ablearesome examplesoflossyparts.Fromourexperience,morethan70%ofth einputlaserpower atthehutch(justbeforethebercoupler)canbedeliveredwi thecientlycoupled andwell-preparedundamagedbercable.Wewereabletodeli vertheaveragepoweras highas500mW,whichcorrespondsto 10nJperpulse(power/PRF)for52.9MHz excitationfrequency,or3nJ/cm 2 laserruence(apulseenergy/beamsize)for1/4inches diameterlaserspot. 6.6ExperimentalTechniquesandSetups Uptothispoint,eachcomponentofcomplexexperimentalsetup wasdiscussed separately.Forthetime-resolvedexperiment,allofthesecom ponentshavetoworkasa

PAGE 145

130 unit.Inthissection,wewilldiscussourvarioustechniquesof steady-stateandpumpprobetime-resolvedmeasurements,andseeanoverallpictureof theexperimentalsetup. Attheend,themethodsofthelaserinsertionatthesamplelocat ionaredescribed aswell.Somesubtletiesinvolvedinusinginterferometersusi ngthepulsedsourcewas discussedin x 5.2.2 6.6.1PhotoinducedMeasurementsSteady-statePhotoinducedMeasurements Insteady-statephotoinducedmeasurements,wesimplylookforch angesinpropertieswhenmaterialisopticallypromotedtoitsexcitedeq uilibriumstatefromthe groundstate.Bytakingadierencebetweensignalswithlaser( excitationsource)on ando,wecanmeasureaspectrumshowingeectssuchasphotoindu cedabsorption, bleaching,orheatingduetophotoexcitation.Thereareseve ralwaystocollectdata forthistypeofmeasurement.Firstofall,thelasercanbeplace dineithertheCW modeormode-locked.Sourcecanbeeithersynchrotronorinte rnalsource,butin caseofusingsynchrotron,itismoreecienttosynchronizethel aserandsynchrotron pulsesneartheircoincidence.Foraspectrometerthatiscapa bleofdoingstep-scan ( e.g. ,SPS-200),thelasercanbechoppedandadierencesignalisdi rectlygenerated byalock-inamplierateachscannerlocation.Aftercompleti ngthewholescan,the photoinducedspectrum( e.g. T or R )isproduced.Thismethodallowsthestudy ofweakersignals,butithasthedrawbackofbeingsusceptibleto falsesignalscaused bysampleheatingifthesamplehasanytemperaturedependence initstransmittance (orrerectance).Alternatively,wecansimplytakespectraint henormalfashionwith thelaseronando,andthentakethedierence.Inthecaseofaf astscanbenchlike theBruker66,datapointsaretakenonthekHzscalewithscanrep etitionrateon theorderofseconds.Therefore,thesecondmethodistheonlyop tionavailable.Normallyphotoinducedspectroscopyrequiresonetodetectverysm allchanges,andthus high-sensitivitydierentialmethodsshouldbeemployedwhen everpossible. Tobemorespecicforthesteady-statemeasurementwiththeBruk er66or125, spectrawiththelaseronandoaretakenbyopeningandclosingt hesafetyshutterin

PAGE 146

131 theU6laserhutch(seeFigure 6{8 ),respectively.Theshutterisdesignedtobeopened (orclosed)remotelybysupplying5(or0)voltsDCtotheelectr onics.Thiscanbe donebyaDCpowersupplyconnectedtothecontrolpanelattheb eamline.Sincethe photoinducedsignalsaretypicallyverysmall,manysetsofscan smustbetakento suppressnoisesasmuchaspossible.Wetookaseriesofinterleaved setsofscanswith laseronandobyusingamacrofortheOPUSNT(thesoftwarefordata acquisition andcontrollingBrukerbench)thatsendscommandstotheDCpo wersupplythrough aserialcable.ForNsetsofMscans,themacroroutinewaswritten totakedatasa follows: Mscanslasero(1)Mscanslaseron(1)Mscanslaseron(2)Mscanslasero(2)Mscanslasero(3) .. Mscanslaseron(N-1)Mscanslaseron(N)Mscanslasero(N) TheM Nspectraforeachonandocasesarethenaveraged.Thisschemew as usedminimizethelongtermdriftsindetectors,source,andoth ercomponents.In manycases,normalizedquantitiessuchas T = T ( T on T off ) = T off and R = R ( R on R off ) = R off aredenedasthephotoinducedsignal,andwewilluse thesequantitiestorepresentphotoinducedsignalsaswell. Asanexampleofthistypeofmeasurement,photoinducedtransmi ttancemeasurementsofasemiconductinglmmayrevealDruderesponsefrom thephotoinduced absorptionatfarinfraredthatiscalculatedfrom T = T (see x 2.4.5 ).Photoinduced

PAGE 147

132 bleachingmayalsobeobservednearthefundamentalabsorption edgeifthelmsisthin enough. 15 Pump-probeTime-resolvedMeasurements Pump-probetime-resolvedmeasurementsarealsophotoinduced measurements,with anaddedcomplexityforobviousreasons.Onetechniqueistosim plysynchronizethe laserwiththeringandthentakeaseriesofphotoinducedspectr aasdescribedabove. Eachspectrumistakenwithaparticulardelaybetweenthelase randsynchrotron pulses,andspectraforasetofdierentdelaysrevealsthetimee volutionofthespectra forthephotoexcitedsystem.Thetransmittanceandrerectance canofcoursebeused tocomputeanintrinsicresponsefunction,suchastheopticalco nductivity,whichis nowalsoafunctionoftime.Thisisaveryusefultechniquesince ittakestimevarying spectroscopic( i.e. ,frequencydependent)data.However,itrequiresimpractic allylong time(longertimethaneverycomponentofexperimenttorema instable)tocollect closelyspaceddataset,andthereforespectraforonlyafewdela ysettingaremeasured. Forexample,thedelayissetsuchthatsynchrotronpulsearrives earlierthanlaserpule ( i.e. ,negativedelayinourdenition),andthenthesinglebeamspe ctrumofnon-excited stateistakenrst.Thisspectrumisusedasareferencespectrumm uchlikespectrum withlaserointhesteady-statemeasurement.Then,thedelayis shiftedbyusinga DCpowersupplytoapplyacertainvoltagetothevoltagecontr olledphaseshifterthat comesaftertheHPpulsegenerator(seeFigure 6{10 ),andthesinglebeamspectrum atdierentdelayismeasured.Thesemeasurementsarerepeated asinthesteady-state measurement,anddierencespectrumfromthereferencespectr umiscalculated. Inanothermethodoftime-resolvedmeasurement,weintroduce aphasemodulation forthelaserpulses.Thiscreatesaditherofthepump-probedel aybyasmallamount t (= t 2 t 1 )aroundagivendelaysetting t (=[ t 2 + t 1 ] = 2).Thechanges 15 Forabulksample,itisdiculttoobservebreachingduetoitsa bruptabsorption edgenearthebandgap.

PAGE 148

133 intheopticalresponse S ( t )( e.g. ,transmissionorrerection)ofthesampledueto modulation t isgivenbythetimederivativeofEq. 5.16 as: S ( t )= I 0 @ @t Z + 1 1 dt 0 I probe ( t 0 + t ) G ( t 0 ) t: (6.6) Thissignalisdetectedasalock-inamplieroutput.Whenasma llmodulationamplitudeisused,thistechniquegivesessentiallythetimederivat iveofthephotoinduced signal.Itisadierential(ormoreaccuratelyquasi-dieren tial)techniquethatismore sensitivetothoseopticalpropertieschangingonthenanosecon dtimescalebutless sensitivetoslowthermaleects.Becausethelaserisirradiating thesampleatveryhigh frequency(53MHz),thesampledoesnotundergotherelatively largeswingintemperaturethatmayhappenincaseofusingalowfrequencychopperfo rthesteady-state measurement.Aseriesofderivativesignalsaretakenataclosel yspaceddelaysettings, andafterafullsetisobtained,theycanbeintegratedtogive thetimedependence (dynamics)ofthephotoinducedresponseofthesample.Wesometim esreferredthis techniqueastheZPDdecaymeasurement.Figure 6{20 showstheoverallexperimental setupforthisparticulartypeofexperimentwiththerowofRF signalandpulsesof bothpumplaserandsynchrotron.Notethataspectrometerisnotsh owninfrontof thesampleforsimplicityofthediagram.Withthistechnique, weeitherconnectedthe Ox-BoxdirectlytotheU12IRbeamlineorstoppedthescannerofsp ectrometeratsome xedposition(ideallyatthezeropathdierence,ZPD).With thissetup,weobviously cannottakespectroscopicdata, 16 butinsteadwemeasurethefrequency-integrated, singlebeamspectrumshapeweightedsignal( i.e. ,thephotoexcitedresponseaveraged overtheentirespectralrangeoftheexperiment)fromwhichw ecandeterminethe overalltimedecayofthesample. 16 Thedithertechniquecanbeemployedtotakespectroscopicdat eifweuseastepscaninterferometer.Theditherfrequencythatcanbeusedisl imitedtoafewhundred HzduetoPZTresponseasexplainedinthecontext.Thisismanyor dersslowerthan thesamplingrateoftherapidscaninterferometermakingunsui tabletousethistechniqueforacquiringspectroscopicdata.

PAGE 149

134 Pulse Generator Coherent Synchro-Lock Coherent Mira Ti:Sapphire laser ~100 Hz Func. Gen. Lock-in Driver Driver 52.9 MHz RF 52.9 MHz RF + Delay Control signals Sample Reference signal 52.9, 17.6, 5.9 MHz synchrotron IR pulses /2 divider/N divider 105.8 MHz52.9 MHz l /2 52.9, 17.6 or 5.9 MHz laser pulses Phase mod.sig. IR detector signal Time-dep. Sig. (Derivative) VUV Ring Fiber optic cable Figure6{20:Schematicofexperimentalsetupwiththemostofm ajorcomponents.It showstherowofelectricalsignalsandpump-probepulses.Noteth ataspectrometeris notshowninfrontofthesampleforsimplicity. Insidethelaserhead,laserditheringisachievedbyoscillatin gthemirror(M3in Figure 6{7 )mountedonthepiezoelectrictransducer(PZT)withafuncti ongenerator. Thecavitylengthischangedinthiswaymodulatingthephaseo flaserpulseswith respecttothatofsynchrotron.Theamountofphasemodulation( ditheramplitude) isdeterminedbythevoltageapplied.Wetypicallychosetouse ditheramplitudeless thanthesynchrotronpulsewidth( e.g. < 700psfordetunedmode).Forthedierential measurementstheidealdithersignalisasquarewave.However,a sweincreasethe ditheramplitude,westartdrivingthePZTbeyonditsmaximum safecurrent,and eventuallylosemode-lock.ThislossoccursbecausethePZTcan notmovethedistance askedforataglowrateofthesquarewave.The20MHzfunctiongen eratorweused certainlyexceedsthebandwidthofthePZT.Fromthestandpoi ntofintrinsicnoise, ahighfrequencyditherwouldbethemostdesirable.However,be causeofthelimited

PAGE 150

135 DC BiasTee RF(53MHz) Function Generator(Square Wave)Signal Out HPPulse Generator (delay) DC Power Supply Phase Shifter (delay) Lock-inAmplifier Reference OutDetector Signal Synchro-Lock 900 Control Box BeamlineU6 HutchAC DC AC+DCFigure6{21:Newschemeofcontrollingditheramplitudeandfr equencyatbeamline. bandwidthofthePZT,highfrequencyditherisnotpossible,an dwetypicallydithered atnear100Hz. Thefunctiongeneratorusedforthedelaymodulationwasconn ecteddirectlyto theSynchro-Lock900controlboxandplacedintheU6laserhutc htodrivethePZT directly(SeeFigure 6{10 ).Inordertocontroltheditheramplitudeandfrequency convenientlyatbeamline,dierentschemeisproposed.Figur e 6{21 showsthisnew method.Inthismethod,aDCbiasteeisintroducedbeforethe pulsegenerator.Itis abroadbandbiasinsertionteewithaDCblockingcapacitorth atisdesignedtohave averylowcutofrequencyofontheorderofonly1kHzwhenusedw ithaninductor. ItpassesfastRFsignalwithDCosetsuppliedfromthefunctiongen erator'ssquare wavewithaminimumofwaveformdistortion.Thus,ifwesettotri ggertheHPpulse generatoratthezerocrossingonthepositiveslopeside,theinpu tsignalfromthebias teeshiftstheRFsignalasthesquarewavechangesitsstateresult ingintheoutputwith delayanddithersignalalltogetheratthebeamline. Thereareafewissuesthatcouldyieldproblemsintheditherme thod.Firstofall, thefactthattheopticalpathinthelaserheadisfolded(seeFi gure 6{7 )couldmove thebeamacrosstheoutputslitasM3movesbackandforthfordit hering.Ifthebeam isnotwellcenteredattheslitthiscausesapowerructuationt hatisinphasewiththe dithersignal,andcanbemisinterpretedasspurioussignal.Thi ssignaltypicallyshows upasaDCoset,mainlyduetoheatingeect.Itismoretrouble someifthesample showsalargesteady-statephotoinducedresponsecomparedtothe time-dependent

PAGE 151

136 response.Byopeningtheslitsucientlywide,thistypeofructu ationcanbereduced. Thereisanothersourceofpowerructuationinthesystem.Asexpl ainedearlier,the EOM/2pulsepickerpasseseveryotherpulsesof105.8MHzpulsespro ducedbythe laser.IfthephaseoftherotatingpolarizerwithinthePockel scellisproperlyadjusted, suchthatthetimedelayisditheredsymmetricallyaroundthep eaktransmission throughthepolarizer,anotherpowerructuationisintrodu ced.Whenthepulsepicker's phaseisnotproperlyadjusted,thewrongsetofpulsesstartsshowi ngupinthesignal fromthediodeafterthepulsepicker.Weadjustedthephasesotha tthewrongpulses disappearandtherightpulseshavethehighestpeakintensityju stbylookingata oscilloscopescreen,butitwouldbemoreaccuratetouselock-in technique.Thedriftof thepulsepickerphaseduringmeasurementcausedtroublefromti metotime. Asmentionedbrieryin x 5.2.1 ,thepump-probemeasurementrequiresthattherebe negligibleexcitationbytheprobepulsesascomparedtothose createdbypumppulses. Becausethesynchrotronisabroadbandsource,itmaycontainsub stantialnumberof photonsthathavehigherenergythanthethresholdforexcita tion.Thisproblemcanbe eliminatedeitherbyusingopticallowpasslterstoconstrain thespectralrangebelow thethresholdenergyorbyusingabandpasslterstorestrictthe spectralrangetothe regionofinterest.Forexample,weusedablackpolyethylene( polyethylenewithcarbon ller)lmjustafterthediamondwindowforthefarinfraredm easurements. 6.6.2LaserInsertion Inordertophotoexcitethesample,pulsesoflaserlightmustbeb roughttothe samelocationasthoseofthesynchrotron.Thisisachievedbyx ingtheendofthe opticalberatafewcentimetersinfrontofthesample.Thela serlightexitingthe bernaturallydivergesata 30degreeangle,andilluminatesanareaupto1cm indiameteronthespecimen.Smallerregionscanbeilluminat edbyeithermoving

PAGE 152

137 Opti-stat cryostat Sample NIR mirror Lens Optical Fiber Cable Synchrotron pulses Windows Opti-stat cryostat Sample Optical Fiber Cable Synchrotron pulses Windows (B) (A) Figure6{22:Schematicrepresentationofthelaserinsertionse tupswithOptistatcryostat.(A)SetupfortheOx-Box.(B)SetupfortheBruker66'ssamp lechamber. theberclosertothesample,orusingsmalllensesorGRIN(gradie ntindex) 17 rods tofocusthelaserlight.Asmallerlaserbeamspotwasusedwheneve rhigherenergy density(ruence)wasnecessaryforagivensample.Weattachedasm allcollimating asphericlens[ThorlabsInc,Fibercollimationpackage,ARCo ating600-1050nm,NA =0.25, f (mm)=11.00]attheveryendoftheberwithSMAconnector,an dsimply maintaineditrelativelyclosetothespecimen.Thismakesthe beamspotapproximately 1/4inchesindiameter.Figure 6{22 (A)showsaschematicrepresentationofthislaser insertionsetup.Theberendiscontainedcompletelywithint hevacuumbox,andthus itiscompletelysafetooperatethelaser.Thisschemewasadopt edforthemostofour pump-probeexperimentswithOptistatintheOx-Box.Noeortw asmadetofocusthe 17 Gradientindexmicrolenseshavearadiallyvaryingindexofr efractionthatcauses anopticalraytofollowasinusoidalpropagationpaththrough thelens.Theycombine refractionattheendsurfacesalongwithcontinuousrefract ionwithinthelens.

PAGE 153

138 Cryostat shroud Sample holder Cold finger Stainless steel fiber guide Optical fiber cable Figure6{23:SchematicofthelaserinsertionsetupwithHeli-tr ancryostat.Fiberoptic cableisfednearthetopofthecryostat. ~1mWDiode laser Last portion of optical fiber cable Sample Sample holder Fiber coupler Figure6{24:Lowpowerreddiodelasercoupledtoopticalber cablewithSMAconnector.Thissourceoflightcanbefedintothesamplevacuumcompa rtmentorheli-tranto checkalignmentofthelightbeamontothesample.light.IncaseofusingthesamplechamberoftheBruker66,there isnotenoughspace toplacetheberendunionwithoutbendingthecablesharply. Therefore,amirrorhas tobeusedtoplacetheberendatmoreconvenientplace.Thisc aseisillustratedin Figure 6{22 (B).Wehavelenseswithseveraldierentfocallengthtoadjust thespot sizeatthespecimen. WhentheAPDHeli-tranisused,thebercableisbroughtnearthe samplethrough asmallstainlesssteeltubewhichisbenttopointthebeamexitin gthebareberonto thesample.SeeFigure 6{23 .Thespotsizeinthissetupisdeterminedbythedistance fromthebertiptothesample. Alignmentoftheopticalber,especiallytoplacetheendofth eberattheproper distancefromthesample,isdonewiththeaidofalowpowervisib lelightsource(0.95 mWdiodelaserat670nm),coupledintothelastportionoftheb ercablewithan

PAGE 154

139 SMAconnector(seeFigure 6{24 ).Thepositionofthebertipisadjusteduntilthe beamspotisvisuallycenteredonthesample.Thisavoidsperfor mingalignmentwith theTi:Sapphirelaser.

PAGE 155

CHAPTER7 OPTICALCONDUCTIVITYOF -MoGeTHINFILMS 7.1Introduction BCStheoryhasbeenproventobeverysuccessfulinexplainingqu antitativelythe phenomenaofsuperconductivity[ 38 ].Thebasicideaisthattheinteractionbetween electronsandlatticevibrations( i.e. ,phonons)causesanattractiveforcebetweenthe electronsbelowacertaintransitiontemperature T c .Thisinturncausestheelectrons toformpairsandalsocausesagaptodevelopinthespectrumofel ectronicexcitations aroundtheFermienergy.Thus,itrequiresanenergyofatleast theenergygap2to breakpairs.InweakcouplingBCSsuperconductors,theenergyg apatabsolutezero temperature,2 0 ,isknowntobeapproximately3.5 k B T c .Astemperatureisincreased toward T c ,electronpairsarebroken,andthegapcloses.Farinfraredspe ctroscopywas thersttechniquetoprovetheexistenceofthegap[ 70 71 ],andcandetectthisenergy gapevolutionwithtemperature.MattisandBardeenapplied theBCStheorytoderive expressionsforthecomplexopticalconductivityfordirtyli mitBCSsuperconductors, fromwhichthetransmissionofelectromagneticradiationthro ughthinsuperconducting lmscanbecalculated[ 45 ].Theircalculationshowsthatatabsolutezerotemperature therealpartofopticalconductivity 1 ( )inthesuperconductingstateiszeroforphotonenergiessmallerthanthegap2 0 .Thisareathusremovedfromtheconductivity, bythesumrule,showsupasadeltafunctionatzerofrequency[ 72 73 ].Theimaginary partoftheopticalconductivity 2 ( )canbecalculatedfrom 1 ( )byKramers-Kronig equations,andthedeltafunctionof 1 ( =0)givesadominant1/ formto 2 ( )at lowfrequencies.Thissortofbehaviorisobservedinmostmetall icsuperconductors. Inthepresenceofdisorder,itiswellknownthatmetallicsystem sexperiencesignificantalterationintheirphysicalproperties.Anomalousdiu sionleadstolocalizationof electronsandarelatedenhancementoftheCoulombinteract ionviareducedscreening 140

PAGE 156

141 ( i.e. ,anincreasein ,therenormalizedCoulombinteractionparameter)[ 4 74 ].With asucientdegreeofdisorder,abulkmetallicsystemcouldevene xperiencesomeform ofmetal-insulatortransition.Inasystemoflowerdimensions,th ecouplingtodisorder increases,andpronouncedeectsareexpected. Inthecaseofsuperconductors,theeectsoflocalizationandt herelatedenhancementintheCoulombinteractioninherentlycompetewithatt ractiveinteraction,thus withsuperconductivity[ 46 75 76 77 ].Therewereanumberofstudiesreportedon thissubjectin80's,beforetheemergenceofhightemperature superconductors,but manyquestionshavenotbeenanswered,yet.Theoriespredictt hatsuchcompetition reducesthetransitiontemperature.Ofparticularinteresta retwo-dimensional(2D) superconductorsinwhichthedegreeofdisordercanbeadjusted byvaryingtheappropriatematerialparameters.Inanideal2Dsystem,therelev antparameteristhe sheetresistance R 2 whichcanbecontrolledwiththelmthickness d .Severaltransport experimentsshowedasharpreductionin T c withincreasing2Ddisordereveninthe weaklylocalizedregime[ 6 7 8 78 79 80 81 82 83 ].AmorphousMoGelmisthoughtto beoneofthebettersystemsthatservesasamodelforstudyingthi sinterplaybetween superconductivityanddisorder.Here,afterbriefdiscussionofa ppropriatetheoretical background,wepresentourresultsofthefarinfraredtransmit tanceandrerectance measurementsonasetofthin -MoGelmswithdierentthicknessinbothnormaland superconductingstates.Astrongsuppressionof T c withincreasing R 2 isobservedas expectedfromtheoryandearliertransportexperiments.Adet ailedanalysisusingthe Mattis-Bardeenexpressionsfortheopticalconductivityisdi scussed.Thedependenceof superconductingparameters,suchassuperruiddensityandmagne ticpenetrationdepth, on R 2 isalsoreported. 7.2Background 7.2.1InfraredPropertiesofSuperconductors Spectroscopictechniqueshavebeenwidelyusedforthestudyof superconductors. Sincetheenergygap2intheelectronicexcitationspectrum correspondstothe energyofphotonsinfarinfrared,itisofparticularintere sttoseehowsuperconductors

PAGE 157

142 behavesinthisfrequencyrange.Here,wewillconsiderasample intheformofthin lmonasubstrate,andlookattheratiooftransmittancethroug hthelminthe superconductingstatetothatinthenormalstate.Thisformofsa mpleisadvantageous (overabulksample)becauseamoderatechangeintheconductiv itycanproducea relativelylargechangeintransmission. Asdiscussedin x 2.4.4 ,thetransmittancethroughathinlm(providedthat multiplererectionswithinasubstrateisneglected)isgiven bytheGlover-Tinkham equation: T = 1 1+ Z 0 ~ d n +1 2 4 n 4 c 1 d + n +1 2 + 4 c 2 d 2 ; (7.1) where d isthethicknessofthelm, n istherefractiveindexofthesubstrate,and Z 0 is theimpedanceoffreespace(4 =c incgs;377ninmks).Thus,thetransmittanceisdirectlyrelatedtotheelectricalpropertiesofthematerial ( i.e. ,thecomplexconductivity ~ ). Forathinlminitsnormalstate,onecangenerallyexpectthe electronscattering frequency(1 = )tobemuchhigherthanthefrequenciesofinteresthere( i.e. 1 inEq. 2.94 ),leadingtoarealandfrequency-independentnormal-state conductivity n Then,thetransmittanceinthenormalstate T n shouldalsobeaconstantdepending onlyon n d T n = 1 1+ Z 0 n d n +1 2 : (7.2) TheDCresistancepersquareofthelm, R 2 =1 = n d = n =d ,canbemeasured experimentally.Thus, T n canbedeterminedfrom R 2 ,andviceversa. Byformingtheratioofthetransmittanceinthesuperconducti ngstatetothatin thenormalstate,onecanndtherelativetransmittance T s = T n as T s T n = 1 h T 1 = 2 n +(1 T 1 = 2 n ) 1 n i 2 + h (1 T 1 = 2 n ) 2 n i 2 : (7.3)

PAGE 158

143 0123 0 1 2 3 s 1 s 2ConductivityRatio(s s/s n)Frequency( w / w g ) 0123 0 1 2 3 T =0.99 T c T =0KTransmittanceRatioFrequency( w / w g ) (/) TT snFigure7{1:TheMattis-Bardeencalculationsforthefrequen cyandtemperaturedependenceofconductivityratioandthetransmittanceratioi nthedirtylimit.Thetemperaturesfortheconductivityratioareat0K,0 : 6 T c ,0 : 8 T c ,0 : 9 T c ,and0 : 99 T c .The temperaturesforthetransmittanceratioareat0K,0 : 5 T c ,0 : 6 T c ,0 : 7 T c ,0 : 8 T c ,0 : 9 T c ,and 0 : 99 T c .Calculationsat T =0Kareshowninthickerlines.Thesampleisassumedto have R 2 =50n, T c =10K,2 0 =24 : 46cm 1 ,1 = =1000cm 1 ,and n =3 : 05. Thus,theformsof 1 ( ) = n and 2 ( ) = n determinethefrequencydependenceofthe relativetransmittance T s = T n .BasedonBCStheory, 1 MattisandBardeendeducedthe frequencydependenceof 1 ( ) = n and 2 ( ) = n [ 45 ].TheMattis-Bardeencalculation wasdoneintheextremeanomalouslimitandareapplicablefo rdirtysamples( l= 0 1),whichisusuallythecaseforthinlms,andsoonappliedtothe transmissionofthin lms[ 18 70 71 88 89 ].Figure 7{1 showsthetheoreticalfrequencyandtemperature dependenceof 1 ( ) = n 2 ( ) = n ,and T s = T n forasamplewith R 2 =50n, T c =10K, 2 0 =24 : 46cm 1 ,1 = =1000cm 1 ,and n =3 : 05.Thetemperaturedependenceinthe Mattis-BardeencalculationarisesfromtheBCStemperatured ependenceofthegap. 1 Transmissionmeasurementsinvolvingstrong-couplingsupercond uctorswereshown todeviatefromtheMattis-Bardeenpredictions[ 84 ].Namintroducedacorrectionfor strongcouplingtotheMattis-Bardeentheory[ 85 86 ].Thiscorrectionwasshowntohave betteragreementwiththeexperimentaldata.Later,Ginsber g,Harris,andDynespublishedarstordercorrectionforstrongcouplingthatonlytak esthechangein 2 ( ) intoaccount[ 87 ].

PAGE 159

144 At T =0K, 1 =0forallfrequenciesbelowthegapfrequency( g 2 = ~ )except at =0whereithasadeltafunctiongivenby 1 ( )= 2 ps 4 ( ) ; (7.4) where ps istheplasmafrequencywhichisrelatedtothedirty-limitma gneticpenetrationdepth (giveninEq. 4.27 )by ps = c= .Notethat ps issmallerthanthe plasmafrequency p whichisrelatedtotheLondonpenetrationdepth L by p = c= L Photonswithenergylessthan2donothaveenoughenergytobr eakCooperpairs, andthustheyarenotabsorbed.Fromthedeltafunctionof 1 ,theKramers-Kronig relationsdeterminethedominantpartof 2 atlowfrequencies( ! g )tobe 2 ( )= 2 ps 4 = c 2 4 2 = N s e 2 m! : (7.5) Since 1 =0below g ,thelosslessinductiveresponse 2 ,whichgoesas1 =! ,governs thebehaviorofthelminthelow-frequencyrange,andinfac t,themonotonicdecrease of 2 resultsintheinitialriseof T s = T n withfrequency.Notethatatlowfrequencythe ratiogoestozeroas 2 duetothediverging 2 .Thetemperaturevariationofthe low-frequencylimit( ! g )of 2 = n isgivenbyasimpleanalyticform 2 n = ~ tanh 2 k B T : (7.6) AssumingthattheBCStemperaturedependenceof( T ),thisequationtogetherwith Eq. 7.5 providesthetemperaturedependenceofthesuperruiddensity N s ( T ).For ! g ,photonshave,atleast,theminimumenergyrequiredtobreak Cooperpairs, andalossyconductivitycomponent 1 appearsandincreaseswithfrequency.Near thegapfrequency g ,both 1 and 2 aresmallresultinginahighertransmissionin superconductingstatethaninnormalstatearound g .Then,as 1 becomesmoreand moreeective, T s = T n startsfallinggradually.Thepeakpositionin T s = T n roughly representsthesuperconductinggapfrequency g ;thisisespeciallytrueforlmswith large R 2 .Infact,apeakintheexperimental T s = T n curvewasanearlyevidencefor thepresenceofanenergygapintheexcitationspectrumofsuper conductors.Ifwe

PAGE 160

145 observe 2 closelynearthegapfrequency,itstartsfallingfasterthan1 =! .Thisisdue toanother 2 contributionfromtheedgeof 1 near g .For ! g ,thepresenceofthe gapbecomesunimportant,andsuperconductingandnormalstat esactessentiallythe same.Atthesefrequencies, 2 becomesnegligiblysmall(solongas 1 = ),andthe lossyconductivity 1 determinesthebehaviorofthelm. Atnitetemperatures(0
PAGE 161

146 thelocalizationandelectron-electroninteractiontheor yproposedbyMaekawaand Fukuyama(MF)[ 46 ].Theirtheorydescribesthequantumcorrectionstothetheo ryof dirtysuperconductorsbyAnderson[ 90 ]andGorkov[ 91 ], 3 andisvalidfor2Dsystem intheweaklylocalizedregime.AccordingtotheMFtheory,th eCoulombinteraction isenhancedandthedensityofstatesofelectronsaredepressedb ylocalizationeects resultinginaconsiderablereductionof T c .Theapproximateresultoftheirperturbation calculationisgivenby ln T c T c 0 = s 2 ln 5 : 4 0 l T c 0 T c 2 s 3 ln 5 : 4 0 l T c 0 T c 3 ; (7.8) where s = g 1 N (0) ~ 2 E F 0 ; (7.9) and T c 0 isthetransitiontemperatureofthebulkmaterial, 0 and l arethecoherence lengthcorrespondingto T c 0 andthemeanfreepathassociatedwithelasticscattering, respectively, g 1 isaparameterthatrepresentstherepulsiveCoulombinteract ion ( g 1 > 0),and N (0)isthedensityofstatesatFermilevel.Theproduct g 1 N (0)isan eectivecouplingconstantwithvalueof 1associatedwiththeCoulombinteraction. E F istheFermienergyand 0 istheelasticscatteringtime.Thesheetresistanceis givenby R 2 = ~ 2 e 2 E F 0 : (7.10) Thersttermontheright-hand-sideofEq. 7.8 isduetothecorrectiontothedensityof statesduetotheCoulombinteraction.Thesecondtermisdueto theenhancementof thescreenedCoulombinteraction( i.e. ,therenormalizedCoulombinteractionparameter mentionedin x 4.2.6 )particularyatlongwavelength,whichisaconsequenceof Proximityeectsmightberelevanttosomeextent,butexperi mentalresultsargue againsttheirbeingtheprimarycauseoftheobservedphenomena .Anothermodelisa simplepair-breakingduetoretardationeects. 3 Intheirtheory, T c isnotaectedbystaticandnonmagneticdisorder.

PAGE 162

147 thedynamicalnatureofthescreeningbroughtaboutbythediso rder.Foramorphous lmswheretheratio 0 =l isexpectedtobemuchlargerthan1,thesecondtermisthe predominantcontributiontothe T c reduction.TheMFtheorypredictsinitiallinear decreasein T c withincreasing R 2 providedthat R 2 isnottoolarge.Thisis,infact, whatobservedalmostuniversallyinvarious2Ddisorderedsystems. By2D,itismeant thatthelmthickness d issmallerthanthethermaldiusionlength( ~ D=k B T ) 1 = 2 whichisthelengthscaleoflocalization,ontheorderof 100 A.Here, D isthe diusionconstantofelectronsgivenby[ e 2 N (0) R 2 d ] 1 .Notethatlmsmightremain3D withrespecttotheelectroniclengthparametersuchasmeanfr eepath l 7.2.32DModelSystems Inordertoexamineinterplaybetweenlocalizationandsuper conductivitywithless complications,itwouldbeidealtousemodelsystemswhichhavef ollowingproperties: 1.Theeectscanbeobservedclearly.2.Themeasureofdisordercanbechangedinacontrolledway.3.Themeasureofdisordercanbechangedoverawiderange.4.Allotherpropertiesarexed.5.Bulkpropertiesarethoroughlycharacterized. Therelevantmeasureofdisorderis1 =E F 0 ,whichisproportionalto in3D and R 2 in2D(seeEq. 7.10 ).Thus,byusinglmswithvarious R 2 ,yetkeeping constant,onecanunambiguouslystudythe2Deectspredictedb ytheMFtheory. 4 Homogeneous,amorphousthinlmscanbegrowntopossessproperti esdesiredfor modelsystems.Sincethistypeofmaterialhasrelativelyhighr esistivity,lmswith sucientlylarge R 2 areaccessibleforahomogeneousmaterial.Also R 2 canbevaried bysimplychanginglmthickness d whilemaintainingthebulkproperty relatively 4 Intypicalthinlmsystems,evenifthenormalstateelectronicp ropertiesdonot change,thelmresistivityoftenchangeswiththelmthickne ss,particularlyfor d 100 A.

PAGE 163

148 constant(providedthat d l ).Theuseofamorphouslmsmakesinterpretationof experimentconsiderablysimplerbecausealldisorder-sensitive band-structure(smearing) eectshavemostlikelyalreadyoccurredandarenotfurthera lteredbyreducingthe lmthickness.Sampleuniformityisalsoimportanttoseparateo uteectson T c dueto localizationandinteractioneectsfromthoseresultingfro mthestructuresbuiltinto thelm( e.g. ,oxidation,clusteringand/orpercolation,orgrossinhomog eneities),which couldalsoinruencetheelectronscreeningatlongwavelength sand T c suppression.As longas ismaintainedconstant,theeectsfromthosestructuresshould benegligible. MoGeisaveryinterestingsystemofatransitionmetal(TM)-meta lloidmixture, inwhichthecompositioncanbevariedwidelyfromalowcoordi nation-numberrandom tetrahedralnetworkinthe -Gelimittoahighcoordination-numbermetallicglasslimit forMo-richalloys.Theamorphousphaseexistsoveraverybroad compositionrange, from20-100%Ge.ThechoiceofaTM-metalloidalloy,insteado faTM-TMalloy,leads tostabilityoftheamorphousphaseatroomtemperature.Inthe formofthinlms, materialswithproperGecontentssatisfythepropertiesliste dabove,andcanserveas modelsystems. 7.3ExperimentalDetails 7.3.1Samples Forouropticalstudy,fourlmsof -MoGewithdierentthicknessweregrown byco-magnetronsputteringfromelementaltargetsinaUHVsystem ontorapidly rotating(3rev/secor1 Adeposited/rev)single-crystalr-cutsapphiresubstrates(1 mmthick, n 3 : 05).A75 A -Geunderlayerwasrstlaiddownonthesubstrates toensuresmoothnessofthesubsequentlydepositedMoGelms.Rapid rotationofthe substrateduringdepositionseemstoimproveuniformcoverageo fultrathinlms.For lmspreparedinsimilarfashion,nosignofcrystallineinclusio nswereobservedbyx-ray andtransmissionelectronmicroscopy. ParametersforthelmsweusedarelistedinTable 7{1 .Thethickness d was determinedfromaquartzthicknessmonitor.Wedene T c asthetemperatureatwhich transmissionthroughalminsuperconductingstate T s becomesindistinguishable

PAGE 164

149 Table7{1:Filmparametersfor -Mo 79 Ge 21 thinlms. R 2 wasopticallydetermined from T n ,andgapparameter 0 isdeterminedbytting T s = T n datatothecurvecalculatedfromtheMattis-Bardeentheory. Film d (nm) T c (K) R 2 (n)2 0 (cm 1 )2 0 =k B T c A4.3 < 1 : 8505-B8.34.526011.53.68 C16.56.113116.53.89 D336.96918.53.85 0.000.050.100.150.200.250.30 0 100 200 300 400 500 R o [ W ]1/ d [nm-1] Ourfilms J.M.Graybeal'stransport Figure7{2:Sheetresistanceasafunctionofinverselmthickn essforfourlmsusedin ouropticalstudyaswellaslmsusedfortransportmeasurementb yJ.M.Graybealfor comparison.fromthatinnormalstate T n .Thethinnestlm(43 A)didnotgosuperconducting atthelowesttemperatureaccessibletooursystem(1.8K).Theshee tresistance R 2 ofalllmswasdeterminedfromEq. 7.2 withanextrapolationof T n to =0 (See x 7.2.1 ).Figure 7{2 shows R 2 asafunctionofinverselmthickness d forlms usedinouropticalstudy.Forcomparison,thesameplotforlmsu sedinGraybeal's transportmeasurementisalsoshown. 5 Thedatapointsforourslmsfallnicelyalong 5 NotethatourlmswerepreparedbyJ.M.Graybealinthesameway ashepreparedforhisthesiswork.Dierencesarethatthelmswith21 %Geusedforhisthesis weredepositedon -Si 3 N 4 substratewith10 A -Geunderlayerand28 A -Sioverlayer.

PAGE 165

150 0100200300400500 0.5 0.6 0.7 0.8 0.9 1.0 M-FTheory T c / T c0R o [ W ] Ourfilms J.M.Graybeal'stransport Figure7{3:Suppressionoftransitiontemperatureswithincre asingsheetresistancefor fourlmsusedinouropticalstudy.Forcomparison,Graybeal's transportresultisalso plottedwithttotheMaekawa-Fukuyamatheory. T c 0 isthebulkvalue(7.25Kfor Mo 79 Ge 21 ).Errorbaronthedatapointsarisesfromerrorincalibratio noftemperature controlleraswellaserrorindetermining T c value. astraightlinethatincludestheorigin,andthusthebulkresi stivity ofourlms hasaconstantvalue( 220 4 n cm)demonstratingsuccessfulrealizationof2D modelsystem.Thefactthat isessentiallyconstantimpliesthatthestructuresbuilt intothelmareinsignicant.Theresistivitywedeterminedhe rewasallmeasuredat 10K,butthetransportmeasurementsonlmspreparedinthesame wayshoweda logarithmicincreaseinresistivityasthetemperatureisdecr eased,whichistypically seenindisorderedsystemsintheweaklylocalizedregime.Aswill bedescribedlater,the gapparameter 0 isdeterminedbytting T s = T n datatothecurvecalculatedfromthe Mattis-Bardeentheory. InFigure 7{3 T c =T c 0 isplottedasafunctionof R 2 where T c 0 isthebulkvalueof thetransitiontemperature(7.25KforMo 79 Ge 21 ).Forcomparison,Graybeal'stransport resultisalsoplottedwithttotheMaekawa-Fukuyamatheory. Thegureshowsthat T c isstronglyandlinearlyreducedwithincreasing R 2 .Forthethinnestlmthatwent superconducting( d =8.3nm), T c issuppressedby 40%withoutshowingnoticeable

PAGE 166

151 changesinthebulkproperty .InGraybeal'swork[ 6 8 ],itwasshownthattherate of T c depressionincreaseswithincreasingGecontent.Ourresultappe arstofallmore rapidlythanthatofGraybeal'swith21%Gecontent.Itmight havebeenintendedto make21%Gecomposition,butourresultisclosertotheGraybeal 'sresultwith23% Gecomposition.Theoverallbehavior,however,seemstobecon sistentwithGraybeal's transportresultswhichwasinterpretedaslocalizationeec tsin2Dsuperconductors. 7.3.2Measurements Thefarinfraredmeasurementswereperformedattwobeamline s,U10AandU12IR oftheNSLSVUVring.U12IR,equippedwithaSciencetechSPS200Ma rtin-Puplett interferometer,wasusedforfrequencybetween5and50cm 1 .Forfrequenciesabove 20cm 1 ,aBrukerIFS-66v/Srapid-scanFourier-transforminterfero meteratU10Awas used.Abolometeroperatingat1.4Kprovidedanexcellentsensi tivityatfarinfrared, butawindowonthebolometerlimitedourmeasurementstofreq uenciesbelow100 cm 1 .TheOxfordInstrumentsOptistatbathcryostatmadeuspossiblet oreducethe temperatureofsamplesdownto1.8K.Detailsofeachexperime ntalapparatusare describedinChapter 6 .Thetransmittance T ( )andrerectance R ( )offourlms weretakenatvarioustemperaturesbelow T c ,andtheresultswerenormalizedtothe respectivenormalstatetransmittanceandrerectancetakenat 10K. 7.4Analysis Figure 7{4 showsourmeasurementsof T s = T n asafunctionoffrequencyatseveral temperaturesforthreelmsthatbecamesuperconducting.Th emeasuredratioappears tohavetheexpectedshape.Asmentionedearlier,thepeakin T s = T n isameasure ofthesuperconductinggap.Fromthegure,wecanclearlyobse rveshrinkinggapas temperatureincreasestoward T c foreachlm.Althoughnotshown,atagivenreduced temperature T=T c thegapshiftstolowerenergywithdecreasingthicknessoflms ( i.e. ,increasing R 2 )asexpectedsince T c goesdownwithdecreasingthickness,too. Themeasured T s = T n werettedtoEq. 7.3 usingEq. 7.2 for T n ontheright-handsideandtheMattis-Bardeenconductivityratioexpressions, 1 ( ) = n and 2 ( ) = n RecallthattheMattis-Bardeencalculationisvalidforadir tylimitBCSsuperconductor.

PAGE 167

152 020406080100 0 1 2 D Frequency[cm-1] 2.2K, 4.0K, 5.0K 6.0K, 6.5K 0 1 2 CTransmittanceRatio 2.2K, 4.0K, 5.0K 5.5K, 6.0K 0 1 2 B 2.2K, 3.0K 3.5K, 4.0K (/) TT snFigure7{4:MeasuredtransmittanceratioofthreeMoGelmsat severaltemperatures. Table7{2:Parametersusedforthettingof T s = T n curves. ParameterDescriptionvaluesnote n refractiveindexofr-cutsapphire3.05 v f Fermivelocity10 8 cm/sestimated l meanfreepath3 Aestimated 1 = scatteringrate17,600cm 1 1 = v F = 2 cl p plasmafrequency70,000cm 1 2 p = n 60 1 resistivity220 4 n cm Figure 7{5 showsthetfor T s = T n measuredat2.2Kforthreelms.Inthet,we allowedonlythegap2 0 tobeafreeparameter.Weused T c and R 2 valuesdetermined fromourmeasurementsforeachlmasdescribedabove.Otherpa rametersnecessary tocalculate T n aregiveninTable 7{2 .Themeanfreepathisestimatedtobe 3 Afor -MoGe,whichisroughlyoneinteratomicspacing.Thettothe dirtylimitBCS predictionlooksquitegood.Fromthet,thevalueof2 0 inTable 7{1 wasdetermined. Then,thisgivestheratio2 0 =k B T c ,whichwasfoundtobeslightlyhigherthanthe BCSweakcouplinglimitof3.5foralllms.Thevariationin2 0 =k B T c withthicknessis

PAGE 168

153 020406080100 0 1 2 DFrequency[cm-1]0 1 2 CTransmittanceRatio0 1 2 B Experimentat2.2K Mattis-Bardeen (/) TT snFigure7{5: T s = T n comparedwiththecalculationaccordingtoMattis-Bardeene xpressionsofconductivity.Only T s = T n takenat2.2Kareshownforeachlm. notnearlyasmuchasthe T c reduction(seeTable 7{1 ),andwemaysafelyconcludethat theyareidenticalwithinexperimentalerror. Inordertodeducetheopticalconstants,transmittancemeasure mentinanarrow spectralrangealoneisnotsucient.Therefore,wemeasuredre rectanceinthesame frequencyrangeasthetransmittancemeasurements.Figure 7{6 showstherelative rerectance R s = R n forthreelms.Justlike T s = T n R s = R n alsottedquitegoodtothe Mattis-BardeencalculationasshowninFigure 7{7 Fromthemeasuredtransmittanceandrerectanceofthelms,wew ereableto extractthecomplexconductivity 1 ( )and 2 ( )foreachlmatvarioustemperatures usinganalgorithmbasedontheapproachesofPalmerandTinkha m[ 89 ]andGlover andTinkham[ 71 ].Figure 7{8 (a)shows 1 ( )and 2 ( )ofeachlmat2.2K.For comparison,theBCSMBconductivityarealsoshown,and 1 tswellforallthree MoGelms.Thegapof2isnowquiteevident.Also, 1 approachesthenormalstatevalueforeachlmathigherfrequencies.Allthreelmsha veapproximatelythe

PAGE 169

154 01020304050 1.0 1.5 D Frequency[cm -1 ] 2.2K 4.0K 5.0K 6.0K1.0 1.5 CReflectanceRatio 2.2K 4.0K 5.0K 5.5K1.0 1.5 B 2.2K (/) RR snFigure7{6:MeasuredrerectanceratioofthreeMoGelmsatsev eraltemperatures. samenormal-stateconductivity, n ,of 4300n 1 cm 1 obtainedfromtransmittance measurementoflminnormalstate.Thisisveryclosetothevalu efoundbytransport measurement. 2 ( )hascorrectlineshapeof 1 =! atlowfrequenciesbuttendstobe abovetheBCScurveespeciallyathigherfrequencies. Thetemperaturedependenceoftherealandimaginarypartof theopticalconductivityforthe16.5nmlmisshowninFigure 7{8 (b).Therealpart 1 showstheclosing ofthegap2asthetemperatureapproaches T c .Theimaginarypart 2 shows 1 =! behaviorbelowthegap,andthereductionoftheinductivere sponseasthesuperruid densitybecomessmaller. 7.5Discussion Fromthe1 =! behaviorof 2 ( )belowthegap,wecanndthemagneticpenetrationdepth ( T )andsuperruiddensity N s ( T )usingEqs. 7.5 and 4.12 inwhich L is replacedby .Theyareproportionalto( 2 ) 1 = 2 and 2 ,respectively.Figure 7{9 showsthedependenceof and N s onthesheetresistance R 2 deducedfromthelow

PAGE 170

155 01020304050 1.0 1.5 D Frequency[cm-1] 1.0 1.5 CReflectanceRatio1.0 1.5 Experimentat2.2K Mattis-Bardeen B (/) RR snFigure7{7: R s = R n comparedwiththecalculationaccordingtoMattis-Bardeene xpressionsofconductivity.Only R s = R n takenat2.2Kareshownforeachlm. Table7{3:Valuesof N s and forthreelmsmeasuredat2.2K. Film d (nm) T c (K) R 2 (n) N s ( 10 21 cm 3 ) (nm) B8.34.52601.12768 C16.56.11311.49687 D336.9691.66652 frequencypartof 2 forthreelmsat2.2K.Table 7{3 liststhevalues.Strong T c suppressionwithincreasing R 2 wasdiscussedearlier(seeFigure 7{3 ).Asmentionedearlier, thiseecthasbeattributedtoelectronlocalizationand/o rCoulombinteractioneects. Dependenceofthesuperruiddensity N s issimilartothatof T c ,butrelationof N s to thelocalizationeectshasnotbeenunderstood,yet. Inaplotoftheconductivityratio 1 ( ) = n ( )asafunctionofphotonenergy ( i.e. ,frequency),missingarea, A ,of 1 ( )belownormalstateconductivity n ( )can beestimatedas n 2 C ,andthus n T c C 0 where C and C 0 aresomeconstants. Thisisareasonableapproximationespeciallyforweaklycoup ledBCSsuperconductors inthelowtemperaturelimit.Bythesumrule,thismissingareag oestotheareaunder

PAGE 171

156 01020304050 0 5000 10000 0 5000 10000 0 5000 10000 DFrequency[cm-1] CConductivity[ W -1 cm -1 ] B s1 s2 sn BCS 0 2000 4000 6000 1.21.41.61.8 50000 100000 s1[ W-1cm-1] 2.2K 4.0K 5.0K 5.5K 10K 01020304050 0 5000 10000 C Frequency[cm-1]s2[ W-1cm-1] s2wg/ w (a)(b)Figure7{8:(a)Opticalconductivitiesofthreelmsextrac tedfromthetransmittance andrerectancedataat2.2K.TheBCS,Mattis-Bardeentisalso shownforcomparison.(b) 1 ( )and 2 ( )atvarioustemperaturesfor16.5nmMoGelm.Insetshows 1 =! behaviorof 2 belowthegapfrequency. deltafunctionof 1 at =0,andhencetothesuperruiddensity N s .Thereforewe expecttohaverelationsas A N s T c .AsshowninFigure 7{10 ,ouropticalresults appeartogivelinearrelationshipbetween N s and T c .Alloftheresultsfromouroptical measurementsaretriviallyconsistentwiththoseexpectedforw eaktointermediate couplingBCSsuperconductors.Wedidnotndanyindication,a tleastoptically,that maybepeculiartotheeectsoflocalizationindisorderedsup erconductorsexceptthe strongsuppressionof T c with R 2 7.6Conclusion Inconclusion,wehavestudiedthefarinfraredconductivity~ ( )extractedfrom transmittanceandrerectancemeasurementsofthinamorphous superconducting MoGelmsofvariousthicknessesatvarioustemperatures.Allth reelmsmeasured appeartobeingeneralagreementwithdirtylimitBCSsuperco nductorswiththeratio 2 0 =k B T c slightlyhigherthanthatofweakcouplingvalue3.5.Strongr eductionof T c withincreasingsheetresistance( i.e. ,withdecreasingthickness)thatwasexplainedas

PAGE 172

157 50100150200250300 600 650 700 750 800 l [nm]Ro[ W ] 50100150200250300 1.0 1.5 2.0 N s [x10 21 cm -3 ]Ro[ W ] Figure7{9: R 2 dependenceofmagneticpenetrationdepth andsuperruiddensity N s forthreelmsmeasuredat2.2K.theeectsoflocalizationandrelatedenhancementofCoulo mbinteractionwasalso observed.Thesuperruiddensityalsodecreasesas R 2 increases,buthowtheseare relatedtotheeectoflocalizationremaintobeanswered.Th innerlmswithmore severelocalizationeectsmayrevealstrongdeviationfromt heresultsexpectedfor

PAGE 173

158 4.55.05.56.06.57.0 1.2 1.4 1.6 1.8 N s [x10 21 cm -3 ]Tc[K] Figure7{10:Relationshipbetween N s and T c of -MoGelms. asuperconductinglmwithoutelectronlocalization.Exper imentforthinnerlms, however,willbeharderbecause T c willbeloweredfurtherrequiringHe3system.

PAGE 174

CHAPTER8 TIME-RESOLVEDSTUDYOF -MoGeTHINFILMS 8.1Introduction Superconductivityisaphenomenonwhereelectronscondense intoboundpairs andanenergygapdevelopsintheelectronicdensityofstates bothaboveandbelow theFermienergy.ThetypicalenergyscaleisseveralmeV.Asweha veshowninthe lastchapter,thisenergygap,akeyparameterindicatingthe overallstrengthofthe superconductingstate,canbesensedbyfarinfraredspectroscopy .Electronictransitions acrossthefullgap(energy2)correspondtobreakingpairs,pr oducingexcitations calledquasiparticles.Breakingasignicantnumberofpairsl eadstoanonequilibrium conditionwherethesuperconductingstateisweakened(indic atedbyasmallerenergy gap)orevendestroyed.Thereturntoequilibriuminvolvesth erecombinationofthe excessquasiparticlesintopairs,releasingenergyofatleast2 (perrecombination event),usuallyasaphonon.Therateforthisprocessinvolves theinteractionbetween quasiparticles,whichisoffundamentalinterestforanytheor yofsuperconductivity. Kaplan etal. havecalculatedtherecombinationtimeforanumberofeleme ntal BCSsuperconductors,obtainingcharacteristicvaluesinthe1 0to100picosecondrange, dependingonmaterialandtemperature[ 92 ].Butthesystemdoesnottrulyrelaxon thistimescale,sincetheresultingexcess2phononsusuallybre akotherpairsat asimilarrate.Sotheexcessenergyistemporarilytrappedina coupledsystemof quasiparticlesandphonons.Thecoupledsystemeventuallyrela xesasthephonons escapetootherpartsofthespecimen. Weperformedtime-resolvedpump-probespectroscopytofollow thiscomplicated relaxationprocess.Thetechniqueexploitsthepulsednatureo fsynchrotronradiation. Amode-lockednear-IR/visiblelaser,synchronizedtothesynch rotronpulses,serves asanexcitation(pump)source.Thephotonsfromthelaserbrea kasmallfractionof 159

PAGE 175

160 Cooperpairs,leadingtoexcessquasiparticlesandanonequili briumstatethatevolves withtime.Thisnonequilibriumstatecanbesensedasasmallweak ening(downward shift)ofthesuperconductingenergygap,andincreasedfarinf raredabsorption.Our uniquepump-probetechniqueallowsustofollowthisabsorpt ion(andthereforethe excessquasiparticles)asafunctionoftime.Themagnitudeoft hissignalatagiventime providesameasureoftheexcessquasiparticleatthattime,and completeresultyields adecaycurveoftheexcessquasiparticledensityfromwhichwec andeducetheoverall relaxationtimeforthesample. Inthischapter,webeginwithasynopsisoftherelevantbackgr oundfornonequilibriumsuperconductivityanditsrelaxation,followedbyanex perimentaldetails.Then, wepresentourresultsoftime-resolvedstudyon -MoGelms.Resultsofmeasured quasiparticlesignalsatvarioustemperaturebelow T c areanalyzedusingthetheoriesby Kaplan etal. [ 92 ]andRothwarfandTaylor[ 93 ].WealsopresentourresultofphotoinducedgapshiftwithananalysisbasedonthetheorybyOwenandSc alapino[ 94 ]. 8.2Background 8.2.1NonequilibriumSuperconductivity Inasuperconductoratanynitetemperaturebelow T c ,quasiparticleexcitations arecontinuouslygeneratedbythermalprocess.Atagiventempe rature(withoutother externalagitation),thereisacompensatingrecombination processsuchthatCooper pairsandquasiparticlesareinthermodynamicequilibrium. Apairstate( k ; k # )is brokenwhenatleastoneoftheelectronsisscatteredintoanew state k 0 where k 0 # isunoccupied. Anyexternalsourceofenergy,suchasphotons,thatcansupplyatl east2of energycanintroduceexcessquasiparticlesintothesystem.Thi sleadstoanexcited statewherethesuperconductingstateisweakened.Experiment sbyTestardishowed thatlightofsucientintensitycanevenconvertthesupercond uctingstatetothe normalstate[ 95 ].Evidencewaspresentedthattheseeectswerenotduetosimpl e lattice-heatingtoatemperatureabove T c ,butwereapparentlyduetoanexcessnumber ofquasiparticlesinducedbyphotonabsorption.OwenandScal apinodevelopeda

PAGE 176

161 modelofsuperconductorsinwhichthenumberofquasiparticle sislargerthanthat ofthermalequilibriumshowingthatanexcessquasiparticlepo pulationreducesthe superconductor'sorderparameter(theenergygap)[ 94 ].Theirresultforthereducedgap attemperatures T T c is 0 3 = 8<: 0 2 + n 2 # 1 = 2 n 9=; 2 ; (8.1) where n isthedimensionlessexcessquasiparticlenumberdensityinunit sof4 N (0) 0 ( = N pairs ). 1 Forsmall n ,thisreducesto 0 1 2 n: (8.2) TheOwen-Scalapinomodelwaslaterconrmedqualitatively byParkerandWilliams frommeasurementsonsuperconductingtunneljunctionsillum inatedwithoptical radiation[ 96 ]andbySai-Halasz etal. frommicrowavererectivitymeasurements[ 97 ]. Whenthenumberofexcessquasiparticlesbecomessucientlyla rge,thegapshrinksto thepointwhereitcollapsestozero,eventhoughtthelattice temperatureisstillbelow T c Whenthesupplyofenergyisstopped,thesystemrelaxestowardth ermodynamic equilibrium.Thedetailsofthisrelaxationprocessesarequi tecomplex.Inanexperiment wherelightpulseofenergyconsiderablylargerthan2( e.g. ,near-IRorvisiblepulse laser)isusedasexcitation,high-energyquasiparticlesarec reated,whichquickly( femtoseconds)relaxtolowerenergybydominantelectron-ele ctron( e e )scattering. Then,theselow-energyquasiparticlesrelaxfurthernowmain lyviaelectron-phonon ( e ph )scattering( picoseconds),eventuallypopulatingquasiparticlestatesnea r thegapedge[ =( T )].Onthewaydowntothegapedge,additionalquasiparticles arecreated(thisprocessiscalledmultiplication).Anoneq uilibriumstateexistsuntil 1 4 N (0) 0 ( = N pairs )isthedensityofelectronsstronglyaectedbyenteringthe pairedstate.Notethathere N (0)isgiveninunitsofstates/eV cm 3

PAGE 177

162 allexcessquasiparticlesrecombineintopairsandrejointhe condensate.The e e 2 and e ph 3 scatteringtimesareexpectedtobeconsiderablyshorterthant heaverage timeforaquasiparticletondamateandrecombine.Therecom binationisprimarily accompaniedbyphononemission,thustransferringenergytoth elattice. 4 EarlyBCS calculationsofthetheoreticalquasiparticlelifetime(or recombinationtime) R for temperatureswellbelow T c werecarriedoutbySchrieerandGinsberg[ 100 ],Rothwarf andCohen[ 101 ],andLucasandStephen[ 102 ].Theytookintoaccountthe e ph interactionandtheavailabilityofquasiparticlesindeter miningatemperaturedependent R ,butignoredphononsarisingfromtherecombinationevents.I naddition,theexcess quasiparticledensity N q wasassumedtobesmallcomparedwiththermalquasiparticle density N q ( T ).RothwarfandTaylor,then,recognizedthattheeectofph ononsemitted viarecombinationevents[ 93 ].Theseextraphonons,possessingenergiesofatleast2, canbreakpairsandrecreatequasiparticleswhichsubsequentl yrecombineintopairs, releasingphononsagain.Inotherwords,theexcessenergyiste mporarilytrappedin acoupledsystemofquasiparticlesandphonons.Thisprocess,theso -calledphonon trappingeect,continuesuntiltheseexcessphononsarelostt otheirsurroundings, leadingtoanenhancedapparent(oreective)lifetime e .Phononscanbelostby variousmechanisms.Forexample,theycanescapeintothesubstra te,orthehelium bath,orthesampleholder,ortheymaydecaybyinelasticscatte ringotherthanpairbreaking[ 103 104 ].Notethatiftheenergyofthephononsisdegradedbelow2,i t 2 Electron-electronscatteringcanplayasignicantroleinme talswithlargeDebye temperaturesandlowsuperconductingtransitiontemperatur essuchasAl[ 98 ]. 3 Theelectron-phononscatteringtimeincreasesasthetempera tureisloweredowing toadecreaseinthethermalphononpopulation. 4 Itisalsopossibleforrecombinationtotakeplaceviaphotonem issionsimultaneouslysatisfyingenergyandmomentumconservation.However,Bur stein etal. calculated thelifetimeforradiativerecombinationismuchtoolongto bethedominantmodeof decay[ 99 ].Forexample,thelifetimeforrecombinationbyphotonemi ssionforleadat2 Kwascalculatedtobe0.4seconds,whilethatbyphononemissionc alculatedbySchriefferandGinsbergforleadat1.44Kwas43nanoseconds[ 100 ].

PAGE 178

163 paired electrons & thermal quasiparticles excessquasiparticles D excess 2phonons D ~picoseconds ~femtoseconds high-energy (~ ) quasiparticles EFlow-energy quasiparticles &phonons EDebye 1/ tR1/ tB h n bottleneckphonon escape 1/ tg Figure8{1:Simpliedmodelofmulti-steprelaxationprocesse sofquasiparticlescreated byabsorptionofphotonsofenergymuchlargerthan2.iseectivelylost,sinceitcannolongerbreakpairs.Theeect ivetimeforphonons tobelostoutoftheenergyrange ~ n 2(orphonon-escapetime) r dependsin complicatedwaysonthelmgeometry,theacousticmatchingo fthelmtosubstrate, andotherenvironmentsaroundthelm,butitisroughlyinde pendentoftemperature. Further,if r isconsiderablylongerthanothertimeconstants,theexcessqua siparticles andphononcannearlyequilibrateonatimescale 1 eq 1 R + 1 B ; (8.3) where R istheintrinsicquasiparticlelifetime(orrecombinationti me)and B isthe phononlifetimeagainstpari-breaking(orpair-breakingti me).Thebottleneckinthe completerelaxationprocessesofquasiparticlesisthephonon escapetime.Figure 8{1 schematicallyshowsamodelofrelaxationprocesseswithalight pulseasanexcitation. Inanexperimentwhereaxedenergyisdepositedinthesuperco nductor,this internalequilibriumconditionallowsonetodeterminehow theexcessenergyisdistributedbetweentheexcessquasiparticlesandexcessphonons. Forexample,consider thecasewherethequasiparticlelifetimeisextremelylongco mparedtothephonon lifetime( R B ).Pairsofquasiparticlesarerarelyremovedbyrecombinati onevents,

PAGE 179

164 andthefewthatdooccurarequicklyfollowedbypair-breaki ngeventsthatrestorethe quasiparticlepairs.Soonewouldndtheexcessenergyinthefo rmofalargenumberof quasiparticlesandveryfewphonons.Thiscanbequantiedas N q ( T ) N q (0) = 0 ( T ) 1+2 B ( T ) R ( T ) 1 ; (8.4) where N q (0)isthequasiparticledensityifalltheexcessenergyisinth eformof quasiparticles.Thefactorof2isaconsequenceofthefactthat pair-breakingcreates twoquasiparticleswhileremovingonlyonephonon.Aswillbed iscussedin x 8.2.2 ,the expectedtemperaturedependenceof R and B impliesthattheexcessenergyresides mostlyinexcessphononsfortemperaturesnear T c ,shiftingpredominantlytoexcess quasiparticlesastemperaturesbecomelowerandlower.Atab solutezero,theexcess energyisentirelyintheformofexcessquasiparticles. RothwarfandTaylarderivedasetofdierentialequationsth atdescribethe behaviorofquasiparticleandphonondensitiesinsuperconduc tingthinlmsinteracting withanexternalquasiparticleinjectionmechanism.Inthewe akperturbationlimit ( i.e. N q N q ( T )),theseequationscanbelinearizedtoobtaincoupledequat ions forexcessquasiparticledensity N q [ N total q N q ( T )]andexcessphonondensity N n [ N total n N n ( T )]as @N q @t = I 0 + 2 N n B 2 N q R ; (8.5) @N n @t = N q R N n B N n r ; (8.6) where I 0 isthequasiparticlesinjectionratepercm 3 .Inanexperimentusingalight pulseasapair-brakingmechanism, I 0 =0afterphotonabsorption.Thetimedependent solution[ 98 ]oftheRothwarf-Taylorequationsappropriateforsuchanex perimentisan

PAGE 180

165 exponentialdecayofexcessquasiparticledensitywithaneec tivelifetimegivenby 5 e r + R 2 1+ r B : (8.7) Atlowtemperature, R 6 istypicallylargecomparedto r and e isapproximated by R r = 2 B provided r B .Attemperaturenear T c R becomessmalland e approaches r .Atheoreticalcalculationoftemperaturedependentlifet imesbyKaplan etal. [ 92 ]isdiscussedinthefollowingsubsection. 8.2.2TemperatureDependenceofLifetimes Inmostsuperconductors,inelasticphononprocesses,particularl yrecombination withphononemission,isthemostdominantlow-energy( i.e. ,neargapedge)quasiparticlerelaxationprocesses.Kaplan etal. derivedtheenergyandtemperaturedependence oftheintrinsicrecombinationtime R ( !;T )intermsoftheelectron-phononspectral density 2 (n) F (n) 7 [ i.e. ,thephonondensityofstates F (n)weightedbythesquare ofthematrixelementoftheelectron-phononinteraction 2 (n)]aswellasthephonon pair-breakingtime B (n ;T )intermsof 2 (n) 8 foradirtylimitsuperconductorinor verynearthermalequilibrium[ 92 ].Theirresultsare 1 R ( !;T )= 2 ~ (1+ )[1 f ( )] Z 1 + d n 2 (n) F (n)Re n [(n ) 2 2 ] 1 = 2 1+ 2 (n ) [ n (n)+1] f (n ) ; (8.8) 5 ForlargerperturbationstheRothwarf-Taylorequationsar enonlinearandcannotbe solvedanalytically. 6 For T T c R istypicallymuchgreaterthan1ns. 7 Inprinciple, 2 F canbedeterminedfromsuperconductingtunnellingmeasureme nts. 8 Thephonondensityofstates F (n)caninprinciplebeobtainedfromneutronscatteringexperiments.Then, 2 (n)canbededucedbytakingratioof 2 (n) F (n)from tunnellingmeasurementsto F (n).

PAGE 181

166 and 1 B (n ;T )= 4 N (0) 2 (n) ~ N i Z n d! ( 2 2 ) 1 = 2 (n )+ 2 [(n ) 2 2 ] 1 = 2 [1 f ( ) f (n )] ; (8.9) where isthequasiparticleenergyrelativetotheFermienergy,nis thephononenergy, f ( )istheFermi-Diracdistribution, n (n)istheBose-Einsteindistribution, isthe electron-phononcouplingconstant(ormass-enhancementpara meter;see x 4.2.6 ), N (0) isthesingle-spinelectronicdensityofstatesattheFermiener gy,and N i istheion numberdensity. Forasimplemodelofametalatsucientlylowfrequencies, 2 (n)isknow toapproachaconstant,and F (n)isproportionalton 2 asfoundfromtheDebye model[ 105 ].Thus,thelow-frequencybehaviorof 2 F canbeapproximatedby 9 2 (n) F (n)= b n 2 ; (8.10) where b isaconstantthatcharacterizesagivenmaterial.Usingthisfo rmof 2 (n) F (n) inEq. 8.8 ,Kaplan etal. demonstratedthattherecombinationrateforquasiparticles at thegapedge[ =( T )]foraBCSweak-couplingsuperconductorfollowsauniversal temperaturedependence: 1 R ( ;T )= 1 R 0 F R ( ;T ) ; (8.11) where F R ( ;T )canbeexpressedintermsofthemodiedBesselfunctions K 0 and K 1 as F R ( ;T )= k B T c 3 1 X n =1 ( 1) n +1 +exp n k B T (" 4+ 3 k B T n +2 k B T n 2 # K 1 n k B T + 4+ k B T n K 0 n k B T ) : (8.12) 9 Somematerials,suchasstrong-couplingsuperconductorsPband Hg,showsignicantstructurein 2 (n) F (n)evenatlowfrequencies.

PAGE 182

167 InEq. 8.11 ,asimplescalefactor R 0 isdenedas R 0 (1+ ) ~ 2 b ( k B T c ) 3 : (8.13) Thisparametercontainsallthenecessarymaterialconstantsa ndhandlesvariationsbetweendierentmaterials.Atlowtemperatures,theseriesinEq 8.12 rapidlyconverges, leadingtolow-temperaturebehavior: 1 R ( ;T ) = 1 R 0 1 = 2 2 0 k B T c 5 = 2 T T c 1 = 2 e 0 =k B T : (8.14) Thus, R increasesexponentiallyas e 0 =k B T atlowtemperatures,rerectingtheexponentialdecreaseinthermalequilibriumquasiparticledensity,w hichgoesas N q ( T ) T T c 1 = 2 e 0 =k B T : (8.15) Therefore,weseethat R ( T ) 1 =N q ( T ),whichisnotdiculttoimaginesincetwo quasiparticlesmustmeeteachotherbeforecondensingintoapa ir. Inasimilarfashion,fromEq. 8.9 ,Kaplan etal. showedthatthepair-breakingrate forphononsatthethresholdenergyn=2( T )alsofollowsauniversaltemperature dependence: 1 B (2 ;T )= 1 B 0 F B (2 ;T ) ; (8.16) where F B (2 ;T )= 0 [1 2 f ()] : (8.17) InEq. 8.16 ,anothercharacteristicscalefactor R 0 containsalltherelevantmaterial parametersspecictoagivematerial,andisdenedas B 0 ~ N i 4 2 N (0) h 2 i 0 ; (8.18) where h 2 i isanaverage 2 denedby 3 h 2 i Z 1 0 2 (n) F (n) d n : (8.19)

PAGE 183

168 0.250.500.751.00 0.0 0.5 1.0 1.5 Lifetimes[ns]Temperature( T / Tc) tR tB teff Figure8{2:Universaltemperaturedependenceofintrinsicrec ombinationtime R phononpair-breakingtime B ,andeectiverelaxationtime e ,whicharevalidfor weak-couplingBCSsuperconductorswitharbitrarilyspecie dparameters R 0 and B 0 Thephononescapetimehereis0.2ns.Notethatthesecurvesareob tainedusingthe approximateformof 2 (n) F (n)= b n 2 Since2phononsmustndavailablepairsbeforebreakingthe m,wecanimagine thatthepair-breakingtimeroughlybehavesas B ( T ) 1 =N s ( T ),where N s ( T )isthe superruiddensity.Thefactor[1 2 f ()]inEq. 8.17 rerectsthissortofbehavior. Figure 8{2 showstheuniversaltemperaturedependenceofintrinsicrecom bination time R andphononpair-breakingtime B usingEqs. 8.11 and 8.16 witharbitrarily speciedparameters R 0 and B 0 .Theeectiverelaxationtime e isalsoplottedusing Eq. 8.7 with0.2nsforthephononescapetime r .Attemperaturesnear T c ,wenotice that e approaches r asmentionedearlier.Notethatthesecurvesareobtainedusing theapproximateformof 2 (n) F (n)= b n 2 ,andarevalidforweak-couplingBCS superconductors. SubstitutingEqs. 8.11 and 8.16 intoEq. 8.4 yieldsthequasiparticlefraction N q ( T ) =N q (0)asafunctionoftemperature.Theshapeofacurveforagive nmaterial dependsontheratio R 0 = B 0 .Thus,measurementsof N q ( T ) =N q (0)canbeusedto

PAGE 184

169 determinethisratio R 0 = B 0 ,whichischaracteristictoaspecicmaterial,andcompare itwiththeory. Therateatwhichtherecombinationeventsoccurisameasureo fthecoupling betweenelectronsandphononsinBCSsuperconductors.Sincet hisistheinteraction responsibleforthepairingprocess,anunderstandingofthereco mbinationiscentralto anunderstandingofsuperconductivity.Unfortunately,itisq uitediculttomeasure themostintrinsicquantities R and B individuallywithreasonableaccuracy.However, wecandeterminetheratio R = B inareliablefashion.Time-resolvedspectroscopycan beausefultoolforstudyingthefundamentalpropertiesofsupe rconductorsinboth equilibriumandnonequilibriumstates. 8.3ExperimentalDetails Therehavebeenseveralexperimentaleortstomeasuretheee ctiverelaxation time e insuperconductors.Mostofthemeasurementsperformedearlier ,however, arerestrictedinsomeways.Forexample,Jaworski etal. indirectlydetermined e insuperconductingPblmsfortemperatureswellbelow T c frommeasurementson opticallyilluminatedtunneljunctions[ 106 ].Hu etal. carriedoutdirecttime-resolved studiesonSn-oxide-Sntunneljunctionsexcitedbylaserpulse s,buttemporalresolution wastensofnanosecondsatbest[ 107 ].Transientelectricalphotoresponsemeasurement onNblmsbyJohnsonwasadirectmeasurementofthelifetimewit hsubnanosecond temporalresolutionattemperaturesnear T c [ 108 ].Thetime-resolvedtechniqueatthe NSLSallowsdirectmeasurementswithatimeresolutionontheor derof100psovera widetemperaturerange( e.g. ,between0 : 28 T c
PAGE 185

170 Table8{1:Filmparametersfor -MoGethinlmsusedforthetime-resolvedexperiment. Film d (nm) T c (K) R 2 (n)2 0 (cm 1 )2 0 =k B T c B8.34.526011.53.68 C16.56.113116.53.89 D336.96918.53.85 absorption(typicallybelow60cm 1 foroursamples),andthepump-probetechnique providesaschemetofollowthepair-breakingandrecombinat ionprocessasafunctionof time.Amode-lockedTi:Sapphirelaser,synchronizedtothesyn chrotronpulses,serveas anexcitation(pump)source.Thelaserwastunedtoemitpulsedl ightatawavelength of 810nm(12,300cm 1 or1.53eV),wherethelasersystemseemstorunstably forlongperiodsoftime.Aneutraldensitylterwasusedtoadj ustthelaserpower deliveredtothesample.Weused14mW(0.25nJ/pulse)powerleve l(measuredatthe veryendofbercable)forreasonswhichwillbediscussedlateri nthissection.Because ourfocusisinfarinfrared,alltime-resolvedexperimentsw ereperformedatU12IRwith eitheraBruker66,Bruker125,orOx-Box(ourcustommadesampl ecompartment) connectedtothebeamline.Forprobepulses, 10 7-bunchdetunedmodewiththepulse widthsbetween0.6and1.0nswasusedforthemostofmeasurement s.Whenhigher temporalresolutionwasnecessary,weswitchedtothe7-bunchco mpressedmodewith pulsewidthsbetween0.3and0.5ns.Allsamplesweremountedvert icallyinserieson acopperclampwhichisinsertedintheOxfordOptistatbathcry ostat.Thesample spaceofthecryostatwascontinuouslypumpedtoachievetemper aturebelow4.2K. A1/4-inch( 6mm)diameteraperturedenedthesampleareailluminatedby laser andsynchrotronpulses.Thefar-infraredtransmissionthroughth elmswasdetected byabolometeroperatedat1.4K.Table 8{2 summarizestheparametersusedforthe time-resolvedexperiment.Detailsofeachexperimentalcom ponent,technique,andsetup arediscussedinChapter 6 10 Inordertoavoidpossibleexcitationbyprobepuleitself,abla ckpolyethylenelter wasplacedbeforethesample.

PAGE 186

171 Table8{2:Parametersusedforthetime-resolvedexperiment. Pumplaserwavelength 810nm(12,300cm 1 or1.53eV) Pumplaserpower 14mW(0.26nJ/pulse) Synchrotronoperationmode 7-bunchdetune(800mA),pulsewidth(0.6-1ns) 7-bunchcompressed(200mA),pulsewidth(0.3-0.5ns) Aperture(illuminationarea) 1/4-inch( 6mm)diameter Ditheramplitude 0.4ns Ditherfrequency 100Hz 8.3.1Time-resolvedMeasurements:QuasiparticleDecay Todeterminetheoveralldecaytime( i.e. e )ofthesamplewedoaspectrally integratedmeasurement.Forthismeasurement,theOx-Boxisd irectlyconnectedtothe beamlinebypassingtheinterferometer,oralternativelythe interferometermodulator (scanner)isleftataxedposition.Withthissetup,wemeasuret hetransmittance averagedovertheentirespectralrangeoftheexperiment,we ightedbythesource spectrumandinstrumenttransmission( i.e. ,thesinglebeamspectrum).Aswillbe justiedin x 8.3.4 ,themagnitudeofthissignalprovidesameasureoftheexcess quasiparticledensity.Inthemeasurements,thearrivalofthep umppulserelative tothatofthesynchrotronpulsewasmodulated(dithered)abou tadelaysetpoint andthedierential(derivative)transmittancesignalwasme asuredwithalock-in amplier.Weusedaditheramplitudeof 0.4ns.Ateachdelaysetpoint,thesignal wasaverageduntiltheS/Nbecamereasonable,thenthedelayw assteppedtothenext setpoint.Aftermeasuringforarelevantrangeofthepump-to-p robedelaytimearound coincidence(zerorelativedelaytime),thederivativesign alwasintegratedtondthe photoinducedchangeinthespectrallyaveragedtransmissionas afunctionoftime. Theresultingcurverepresentsadecayoftheexcessquasipartic lesfromwhichwecan determine e .Asanexample,Figure 8{3 showsboththedierentialandintegrated signalsforthe16.5nmlmat2.2K.Wehavebeencallingthisty peofmeasurementthe quasiparticledecaymeasurement.Moredetailsofthistechni quearediscussedin x 6.6.1 ModellingQuasiparticleDecaySignal Assumingthatonlyonekindoftimeconstantdeterminestheovera llrelaxationof thesample,thedecayofthecoupledsystemcanbeexpressedasasimp leexponential

PAGE 187

172 -10123456 -10 0 10 20 MoGe16.5nmat2.2KPhoto-inducedIRsignal[arb.]Time[ns] differential integrated Figure8{3:PhotoinducedierentialIRsignalvs.pump-to-pr obedelaytimeandthe resultofintegrationfor16.5nmlmmeasuredat2.2K.decay: G ( t )= 8><>: 0 t
PAGE 188

173 -10123456 0 10 20 Photo-inducedIRSignal[arb.]Time[ns] experiment fit exponentialdecay Figure8{4:Quasiparticledecaysignal(integratedsignalshow ninFigure 8{3 withat tothemodelfunction.Curveinbluedotsisasimpleexponenti aldecay. andtheGaussiansynchrotronpulse: 12 S ( t )= I probe ( t ) G ( t )= A p 2 Z 1 1 exp t 0 t 0 e exp ( t t 0 ) 2 2 2 dt 0 ; (8.22) whichhasananalyticalsolutionof S ( t )= A 2 exp 2 2 2 e t t 0 e 1 erf p 2 e t t 0 p 2 ; (8.23) whereerf( z )istheerrorfunction. Theintegratedsignalfrommeasurementsisttedtothemodelf unction 8.23 ,from whichwecandeducetheparameters e A ,and t 0 .Figure 8{4 demonstratesthe resultoftstothe16.5nmlmmeasuredat2.2K.Theexcellenta greementreassures usinouruseofasimpledecaymodelwithasinglecharacteristict ime.Thegurealso showssimpleexponentialdecay,drawnusingtheparameters A t 0 ,and e foundby tting.Wecannoticethatthepeakheightoftheintegratedsi gnalisconsiderably 12 Here,thepumppulseisassumedtoberepresentedbyadeltafunctio n.Thisisreasonablesincethepumppulseismuchshorterthantheprobepulse.

PAGE 189

174 smallerthanthemagnitudeoftheexponentialdecay A ;moreover,itisshiftedfrom t 0 atwhichtheexponentialdecaybeginsfalling.Thesearethec onsequenceofthe synchrotronpulsewidthbeingclosetotheeectivelifetimeof theexponentialdecay ( i.e. e 2 ).Inthelimitof e 2 ,theshapeoftheintegratedsignalcomesto coincidewiththesimpleexponentialdecay.Intheotherlimi t, e 2 ,theshape oftheintegratedsignalapproachesthatofthesynchrotronpu lse,andthedecayof thesamplecannolongerberesolved.Thus,thetime-resolutiono fourexperimentis determinedbythesynchrotronpulsewidth,whichisabout0.3n satbest. Asanalternativewaytoextractingthettingparameters,wec anusethederivative ofEq. 8.23 tottherawdierentialsignal: S 0 ( t )= S 0 0 A 2 e exp 2 2 2 e t t 0 e ( 1 erf p 2 e t t 0 p 2 r 2 e exp p 2 e t t 0 p 2 2 #) ; (8.24) wherewehaveaddedanotherconstantparameter S 0 0 .Thisprocedureissometimes easierordesirablebecauseitcantakecareofanosetthatmayex istinthederivative signal.8.3.2PhotoinducedGapShiftMeasurements Inprinciple,wecanobtainspectraateachpointonthequasipa rticledecay curve,whichwouldrevealhowphotoinducedspectrumchanges asafunctionoftime ( i.e. ,time-resolvedspectroscopy).Unfortunately,thesephotoindu cedspectralchanges areminusculeinmanycases,requiringagreatdealofaveraging toreachanacceptableS/N.Insteadofdoingthis,wemeasuredthephotoinducedsign al T = T where T ( T b T a )isthechangeintheinfraredtransmissionofalmbetweentwop oints onthedecaycurveshowninFigure 8{5 .Thewaywedothisexperimentissimilarto thatofsteady-statephotoinducedmeasurementsdescribedin x 6.6.1 .Insteadofopening andclosingashutter,wesupplyacertainDCvoltage(typically between1to2volts) tothevoltagecontrolledphaseshifterinordertomovethepum p-to-probedelaytime fromthepoint a tothepoint b .See x 6.4.4 formoredetailsonthesetup.Aseriesof

PAGE 190

175 0 0 Photo-inducedIRSignalTime a b Figure8{5:Twopointsbetweenwhichphotoinducedtransmitt ancechangeweretaken onadecaycurveforaphotoinducedgapshiftmeasurements.transmittancespectraweretakeat a and b inaninterleavedorder,and T = T was calculatedafterward.Notethatwedonotneedtoditherthepu mp-to-probedelaytime forthisexperiment,andobviouslytheinterferometermodul atorneedstobescanning unlikethequasiparticledecaymeasurement. Usingthesameparametersasfor T s = T n (seeChapter 7 ),wecant T = T allowingachangeintheenergygap asanonlyttingparameter.AsinEqs. 8.1 and 8.2 isrelatedtotheexcessquasiparticledensity N q [ 94 96 ].Foraweakperturbationandtemperaturesmuchlowerthan T c ,itcanbeshownafollowingapproximate relationship: = 2 N q 4 N (0) 0 = 2 N q N pairs : (8.25) Forthisexperiment,theBruker125atU12IRwasused.A125 mMylarbeamsplitterwaschosenforabettereciencybelow25cm 1 .Wealsousedathickruorogold lterinfrontofthedetectortocutoeverythingabove30cm 1 toimprovesensitivity aslowfrequencyaspossible.Forthesynchrotron,wetriedboth 7-bunchdetunedand

PAGE 191

176 050100150200 0.5 1.0 1.5 2.0 MoGe8.3nmat T =2.0K(0.44 T c )t eff [ns]Power[mW] Figure8{6:Fluencedependenceof e for8.3nmlmmeasuredataxedtemperature of2.0K(=0 : 44 T c ). compressed,butdetunedmodewaselectedsimplybecauseofbette rS/Nowingto higherbeamcurrent.8.3.3FluenceDependence AspointedoutbyRothwarfandTaylor[ 93 ],theassumptionofsmallexcess quasiparticledensitycomparedtothethermalquasiparticled ensitycaneasilybecome invaliddependingontheinjectionlevelsandtemperatureu sed.Althoughthepropertie ofhighlynonequilibriumstateofsuperconductorsisaveryin terestingsubjectinitsown right,wemadesurethatweareintheweakperturbationlimit[ i.e. N q N q ( T )]in ourquasiparticledecaymeasurementssincethatiswhatthethe oriesdiscussedabove arebasedon.Thisconditioncanbesatisedbyusingsucientlylo wlaserruence ( i.e. ,excitationpowerperpulse)andtemperaturesnottoolow.In ordertoassurethat wearetrulyinthedesiredlimit,wemeasuredtheruencedepend enceof e onthe8.3 nmlminasuperruidenvironmentat2.0K.AsFigure 8{6 shows, e isindependent ofthelaserpowerbelow 25mW,andbecomesfasterathigherpowers( i.e. ,higher quasiparticleinjection).Table 8{3 lists e and A foundbytting.Whenquasiparticles areoverlypopulatednearthegapedge,itiseasierforthemto ndmateswithwhichto

PAGE 192

177 Table8{3:Fluencedependenceof e and A .Thepowershownherewasmeasuredat theveryendofberopticcableatthebeamline. Power(mW) e (ns) A (arb.) 8 1.77 14.3 12 1.74 21.9 16 1.80 29.1 23 1.73 42.8 35 1.54 65.1 70 1.04 124 140 0.73 246 210 0.63 291 recombine,resultinginfasterrelaxation.Thetemperature2 .0Kcorrespondsto0 : 44 T c forthe8.3nmlm.Fromthisresult,wedecidedtouse14mW(0.26 nJperpulse)for thelaserpowerandtemperaturesabove0 : 44 T c foralllms. Wecancrudelyestimatetheexcessquasiparticledensityasfoll ows.Within 0.26nJperpulse,becauseofrerectivelossduetoseveralwindow sandsampleitself andotherlosses,let'ssay1/8oftheenergyisabsorbedinthelm. If1/2ofthe energyappearsasexcesslow-energyquasiparticles,approxim ately5 10 10 pairsare broken.For16.5nmlm(2 0 =16 : 5cm 1 )witha6mmaperture,thisresultsin N q 2 10 17 cm 3 excessquasiparticledensity.Using N (0)=0 : 33states = eV atom forMo 3 Ge[ 109 ]and6 : 42 10 22 atoms = cm 3 forMo,thisnonequilibriumdensity correspondsto0.2%ofthedensityofelectronsstronglyaecte dbyenteringthepaired state, N pairs = 4 N (0) 0 =8 : 5 10 19 cm 3 13 Thethermalquasiparticledensityforlow reducedtemperaturesisgivenby[ 96 ] N q ( T ) = 4 N (0)[ ( T ) k B T= 2] 1 = 2 e ( T ) =k B T : (8.26) At T =3K,wend N q ( T ) 10 18 cm 3 .Thus,theexcessquasiparticledensityis estimatedtobeabout20%ofthethermalquasiparticledensity, whichisnottoobad 13 Notethat N (0)isthesinglespindensityofstatesaswehavebeenusingthroug hout,andnottobeconfusedwiththenumberdensityat T =0K.

PAGE 193

178 0.00.20.40.60.81.0 0.0 0.2 0.4 0.6 0.8 1.0 NormalizedMagnitudeTemperature( T / Tc) Experiment(33nm) Ns(weak-coupling) Ns(strong-coupling) Figure8{7:Spectrallyaveragedfar-IRtransmittionvs. T=T c .Temperaturedependence ofsuperruiddensityforbothweak-andstrong-couplingBCSsupe rconductorareshown insolidlines.tobeconsideredastheweakperturbationlimit.Thisestimate willbecomparedtothe resultsfromthegapshiftmeasurements.8.3.4SpectrallyAveragedFarInfraredTransmission InChapter 7 ,wehaveseenthat T s = T n asafunctionoftemperaturegivesanidea ofhowthegapandthesuperruiddensityvarywithtemperature. Wementionedearlier thatthespectrally-averagedfar-infraredtransmissionprovi desameasureoftheexcess quasiparticledensity.Inthequasiparticledecaymeasurement s( x 8.3.1 ),wemeasurethe photoinducedchangeinthespectrallyaveragedtransmission T ave ,butwanttoknow N s (andinversely,thefreezingoutofthequasiparticles, i.e. N s is N q ).Inorderto determinetherelationshipbetween T ave and N s ,welookedatthespectrally-averaged far-infraredtransmissionasafunctionoftemperature.Figur e 8{7 showsthenormalized resultaftersubtractingthetransmissioninthenormalstate,tha tis, T ave ( T ) = T ave (0), where T ave ( T )= h T s ( T ) T n i .ThemeasurementsweredoneatU12IRwiththeOxBoxconnecteddirectly.Thesynchrotronlightwaschoppedat 100Hz,andthedetector signalwasmeasuredbyalock-inamplier.Then, T ave ( T ) = T ave (0)canbecompared

PAGE 194

179 with N s ( T )sothatadenitiverelationshipcanbedetermined.Ascanbesee ninthe gure, T ave ( T ) = T ave (0)closelycoincidewith N s ( T )givingarelationship: T ave ( T ) = T ave (0) N s ( T ) : (8.27) Thus,thespectrallyaveragedfar-infraredtransmission T ave sensesthenumberofpairs. Thistellsthatthespectrallyaveragedphotoinducedtransmi ssion T ave issimplyrelated to N s and N q as T ave N s = N q : (8.28) Therefore,ourmeasurementsofthephotoinducedtransmissionc hangeisameasureof theexcessnumberofquasiparticles,includingasafunctionof time. NotethattherelationshipgivenbyEq. 8.27 isnothingbutanempiricalobservation.ItalsohasbeenobservedforothersimpleBCSsupercondu ctors,suchasPb andNbN.Thisisprobablybecausethespectrallyaveragedtransmi ssionismuchmore sensitivetothechangesinareaunder T s = T n curvenearthepeakpositionthanthatat frequencieswhere T s = T n goesunder1becausethesinglebeamintensityapproacheszero inthesamespectralregion. 8.4AnalysisandDiscussion 8.4.1RelaxationTimes Wetookdataonthequasiparticledecayforallthreelmsfort emperatures between0.44 T c and T c .Alldatacouldbettedreasonablywellbythemodeldecay function,especiallyfordatatakenatlowreducedtemperatu rewheretheamplitude ofthesignalandtheS/Nwerehigher.Figure 8{8 showsthequasiparticledecaycurve ( i.e. ,photoinducedIRsignalafterintegrationofdierentialsig nal)asafunctionof pump-to-probedelaytimeforthe16.5nmforvarioustempera tures.Itisplottedona semi-logscale,withstraightlinesdrawnasaguidetotheeye,i llustratingchangesin slope.Notethatthecurvesinthegureshowsonlytheearlypart ofthedecaycurves. Theentiredecayprocessends(i.g.,becomesindistinguishabl efromthenon-excited state)after4to6nsfromexcitation.Theothertwolmsshowed similarcurves.Unlike

PAGE 195

180 012 0.1 1 10 PhotoinducedIRSignal[arb.]Time[ns] 0.44 T c 0.57 T c 0.67 T c 0.77 T c 0.89 T c Figure8{8:Quasiparticledecaysignalvs.pump-to-probedela ytimeforthe16.5nm lmplottedonasemi-logscale.Thelinesaredrawnasaguideto theeye,illustrating changesinslope.Thegraphshowsonlytheearlypartofthedeca ycurves. theresultsofJohnson[ 108 ]andCarr etal. [ 2 ],wedidnotndatwo-componentdecay: excessquasiparticledecayfollowedbyheatrow.Thisisproba blybecauseoursamples wereindirectcontactwithheliumgas,whichismuchmoreeci enttoextractheatfrom thesystemthanthecoolingthatreliesonthermalconductiont hroughcopperblock. Fromthet,wededucedparameters e A ,and t 0 inEq. 8.23 .Table 8{4 shows e and A forallthreelmsforvarioustemperatures.Thevaluesofpul sewidth2 : 35 Table8{4:Fitparameters e and A forallthreelmsatvarioustemperatures.Fitsare basedonthemodelfunctiongivenbyEq. 8.23 .Theuncertaintyindetermining e by ttingwasasmuchas 0 : 1ns. 33nm 16.5nm 8.3nm T=T c e (ns) A (arb.) T=T c e (ns) A (arb.) T=T c e (ns) A (arb.) 0.45 1.18 3.30 0.44 1.29 10.8 0.44 1.76 15.0 0.58 0.75 3.02 0.57 0.68 10.3 0.51 1.10 14.7 0.67 0.63 2.56 0.67 0.55 9.85 0.58 0.84 14.5 0.72 0.60 2.50 0.77 0.50 8.60 0.67 0.64 14.2 0.78 0.59 2.23 0.88 0.47 7.35 0.78 0.51 13.3 0.88 0.57 1.75 0.88 0.46 12.2 0.94 0.61 1.63

PAGE 196

181 0.40.50.60.70.80.91.0 0.0 0.5 1.0 1.5 2.0 t eff [ns]Temperature( T / T c ) 8.3nm 16.5nm 33.0nm Figure8{9: e vs. T=T c forthreelms.SolidlinesarethetstoEq. 8.7 usingtheuniversaltemperaturedependenceof R and B (Eqs. 8.12 and 8.17 )derivedbyKaplan et al. Allthreelmsweretusingthesamematerialparametersinthesc alefactors R 0 and B 0 (Eqs. 8.13 and 8.18 ).Thesame T c and2 0 valuesasfor T s = T n tswereused foreachlm.foundfromthetwereconsistentwiththeFWHMofthesynchrotron pulsesatthetime ofmeasurement. InFigure 8{9 e vs. T=T c (fromTable 8{4 )forthreelmsareshown,along withtstoEq. 8.7 usingtheuniversaltemperaturedependenceof R ( T )and B ( T ) (Eqs. 8.12 and 8.17 )derivedbyKaplan etal. Allthreelmsshowsimilarbehavior.As thetemperatureincreasestoward T c ,therearemanythermalquasiparticlesavailable forexcessquasiparticlestorecombinewith,resultinginashor tintrinsicrecombination time R .Wesee e decreasesgraduallyandnallyapproachesconstantvalue.Ph onon escapetime r canbeestimatedfromthisconstantvalueof e near T c .Wefound 500 psasthevalueof r .Therearesomevariationamongthelms,whichisprobablydue tovariationinheliumenvironmentatdierentsamplelocati on.Asthetemperature decreases,ontheotherhand,excessquasiparticleshavemorean dmorediculttimeto ndtheirmatesfromthermalquasiparticlesleadingtorapid lyincreasing R .Then, e isapproximatedby R r = 2 B .Below0 : 5 T c R wasfoundtoexceed1nsforalllms.

PAGE 197

182 Table8{5:Materialparametersthatcontributetothechara cteristicscalefactors R 0 and B 0 (Eqs. 8.13 and 8.18 ).Thesameparametervalueswerefoundtotreasonably wellforallthreelmsasshowninFigure 8{9 Z 1 (0)[=1+ ] 1.3 0.1 10 3 b (meV 2 ) 9 1 h 2 i (meV) 0.9 0.1 N (0)(10 22 states/eV) 2 0.2 N i (10 22 cm 3 ) 6 0.5 Table8{6:Relaxationtimes r R 0 ,and B 0 ,andtheratio R 0 = B 0 forallthreelms. ValueswerefoundfromttingofFigure 8{9 .Estimateduncertaintiesof R 0 B 0 ,and R 0 = B 0 inttingwere 10ps, 10ps,and0.05,respectively. Film d (nm) r (ps) R 0 (ps) B 0 (ps) R 0 = B 0 B 8.3 420 259 78 3.3 C 16.5 450 104 54 1.9 D 33 540 72 48 1.5 Forthetting,weneedthematerialparametersthatgointot hecharacteristic quasiparticleandphonontimes( R 0 and B 0 )inEqs. 8.13 and 8.18 .Unfortunately,the valuesoftheseparameters[ N (0), N i , b ,and h 2 i ]forMo 79 Ge 21 (thecomposition ofoursamples)arenotavailableanywhere.Thus,werstlookeda tdataforthe16.5 nmlm,andvariedthevaluesof b ,and h 2 i whilekeepingthevaluesof N (0) and N i xedtothoseforMo 3 Ge( 2 10 2 states/eV)andforMo( 6 10 22 cm 3 ),respectively.Then,wefoundthatthesameparametervalues werefoundtot reasonablywellfortheothertwolmsjustbychanging T c and2 0 totheappropriate valuesandadjustingonly r .Thematerialparametersusedinthettingaregivenin Table 8{5 .Theseparametersdeterminethecharacteristictimes R 0 B 0 ,andtheirratio R 0 = B 0 .Table 8{6 liststhemincluding r .Thettingwasverysensitivetothevalues of b ,and h 2 i changingthevaluesof R 0 and B 0 byafactorof2.Thus,thevalues of R 0 and B 0 shouldnotbetakenasaccuratenumbers.However,theratio R 0 = B 0 is muchlesssensitivetotheparameters.Thisgivesuscondenceto believethatthevalue of R 0 = B 0 isclosetotruevalueintrinsictothelms.

PAGE 198

183 45678 2 3 4 5 6 7 8 9 10 20 2 D 0 t B0 / t R0 [cm -1 ]T c [K] Figure8{10:2 0 B 0 = R 0 vs. T c .Forcomparison, T 3 c dependencepredictedbythetheory isshowninblue( i.e. ,aslopeof3).Theerrorbararetheresultsofthepropagationo f errorsindetermining2 0 and R 0 = R 0 Table8{7:2 0 B 0 = R 0 forallthreelms. Film d (nm) 2 0 (cm 1 ) T c (K) 2 0 B 0 = R 0 (cm 1 ) B 8.3 11.5 4.5 3.5 C 16.5 16.5 6.1 8.6 D 33 18.5 6.9 12 Assumingthatmaterialparametersarethesameforallthreelms, thetheory predicts: 2 0 B 0 R 0 / T 3 c : (8.29) Figure 8{10 showsourexperimentallydetermined2 0 B 0 = R 0 vs. T c alongwithadotted linewithslopeof3forcomparisonthetheoreticalprediction .Table 8{7 liststhevalues. Wefoundourresultisconsistentwiththetheory,supportingthe analysisofKaplan et al [ 92 ]. Inordertocompareourexperimentallydeterminedrelaxati ontimesforMoGelms withthoseforothermaterials,thecalculatedvaluesbyKapla n etal. [ 92 ]aregivenin Table 8{8 .ThevaluesforMoGeareonthesimilarorderofthoseforPb,In, andNb. Thetablealsoshowssomeassociatedmaterialparameters.Inaneo rttondsome

PAGE 199

184 Table8{8:Characteristicquasiparticleandphonontimes( R 0 and B 0 )andtheirratio aswellassomeassociatedparametersgiveninthepaperbyKapla n etal. Notethat Z 1 (0)=1+ Material R 0 (ns) B 0 (ns) R 0 = B 0 Z 1 (0) 10 3 b (meV 2 ) h 2 i (meV) Pb 0.196 0.034 5.76 2.55 5.72 1.34 In 0.799 0.169 4.73 1.81 9.43 0.913 Sn 2.30 0.110 20.9 1.72 2.32 1.14 Hg 0.0747 0.135 0.55 2.63 78.4 0.833 Tl 1.76 0.205 8.59 1.80 13.2 0.666 Ta 1.78 0.0227 78.4 1.69 1.73 1.38 Nb 0.149 0.00417 35.7 2.84 4.0 4.6 Al 438. 0.242 1810 1.43 0.317 1.93 Zn 780. 2.31 338 1.34 0.420 0.596 sortofregularity,wehaveplotted R 0 = B 0 against b asshowninFigure 8{11 14 Itis interestingtoseethatdatapointsforallthematerialslisted inthetableaswellasour MoGefallinthevicinityofthelineof b 3 = 2 ,buttherelationshipbetween R 0 = B 0 and b arenotclear. Indevelopingthetheoryofquasiparticleandphononlifetim es,Kaplan etal. assumedweak-couplingBCSsuperconductors,constant 2 ,andsimpleDebyelike n 2 dependenceofthephonondensityofstates.Ourresultsforthere laxationtime measurementsareconsistentwiththistheory,suggestingthatth ematerialparameters appeartobeconstantforallthreelmsofMoGe.Fromthemeasur ementsofnormal statetransmittance(seeChapter 7 ),wefoundtheresistivitystaysalsoconstantfor allthreelmsdespitetheirthicknesschange.Theresultsofop ticalconductivity measurementswerealsoconsistentwiththetheoryofweaktointe rmediatecoupling BCSsuperconductors.Onceagain,wedidnotndanyindication oftheeectsof localizationandrelatedenhancementofCoulombinteracti onwhichoughttochange somematerialparametersastheseeectsincrease.Aswemention edinChapter 7 ,our samplesmaynotbethinenoughtorevealsizabledeviationsfro mthesimpletheory andvariationsinmaterialconstants,butwestillcannotexpla inthesuppressionof 14 ThiswasdoneoriginallybyG.L.CarrattheBrookhavenNation alLaboratory.

PAGE 200

185 10 -4 10 -3 10 -2 10 -1 10 -1 10 0 10 1 10 2 10 3 10 4 8.3 16.5 33 Hg Tl In Pb Nb Sn Ta Zn Al a 2 ( W ) F ( W )= b W 2 t R0 / t B0 ~ b -3/2 tR0 /tB0b [meV -2 ] Figure8{11: R 0 = B 0 vs. b .ValuesforMoGelmsarededucedfromexperiment,while othermaterialsarethecalculatedvaluesbyKaplan etal [ 92 ]. T c asthethicknessofthelmsdecreases.However,thefactthatwec anhandlethe time-resolveddataforallthreelmswiththesamematerialpa rameterswhilechanging T c withdierentthicknessprovidesustotesttheanalysismadeby Kaplan etal. aswe sawinFigure 8{10 .ThisaddsuniquenesstotheMoGelms.Itwouldbeinterestingt o performsameopticalexperimentsonMoGelmswiththicknesst hinnerthanwehave now,butthen,theexperimentbecomesmoredicultas T c goesdownfurther.Weneed LHe 3 opticalcryostattothis. 8.4.2PhotoinducedGapShift Wealsomeasuredthephotoinducedchangesinfarinfraredtran smissionspectrum (photoinducedsignal) T = T betweentwopointsonthequasiparticledecaycurve showninFigure 8{5 .Detailsofthisexperimentwerediscussedin x 8.3.2 .Figure 8{12 showstheresultsfortwolaserpowers,23mW(0.43nJ/pulse)and53 mW(1nJ/pulse), onthe16.5nmlmat3K.ThesolidlinesaretheBCStsusingthesa meparameters determinedfromthe T s = T n measurements,butallowingthegaptobereducedby fromitsfullvalueatagiventemperature.Inmakingthet s,weassumedthat temperatureremainedconstantthroughout.Althoughthedata aresomewhatnoisy,

PAGE 201

186 101520 -0.02 0.00 0.02 23mW 53mW Frequency[cm-1] -/dTTFigure8{12:Photoinducedspectralchangesforthe16.5nml mat3K.Theresultsof twodierentlaserenergies23mW(blacksquares)and53mW(redc ircles)areshown, alongwithBCStsassuming0.6%and1.33%reductioninthegap, respectively. Table8{9:Photoinducedgapshiftsandfractionsofpairsbro kenbyphotoexcitationat twolaserpowersforthe16.5nmlmat3K. Power(mW) Energy(nJ/pulse) (cm 1 ) N q =N pairs (%) 23 0.43 0.05 0.30 53 1.0 0.11 0.67 gapshiftsof =0.05cm 1 and0.11cm 1 gaveacceptabletsfor23and53mW powerlevels,respectively.Notethatthetheoreticalcurvesa resmoothedtohavethe sameresolutionastheexperimentaldata.UsingEq. 8.25 ,wefoundthatapproximately 0.30and0.67%oftheCooperpairswerebrokenbyphotoexcita tion,respectively.These resultsareinreasonableagreementwiththeestimate(0.2%)we madein x 8.3.3 .The resultsaresummarizedinTable 8{9 .In x 8.3.3 ,wecalculated N pairs 8 : 5 10 19 cm 3 and N q ( T =3K) 10 18 cm 3 .Then,thedensityofexcessquasiparticlescreated by53mWofpowerleveliscomparabletothethermalpopulatio n( i.e. ,weareinthe intermediateperturbationlimit).Thisleadstoahigherpr obabilityforquasiparticles tondeachothercausingfasterrelaxationasweobservedinthe ruencedependence measurements(seeFigure 8{6 ).

PAGE 202

187 8.5Conclusion Inthischapter,wereportedtheresultsoftime-resolvedfari nfraredstudieson superconducting -MoGethinlmsofthreedierentthicknesses.Weusedamodelockednear-IR/visiblelasertoexcite(pump)thesystemandsync hrotronradiationto probethedynamicsofexcessquasiparticlesandphononswitha timeresolutionuptoa fewhundredpicoseconds. Thespectrally-averagedphotoinducedfar-infraredtransmi ssionwasfoundtobe closelyrelatedtothechangeinsuperruiddensitycausedbythep hotoexcitation.This empiricalobservationgivesusadeniterelationshipbetwee nthephotoinducedtransmission( i.e. ,far-infraredabsorptionchanges)andtheexcessnumberofqua siparticles. Bymeasuringthephotoinducedtransmissionatvarioustimingbe tweenpumpand probe,wewereabletoobservethedecay( i.e. ,relaxation)oftheexcessquasiparticlesas afunctionoftime,andtodeduceaneectiverelaxationtime atvarioustemperatures below T c usingaconvolutionofasimpleexponentialdecayandaGaussiansy nchrotron pulsestructureasattingfunction.Then,thetemperaturede pendenceofthiseective relaxationwasanalyzedbyusingtheeectiverelaxationtim eexpressionfoundasa solutionoftheRothwarf-Taylorequationsfornonequilibri umsuperconductorsandthe universaltemperaturedependenceoftheintrinsicrecombina tiontime(quasiparticle lifetime)andthepair-breakingtime(phononlifetime)der ivedbyKaplan etal. Thereasonabletstotheorywereachievedwithoutvaryinganymater ialparametersinallthree lms,andsomeinformationaboutthecharacteristicquasiparti cleandphononlifetimes wereobtained.Ourresultsarequiteconsistentwiththetheory byKaplan etal. ,which isbasedonweak-couplingBCStheory.Justasintheresultsofli nearspectroscopy,it seemsnoneofmaterialparametersarechanging,but T c changeswiththickness.We thinkthatthisisnotunderstoodcompletelyyet.Thinnerlm smayrevealsomeinterestingdeviationsrelatedtoelectronlocalizationandrela tedCoulombinteractions,but theexperimentbecomesprogressivelymoredicultas T c goesdownfurther. Wealsoreportedthephotoinducedchangesinthefar-infrare dtransmissionspectrumasalmisexcitedfromequilibrium.Theresultsoftwoex citationpowerlevels

PAGE 203

188 werettedwiththeBCScalculationallowingonlythesuperco nductingenergygapto changebyasmallamount.BasedonthetheorybyOwenandScalapi no,wededuced thedensityofexcessquasiparticles,whichisinreasonableagre ementwiththeestimate basedonthephotonruence.

PAGE 204

CHAPTER9 MAGNETO-OPTICALSTUDYOF -MoGeTHINFILMS 9.1Introduction Whentheappliedmagneticeldisbetweenalowercriticale ld H c 1 ( T )and anuppercriticaleld H c 2 ( T ),typeIIsuperconductorsallowapartialpenetration ofmagneticruxintothespecimen,developingnormalstatereg ionsintheformof thinlaments,whicharereferredasvortexlines.Thetypesof superconductorswere describedin x 4.2.3 .Asthestrengthoftheappliedeldincreasestoward H c 2 ( T ),a largerfractionoftheareaturnsnormal,andat H c 2 ( T ),thespecimenrevertscompletely tonormal. Inthedirtylimit( l 0 ,where l isthemeanfreepathand 0 isthePippard coherencelengthgiveninEq. 4.13 ),theeectivecoherencelength(Eq. 4.24 )isdeterminedbythemeanfreepath(seeEq. 4.26 ).Themeanfreepathofahighlydisordered materialismuchshorterthanitsLondonpenetrationdepth,a ndthustheyareusuallya typeIIsuperconductorhavingacondition 1,where istheGLparameterdened inEq. 4.22 -MoGethinlmswiththemeanfreepathofroughlyatomicspaci ng( 3 A)areextremelydirtymaterial,andaretypeIIsuperconducto rs. Wehaverecentlyattachedavertical-boresuperconductingm agnettothespectrometer,Bruker125HR,atthebeamlineU12IR.Withthismagne t,wetriedmagnetoopticalmeasurementsonthe33nm -MoGelm.Becausethesetupwasnewtoall ofus,ourexperimentservedthreepurposes:testinghowtheentir esystem,includingthespectrometer,themagnet,andothercomponents,funct ionswiththemagnet running,ndingthecorrecttiming( i.e. ,ndingalaser-synchrotroncoincidencefortimeresolvedexperiment),andconductingmeasurementsatthesame time.Throughthe measurements,wefoundseveralmattersthatshouldbeconsidered foroptimizinglater 189

PAGE 205

190 20406080100 1.0 1.5 2.0 TransmittanceRatioFrequency[cm -1 ] 0T 1T 2T 4T 6T 8T 10T (/) TT snFigure9{1:Measuredtransmittanceratioforthe33nmlmat3K inmagneticelds. experiments.Inthischapter,wemerelyshowourdataforthetr ansmittanceratioand quasiparticledecayinappliedexternalelds,andnospecicc onclusionsarediscussed. 9.2TransmittanceRatioinMagneticFields Figure 9{1 showstheelddependenttransmittanceratio T s ( H ) = T n ofthe33 nm -MoGelmat T =3K.Thenormalstatetransmittance, T n ,wasmeasuredat T =8Kwithoutapplyingtheeld.Theshapesoftheratioaregene rallythesameas weobservedintemperaturedependenceofthetransmittancera tiodiscussedin x 7.4 Asthestrengthoftheeldisincreased,thepeakheightdiminish edasiftemperature wereincreasedtoward T c ,andatapproximately10tesla,thetransmittancebecomes indistinguishablefromthatinthenormalstate.Thus, H c 2 ( T =3K)forthislmis approximately10tesla.Unlikethetemperaturedependentdat a,however,thepeak positionof T s ( H ) = T n staysnearlyatthesamefrequency.Althoughnotshownhere, thecurveforzeroeldtswelltotheMattis-Bardeentheory[ 45 ]onlyifwesetthe temperatureto4K,butotherwiseusingthesameparametersprev iouslydetermined (seeChapter 7 ).Atthetimeofmeasurements,wehadsomedoubtsincalibration ofthe

PAGE 206

191 0123 0.1 1 MoGe33nmat3.0KPhoto-inducedIRSignal[arb.]Time[ns] 0T 4T 8T Figure9{2:Quasiparticledecaysignalvs.pump-to-probedela ytimeinmagneticeld forthe33nmlmplottedinsemi-logscale.Thelinesaredrawnf oraguide.Thegraph showsonlyearlypartofthedecaycurves.temperaturesensor.Thus,itmighthavewellbeen4Kratherthan 3K.Obviously,the sensorhastobecalibratedbeforenextexperimentisconducte d. 9.3RelaxationTimesinMagneticFields Figure 9{2 showsthequasiparticledecaycurvesofthe33nm -MoGelm.Again thetemperaturereadingmeasuredusingthesamesensorwas T =3K.Withthe magneticeldapplied,quasiparticlesmaydiusetowardvort exeswherethereisno gapandthusnobottleneck.Astheeldstrengthincreases,norma lstateregionsgrow, andthereforeweexpectfasterrelaxationtime.However,what weobservedisaeld independenteectiverelaxationtime, 1 : 1ns,foralleldsupto8T.Notethat thevalueoftheeectiverelaxationtimeherecannotbecomp areddirectlytothat foundinthepreviouschapterbecausethesampleisincomplete lydierenthelium gasatmosphere,andalsobecausewecannotdenethetemperatur ewell.Aswecan seeinFigure 9{1 ,thetransmittanceat8Tisbarelydistinguishablefromthenor mal stateimplyingthatthemostofregionsareconvertedtothenor malstate.Thiseld independencecannotbeexplainedatthismoment.

PAGE 207

CHAPTER10 SUMMARYANDCONCLUSION Thisdissertationhaspresentedresultsofanextensivefarinfra redstudieson superconducting -MoGethinlmsofincreasingdisorder.Bothlinearandtime-r esolved measurementshavebeenmade.Inthischapter,wesummarizethe resultsofour experiments,andendthisdissertationwithconcludingremark s. OpticalConductivity Theopticalconductivity~ ( )of -MoGethinlmsofvariousthicknesseson athicksubstrateatvarioustemperatureswereextractedfrom transmittanceand rerectancemeasurementsinthefarinfrared.Threeoutoffou rlmsturnedtobe superconductingbythelowesttemperatureaccessibletoouropt icalcryostat.Transition temperature T c forthesethreelmswerefoundtobereducedprogressivelywith decreasingthickness(orincreasingdisorder).Thesuppressionof T c hasbeenattributed totheeectsoflocalizationandrelatedenhancementofCou lombinteraction,which inherentlycompetewiththeattractiveinteractionthatbo undselectronsintopairs.The sheetresistance,whichisarelevantmeasureofdisorderinourl ms,wasdetermined fromthenormalstatetransmittance.Itwasfoundtobeinversel yproportionaltothe thicknessofthelms,provingthenormal-statebulkresistivity remainsconstantfor allthreelms.Thissuggeststhattheobserved T c reductionisa2Deectsandnot duetothechangesinbulkproperties.Theobserved T c reductionasafunctionofsheet resistancewasconsistentwiththeMaekawa-Fukuyamatheory[ 46 ]onlyifweassume thattheGecontentsofourlmsaresomewherebetween21%Ge,w hichwasprobably intendedduringsynthesis,and25%Ge,whichrepresentsthestoic hiometriccompound Mo 3 Ge. Therelativetransmittanceaswellasrerectanceofathinlm [ i.e. ,aratioof transmittancethough(orrerectancefrom)alminitssuperco nductingstatetoits 192

PAGE 208

193 normalstate]aredeterminedbythefrequencydependenceoft hecomplexconductivity, ascalculatedbyMattisandBardeen[ 45 ]basedontheweak-coupling,dirtylimit BCStheory.Ourexperimentally-observedrelativetransmitt anceandrerectancewere generallyconsistentwiththeMattis-Bardeentheory,andfrom thetwedetermined theenergygap2 0 .Theratio2 0 =k B T c wasfoundtoberoughlythesameforallthree lmswiththevalueslightlyhigherthantheBCSresultof3.5. Therealpartoftheopticalconductivity 1 ( )extractedfromtransmittance andrerectancemeasurementsclearlydisplayedthepresenceof anenergygap,which shrinksastemperatureapproaches T c .Theimaginarypart 2 ( )representsthelossless inductiveresponseofthelms.Itshowedroughlya1 =! behaviorbelowthegap frequency2 = ~ ,andbecomessmallerasfewerelectronsparticipateinpairi ng.Fromthe 1 =! behaviorof 2 ( ),superruiddensityandmagneticpenetrationdepthwerededu ced. Wefoundthatthesuperruiddensitydecreasesasthesheetresistan ceincreases,but howthesearerelatedtotheeectoflocalizationremaintobe answered.Thesuperruid densityalsoseemstodependlinearlyon T c ,whichistriviallyconsistentwiththe expectationfortheweaktointermediatecouplingdirty-li mitBCSsuperconductors. Theeectofreducedthicknessinthesesamplesistodepress T c andthesuperruid density.Atthesametime,thenormal-stateconductivityappea rsunchanged.Thinner lmswithlower T c andmoreseverlocalizationeectsmayrevealstrongdeviatio nfrom theresultsexpectedforasuperconductinglmwithoutelectr onlocalization. Time-resolvedStudy Quasiparticledynamicswasexploredbyusingauniquepump-pr obetechnique, usingapulsefromaTi:Sapphirelaserasanexcitationsourceand apulseofsynchrotron radiationasaprobesource.Photonsofthepumppulsebreakasig nicantamountof Cooperpairsleadingtoanonequilibriumcondition,whichc anbesensedasasmall decreaseintheenergygapandincreaseinthefarinfraredabsor ption.Weempirically foundthatthespectrallyaveragedtransmittancecloselyfoll owsthetemperature dependenceofthesuperruiddensitypredictedbyBCStheory.T hisgaveadenite

PAGE 209

194 relationshipbetweenthephotoinducedchangeinthespectral lyaveragedtransmittance andtheexcessnumberofquasiparticles. Byadjustingtherelativedelaytimebetweenthepumpandthep robepulses,we followedtherelaxationofexcessquasiparticlesasafunctio noftime.Thequasiparticle decaysignalwasmodelledasaconvolutionofasimpleexponent ialdecayandasynchrotronGaussiantemporalstructure,fromwhichwededucedth eeectiverelaxation timeatvarioustemperaturebelow T c forthesamethree -MoGethinlmsusedinthe linearspectroscopicmeasurements.Thetemperaturedependenc eoftheeectiverelaxationtimewasanalyzedusingasolutionoftheRothwarf-Taylo requations[ 93 ],which describethebehaviorofexcessquasiparticlesandphononsinn onequilibriumsuperconductors,andtheuniversaltemperaturedependenceofintrinsi cquasiparticlelifetime (recombinationtime) R andphononlifetime(pair-breakingtime) B ,whichwerederivedbyKaplan etal. [ 92 ]basedonweak-couplingBCStheory.Notethatboththeories assumesweakperturbationlimit, i.e. ,thecaseoftheexcessquasiparticledensitymuch smallerthanthethermalquasiparticledensity,andwemadesure thatwewereinthis limitduringourexperiments.In R and B ,simplescalefactors R 0 and B 0 containall thematerialparametersrelevanttothetheory,andwewerea bletotourdatawithout varyingthematerialparametersfordierentthickness.Justa stheresultsoflinear spectroscopy,itseemsnoneofmaterialparametersarechangin g,but T c changeswith thickness,andwethinkthisisnotunderstoodcompletelyyet.T hevaluesof R 0 and B 0 wereontheorderof100psand10ps,respectively,whichwerein thesamerangeasfor materialslikePb,In,andNb.Inmakingthets,weobservedthat theratio R 0 = B 0 is lesssensitivetothechangeinthematerialparametersthanind ividual R 0 and B 0 ,and webelievethattheratiorepresentsthepropertiesof -MoGelmsmoreaccurately.The theorybyKaplan etal. predictsthattheratio2 0 B 0 = R 0 isproportionalto T 3 c .This isexactlywhatweobservedinourexperiments,supportingthet heory.Wealsolooked athowthecalculatedvaluesof R 0 = B 0 forvariouselementalsuperconductors[ 92 ]are relatedto b ,where b isaconstantintheassumption 2 F (n)= b n 2 .Wesawtheratio ofallmaterialsincludingourMoGefallssomewhereinthevic inityoftheline b 3 = 2 .We

PAGE 210

195 didnotdrawstrongconclusionsforthisobservationbecausewed onotreallyknowthe correctvalueof b forMoGe. Wealsomeasuredthephotoinducedsuperconductinggapshiftfor twolaser ruences.Assumingthattemperatureremainedconstantbeforeand afterexcitation, BCStsusingthesameparametersfoundinlinearspectroscopyme asurementsallowed ustondasmallreductionintheenergygapbyexcitationwith laserpulses.Basedon thetheorybyOwenandScalapino[ 94 ],wedeterminedthatapproximately0.30%and 0.67%ofpairswerebrokenbyphotoexcitationwith0.43and1 .0nJ/pulseofruence, respectively.Theresultswereroughlyinagreementwiththee stimatebasedonthe photonruenceitself.Magneto-opticalMeasurements Ourmostrecentexperimentsoftransmittanceaswellasquasipa rticledecayin magneticeldsweredescribed.TheexperimentsweredoneatU1 2IRwithrecently installednewspectrometerBruker125HR.Avertical-boresuper conductingmagnet wasconnectedtothespectrometerforthersttime.Thus,ourex perimentserved totesthowtheentiresystem,includingthespectrometer,thema gnet,andallother setup,functionswiththemagnetrunning,tondacorrecttim ing( i.e. ,ndingalasersynchrotroncoincidence)forthenewopticalpath,andtocon ductmeasurementsatthe sametime.Throughthemeasurements,wefoundseveralmattersth atshouldbeconsideredforoptimizinglaterexperiments.Nonetheless,weobserved thattransmittanceratio of -MoGe(33nmlm)at T =3Kbehavesasiftemperaturewereincreasedtoward T c astheeldstrengthwasincreasedexceptthepeakpositionrema inedstationary,and approximately10teslaofmagneticelddrivesthesupercondu ctingstatetoitsnormal state. Withthemagneticeldapplied,quasiparticlesmaydiusetow ardvortexeswhere thereisnogapandthusnobottleneck.Astheeldstrengthincr eases,normalstate regionsglow,andthereforefasterrelaxationtimeisexpect ed.However,whatwe observediseldindependenteectiverelaxationtime( 1 : 1nsforalleldsupto8 tesla),whichcannotbeexplainedatthismoment.

PAGE 211

196 ConcludingRemarks Overall,thisdissertationdescribesthefacilityattheNSLSan dresultsofour experimentsconductedthereon.Useoflargeexperimentalfac ilitiessuchassynchrotrons couldprovideopportunitiestoconductexperimentsthatmi ghtbeuniqueorthatcan notbedonewithinanordinarylaboratoryscale.TheNSLS,inpa rticular,oersarange ofcapabilitiesofperformingopticalstudiesowingtoitshi ghbrightness,broadband characteristics,andpulsednature.Withthelaser-synchrotron pump-probetechnique developedattheNSLS,wecanfollowthedynamicsofvarioussyst emsthatevolveas fastasatimescaleofafewhundredpicoseconds.Althoughthisisn otparticularlyhigh speedcomparedwiththecoherentterahertzlaserspectroscopyt echnique[ 110 ],there aremanyphenomenathatcanbestudiedatthistimescale.Throu ghthisdissertation webelievethatwewereabletoshowhowthesynchrotronsourceca nbeusefulfor investigatingfundamentalpropertiesofsolidstatephysics.

PAGE 212

APPENDIXA VUVSTORAGERINGPARAMETERS Thisappendixcontainstablesofvariousparametersforthe NSLSVUVstorage ring,thelinac,andtheboosterring[ 63 ].TheparametersfortheNSLSX-raystorage ringarenotlistedhere. TableA{1:TheVUVstorageringparameters(2002). NormalOperatingEnergy0.808GeVPeakOperatingCurrent(multibunchOps.)1.0amp(1 : 06 10 12 e ) Circumference51.0metersNumberofBeamPortsonDipoles18NumberofInsertionDevices2MaximumLengthofInsertionDevices 2.25meters c (E c ) 19.9 A(622eV) B( ) 1.41Tesla(1.91meters) ElectronOrbitalPeriod170.2nanosecondsDampingTimes x = y =13msec; z =7msec Lifetime@200mAwith52MHz360min(with211MHzBunchLengthening)(590min)LatticeStructure(Chasman-Green)SeparatedFunction,Quad,DoubletsNumberofSuperperiods4MagnetComplement 8<: 8Bending(1.5meterseach)24Quadrupole(0.3meterseach)12Sextupole(0.2meterseach) 9=; NominalTunes( x ; y )3.14,1.26 MomentumCompaction0.0235RFFrequency52.887MHzRadiatedPower20.4kW/ampofBeamRFPeakVoltagewith52MHz(with211MHz)80kV(20kV)DesignRFPowerwith52MHz(with211MHz)50kW(10kW)SynchrotronTune( s )0.0018 NaturalEnergySpread( e /E)5.0 10 4 ,I b < 20mA BunchLength(2 )9.7cm(I b < 20mA) (2L rms with211MHzBunchLengthening)(36cm) NumberofRFBuckets9TypicalBunchMode7HorizontalDampedEmittance( x )160nm-rad VerticalDampedEmittance( y ) 0.35nm-rad(4nm-radinnormalops.) PowerperHorizontalMilliradian(@1A)3.2Watts 197

PAGE 213

198 TableA{2:TheVUVstoragering'sarcsourceparameters(2002). BetatronFunction( x ; y )1.18to2.25m,10.26to14.21m DispersionFunction( x ; 0 x )0.500to0.062m,0.743to0.093m x;y = 0 x;y = 2-0.046to1.087,3.18to-0.96 r x;y =(1+ 2 x;y )/ x;y 0.738to0.970m 1 ,1.083to0.135m 1 SourceSize( x ; y )536to568 m, > 60to > 70 m (170-200 minnormalops.) SourceDivergence( 0 x ; 0 y )686to373 rad,19.5to6.9 rad (55-20 radinnormalops.) TableA{3:TheVUVstoragering'sinsertiondeviceparameters(20 02). BetatronFunction m( x ; y )11.1m,5.84m SourceSize( x ; y )1240 m, > 45 m(220 minnormalops.) SourceDivergence( 0 x ; 0 y )112 rad, > 7.7 rad(22 radinnormalops.) y isadjustable TableA{4:TheNSLSlinacparameters(2002). InjectionEnergy100keVFinalEnergy120MeVNumberofSections3NumberofKlystrons3Frequency2856MHz TableA{5:TheNSLSboosterparameters. InjectionEnergy120MeV MinimumVerticalBeta1.73m ExtractionEnergy750MeV MaximumDispersion1.21m Circumference28.35m MinimumDispersion0.41m NumberofSuperperiods4 MomentumCompaction0.106 DipoleBendingRadius1.91m PeakRFVoltage25kV NominalHorizontalTune2.42 RFFrequency52.88MHz NominalVerticalTune1.37 HorizontalAcceptance1.66E-04m-rad MaximumHorizontalBeta8.63m VerticalAcceptance6.11E-05m-rad MinimumHorizontalBeta1.01m MomentumAcceptance 0.0025 MaximumVerticalBeta5.26m TableA{6:TheNSLSboostermagneticelements(eldsat750MeV). NameTypeQuantityB(kG)B'(kG/m)B"(kG/m)EectiveLength(m) BBDipole813.099-7.97-1251.5Q1Quadrupole468.820.3Q2Quadrupole493.600.3SFSextupole41223.70.2

PAGE 214

APPENDIXB INFRAREDBEAMLINES Mostofthesynchrotronfacilitiesallovertheworldaredesign edandoptimized forproducingphotonsmainlyintheVUVthroughX-raysspectrum. Meanwhile, theuseofthelowenergyendsofsynchrotronradiationarealsor ealized,andseveral facilities(notablytheVUVringatNSLSandUV-SORinOkazaki,Jap an)nowfacilitate beamlinesoptimizedforfarinfrared.Asthesubjectssuchasth ecoherentsynchrotron radiation(CSR)andtheTHzradiationstartgettingattention ,needsofinfrared beamlineshavebeenincreased,andevenawholestorageringop timizedforlong wavelengthiscurrentlyunderconstructionattheAdvancedLi ghtSource(ALS)ofthe Lawrence-BerkeleyNationallaboratory.Thisappendixserve sadditionalinformation aboutinfraredbeamlinesattheNSLSVUVring. B.1InfraredProgramsatNSLSVUVring TableB{1:Examplesofresearchsubjectsandaliationsofresp ectiveinfraredbeamlinesoftheVUVring. Beamline ResearchSubjectsandAliation Ultra-highpressurespectroscopy/microscopy U2A CarnegieInstitutionofWashington Proteindynamicsandbiologicalmicroscopy U2B AlbertEinsteinCollegeofMedicine Surfacevibrationalspectroscopy/advancedmicroscopy U4IR NSLS/UniversityofWisconsin-Milwaukee Dynamicsofcomplexmetals U10A BrookhavenNationalLaboratory,NSLS Biological/ruorescence-assistedmicroscopy U10B NSLS,NorthropGrummanandCanadianLightSource Time-resolved,high-eld,far-IRspectroscopy U12IR UniversityofFlorida,StonyBrook,NSLS TherearesixbeamlinescurrentlyoperationalasapartofVUVri ngforlong wavelengthstudies.Table B{1 listsexamplesofresearchsubjectsandthealiationof respectivebeamlines. 199

PAGE 215

200 481216202428 0 5 10 15 20 Intensity[a.u.]Wavenumber[cm -1 ] 1cm -1 0.1cm -1 0.10.20.30.40.50.60.70.80.9 Frequency[THz] 50001000015000 23456 0 5 10 15 20 0.1cm-1 0.01cm-10.100.15 ebunch at t 1 ebunch at t 2 Ring bend IR emission Chamber wall reflection (A) (B)FigureB{1:(A)Highresolutionfarinfraredspectraofsynchrotr onradiationtakenat U12IR.Theinsetintheuppergraphdisplaystheinterferogramf or0.1cm 1 resolution. Lowergraphshowsspectraonanexpandedscalewithevenhigherr esolutionof0.01 cm 1 .(B)Modelofexplainingtheobservedfringes. B.2HightResolutionFar-infraredSpectraatU12IR ThespectraofsynchrotronradiationtakenwiththeSPS-200re vealapeculiar characteristicinhighresolutionfarinfraredspectraatU12IR .Figure B{1 (A)displays fringesinthespectratakenat0.01cm 1 ,0.1cm 1 and1cm 1 resolutions.Insetin thetopplotistheinterferogramwith0.1cm 1 resolution,andshowspeaksotherthan thecenterburstduetothefringeperiodof 1cm 1 .Asthevacuumchamberofthe VUVringchangesslightlyitsdimensionduetotemperaturevaria tion,thefringepattern moveswithtime.Thismaybetroublesomeforthosewhowanttota kehighresolution spectrum.Figure B{1 (B)showsapossibleexplanationfortheobservedfringes.

PAGE 216

APPENDIXC LASERSAFETYANDOPERATINGPROCEDURES C.1HazardousBeamControl Controlofthelaserradiationisaccomplishedbythreesystems:( 1)theU6hutch whichhousesthelaserandaccessoryoptics,(2)theopticalberc ableand(3)the endstationenclosure.TheU6hutchallowsproperlytrainedand protectedpersonnel toworkwiththelasersystemoptics.Allhazardsarecontainedwit hinthehutch. ProtectivegogglesforbothTi:SapphireandNd:YVO 4 wavelengthsarelocatedinside theU6hutch.Aninterlocksystemonthehutchdoorwayentranceis interfacedtoa shutterdirectlyattheexitapertureofthelaser.Entrybyuna uthorizedpersonneltrips theinterlockcausingthebeamtobecontainedinsidethelaser' sownenclosure.The doorwayentrancetotheU6hutchwillcarrystandardpostingsfo rboththepulsed Ti:Sapphirelaser,andtheparticularpumplaser(presentlya6 WNd:YVO 4 solidstate laser).Asignwiththemessage"INTERLOCKED"willilluminatetoi ndicatethat thedoorsysteminterlockisfunctioning.Thebercablerunsa longthecabletrays abovetheVUVringitself,andisthereforenotnormallyaccessibl etounauthorized personnel.TheKevlarreinforcingbersprovideprotection againstinadvertentbreakage. ThecablesendatthebeamlinewithanSMAtypeconnector.Ari gidscrew-type unionconnectorattachesthecabletoanothercablewhichen dsinsideanenclosed sample/experimentchamber,orafastopticaldetectorenclosu re. C.2PersonalProtectiveEquipment C.2.1EyeProtection TheU6beamlinehutchhas3pairsofprotectiveeyeglassesforth eVerdiNd:YVO 4 laser,theTi:Sapphirelaser,andGaAswavelengths(GlendaleM odel2175;OD > 9for 190nm-520nm;OD > 5for750nm-850nm)and2pairsofprotectiveeyewearfor theTi:SapphirelaserandGaAslaserdiodes(GlendaleModel222 6OD > 5for750nm 201

PAGE 217

202 -850nm).Duringnormaloperations,personnelenteringthehu tcharerequiredtowear protectiveglassesforTi:Sapphirelaserlight. TheNd:YVO 4 beamiscompletelycontainedduringbothalignmentandoper ational modesoftheU6laser,thuseyeprotectionisnotnecessary.Forro utinemaintenanceand servicing,protectiveeyewearwillbeworn.C.2.2SkinProtection NoUVlightispresentlyavailablefromthelaser.Exposingskintot helaserbeam willbeavoided,howevernospecialprotectivewearismandat ed. C.3LaserSafetyTraining OperatorsofANSIClass3band4laser( e.g. ,MiraandVerdi)mustcomplete sucienttrainingtoassurethattheycanidentifyandcontrolt heriskspresentedby thelasersystemstheyuse.QualiedLaserOperatorsmustcomplete theBNLlaser safetytrainingcourse,system-specicorientationwiththesyste mowner/operator,anda baselinemedicaleyeexaminationpriortolasersystemoperatio n. C.4Alignment C.4.1GrossAlignment DuringinitialdailyalignmentoftheTi:Sapphirelaser,pro tectiveeyewearwill bewornforanygrossalignments.PhotosensitiveIRsensorcardsor IRimageconverter/viewerswillbeusedtolocatethebeamandsteeritthro ughthevariousoptical elements.C.4.2FineAlignment Forcriticalnealignments( e.g. ,throughthePockelscells),itisnecessarytobe abletodetectthebeamdirectlyusingwhitebusinesscardwitho utprotectiveeyewear. Duringtheseoperations,thelaserwillbeoperatedatreducedp ower( < 100mW)to reduceriskofeyeinjurytoanacceptablylowlevel.Neutralde nsityltersonrigid opticalmountswillbeplacedupstreamoftheopticstobealig ned,andthepower levelmeasuredtoensurelowoutputbeforesuchalignmentisbeg un.Followingisthe proceduretobeexercisedduringnealignment.

PAGE 218

203 1.WithglassesON,setTi:Sapphirelaserto700nmendoftuningran ge(increases visibilityatlowpowers). 2.ImmediatelydownstreamoftheOpticalIsolator,xsupportf orNDlters, followedbythelaserpowermeterimmediately. 3.InstallNDlterstoreducepowertobelow100mW.4.Closelasershutterandplacepowermeter(ormetalbeamblock )downstreamof opticalsectiontobealigned. 5.UsingIRviewer,conrmthatthebeamisfallingontoeachopt icalelement. Surveytheroomforextraneousrerectionsandeliminateany 6.Performminoralignment(withoutglassesasneeded),usingd iusewhitecard (tocheckaccuratepositioning).Mirrorsorotheropticsshal lNOTbeusedtoobserve anypartsofthebeampath. 7.Returntousinglaserglasses/gogglesbeforeremovingtheneut raldensity lter(s).C.4.3AtBeamlineEndstation AlignmentofberopticsatbeamlinewillONLYbedoneusinglowp ower( 1 mW)reddiodealignmentlaser.Thesolid,opaquemetalvacuume nclosurewillbe securelyfastened(boltedand/orundervacuum)anytimethepo ssibilityexistsfor > 5 mWlaserpowerthroughthebercableintotheenclosure.Alllase rlightcomingfrom theU6hutchthroughthebercablewillbecontainedatalltim es. C.5DailyOperationProcedure Thissectionservesasachecklistforturningon/othelasersyste m,mode-locking, andsynchronizing.Adetaileddescriptionofthelaseroperati on,alignmentofinternal optics,maintenance,andtroubleshootingcanbefoundintheo perator'smanualsfor MiraandVerdi.TheSynchro-Lock900operator'smanualprov idesthroughinstruction forsynchronizingthelasertotheVUVring.Followinginstructio nisforthesystem atthetimeofwritingthisdissertation,andtheprocedureissu bjecttochangedue tomodicationofsynchronizationmethodandopticssetup.Iw illassumethatthe

PAGE 219

204 alignmentthroughthedownstreamopticsandecientcouplin gintotheopticalberare wellestablishedbeforethedailyoperation. Toturnonthesystem;1.Checkiftheairconditioningsysteminsidethehutchisturne don,andthe temperaturessetatbetween73and75 F.Thisisfortheoptimalstabilityofthelaser system. 2.Verifythatthechillerwatertemperatureissettoapproxi mately20 C,andthe waterlevelisbetweenahighandlowlevelmarker.Thenturni ton.Thebaseplate temperatureshouldbemaintainedbelow55 C. 3.MakesurethatU6hutchdoorLaserHazardpostingsisinplace,an dthe INTERLOCKandwarninglightoperational. 4.Insurethatthesafetyshutterisclosed.5.Beamblock(blackmetalmonumentorpowermeterhead)shoul dbeinstalledin beampathupstreamofbercoupler.Wheneverthebeamistransf erredtoabeamline, makesurethatthebeamiscompletelycontainedwithinanendst ationenclosure. 6.TurnthekeyswitchonthepowersupplyfrontpaneltoON,andop entheVerdi shutter(Thisshutterisnormallykeptopen).Ifnecessary,adju stthePOWERADJUST knobforthedesiredoutputpowerlevel.Wenormallyoperatea t5.0watts,butitcanbe ashighas5.5watts. 7.Warmthesystemforapproximately1houruntiltheunitachie vesstable emission. 8.WiththemodeselectswitchontheMiracontrollerintheCWpo sition,optimize theoutputpowerbyadjustingpumpmirrorcontrolsandGTIali gnmentcontrols.Make surethebeamiswellcenteredattheslit. 9.Atthispoint,alltheotherelectronics,suchasdigitalosci lloscope,pulse-picker powersupply,functiongenerator,andbiasofphotodiodeaft erthepulse-picker,canbe powered.Aslongastheamplitudeoffunctiongeneratorissett oitsminimum, 1.53 mV,itcanbeleftpoweredallthetime.

PAGE 220

205 10.Mode-lockedoperationcanbeestablishedbyswitchingthem odeselectionto eitherMLor L.AdjusttheBRFmicrometeruntiltheCWcomponentintheoutpu t beambecomesnegligible. 11.Turnonthepulsegeneratoratthebeamline.TheSynchro-l ock900software allowsthesynchronizationoftheopticalpulsesfromMirawit hastableexternal frequencysource,whichisinthiscasethepulsegenerator. Toturnofthesystem;1.Unlockthesynchronizationfromthesoftware.2.SwitchthemodeselectiontotheCW.3.TurnothekeyswitchoftheVerdipowersupply.4.Turnothechiller.5.Eithersettheamplitudeoffunctiongeneratortominimumo rturnito. 6.Allotherelectronicscanbeturnedo.Especiallydonotfor gettoturnothe biasofbothphotodiodeandpowermeter. C.6OptimizationoftheDownstreamOptics Thissectiondescribestheproceduretofollowforoptimizing thethroughputofthe downstreamoptics[ 21 ]. 1.Maximizethepowerpassingthroughtheopticalisolatorbyad justingthemirror rerectingthebeamintotheisolator. 2.Withtherejectedbeamblocked,maximizethepowerpassingt hroughtherst pulse-pickerbyadjustingtheinputmirrorandthepulse-picke rposition.Thispartof alignmentissensitiveandthebeamshouldpassthroughthecente rofentranceaperture withnodistortions.Thismustbedonewiththelasermode-locked andthepulse-picker operating. 3.Maximizethepowerthroughthesecondpulsepickerbyadjusti ngitsposition andtheinputmirror(alsousedfortherstpulse-picker).Afewi terationsofstep2and 3maybenecessarytoachieveagoodalignment. 4.Onceagoodalignmentoftheprimarypulsehasbeenachieved ,unblockthe rejectedpulsebeamandalignitvisuallyuntilitisontheedge ofthemirrorusedto

PAGE 221

206 re-insertitintothemainbeampathatthesameheightasthepri marybeam.Then adjustthatmirroruntilthesecondbeamiscoincidentwiththe primarybeamatapoint afterthesecondpulsepicker. 5.Placeapowermeteratthepositionwherethetwobeamsoverl ap.Adjustthe half-waveplatetomaximizethepower. 6.Blockthesecondbeamandoptimizethecouplingoftherstin totheoptical berusingtheadjustmentsofthebercoupler.Thenunblockth esecondbeamand optimizeitscouplingbyadjustingthere-insertionmirror.B ylookingatthebeamgoing intoaberthroughanIRviewer,optimalcouplingcanbeeasil yachieved. Asacriterionofgoodalignment,amaximumpowerjustinfronto fbercoupler shouldbeabove400mW.Underidealconditionsamaximumofnear ly500mWcanbe achieved.Usingwellprepared,undamagedbercableandSMAty peconnectors,more than70%ofpowergoingintothebershouldbedeliveredtothe beamlineprovidedthe ecientcouplinghasachieved. C.7ANSILaserClassications Lasersafetystandardsarederivedfromgovernmentmandatedre gulationsand voluntarystandards.Thestandardrequiresthatlasersbeprope rlyclassiedand labelledbythemanufacturer.Thus,formostlasers,measurement sorcalculations todeterminethehazardclassicationarenotnecessary.Inaddi tion,thestandard establishescertainengineeringrequirementsforeachclassa ndrequireswarninglabels thatstatemaximumoutputpower.Extensiverecommendationsf orthesafeuseoflasers havebeendevelopedbytheAmericanNationalStandardsInstitu te(ANSIZ136.1-2000). Theappropriateclassisdeterminedfromthewavelength,pow eroutput,andduration ofpulse(ifpulsed).Classicationisbasedonthemaximumaccessib leoutputpower. Therearefourlaserclasses,withClass1representingtheleasthaz ardous.Alllasers, exceptClass1,mustbelabelledwiththeappropriatehazardcl assication. Class1 Class1laserdevicescannotproducedamagingradiationlevel stotheeyeevenif viewedaccidentally.Prolongedstaringatthelaserbeamhowe ver,shouldbeavoidedas

PAGE 222

207 amatterofgoodIndustrialHygienepractice.Thisclasshasapo weroutputlessthan 0.4 Wforcontinuouswave(CW)lasersoperatinginthevisiblerang e.Acompletely enclosedlaserisclassiedasaClass1laserifemissionsfromtheenc losurecannot exceedlimitsforaClass1laser.Iftheenclosureisremoved, e.g. ,duringrepair,control measuresfortheclassoflasercontainedwithinarerequired.Class2 Class2lasersareincapableofcausingeyeinjurythedurationo ftheblink,or aversionresponse(0.25sec).Althoughtheselaserscannotcauseeye injuryunder normalcircumstances,theycanproduceinjuryifvieweddirec tlyforextendedperiods oftime.Class2lasersonlyoperateinthevisiblerange(400-70 0nm)andhavepower outputsbetween0.4 Wand1mWforCWlasers.ThemajorityofClass2lasersare helium-neondevices.Class3a Class3alaserscannotdamagetheeyewithinthedurationofthe blinkoraversion response.However,injuryispossibleifthebeamisviewedthroug hbinocularsorsimilar opticaldevices,orbystaringatthedirectbeam.Poweroutput sforCWlasersoperating inthevisiblerangearebetween1-5mW.Class3b Class3blaserscanproduceaccidentalinjuriestotheeyefrom viewingthedirect beamoraspecularlyrerectedbeam.Class3blaserpoweroutputs arebetween5-500 mWforCWlasers.ExceptforhigherpowerClass3blasers,thisclass willnotproduce ahazardousdiusererectionunlessviewedthroughanoptical instrument. Class4 Class4lasersarethemosthazardouslasers.Exposuretotheprimar ybeam,specularrerections,anddiusererectionsarepotentiallytothe skinandeyes.Inaddition, class4laserscanigniterammabletargets,createhazardousai rbornecontaminantsand usuallycontainapotentiallylethalhighvoltagesupply.The poweroutputforCWlasers

PAGE 223

208 operatinginallwavelengthrangesisgreaterthan500mW.All pulsedlasersoperating intheocularfocusregion(400nmto1,400nm)shouldbeconside redClass4. UnknownClass Laserclassicationcanbedeterminedbymeasuringtheoutputir radianceor radiantexposureusinginstrumentstraceabletotheNationalBu reauofStandards. Thesemeasurementsshouldonlybeperformedbyqualiedpersonn el.Thelaserclass canalsobedeterminedfromcalculations.ForCWlasers,thewave lengthandaverage poweroutputmustbeknown.Classicationofpulsedlasersrequir esthefollowing information:wavelength,totalenergyperpulse(orpeakpow er),pulseduration,pulse repetitionfrequency(PRF),andemergentbeamradiantexpo sure.Inadditiontothe aboveinformationlasersourceradianceandmaximumviewinga nglesubtendedbythe lasermustbeknownforextended-sourcelasers,suchasinjectionl aserdiodes.Detailed informationonclassifyinglasersmaybefoundintheANSIZ136.12000.

PAGE 224

APPENDIXD USEFULINFORMATION Thisappendixcontainstablesofvarioususefulinformation D.1FrequencyRanges Thissectioncontainsfrequencyrangesofinfraredspectralr egions,conventional lightsources,beam-splitters,detectors,andopticalwindowsa ndlters. TableD{1:Infraredspectralregions. Region Wavelength( m) Wavenumber(cm 1 ) Frequency(Hz) Near-IR 0.78-2.5 4000-12800 1.2 10 14 -3.8 10 14 Mid-IR 2.5-50 200-4000 6.0 10 12 -1.2 10 14 Far-IR 50-1000 10-200 3.0 10 11 -6.0 10 12 TableD{2:Frequencyrangesofconventionallightsources. Source Range(cm 1 ) PrimaryApplication Mercury-arclamp 10-700 FarIR SiCglobar 100-6000 MidIR Tungstenlamp 4000-40000 VIS TableD{3:Frequencyrangesofdetectors.PEinthewindowcol lumstandsfor polyethylene. Detector Window Temperature(K) Range(cm 1 ) PrimaryApplication Si:BBolometer PE 4.2(LHe) 10-600 FarIR DTGS PE 300(ambient) 10-600 FarIR DTGS KBr 300(ambient) 400-7000 MidIR Si:B KRS-5 4.2(LHe) 350-4000 MidIR Ge:Cu KRS-5 4.2(LHe) 350-4000 MidIR MCT 77(LN 2 ) MidIR InSb Sapphire 77(LN 2 ) 1850-15000 NearIR SiPhotodiode 300(ambient) 9000-28000 VISandUV GaPPhotodiode 300(ambient) 18000-33000 VISandUV 209

PAGE 225

210 TableD{4:Spectralrangesofbeam-splittermaterials. Material Type Range(cm 1 ) PrimaryApplication MetalMesh 20(lines/mm) 40 $ 750 FarIR 8 40 $ 750 FarIR Mylar 3.5( m) 125 $ 750 FarIR 6.0 80 $ 450 FarIR 12.0 40 $ 220 FarIR 23.0 20 $ 110 FarIR 50.0 15 $ 55 FarIR 125.0 5 $ 22 FarIR Gecoated 30 $ 680 FarIR KBr Gecoated 370 $ 7800 MidIR Gecoated(widerange) 400 $ 10000 MidIR CsI Gecoated 200 $ 5000 MidIR ZnSe 500 $ 5000 MidIR Quartz 9000 $ 25000 VIS TableD{5:Transmissionrangeofopticalwindowandltermater ials. Material Transmissionrange(cm 1 ) KBr 400|40,000 NaCl 625|40,000 SiO 2 (Quartz) 0|250 2700|65,000 Sapphire 0|350(below50K) 2000|65,000 Diamond 10|45,000 ZnSe 720|17,000 ZnS 830|17,000 CsI 200|40,000 GaAs 600|5,500 AgCl 360|10,000 AgBr 290|22,000 Polyethylene < 600 CaF 2 1,200|66,000 BaF 2 740|67,000 MgF 2 1,250|87,000 LiF 1,700|95,000 CdTe 400|20,000 KRS-5(Thallium-Bromide-Iodide) 250|20,000 Fluorogold < 60(dependsonthickness) Blackpolyethylene < 600

PAGE 226

211 D.2EnergyandPressureUnitsConversion Thissectionprovidesrelationsbetweenvariousenergyandp ressureunits. TableD{6:Relationsbetweenenergyunits. 1meV=8 : 0658cm 1 =242GHz=11 : 6K 1cm 1 =0 : 124meV =30GHz=1 : 439K 1THz=33 : 33cm 1 =4 : 133meV =48K 1K=0 : 695cm 1 =0 : 086meV TableD{7:Relationsbetweenpressureunits. 1atmosphere(atm) 101 ; 325Pa 1 : 01325bar =760torr=14 : 7psi 1013 : 25millibar 1bar 100 ; 000Pa =0 : 987atm 1millibar 100Pa 1hPa =0 : 75torr 1torr(mmHg,0 C)=133 : 32Pa =1 : 32 10 3 atm 1millitorr(micron)=1 : 32 10 6 atm 1psi(lbf/in. 2 )=6894 : 8Pa D.3Gas-phaseContamination Waterandcarbondioxidearethetwomostcommonlydetectedco ntaminantpeaks inaspectrumtakeninair.Evacuationofthesamplecompartmen tshouldsignicantly reducetheabsorptionduetothesemolecules.Purgingthesample compartmentwith drynitrogencanalsoreducethelevelsofthesecontaminantsb utnotaseectivelyas

PAGE 227

212 evacuation.Table D{8 showsthepeaklocationsofwatervaporandcarbondioxideabsorptions. TableD{8:AbsorptionpeaksforH 2 OandCO 2 vapor. Contaminant PeakLocation(cm 1 ) Notes WaterVapor 3480-3960 Seriesofsharppeaks (H 2 O) 1300-1950 Seriesofsharppeaks < 500 Seriesofsharppeaks CarbonDioxide 2280-2390 Usuallyunresolveddoubletwithcentralmaximum (CO 2 ) (transmission)at2348cm 1 665-672 Sharpminimumat667cm 1 (transmission)

PAGE 228

REFERENCES [1]R.P.S.M.Lobo,J.D.LaVeigne,D.H.Reitze,D.B.Tanner,a ndG.L.Carr. Rev.Sci.Inst. ,73:1,2002. 1.1 5.2.1 5.2.2 6.5.6 [2]G.L.Carr,R.P.S.M.Lobo,J.LaVeigne,D.H.Reitze,andD. B.Tanner. Phys. Rev.Lett. ,85:3001,2000. 1.1 8.4.1 [3]E.Abrahams,P.W.Anderson,D.C.Licciardello,andT.V.Ramak rishnan. Phys. Rev.Lett. ,42:673,1979. 1.2 [4]B.L.Altshuler,A.G.Aronov,andP.A.Lee. Phys.Rev.Lett. ,44:1288,1980. 1.2 7.1 7.2.2 [5]R.C.DynesandP.A.Lee. Science ,223:355,1984. 1.2 [6]J.M.GraybealandM.R.Beasley. Phys.Rev.B ,29:4167,1984. 1.2 7.1 7.2.2 7.3.1 [7]J.M.Graybeal. Physica ,135B:113,1985. 1.2 7.1 7.2.2 [8]J.M.Graybeal. CompetitionBetweenSuperconductivityandLocalizationi n UltrathinAmorphousMolybdenum-GermaniumFilms .PhDdissertation,Stanford University,Stanford,CA,1985. 1.2 7.1 7.2.2 7.3.1 [9]JohnDavidJackson. ClassicalElectrodynamics .JohnWiley&Sons,Inc.,New York,NY,2ndedition,1975. 2.3 6 5.1.1 5.1.2 [10]EugeneHecht. Optics .Addison-Wesley,Reading,MA,3rdedition,1998. 2.3 4 5 [11]MilesV.KleinandThomasE.Furtak. Optics .JohnWiley&Sons,Inc.,New York,NY,2ndedition,1986. 2.3 [12]FrederickWooten. OpticalPropertiesofSolids .AcademicPress,NewYork,NY, 1972. 2.3 [13]J.N.Hodgson. OpticalAbsorptionandDispersioninSolids .ChampmanandHall Ltd.,London,1970. 2.3 [14]MarkFox. OpticalPropertiesofSolids .OxfordUniversityPressInc.,NewYork, NY,2001. 2.3 [15]O.S.Heavens. OpticalPropertiesofThinFilms .DoverPublications,Inc.,New York,NY,1991. 2.3 2.4.4 [16]FengGao. TemperatureDependenceofInfraredandOpticalPropertieso fHigh TemperatureDuperconductors .PhDdissertation,UniversityofFlorida,Gainesville, FL,1999. 2.3 213

PAGE 229

214 [17]R.M.A.AzzamandN.M.Bashra,editors. EllipsometryandPolarizedLight North-HollandPub.Co.,Amsterdam,1977. 8 [18]M.Tinkham. Phys.Rev. ,104:845,1956. 2.4.4 7.2.1 [19]S.S.MitraandS.Nudelman,editors. FarinfraredPropertiesofSolids .Plenum Press,NewYork,NY,1970. 2.4.4 [20]A.Vasicek,editor. OpticsofThinFilms .North-HollandPub.Co.,Amsterdam, 1960. 2.4.4 [21]JosephD.LaVeigne. Time-resolvedInfraredSpectroscopyattheNSLSU12IR Beamline .PhDdissertation,UniversityofFlorida,Gainesville,FL,1999 3.2.1 5.1.4 5.1.7 5.2.2 11 C.6 [22]PeterR.GrithsandJamesA.deHaseth,editors. FourierTransformInfrared Spectrometry .JohnWiley&Sons,Inc.,NewYork,NY,1986. 3.2.1 3.2.2 3.3 [23]HansKuzmany,editor. Solid-StateSpectroscopy,AnIntroduction .Springer-Verlag, Berlin,Germany,1998. 3.2.1 [24]H.HappandL.Genzel. InfraredPhys. ,1:39,1961. 3.2.2 [25]R.H.NortonandR.Beer. J.Opt.Soc.Am. ,66:259,1976. 3.2.2 [26]L.Mertz. IfraredPhys. ,7:17,1967. 3.2.4 [27]C.D.PorterandD.B.Tanner. Int.J.InfraredandMillimeterWaves ,4:273, 1983. 3.2.4 [28]D.B.TannerandR.P.McCall. Appl.Opt. ,23:2363,1984. 3.2.4 [29]P.L.Richards. J.Opt.Soc.Am. ,54:1474,1964. 3.3 [30]D.H.MartinandE.Puplett. IfraredPhys. ,10:105,1969. 3.3 [31]P.A.R.Ade,A.E.Costley,C.T.Cunningham,C.L.Mok,G.F.Nei ll,andT.J. Parker. IfraredPhys. ,19:599,1979. 3.3 [32]V.M.DaCostaandL.B.Coleman. AppliedSpectroscopy ,44:1301,1990. 9 [33]V.M.DaCostaandL.B.Coleman. Rev.Sci.Inst. ,61:2113,1990. 9 [34]H.K.Onnes. Akad.vanWatenschappen(Amsterdam) ,14:113,818,1911. 4.1 [35]W.MeisnnerandR.Ochsenfeld. Naturwissenschaften ,21:787,1933. 4.1 [36]F.LondonandH.London. Z.Physik ,96:359,1935. 4.1 [37]V.L.GinzburgandL.D.Landau. SovietPhys.JETPUSSR ,20:1064,1950. 4.1 4.2.4 [38]J.Bardeen,L.N.Cooper,andJ.R.Schrieer. Phys.Rev. ,108:1175,1957. 4.1 4.2.5 7.1

PAGE 230

215 [39]J.G.BednorzandK.A.Muller. Z.Physik ,B64:189,1986. 4.1 [40]P.deGennes. SuperconductivityofMetalsandAlloys .Addison-Wesley,Redwood City,CA,1989. 4.1 4.2.4 4.2.4 4.2.4 [41]M.Tinkham. IntroductiontoSuperconductivity .KriegerPublishingCo.,Malabar, FL,1980. 4.1 [42]E.A.Lynton. Superconductivity .Methuen&Co.LTD.,London. 4.1 [43]G.Rickayzen. TheoryofSuperconductivity .IntersciencePublishers,NewYork, NY,1965. 4.1 [44]R.D.Parks,editor. Superconductivity .MarcelDekker,Inc.,NewYork,NY,1969. 4.1 4.2.4 9 4.2.5 4.2.6 [45]D.C.MattisandJ.Bardeen. Phys.Rev. ,111:412,1958. 4.1 7.1 7.2.1 9.2 10 [46]S.MaekawaandH.Fukuyama. J.Phys.Soc.Jpn. ,51:1380,1981. 4.1 7.1 7.2.2 10 [47]C.J.GorterandH.Casimir. Physica ,1:306,1934. 4 [48]A.B.Pippard. Proc.Roy.Soc.(London) ,A216:547,1953. 4.2.4 [49]D.Saint-James,G.Sarma,andE.J.Thomas. TypeIIsuperconductivity .PergamonPress,NewYork,NY,1969. 4.2.4 [50]L.N.Cooper. Phys.Rev. ,104:1189,1956. 4.2.5 [51]H.Frohlich. Phys.Rev. ,79:845,1950. 7 [52]N.W.AshcroftandN.D.Mermin. SolidStatePhysics .SaundersCollege Publishing,Philadelphia,PA,1976. 4.2.5 [53]G.M.Eliashberg. SovietPhys.JETP ,11:696,1960. 4.2.6 [54]G.M.Eliashberg. SovietPhys.JETP ,12:1000,1961. 4.2.6 [55]J.P.Carbotte. Rev.Mod.Phys. ,62:1027,1990. 4.2.6 4.2.6 [56]P.MorelandP.W.Anderson. Phys.Rev. ,125:1263,1962. 4.2.6 [57]W.L.McMillan. Phys.Rev. ,167:331,1968. 4.2.6 [58]P.B.AllenandR.C.Dynes. Phys.Rev.B ,12:905,1975. 4.2.6 4.2.6 [59]GiorgioMargaritondo. Introductiontosynchrotronradiation .OxfordUniversity PressInc.,NewYork,NY,1988. 5.1.1 5.1.2 5.1.5 [60]HermanWinickandS.Doniach,editors. Synchrotronradiationresearch .Plenum Press,NewYork,NY,1980. 5.1.1 5.1.2 [61]J.Schwinger. Phys.Rev. ,75:1912,1949. 5.1.2 5.1.3

PAGE 231

216 [62]W.D.DuncanandG.P.Williams. AppliedOptics ,22:2914,1983. 5.1.6 [63]LisaM.MillerandPatricePages,editors. NationalSynchrotronLightSource ActivityReport2002 .BrookhavenNationalLaboratory,Upton,NY,2002. 6.2.1 A [64]R.P.S.M.Lobo,J.D.LaVeigne,D.H.Reitze,D.B.Tanner, andG.L.Carr. Rev.Sci.Inst. ,70:2899,1999. 6.2.3 [65]R.S.Sussmann,C.S.J.Pickles,J.R.Brandon,C.J.H.Wort,S .E.Coe, A.Wasenczuk,C.N.Dodge,A.C.Beale,A.J.Krehan,P.Dore,A.Nucara ,and P.Calvani. IlNuovoCimento ,20:503,1998. 2 [66]W.Kaiser,editor. Ultrashortlaserpulses:Generationandapplication .SpringerVerlag,Berlin,Germany,2ndedition,1993. 6.4.2 [67]JeHecht. TheLaserGuidebook .McGraw-Hill,Inc.,NewYork,NY,2ndedition, 1992. 6.4.2 [68]JamesD.IngleandStanleyR.Crouch. SpectrochemicalAnalysis .PrenticeHall, UpperSaddleRiver,NJ,1988. 6.5.4 [69]GerdKeiser. Opticalbercommunications .McGraw-Hill,Inc.,NewYork,NY, 1983. 6.5.6 [70]R.E.Glover,IIIandM.Tinkham. Phys.Rev. ,104:844,1956. 7.1 7.2.1 [71]R.E.Glover,IIIandM.Tinkham. Phys.Rev. ,108:243,1957. 7.1 7.2.1 7.4 [72]R.A.FerrellandR.E.Glover,III. Phys.Rev. ,109:1398,1958. 7.1 7.2.1 [73]M.TinkhamandR.A.Ferrell. Phys.Rev.Lett. ,2:331,1959. 7.1 7.2.1 [74]P.W.Anderson,E.Abrahams,andT.V.Ramakrishnan. Phys.Rev.Lett. ,43:718, 1979. 7.1 7.2.2 [75]P.W.Anderson,K.A.Muttalib,andT.V.Ramakrishnan. Phys.Rev.B ,28:117, 1983. 7.1 7.2.2 [76]A.KapitulnikandG.Kotliar. Phys.Rev.Lett. ,54:473,1985. 7.1 7.2.2 [77]H.Ebisawa,H.Fukuyama,andS.Maekawa. J.Phys.Soc.Jpn. ,54:2257,1985. 7.1 7.2.2 [78]D.G.NaugleandR.E.Glover,III. Phys.Lett. ,28a:611,1969. 7.1 7.2.2 [79]D.G.Naugle,R.E.Glover,III,andW.Moormann. Physica ,55:250,1971. 7.1 7.2.2 [80]M.Strongin,R.S.Thompson,O.F.Kammerer,andJ.F.Crow Phys.Rev.B 1:1078,1970. 7.1 7.2.2 [81]H.Ray,R.B.Laibowitz,P.Chaudhari,andS.Maekawa. Phys.Rev.B ,28:6607, 1983. 7.1 7.2.2

PAGE 232

217 [82]S.Okuma,F.Komori,Y.Ootuka,andS.Kobayashi. J.Phys.Soc.Jpn. ,52:2639, 1983. 7.1 7.2.2 [83]D.B.Haviland,Y.Liu,andA.M.Goldman. Phys.Rev.Lett. ,62:2180,1989. 7.1 7.2.2 [84]D.M.Ginsberg,P.L.Richards,andM.Tinkham. Phys.Rev.Lett. ,3:337,1959. 1 [85]S.B.Nam. Phys.Rev. ,156:470,1967. 1 [86]S.B.Nam. Phys.Rev. ,156:487,1967. 1 [87]D.M.Ginsberg,R.E.Harris,andR.C.Dynes. Phys.Rev.B ,14:990,1976. 1 [88]D.M.GinsbergandM.Tinkham. Phys.Rev. ,118:990,1960. 7.2.1 [89]L.H.PalmerandM.Tinkham. Phys.Rev. ,165:588,1968. 7.2.1 7.4 [90]P.W.Anderson. J.Phys.Chem.Solids ,11:26,1959. 7.2.2 [91]L.P.Gorkov. Sov.Phys.-JETP ,10:998,1960. 7.2.2 [92]S.B.Kaplan,C.C.Chi,D.N.Langenberg,J.J.Chang,S.Ja farey,andD.J. Scalapino. Phys.Rev.B ,14:4854,1976. 8.1 8.2.1 8.2.2 8.4.1 8{11 10 [93]A.RothwarfandB.N.Taylor. Phys.Rev.Lett. ,19:27,1967. 8.1 8.2.1 8.3.3 10 [94]C.S.OwenandD.J.Scalapino. Phys.Rev.Lett. ,28:1559,1972. 8.1 8.2.1 8.3.2 10 [95]L.R.Testardi. Phys.Rev.B ,4:2189,1971. 8.2.1 [96]W.H.ParkerandW.D.Williams. Phys.Rev.Lett. ,29:924,1972. 8.2.1 8.3.2 8.3.3 [97]G.A.Sai-Halasz,C.C.Chi,A.Denenstein,andD.N.Langenberg Phys.Rev. Lett. ,33:215,1974. 8.2.1 [98]K.E.Gray. J.Phys.F ,1:290,1971. 2 8.2.1 [99]E.Burstein,D.N.Langenberg,andB.N.Taylor. Phys.Rev.Lett. ,6:92,1961. 4 [100]J.R.SchrieerandD.M.Ginsberg. Phys.Rev.Lett. ,8:207,1962. 8.2.1 4 [101]A.RothwarfandM.Cohen. Phys.Rev. ,130:1401,1963. 8.2.1 [102]G.LucasandM.J.Stephen. Phys.Rev. ,154:349,1966. 8.2.1 [103]W.A.Little. Can.J.Phys. ,37:334,1959. 8.2.1 [104]I.SchullerandK.E.Gray. Phys.Rev.B ,12:2629,1975. 8.2.1 [105]CharlesKittel. IntroductiontoSolidStatePhysics .JohnWiley&Sons,Inc.,New York,NY,7thedition,1996. 8.2.2

PAGE 233

218 [106]F.Jaworski,W.H.Parker,andS.B.Kaplan. Phys.Rev.B ,14:4209,1976. 8.3 [107]P.Hu,R.C.Dynes,andV.Narayanamurti. Phys.Rev.B ,10:2786,1974. 8.3 [108]M.Johnson. Phys.Rev.Lett. ,67:374,1991. 8.3 8.4.1 [109]M.Gurvitch,A.K.Ghosh,B.L.Gyory,H.Lutz,O.F.Kammer er,J.S.Rosner, andM.Strongin. Phys.Rev.Lett. ,41:1616,1978. 8.3.3 [110]N.KatzenellenbogenandD.Grischkowsky. Appl.Phys.Lett. ,58:222,1991. 10

PAGE 234

BIOGRAPHICALSKETCH HidenoriTashirowasborninKudamatsuCityofYamaguchi-prefe cture,Japan. Hidenoriwasanexceedinglyathleticchild,anddedicatedmo stofhistimeplaying soccer,baseball,andgolf.HeattendedtheKudamatsuHighSchool inthesametown hewasraised.In1996,hegraduatedwithaB.S.inphysicsfromt heStateUniversity ofNewYorkatBualo.In1997hestartedattendingtheUniversity ofFlorida,and receivedhisM.S.inphysicsin2001.Inthesameyearhebeganwo rkingforProfessor DavidTanner,andin2002,hemovedtoUpton,NewYork,toworkfu ll-timeforhis dissertationprojectattheNationalSynchrotronLightSource ofBrookhavenNational Laboratory.Aftertwoyears,hecamebacktoFloridaandcomple tedhisPh.D.in2004. Hemethisextremelykindwife,Yasuko,whenhecametotheUnited Statesfortherst time,andtwoboys,MitsuruandHikaru,werebornsincethen. 219


Permanent Link: http://ufdc.ufl.edu/UFE0008001/00001

Material Information

Title: Time-resolved infrared studies of superconducting molybdenum-germanium thin films
Physical Description: Mixed Material
Language: English
Creator: Tashiro, Hidenori ( Dissertant )
Tanner, David B. ( Thesis advisor )
Hebard, Arthur F. ( Reviewer )
Cheng, Hai-Ping ( Reviewer )
Hagen, Stephen J. ( Reviewer )
Pearton, Stephen J. ( Reviewer )
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2004
Copyright Date: 2004

Subjects

Subjects / Keywords: Physics thesis, Ph. D.
Dissertations, Academic -- UF -- Physics

Notes

Abstract: Superconducting amorphous molybdenum-germanium (alpha-MoGe) thin films show progressively reduced transition temperatures T sub c as the thickness is reduced. This suppression has been explained in terms of electron localization effects and reduced screening. This dissertation presents the results of both linear spectroscopy and time-resolved studies of a set of alpha-MoGe films to understand more fully this weakened superconducting state. The observed optical conductivity shows the presence of an energy gap. The effects of reduced thickness in these films are to depress T sub c and the superfluid density, while maintaining the normal-state resistivity. All of the results from our linear optical measurements appear to be consistent trivially with those expected for weak to intermediate coupling dirty limit superconductors. Our time-resolved study reveals the overall relaxation of the samples at a time scale on the order of 100 ps. The temperature dependence of the relaxation time seems to be consistent with the prediction based on weak-coupling BCS theory for all films we measured without changing any material parameters for different thickness. The application of magnetic field did not change the relaxation times, which was unexpected.
Subject: amorphous, BCS, conductivity, disorder, dynamics, films, infrared, lifetime, MoGe, NSLS, optical, pump, quasiparticles, recombiantion, relaxation, spectroscopy, superconductivity, superconductors, synchrotron, time
General Note: Title from title page of source document.
General Note: Document formatted into pages; contains 234 pages.
General Note: Includes vita.
Thesis: Thesis (Ph. D.)--University of Florida, 2004.
Bibliography: Includes bibliographical references.
General Note: Text (Electronic thesis) in PDF format.

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0008001:00001

Permanent Link: http://ufdc.ufl.edu/UFE0008001/00001

Material Information

Title: Time-resolved infrared studies of superconducting molybdenum-germanium thin films
Physical Description: Mixed Material
Language: English
Creator: Tashiro, Hidenori ( Dissertant )
Tanner, David B. ( Thesis advisor )
Hebard, Arthur F. ( Reviewer )
Cheng, Hai-Ping ( Reviewer )
Hagen, Stephen J. ( Reviewer )
Pearton, Stephen J. ( Reviewer )
Publisher: University of Florida
Place of Publication: Gainesville, Fla.
Publication Date: 2004
Copyright Date: 2004

Subjects

Subjects / Keywords: Physics thesis, Ph. D.
Dissertations, Academic -- UF -- Physics

Notes

Abstract: Superconducting amorphous molybdenum-germanium (alpha-MoGe) thin films show progressively reduced transition temperatures T sub c as the thickness is reduced. This suppression has been explained in terms of electron localization effects and reduced screening. This dissertation presents the results of both linear spectroscopy and time-resolved studies of a set of alpha-MoGe films to understand more fully this weakened superconducting state. The observed optical conductivity shows the presence of an energy gap. The effects of reduced thickness in these films are to depress T sub c and the superfluid density, while maintaining the normal-state resistivity. All of the results from our linear optical measurements appear to be consistent trivially with those expected for weak to intermediate coupling dirty limit superconductors. Our time-resolved study reveals the overall relaxation of the samples at a time scale on the order of 100 ps. The temperature dependence of the relaxation time seems to be consistent with the prediction based on weak-coupling BCS theory for all films we measured without changing any material parameters for different thickness. The application of magnetic field did not change the relaxation times, which was unexpected.
Subject: amorphous, BCS, conductivity, disorder, dynamics, films, infrared, lifetime, MoGe, NSLS, optical, pump, quasiparticles, recombiantion, relaxation, spectroscopy, superconductivity, superconductors, synchrotron, time
General Note: Title from title page of source document.
General Note: Document formatted into pages; contains 234 pages.
General Note: Includes vita.
Thesis: Thesis (Ph. D.)--University of Florida, 2004.
Bibliography: Includes bibliographical references.
General Note: Text (Electronic thesis) in PDF format.

Record Information

Source Institution: University of Florida
Holding Location: University of Florida
Rights Management: All rights reserved by the source institution and holding location.
System ID: UFE0008001:00001


This item has the following downloads:


Full Text









TIME-RESOLVED INFRARED STUDIES OF SUPERCONDUCTING
MOLYBDENUM-GERMANIUM THIN FILMS
















By

HIDENORI TASHIRO


A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL
OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF
DOCTOR OF PHILOSOPHY

UNIVERSITY OF FLORIDA


2004

































Copyright 2004

by

Hidenori Tashiro



































To my mother, Kimiko Tashiro













ACKNOWLEDGMENTS

Over the past few years, I have received full of support, encouragement, and valu-

able advice from many people. Here, I would like to acknowledge some individuals who

helped me in various v--v-. I would like to express my foremost and sincere gratitude

to Professor David B. Tanner, my research advisor. My work could not possibly have

been completed without his guidance and support. He not only continuously encour-

aged me to keep going but also supplied me just the right amount of pressure to get

things done. The many things I have learned from him will be my treasure. I am truly

grateful to Professor ('!Ci -l"1 .1!. r J. Stanton for introducing me to Dr. Tanner. I would

like equally to thank my supervisory committee members, Arthur F. Hebard, Hai-Ping

('C!, i- Stephen J. Hagen, and Stephen J. Pearton, for their guidance and reading this

dissertation.

I would also like to express my appreciation to Professor David H. Reitze for his

occasional advice and his step-by-step instruction for using and maintaining the laser

system used in my work, Johon M. Graybeal for supplying me a set of samples and

information about them, and ('! i l. Porter for providing me with algorithms which

helped the data analysis.

I would like to express my special thanks to G. Lawrence Carr, who was my daily

advisor at the National Synchrotron Light Source (NSLS). His guidance, input, and

patience made my project to go smoothly. I equally thank Ricardo Lobo, who is the

author of valuable programs used for data acquisition and analysis, for helping me to

start my project during his visit at the NSLS. Additional thanks go to Jiufeng J. Tu,

('!Ci -I 1.!i. r Homes, Laszlo Mihaly, Diyar Talbayev, Gregory D. Smith, Randy J. Smith,

and all of who helped me at the Brookhaven National Laboratory (BNL).

I am dearly grateful to all of my past and present colleagues in Dr. Tanner's group

for their cooperation, conversations, and mostly friendship. I am also thankful to Kevin








T. McCarthy, Stephen Arnason, Zhihong C'!li n Suzette A. Pabit, Amol Patel, Susumu

Takahashi, and Naoki Matsunaga.

I would also like to acknowledge the help of the members of the machine shop,

electronic shop, and cryogenics team of the University of Florida Physics Department,

as well as the members of technical staff at the NSLS. Acknowledgement also goes to

the Physics Department staff for their assistance, especially Jill Kirkpatrick and Darlene

Latimer for taking care of the bureaucratic details while I was at the BNL.

Finally, I would like to address my exceptional thanks to my parents, Hiroyuki and

Kimiko Tashiro, for their support over my entire life. Finally, my deepest appreciation is

due to my wife and two sons, Yasuko, Mitsuru, and Hikaru, for their constant support

and patience. They made my life so much fun.













TABLE OF CONTENTS
page

ACKNOWLEDGMENTS ..................... .......... iv

LIST OF TABLES .................................... x

LIST OF FIGURES ...................... ........... xii

ABSTRACT ....................................... xv

CHAPTER

1 INTRODUCTION ................................. 1

1.1 Introductory Remarks ........................... 1
1.2 M otivation . . . . . . . . 2
1.3 Organization ................... ............. 3

2 OPTICAL PROPERTIES ............................. 4

2.1 Introduction . . . . . . . . 4
2.2 Optical Phenomena ............................. 4
2.3 Interaction of Light with Matter .................. 7
2.4 Experimental Determination of Optical Constants . . ... 15
2.4.1 Reflection and Transmission at a Plane Interface . ... 15
2.4.2 Kramers-Kr6nig Dispersion Relations . . . 16
2.4.3 Reflection and Transmission at Two Parallel Interfaces ...... .18
2.4.4 Optics in Thin Film on a Substrate . . ..... 20
2.4.5 Photoinduced Absorption ................ .. 23
2.5 Microscopic Models ............... ......... .. 23
2.5.1 Lorentz M odel ....... . . . 24
2.5.2 Free Carrier Response and Drude Model . . 27
2.5.3 Drude-Lorentz Model ................ .. .. 31
2.5.4 Sum Rules ............... .......... .. 31

3 FOURIER SPECTROSCOPY ............... ....... .. 32

3.1 Introduction ............... ............ .. 32
3.2 Fourier Transform Interferometry ............... .. .. .. 33
3.2.1 General Principles .................. .. .... .. .. 33
3.2.2 Finite Retardation and Apodization . . 36
3.2.3 Sampling .............. . . ... 38
3.2.4 Phase Error and Correction ................... ... 41
3.2.5 Step-Scan and Rapid-Scan Interferometers . . ... 43
3.3 Polarization Modulation .................. ..... .. 45








4 SUPERCONDUCTIVITY .............................

4.1 Introduction . . . . . . . . .
4.2 Fundamentals of Superconductivity .. ................
4.2.1 Fundamental Phenomena .. ..................
4.2.2 Thermodynamic Properties .. .................
4.2.3 Types of Superconductor .. ..................
4.2.4 Length Scales . . . . . . .
4.2.5 B C S Theory . . . . . . . .
4.2.6 Eliashberg Formalism .. ....................

5 SYNCHROTRON RADIATION AND PUMP-PROBE TECHNIQUE .....

5.1 Synchrotron Radiation .. ......................
5.1.1 Introduction . . . . . . . .
5.1.2 Radiated Power from a Bending Magnet .. ............
5.1.3 Angular Collimation and Polarization .. ............
5.1.4 RF Cavity and Pulsed Nature .. ...............
5.1.5 Beam Lifetim e . . . . . . .
5.1.6 Infrared Synchrotron Radiation .. ..............
5.1.7 Source Comparison .. ....................
5.2 Principle of Pump-Probe Studies .. .................
5.2.1 Laser-Synchrotron Pump-Probe Measurement .. .........
5.2.2 Interferometry Using Pulsed Source .. .............
5.2.3 Advantage of Laser-Synchrotron Technique .. ..........

6 EX PERIM ENT . . . . . . . . .


6.1 Introduction . . . . .
6.2 National Synchrotron Light Source .. .....
6.2.1 G general . . . . .
6.2.2 Vacuum Ultraviolet Ring .. .......
6.2.3 Beamlines U12IR and U10A .......
6.3 Spectrometers .. ................
6.3.1 Bruker IFS 66v/S .. ...........
6.3.2 Bruker IFS 125 HR .. ..........
6.3.3 Sciencetech SPS-200 .. ..........
6.4 Pump Laser System .. .............
6.4.1 System Overview .. ..........
6.4.2 Mode-locked, Solid-State Ti:Sapphire Las'
6.4.3 Optics and Light Distribution ......
6.4.4 Laser-Synchrotron Synchronization .
6.5 Other Experimental Components .. ......
6.5.1 Oxford Optistat Bath Cryostat ......
6.5.2 Ox-Box Custom-made Sample C('i ihler .


6.5.3
6.5.4
6.5.5
6.5.6


Oxford Instruments Vertical-bore Supercoi
D etectors . . . . .
Ratio Box . . . . .
Fiber Optic Cable and Pulse Delivery .


r . . .






iducting Magnet


e








6.6 Experimental Techniques and Setups .................. 129
6.6.1 Photoinduced Measurements ............. .. 130
6.6.2 Laser Insertion ............. . . ...... 136

7 OPTICAL CONDUCTIVITY OF c-MoGe THIN FILMS . . .... 140

7.1 Introduction ................... . . ..... 140
7.2 Background ................ ............. ..141
7.2.1 Infrared Properties of Superconductors . . ..... 141
7.2.2 Effects of Disorder upon 2D Superconductivity . .... 145
7.2.3 2D Model Systems ............... .... .. 147
7.3 Experimental Details .................. ....... 148
7.3.1 Samples .................. . . ..... 148
7.3.2 M easurements .................. ....... 151
7.4 Analysis ............... ............. ..151
7.5 Discussion ................... . . ... 154
7.6 Conclusion . . . . . . . .... 156

8 TIME-RESOLVED STUDY OF c-MoGe THIN FILMS . . ... 159

8.1 Introduction ................. . . 159
8.2 Background .................. ............. .. 160
8.2.1 Nonequilibrium Superconductivity . . 160
8.2.2 Temperature Dependence of Lifetimes . . .... 165
8.3 Experimental Details ......... . . . ..... 169
8.3.1 Time-resolved Measurements: Quasiparticle Decay . ... 171
8.3.2 Photoinduced Gap Shift Measurements . . 174
8.3.3 Fluence Dependence ................. .... 176
8.3.4 Spectrally Averaged Far Infrared Transmission . .... 178
8.4 Analysis and Discussion ............... .... .. 179
8.4.1 Relaxation Times .................. .. ..... 179
8.4.2 Photoinduced Gap Shift . ........... . 185
8.5 Conclusion .................. . . 187

9 MAGNETO-OPTICAL STUDY OF c-MoGe THIN FILMS . .... 189

9.1 Introduction ............... . . . ..... 189
9.2 Transmittance Ratio in Magnetic Fields ..... . . 190
9.3 Relaxation Times in Magnetic Fields .................. .. 191

10 SUMMARY AND CONCLUSION .................. ..... 192

APPENDIX

A VUV STORAGE RING PARAMETERS ............... .. 197

B INFRARED BEAMLINES .................. .......... 199

B.1 Infrared Programs at NSLS VUV ring .................. 199
B.2 Hight Resolution Far-infrared Spectra at U12IR . . 200








C LASER SAFETY AND OPERATING PROCEDURES ............ 201

C.1 Hazardous Beam Control .......... ............... 201
C.2 Personal Protective Equipment ............ ... . 201
C.2.1 Eye Protection .................. ......... .. 201
C.2.2 Skin Protection .................. ........ .. 202
C.3 Laser Safety Training .................. ......... .. 202
C.4 Alignment .................. .............. 202
C.4.1 Gross Alignment .................. ...... .. .. 202
C.4.2 Fine Alignment .................. ...... .. .. 202
C.4.3 At Beamline Endstation. ................. .. 203
C.5 Daily Operation Procedure .................. ..... 203
C.6 Optimization of the Downstream Optics ................ .. 205
C.7 ANSI Laser Classifications .................. ..... 206

D USEFUL INFORMATION ........... ...... . . .. 209

D.1 Frequency Ranges .................. ......... .. .. 209
D.2 Energy and Pressure Units Conversion ................. .. 211
D.3 Gas-phase Contamination .... ............ ..... .. 211

REFERENCES ................... ..... .... ....... 213

BIOGRAPHICAL SKETCH ........... ....... . .... 219















LIST OF TABLES


Transition temperatures for several superconductors


6-1 Operation modes of the VUV ring .

6-2 Frequency ranges of various sources .

6-3 Frequency ranges of various beam-splitters

6-4 Frequency ranges of various detectors .

6-5 Specifications of the SPS-200 . ..

6-6 Specification of the Mira . ....

6-7 Properties of Oxford cryostat windows .

6-8 ('!CI i i:teristics of fiber optic cable .

7-1 c-MoGe film parameters . .

7-2 ,I / 4, fitting parameters . ...

7-3 Values of N, and A ....... ......

8-1 a-MoGe film used for timing experiment

8-2 Parameters for the timing experiment .

8-3 Fluence dependence data . ....

8-4 Teff and A at various temperatures .

8-5 Material parameters in TRo and TBo .

8-6 T R To, TBO, and -Ro/TBO . .

8-7 2Ao Bo/TRo ....... .........

8-8 Relaxation times and material parameters

8-9 Photoinduced gap shifts . ....

A-1 VUV storage ring parameters . .

A-2 VUV storage ring's arc source parameters


. ... . 88

. ... . 95

. . 96

. ... . 96

. . .. . 10 1

. . .. . 0 3

. ... . 14

. . ... . 2 7

. . .. . 4 9

. . .. . 5 2

. . . . . 5 5

.. . . 70

. ... . 17 1

. . .. . 7 7

. . ... . 8 0

. ... . 8 2

. . .. . 8 2

. . . . . 8 3

from Kaplan et al. . . 184

. . .. . 8 6

. . .. . 9 7

.. . . 98


A-3 VUV storage ring's insertion device parameters ......


Table

41


page

51








NSLS linac parameters . .....

NSLS booster parameters . ...

NSLS booster magnetic elements . .

Infrared beamlines of the VUV ring .

Infrared spectral regions . ....

Frequency ranges of conventional light sou

Frequency ranges of detectors . .

Spectral ranges of beam-splitters . .

Transmission range of optical window and

Relations between energy units . .

Relations between pressure units . .

Absorption peaks due to air . ..


rces .


filter mater


. .. . 98

. .. . 98

. .. . 98

. .. . 99

. .. . 209

. . 209

. .. . 209

. .. . 210

rials . ... 210

. .. . 211

. .. . 211

. .. . 212













LIST OF FIGURES
Figure page

2-1 Reflection and transmission at two parallel interfaces . ..... 18

2-2 Reflection and transmission with a thin film on a substrate . ... 21

3-1 Spectrometer classification .................. ........ .. 32

3-2 Schematic view of a Michelson interferometer . . . 34

3-3 Sine function convolved with a single spectral line ........... .37

3-4 Comparison of the Happ-Genzel and boxcar apodization . ... 39

3-5 Relation between spectrum replication and sampling rate . ... 40

3-6 Two sine waves drawn through the same sampling points . ... 41

3-7 Schematic view of a Martin-Puplett interferometer . . 46

3-8 Interferograms produced by a polarizing interferometer . .... 47

4-1 Density of states for a BCS superconductor ................. ..65

4-2 Variation of the gap with temperature in the BCS approximation . 66

5-1 Incoherent and coherent radiations .................. ..... 72

5-2 Angular distribution of the radiation .................. .. 72

5-3 Angular distribution of polarization components .............. ..74

5-4 RF and higher harmonic cavity voltages .................. 76

5-5 Natural opening angle of IRSR with the VUV ring parameters ...... ..78

5-6 Power comparison between blackbody and synchrotron . .... 79

5-7 Brightness comparison between blackbody and synchrotron . ... 80

5-8 Principle of the pump-probe experiment ............... .. 81

6-1 C('!i 1, of the pulse width during the detuned mode operation ...... ..89

6-2 Elevation view of U12IR beamline .................. ...... 91

6-3 Transmitted power with and without a light cone ............. ..92

6-4 Emission spectra of conventional internal sources .............. ..95








6-5 Bruker IFS 125HR . ........

6-6 Sciencetech SPS-200 . .

6-7 Optical schematic of the Mira laser head .

6-8 Optical Layout of the U6 laser system .

6-9 Effects of the pulse pickers . ....

6-10 Timing scheme . ..........

6-11 Synchronized laser and synchrotron pulses

6-12 Oxford Optistat bath cryostat . ..

6-13 Custom made sample compartment .

6-14 Off-axis paraboloidal reflector . ..

6-15 Oxford magnet setup . .......

6-16 Transfer function . .........

6-17 Classification of detectors . ....

6-18 Composite bolometer . ......

6-19 Structure and profile of typical optical fiber

6-20 Experimental setup for timing experiment

6-21 New dithering scheme . ......

6-22 Laser insertion setups with Optistat .

6-23 Laser insertion setup with Heli-tran .

6-24 Coupling of diode laser with optical fiber ca

7-1 Mattis-Bardeen relative conductivity and tr

7-2 R i vs. 1/d . . . . .

7-3 T,/To vs. R. . ...

7-4 Measured transmittance ratio . ..

7-5 Mattis-Bardeen fit to / . .

7-6 Measured reflectance ratio . ....

7-7 Mattis-Bardeen fit to J, / . .

7-8 Optical conductivities of a-MoGe . .

7-9 A, N vs. R ....... ........


. .. . 98

. .. . 99

.. . 102

... . 105

. .. . 0 7

. .. . 0 8

.. . . 10

. .. . 11 1

. ... . 17

. .. . 18

. .. . 19

. .. . 12 1

. .. . 2 2

. .. . 24

cable . . ..... 128

. . . 134

. .. . 135

. ... . 137

. ... . 138

ble . . .... 138

ansmittance . . 143

. . . . . 4 9

. . .. . 5 0

. . .. . 5 2

. . .. . 153

. . .. . 5 4

. . .. . 5 5

. . .. . 5 6

. . . . . 5 7








10 N vs. T . . . . .

1 Simplified relaxation processes . ............

2 Universal temperature dependence of lifetimes . ....

3 Differential, integrated signal vs. time . ........

4 Quasiparticle decay signal vs. time and model function .

5 Points on a decay curve for gap shift measurements . .

6 Fluence dependence of eff . .....

7 Spectrally averaged far-IR transmittion vs. T/T . ..

8 Quasiparticle decay signal for 16.5 nm film . .....

9 Teff vs. T/Tc ... . ...................

10 2AoBo/T o Vs. T ... ...........

11 TRO/TBO vs. b . . . . . . .

12 Photoinduced spectral changes . ............

1 Measured transmittance ratio in magnetic fields . ...

2 Quasiparticle decay signal in magnetic field for the 33 nm film

1 High resolution far-IR synchrotron spectra at U12IR . .


. . 158

. . 163

. . 168

. . 172

. . 73

. . 175

. . 176

. . 178

. . 180

. . 181

. . 183

. . 185

. . 186

. . 190

. . 191

. . 200













Abstract of Dissertation Presented to the Graduate School
of the University of Florida in Partial Fulfillment of the
Requirements for the Degree of Doctor of Philosophy

TIME-RESOLVED INFRARED STUDIES OF SUPERCONDUCTING
MOLYBDENUM-GERMANIUM THIN FILMS

By

Hidenori Tashiro

December 2004

C'!I i': David B. Tanner
Major Department: Physics

Superconducting amorphous molybdenum-germanium (a-MoGe) thin films show

progressively reduced transition temperatures T, as the thickness is reduced. This

suppression has been explained in terms of electron localization effects and reduced

screening. This dissertation presents the results of both linear spectroscopy and time-

resolved studies of a set of a-MoGe films to understand more fully this weakened

superconducting state. The observed optical conductivity shows the presence of an

energy gap. The effects of reduced thickness in these films are to depress T, and the

superfluid density, while maintaining the normal-state resistivity. All of the results from

our linear optical measurements appear to be consistent trivially with those expected

for weak to intermediate coupling dirty limit superconductors. Our time-resolved

study reveals the overall relaxation of the samples at a time scale on the order of 100

ps. The temperature dependence of the relaxation time seems to be consistent with

the prediction based on weak-coupling BCS theory for all films we measured without

changing any material parameters for different thickness. The application of magnetic

field did not change the relaxation times, which was unexpected.













CHAPTER 1
INTRODUCTION

1.1 Introductory Remarks

Spectroscopy is a very useful technique for investigating the properties of various

types of materials. Information on the material is encoded in the radiation spectrum

modified through interaction with the material. The extensive energy range covered by

electromagnetic radiation allows us to study many properties (e.g., electronic, magnetic,

lattice, and so on) depending on the frequency ranges. For example, the conductivity

peak for free carriers is centered at zero frequency. Lattice vibrations (i.e., phonons)

interact with electromagnetic radiation at far-infrared frequencies. Electronic transitions

across the energy gap of a semiconductor like Si happen in the near infrared. Transitions

from core levels require even higher energies. In superconductors, an energy gap

develops in the electronic density of states around Fermi energy. The typical energy

scale of this gap is in meV, which corresponds to the frequencies between microwave and

far infrared. Thus, optical studies in this frequency range provide an important tool for

investigating superconductors.

A synchrotron is a source of high brightness electromagnetic radiation emitted from

electrons orbiting around a closed path of a storage ring. It is a very broad-band source,

extending from the very far infrared to the hard x-ray. Because electrons are bunched

as they travel, the radiation emitted from the synchrotron source is pulsed. Beamlines

U10A and U12IR are two beamlines on the VUV ring at the National Synchrotron

Light Source (NSLS) of Brookhaven National Laboratory (BNL) dedicated to solid-state

physics experiments. The NSLS provides a powerful, tunable, near-infrared/visible

mode-locked Ti:Sapphire laser, which produces pulses of a few picoseconds duration

synchronized to the synchrotron pulses. A specimen can be excited (pumped) by laser

pulses, and probed by infrared subnanosecond-duration synchrotron pulses from the








VUV ring [1, 2]. Depending on the mode of synchrotron operation, this facility provides

a unique opportunity for measuring transient phenomena on time scales in a few 100

ps up to 170 ns range over a broad spectral region. With proper tuning of excitation

energy, the dynamics of various systems can be investigated: quasiparticle relaxation

in conventional BCS superconductors, recombination of the photogenerated electron-

hole plasma in semiconductors, dynamics of the photodoped polarons and solitons

in conducting polymers, and relaxation of photoinduced conductivity effects in the

insulating phase of high-T, superconductors, to name a few. Use of a superconducting

magnet also allows us to study materials in magnetic fields.

1.2 Motivation

This dissertation describes optical studies on a set of superconducting amorphous

molybdenum-germanium (a-MoGe) thin films deposited on thick insulating substrates.

All measurements were performed at the two beamlines on the NSLS VUV ring. It is

well known that increasing disorder leads to localization and the related enhancements

of the repulsive electron-electron Coulomb interaction [3, 4, 5]. It is also well known

that in superconductors, two electrons form a pair due to phonon mediated attractive

interaction. Thus, the enhanced Coulomb interaction inherently competes with super-

conductivity. a-MoGe is a well-studied disordered system used for studying the interplay

between superconductivity and disorder. Its transport properties were investigated by

Graybeal [6, 7, 8], and showed progressively reduced transition temperatures (i.e., a

weakened superconducting state) as the thickness is decreased. In this work, we have set

out to understand this system even further, and possibly find some sort of connections

between reduced transition temperature and the degree of disorder. For this purpose,

we first undertook a thorough study of linear spectroscopy in the far infrared. Then,

the dynamics of the system was studied by a pump-probe technique. Driving super-

conductors to nonequilibrium states corresponds to breaking Cooper pairs, producing

excitations called quasiparticles. In returning to equilibrium, these quasiparticles recom-

bine into pairs, releasing energy usually as phonons. The rate at which this relaxation








progresses involves the interaction between quasiparticles, which is of fundamental

interest for any theory of superconductivity.

1.3 Organization

In C'!i lpter 2 we review a basic theory of optical properties. Some of the common

techniques and models used for extracting optical parameters from experiments are

discussed. C'!i lpter 3 provides the concepts of Fourier spectroscopy. Two types of

interferometers are described: amplitude modulation and polarization modulation.

C'! Ilpter 4 summarizes a few fundamental properties of superconductors within the

framework of BCS theory. The first part of ('!i lpter 5 describes the properties of

synchrotron radiation. Comparison to conventional thermal sources reveals advantages

of using synchrotron radiation for spectroscopic study particularly in the far infrared

frequencies. The second part of the chapter is intended to introduce the basic idea of

the pump-probe technique using a laser as the pump source and synchrotron radiation

as the probe source. Reading this part of the chapter prior to reading the following

chapters is recommended. ('!i lpter 6 describes in detail all experimental components,

techniques, and setups used in this project. The specifics of the apparatus such as the

NSLS VUV storage ring, beamlines, spectrometers, laser system, and others are all

included in this chapter. ('!i lpters 7 and 8 discuss our experimental results of linear

and time-resolved study on a-MoGe thin films, respectively. Each chapter contains a

theoretical background specific to the analysis used in the chapter. Finally, Chapter 9

shows the results of our most recent experiment of magneto-optical measurements.

In optical studies, different energy units are quite common for the different tech-

niques, frequency ranges, and disciplines. In the infrared spectral region, the most

commonly used unit is the wavenumber given by cm-1. It is defined as the frequency in

Hz divided by the speed of light in cm/s or the reciprocal of wavelength in cm. In this

dissertation, the wavenumber is used interchangeably with frequency or energy since the

values for these units are simply related.













CHAPTER 2
OPTICAL PROPERTIES

2.1 Introduction

In this chapter, we will provide a general background of the theory of optical

properties. The chapter begins with very introductory discussion of a number of

phenomena that can occur as light propagates through a medium and the coefficients

that are used to quantify them. The basic results of Maxwell's equations also will be

summarized. In the following section, we will show several techniques for extracting

optical parameters from experimental data measured on samples in common forms. At

the end several microscopic models will be developed to explain the optical phenomena

that are observed in the solid state. The main purpose of the chapter is to give a basic

theory and techniques in general terms, and also to be used as quick reference.

2.2 Optical Phenomena

In the simplest way, reflection, transmission, and propagation are the three sim-

plest groups of optical phenomena that are observed in solid state materials. When a

light wave propagating in one medium encounters another medium, some of the light is

reflected from the interface, while the rest transmits into the medium and propagates

through it. The light also experiences a v ii, I v of optical phenomena during the propa-

gation within each medium. The light rays are bent at the interface due to the change

in the velocity of the light wave in different media. This is known as refraction, and is

described by Snell's law. The light may be attenuated as it propagates caused by pro-

cesses such as absorption or scattering. Absorption occurs if the frequency (i.e., energy

of photon) of the light is resonant with the transition energy of the atoms and electrons

in the medium. Hence, absorption causes reduction of the number of photons in the

forward direction. In the event of scattering, the light beam is re-directed in other direc-

tions caused by the presence of impurities, defects, or inhomogeneities. This obviously








causes attenuation in the original direction in an analogous way to absorption even

though the number of photons is unchanged. Scattering can also accompany changes in

frequency of the light. If the frequency of the scattered light is changed, it is said to be

inelastic; if it is unchanged, it is said to be elastic. Luminescence is the phenomenon of

spontaneous emission of light by the excited atoms in a medium. The light is emitted in

all directions, and has a different frequency to the incoming light.

With conventional sources of light, optical properties are described by linear optics,

where it is assumed that quantities such as the refractive index, absorption coefficient,

and reflectivity are independent of light intensity. This is based on an approximation

that is only valid in the low intensity limit, and practically everything we will be

discussing in this dissertation falls into the realm of linear optics. When high intensity

light propagates through a medium, a number of nonlinear phenomena can occur.

Frequency doubling and tripling are examples of these nonlinear effects, and are realized

through the use of lasers. This is the subject of nonlinear optics, where it allows the

electric susceptibility as well as all the properties that follow from it to vary with the

strength of the electric field of the light beam. Even though nonlinear optics is an

interesting subject in its own right, it will not be discussed further.

Optical phenomena can be quantified by a number of optical constants (optical

parameters) that describe the macroscopic behavior of the medium. The reflection from

an interface of different media is described by the reflectance J, defined as the ratio

of the power of reflected light to that of incident light on the surface. Transmission

through the interface, on the other hand, is described by the transmittance 3, defined

as the ratio of the transmitted power to the incident power. At the every interface the

light wave encounters, conservation of energy requires that


+ 1. (2.1)


The refraction is described by the refractive index n, defined as


n (2.2)
U-








where c and v are the speed of light in free space and in the medium, respectively.

The refractive index depends on the frequency of the light wave, which is known

as dispersion, and characterizes the propagation of the light through a transparent

(i.e., non-absorbing) medium.

The absorption of light by a medium is quantified by the absorption coefficient a,

defined as the fraction of the power absorbed in a unit length of the medium. In terms

of a differential equation, the effect of absorption is given by


dl -adx I(x) (2.3)


where I(x) is the intensity of light at position x. The solution to this equation is the

exponential decay of light intensity as it propagates through the medium:


I(x) = 1o e-C (2.4)


The frequency dependence of the absorption coefficient is responsible for the color of

materials.

Rayleigh scattering is caused by variations of the refractive index of the medium on

a length scale smaller than the wavelength of the light. As mentioned earlier, scattering

has similar attenuation effect as absorption, and the intensity of light as it propagates

can be expressed by

I(x) = Io e-Nez (2.5)

where N is the number of scattering center per unit volume, and o-, is the scattering

cross-section of the scattering center.

The frequency dependent refractive index n(w) and absorption coefficient a(w)

are the two important quantities that characterize the propagation of light wave in a

medium since they describe the dispersive and absorptive nature of a material in the

most direct way. The refraction and absorption of a medium can be described by a








single quantity called the complex refractive index:1


N n+ i (2.6)


where n (real part of N) is the refractive index defined in Eq. 2.2, and K (imaginary

part of N) is the extinction coefficient that is directly related to the absorption coeffi-

cient a as will be discussed shortly.

A few examples of optical quantities that have been discussed so far provide

descriptions of the optical phenomena only from the point of view of the reflection,

transmission, and propagation, and offer the most useful information to manufacturers

of optical elements. The frequency dependent reflectance J (w) and transmittance 7(w)

are the experimentally measurable quantities from which other parameters such as the

complex refractive index N can be derived. The microscopic models, however, usually

enable us to calculate other parameters such as the complex dielectric function E and

complex conductivity a rather than N. The relationship between E and N provides

direct connection between microscopic models of materials and propagation properties of

electromagnetic waves.

2.3 Interaction of Light with Matter

This section summarizes the principal results of electromagnetism that are sufficient

for the study of optical properties of solids. Details of the subject can be found in most

books on optics and electromagnetism [9, 10, 11, 12, 13, 14, 15, 16]. CGS units are used

throughout unless otherwise specified.

The response of a material to external electric fields E is characterized by a few

macroscopic vectors: polarization P, electric displacement D, and current density J.

Within the linear approximation, these three vectors are proportional to the fields E



1 The use of complex quantities such as the complex refractive index, dielectric con-
stant, and conductivity to describe properties of medium naturally arrives from the use
of complex solutions to the Maxwell's equations. This point will be clear after reading
2.3.








(e.g., P oc E), and their proportionality constants are the linear response functions

which describe properties of the solid-state system itself and are independent of the

driving force. The linear response is formulated in time and space. Since the response is,

in general, frequency and wave vector dependent and it is convenient to handle harmonic

functions, a discussion in Fourier space, both with respect to time and coordinates, is

more appropriate. Thus, rather than studying the response function directly, the linear

relation between the Fourier transform of the driving force and the Fourier transform

of the system response is considered. Also, we will use the time-varying E in the

form of exp(-iat), and express the proportionality constant as a complex quantity to

account for the phase shift between two fields: a real (an imaginary) part represents the

response of a medium in (out of) phase with the applied electric field. In addition, the

assumption of isotropic, homogeneous medium was made to simplify the discussions.2

The polarization is defined as the net dipole moment per unit volume. Within the

assumption made above, the microscopic dipoles (both permanent and induced dipole

moments) tend to align in the direction of the external field. This allows us to define a

polarization as

P = XE (2.7)

where X) is the complex electric susceptibility of the medium, which is one of the most

fundamental response function.

The electric displacement of the medium is defined by


D E + 47rP (2.8)


The above two equations can be combined to give an alternative expression:


D =E, (2.9)



2 Anisotropic crystals have nonequivalent optical properties along different (< i 11iw'
axes. The phenomenon of birefringence is an example of optical anisotropy. In such ma-
terials, the proportionality constants must be represented by a tensor.








where

SC1 + i2= 1 + 47re (2.10)

The parameter E is a complex dielectric constant (or dielectric function).

When time varying E is applied, there is an associated motion of each element of

charge. This leads to a relationship between the current density J and polarization as

dP
J -iwP (2.11)
at

In a similar way to P and D, the current density can also be written as


J = E, (2.12)


where

a i + ia2 (2.13)

The parameter a is the complex conductivity of the medium. Generally, the current

density J is the sum of two contributions: one arising from the motion of charges that

are free to move through the medium J free, and the other arising from charges that are

restricted to localized motion Jbound.

Optical constants such as Xe, e, and a represent the response of a medium (i.e., re-

sponse functions) to a perturbing field of frequency c.3 All of these parameters,

however, are not independent. They are all interrelated to one another. As can be

seen from Eq. 2.10, Xe and E provide the same information. Using Eqs 2.7, 2.10, 2.11,

and 2.12, we can find a useful relationship between E and a:

47ra
=1 + i- (2.14)




3 The response functions should be considered as a function of both frequency w
and wave vector k. However, the explicit dependence of the response functions on k
(i.e., wavelength), the so-called spatial dispersion, can be neglected in case the fields
could be averaged over a unit cell. Spatial dispersion arises whenever the relation be-
tween D and E is not exactly local with D at a particular point determined solely by E
at that point.








or explicitly


a-1 2 (2.15)
47
0(1 el)
wo2 (2.16)
47

Thus optical measurements of E(w) are equivalent to conductivity measurements of o(w).

In case our interest is in the optical responses due to the free carrier gas in materials

such as metals and doped semiconductors, optical data are frequently discussed in terms

of the conductivity rather than the dielectric constant.

Later, we will show the connection between the optical parameters described here

and the propagation constants of electromagnetic waves in a medium, namely the

complex refractive index N.

The response of a material to external magnetic fields is characterized in a similar

way. The magnetization M is defined as the net magnetic moment per unit volume, and

is proportional to magnetic field strength H:


M = H. (2.17)


The parameter X is the magnetic susceptibility.

The magnetic flux density B is defined by


B H + 47M (2.18)


The above two equations can be combined to give


B = H, (2.19)


where

I = 1 + 47m (2.20)

The parameter p is the permeability of the medium. At optical frequencies, any

paramagnetic or ferromagnetic moments can not follow the rapid oscillations of magnetic

field because of their long relaxation times. The remaining diamagnetic moments are







so small as to have no appreciable effect on optical behavior. Thus, unless we study

magneto-optical phenomena, we can set B = H.

The starting point for the treatment of interaction between electromagnetic fields

and matter is contained within the four Maxwell's equations for the average fields.4 In

the absence of external charges, these equations are given by

V eE = 0, (2.21)

VH 0, (2.22)
1 8H
V x E H (2.23)
c Bt '
1Eat
Vx H -= (2.24)

where E is the complex dielectric constant defined in Eq. 2.14, which allows the current

density arising from free carriers (i.e., Ohm's law) to be included in Eq. 2.24.

We consider the solution corresponding to a plane wave of the angular frequency w:


(H) (E)exp[i(k -x t)] (2.25)

where a constant amplitude vector Eo is in general complex. The complex wave vector

k was used to describe energy dissipation of the wave. Substitution of Eq. 2.25 into the

Maxwell's equations yields

k E 0 (2.26)

k H 0, (2.27)

k x E H (2.28)

k x H --E (2.29)
c



4 The use of the so-called macroscopic Maxwell's equations can be justified as follows.
In optical measurements, features that can be probed are the size of the order of a wave-
length of light or larger. Since a solid contains numerous atoms within the length scale
of the wavelength of light, it can be treated as a continuous medium








Here we have assumed an isotropic, homogeneous, and non-magnetic medium so that

E has no spatial variation. Equations are separately correct for both the real and

imaginary parts. These equations are combined to yield a relation between the wave

vector and frequency known as the dispersion relationship:


k.k (2.30)


In a non-absorbing medium of refractive index n, the wavelength of the light is

reduced by a factor n compared to the free space wavelength Ao (= 2rc/.). Therefore,

wave vector k is given by
2k r wn
k (2.31)
Ao/n c
This leads to the phase velocity u/k =c/n in Eq. 2.2. The wave vector can be

generalized to the case of an absorbing medium by allowing n (and as a result k,

too) to be complex:

k= N -(n + i) (2.32)
c c
Eq. 2.30 and Eq. 2.32 allow us to relate the propagation properties of light through a

medium to the response of the medium in the electromagnetic fields as


N = (2.33)


or explicitly


1 n2 2 (2.34)

C2 2nK (2.35)


and


2 Li
S- [- + (C + C2)2] (2.37)





13

Eqs. 2.26-2.29 also show that E, H, and k are mutually perpendicular (i.e., trans-

verse waves), and the scalar relation between E and H is given by


H vE = NE (2.38)


The ratio (47/c)E/H is called the wave impedance Z:

Z E 1 1
Z H -t t (2.39)
Zo0 H c N'

where Zo is the wave impedance of free space, which has a value of Zo = 47/c (or 377 Q

in SI).

On substituting Eq. 2.32 into Eq. 2.25, we find that the fields attenuate as e- K/c.

The optical intensity of light is proportional to the absolute square of the electric

field5 (I oc E*E). Thus, from Eq. 2.4, we find that

2wJc 47Tr
a (2.40)
c Ao

where a and K are the absorption and extinction coefficients, respectively. The pen-

etration (or skin) depth 6 is the characteristic length of the fields' penetration into a

medium defined by
2 c
= (2.41)
a wtK

The average rate of dissipation of electromagnetic energy density is

1 1
W =(Re(E) Re(J)) Re(E* J) t|E|2 (2.42)
2 2

Thus only the current that is in phase with E contributes to an energy loss, and a1

represents the resistive response (i.e., absorption that accompanies the energy loss)

of the medium in the fields. The out of phase current, on the other hand, does not

accompany the energy loss, and a2 describes the reactive response. The a is called the



5 The time-averaged energy flow in the electromagnetic wave is calculated from the
real part of the complex Poynting vector S (E x H*). The magnitude of this vector
gives the intensity of the light wave proportional to the square of the field.







optical conductivity since the response concerned here arises from transitions as a result

of photon absorption.

We have so far considered only transverse waves (i.e., k I E). However, Eq. 2.26

can also be satisfied for longitudinal waves (i.e., k I| E) for any frequency Ui provided

that e(1) = 0. At this frequency, longitudinal waves can propagate through a medium

and contribute to the energy loss that is proportional to the so-called loss function

defined as
(1 62 2n
-Im n (2.43)
G)j +1 | (n +K2)2
The longitudinal waves can excite LO phonon modes at the LO frequencies.

In an only weakly absorbing medium (i.e., n > K), Eqs. 2.34 and 2.35 simplify to


n = V (2.44)

C2 =Ao (2.45)
2n en

These equations tell us that the refractive index n is approximately determined by C1,

while the absorption is mainly determined by C2 (or Ol).

The purpose of this section has been to provide some of the optical constants

that describe optical properties of a medium, as well as the relationship between these

constants. The relations such as Eq. 2.30 and 2.33 are the connections between the

macroscopic optical parameters such as N and quantities that can be calculated by

microscopic theory such as E. Note that all the optical constants described here are in

general frequency dependent providing information about how photons of particular

energy, hw, interact with electrons, phonons, and other excitations in the system.

Detailed analysis of optical constants allows us to understand various properties of

solids. For example, knowledge of the electronic properties of solids is the key to

understanding most of their physical and chemical properties.





15

2.4 Experimental Determination of Optical Constants

Information about solid materials is often obtained by studying the electromagnetic

waves reflected from and/or transmitted across interfaces between materials with dif-

ferent optical properties. This can be done by considering the boundary conditions of

the E and H fields and the energy conservation. In experiment, we usually measure the

fraction of energy reflected [i.e., reflectance, J (w)] from and/or transmitted [i.e., trans-

mittance, 9(u()] through a specimen. The form of a specimen usually determines which

measurement technique has to be employ, ,1 Our main goal is to deduce the dielectric

function as well as other functions directly related to it. In this section, we will discuss a

few examples of simple procedures used for determining optical constants.

2.4.1 Reflection and Transmission at a Plane Interface

We first consider the transmission and reflection of light at a plane interface

between two media with different refractive indices, 1N and N2. For simplicity, we will

assume the light is incident normal to the interface. Then, the boundary conditions

require that the tangential components of the electric and magnetic fields are conserved

such that

E, + E = Et and H, H = H, (2.46)

where i, r, and t refer to the components of the incident, reflected, and transmitted

fields, respectively. Using the relation between E and H from Eq. 2.38 the bound-

ary conditions yield the amplitude reflection coefficient and amplitude transmission

coefficient as6
E, N,- 1N2
Ei 1,+ 12 (2.47)

and
Et 2N1
t l+ f 1 (2.48)
E, 1,+ 1N2



6 For an arbitrary angle of incidence a more general treatment is required. The reflec-
tion and transmission coefficients are then given by formulae known as Fresnel's equa-
tions [9].







The reflectance (or reflectivity) is the intensity reflection coefficient. If the light is

incident on a medium from a vacuum side, the reflectance off the medium is simply

given by

S ( n + (2.49)
(1 + n)2 + K2
where we have used N = 1 and 2 = n + iM. This is the valid equation for the

single-bounce reflectance measured from a thick < i, ii (i.e., a bulk material) with its

thickness much greater than the penetration depth (d > 6).

From Eq. 2.49, it is obvious that reflectance data alone can not determine both n

and K. It is in general not possible to determine both components from the measure-

ment of just one optical parameter, such as reflectance. Therefore, we need separate

measurement of either n or K by some other means, or to do something else in con-

junction with reflectance measurement. The Kramers-Krinig relations offer practical

solution to this problem as discussed below.

2.4.2 Kramers-Kr6nig Dispersion Relations

The Kramers-Kr6nig relations (KK) are integral relationships between real and

imaginary parts of a complex function, such as the linear response functions e(w),

(cju), and N(w), as a result of invoking the law of causality and applying the complex
ai 1,v-i- 7 One of the requirements for the relationships to be valid is that the response

function vanishes for w -- oo. The KK relations for the complex refractive index and the

complex dielectric function may be stated as follows:

n^)- 1 j^j J dcJ, (2.50)
2 J (') 1

(w) 2 -J L2dwu (2.51)
7T Jo U 'LC)/2 LC)2



7 In a physical system, response functions must satisfy G(-w) = G*(w). For the di-
electric function, this condition leads to cl(-uw) = ci(w) and 2(-w) = -C2(o). In other
words, 1(w) is an even and c2(w) is an odd function of the frequency w.







and

61(W)- 1 2 2~- d-cJ (2.52)

C (w) 2= ') d (2.53)
7" J0 )2 a) 2

where 2 stands for the Cauchy principal value of the integral. Similar relations are

available for other linear response functions. From these relations we see that if the real

part of a response function is known over an entire frequency range (0 < w < oo), the

imaginary part can be determined, and vice versa. In real experimental situations, there

is a limit in frequency range that can be measured. Therefore, this technique requires

proper extrapolations for the frequencies outside the range covered by measurement.

Inappropriate extrapolations may result in severe errors in the calculated counterparts.

Returning to the discussion of the single-bounce reflectance at a plane interface,

the amplitude reflection coefficient given in Eq. 2.47 is a complex quantity which can be

expressed as r(w) = &(w) ei( or

lnr(w) In (w) + i(w) (2.54)

where J (w) is the reflectance given by Eq. 2.49 and 0(w) is the phase shift of the

reflected electric field, which is related to n and K by

Im[F] -2r
tan (2.55)
Re [r] 1 n2 K2

One of commonly used technique is to measure the reflectance over a wide frequency

range. Then, the KK-related phase shift is calculated by

w [ ln ()- In () d
O(w) = w2 2i (2.56)
1 + co d-ln (w' )
In ada' (2.57)
27r 0o 'c Lo dud'










Medium 1, N,



Medium 2, N2 -- d



Medium 3, N3



Figure 2-1: Reflection and transmission at two parallel interfaces. The thickness of the
second medium is d. We assume the case of normal incidence, but the beams are drawn
at an angle for a clarity.

From Eq. 2.49 and Eq. 2.55, we can determine n(w) and (aw), the dielectric function,

and all other related functions.8

2.4.3 Reflection and Transmission at Two Parallel Interfaces

If the light is incident on a plane interface (between medium 1 and medium 2),

and transmitted through the second parallel plane interface (between medium 2 and

medium 3), the expressions of transmittance and reflectance become more complicated

since now we have to consider the multiple reflection as well as absorption absorption

within the second medium. This situation is depicted in Figure 2-1. The first and third

media are assumed to be non-absorbing, and span the semi-infinite space with their

complex refractive index N1 and N3, respectively. The second medium has its thickness

d with the refractive index N2. We again assume normal incidence for simplicity. Then,

the general formulae for the resultant amplitude transmission and reflection coefficients



8 This technique is quite practical, yet the requirements of wide range measurement
can be inconvenient in some situation. One of the technique called ellipsometry can de-
termine simultaneously both real and imaginary parts of the dielectric function over a
limited frequency range, and may serve as an alternative method to consider [17].








including multiple reflections are


t d ti23 C6[1t ( 23 21 Ci26) + (r2321 ei2)2 +


1 r23r21 (2.58)

and


r = 12 + t12r21 i[ + (r2123 6i2e) + ( 23 6e12)2 + *
r12 + r23 i2 (2.59)
1 r21r23 6i2

where rij and tij are the amplitude reflection and transmission coefficients between

mediums i and j as given by Eqs. 2.47 and 2.48, and 6 is the complex phase depth of

the second medium which is defined by

S w a
6 -N2d -n2d + -d (2.60)
c c 2

where a is the absorption coefficient defined by Eq. 2.40. From Eqs. 2.58 and 2.59, the

resultant transmittance and reflectance are obtained:

n3 2 n3 1212 12 23 12 -ad
|t| 1+ 12C2 r233 2 Cud s (2.61)
nI ni 1 + lr23 121 rll -2 2 r3 r2l -a cos 0

and
SI 1 2 2 + 1 r23 2 e-2ad +21 r3 1112 e-ad Cos (
S- 1 + |r232 r21 2 e-2ad 2 23 21 e-adcos (

with

S2-n2d + 23 + 21 (2.63)

where ', is the phase shift upon reflection at either interface. The cosine term leads

to interference fringes in the spectrum due to multiple internal reflection in the second

medium. When the second medium is thick (d > A) or wedged, there is no coherence

among multiple reflections. In a low resolution measurement, those fringes are not

resolved, and the transmittance or reflectance is averaged over the phase angle for the








partial beams as
S -12 r23 11212 -ad (2.64)
g v 1 1 23 1 21 2 | 1

and
1 i22 2 -2ad 2 ^12 2 -2rd
Jaoe -12 2 23 2 923 12 (2.6)
S- 23 122112 -2d (2.5)

When a thick sample of thickness d with complex refractive index n is measured in

a vacuum, it is straight forward to find the averaged transmittance and reflectance:

(1 _- )2+ 2/n2) -ad
ave -2ad (2.66)

and

ave ( +Js(?1 0e ad) (2.67)

where Js is the single-bounce reflectance given by Eq. 2.49. Experiments of this type

are very important and are often applied to measure absorption coefficients of solids.

When wavelengths of incident light are comparable to the thickness d, the interfer-

ence fringes are resolved with sufficiently high resolution measurements. From Eq. 2.63,

it is apparent that the spectrum exhibits periodic fringes of the frequency spacing

between two successive fringes given by

1
AV =2 (2.68)
2nd

where Av is in cm-1 and d is in cm. This equation is sometimes useful to determine the

thickness of the sample from the fringe -I. ii.- and vice versa. For example, mylar films

used as a beam-splitter in far infrared have the refractive index between 1.64 and 1.67.

Then, we can expect that the first minimum for 6 pm mylar beam-splitter appears near

500 cm-

2.4.4 Optics in Thin Film on a Substrate

A structure of a thin film of thickness d (< wavelength or penetration depth) laid

on a thick but non-absorbing (or weakly absorbing) substrate with refractive index

n and thickness x is quite common in the optical experiment. Figure 2-2 shows the

schematic diagram of the situation. Again we only consider the normal incidence to a








vacuum

t h in f ilm .........................................

substrate o ......... n x


vacuum



Figure 2-2: Reflection and transmission with a thin film on a weakly absorbing sub-
strate. The thickness of the thin film and the substrate are d and x respectively. We
assume the case of normal incidence, but the beams are drawn at an angle for a clarity.

sample in free space. It is obviously more complicated since now we are dealing with a

four 1 1-, i. I structure. In such case, the KK technique is inapplicable. However, it is

possible to extract linear response functions from measurements of both reflectance and

transmittance over a finite frequency range.

At first we consider the case when multiple reflections inside the substrate may be

neglected. This simplifies the situation significantly since the thickness of the substrate

x becomes unimportant, and the system can be considered as a three 1 ,li. I structure

(vacuum-film-substrate) just like the one discussed above. Then, from Eqs. 2.58 and 2.59
with the following approximations:

I N2 1 ,

IN21 >N3 n3 n (3 < n3) (2.69)
d < wavelength or skin depth ,

it can be shown that the transmittance across the film into substrate and the reflectance

from the film are given by the Glover-Tinkham equations [18, 19]:

1 4n
*7 = 4 (2.70)
1 + 1 12 (y + +1)2+ (7
n+1
and
(y + n- 1)2 +y
1 +2 (2.71)
f (y +n+1)2 2








where n is the refractive index of the substrate, yl and Y2 are the real and complex

part of the dimensionless complex admittance of the film, y, respectively. y is related

to the complex conductivity a = r1 + ia2 of the film by y =Zoad where Zo is the

impedance of free space (4r/c in cgs; 377 Q in mks). Thus, the optical behavior of a

film is determined by its electrical properties of the film that is modified by the surface

effects.

The actual measured transmittance and reflectance are influenced by multiple

internal reflections within the substrate of the thickness x and the absorption coefficient

a. Then, the system is a four 1li,. structure with vacuum as the forth medium. If a

substrate is thick (x > A) or wedged, coherence among multiple reflections are lost, the

measured transmittance and reflectance are simplified to

(1 J- 3)p-ax
3= e-2-x (2.72)
1 4s4e-2ax

and

g 1 j e-2ax





(yi + n + 1)2 + y2

and 4, is the single-bounce reflectance of the substrate given by Eq. 2.49. For a weakly

absorbing substrate such that = ca/2C < n, J4s may be approximated as

1- n\ 2
t ~ (2.75)
t +n)2

This is usually satisfied for measurements at low temperature and low frequencies.

From measurements of the transmittance and reflectance of the bare substrate, we

can find the index of refraction n and the absorption coefficient a of substrate using

Eqs. 2.66 and 2.67. Note that the term 2 /n2 in Eq. 2.66 can be neglected for a weakly

absorbing substrate.








With the knowledge of substrate's optical properties, al and -2 and in turn all

other response functions can be extracted by inverting Eqs. 2.72-2.74 after measuring

both transmittance and reflectance of the film-on-substrate system. For a structure

with more V1 --iSr (e.g., vacuum-film-buffer-substrate-vacuum), the analysis becomes

progressively more complicated. A more general discussion of the optical response from

multi-l .,-,;r is given in [15,20].

2.4.5 Photoinduced Absorption

In the photoinduced measurements, we are interested in changes in the optical

behavior of a sample in photoexcited state with respect to non-excited state (ground

state). For a sample in the form of film with thickness d deposited on a substrate, it

would be ideal to have a substrate material that is insensitive to the photoexcitation.

In such case, the photoinduced change in the transmittance, A9, is due to the photoin-

duced absorption by the film itself. If the measurement is done in low resolution, the

transmittance through the film into substrate is given by Eq. 2.66, and it can be shown

that the normalized photoinduced transmittance is written as

-- (Aa)d (2.76)


where I and go are the transmittance of the film in excited state and ground state,

respectively. Note that the negative of the quantity Al/9 is customary used as the

photoinduced signal.

2.5 Microscopic Models

Up to this point, we have not described the optical phenomena from a microscopic

point of view. There are various microscopic models that try to explain the optical

behavior observed experimentally. These models may be classified as either classical,

semiclassical, or quantum mechanical, depending on how we treat interaction between

light and matter.

In the classical model, both light and matter are treated classically. The dipole

oscillator model (Drude-Lorentz model), which will be discussed shortly, is a example








of a classical treatment. This model has been proven to be very successful, and is often

used for understanding the general optical properties of medium.

In the semiclassical approach, the atoms in the medium are treated quantum

mechanically, while the light is still treated as a classical electromagnetic wave. The

absorption coefficient or oscillator strength due to transition between two states or two

bands can be calculated using Fermi's golden rule, which requires knowledge of the wave

functions of the states.

In the completely quantum approach, the light is also treated quantum mechani-

cally, namely as photons. Feynman diagrams can be drawn to represent the interaction

processes between photons and atoms.

In this section, we will discuss only a few of microscopic models that are commonly

used during analysis.

2.5.1 Lorentz Model

In a solid, there are various processes (or excitations) that contribute to the

dielectric function which, in turn, describes its optical behaviors. For example, free

carrier absorption and phonon (including multi-phonon) absorption are the typical

processes at far- and mid-infrared frequencies.9 In the spectral range of near-infrared

and ultraviolet, processes such as excitons and fundamental absorption across the

energy gap, interband transitions, and plasma absorption may be seen. In the vacuum-

ultraviolet and X-ray spectral region, the transitions of the core electrons can be

expected to dominate the dielectric function. At the very high energies beyond nuclear

excitations, nothing can respond to the driving field, and the dielectric function becomes

unity since the medium does not possess any polarization. Note that all transitions

require the conservation of energy and momentum.


9 In principle, magnetic excitations could exist at even lower energies.








The Lorentz model is a simple, yet very useful classical model dielectric function

that can be derived for a set of damped harmonic oscillators. When a harmonic oscilla-

tor with mass m, charge q, damping constant 7, and resonant frequency wo is excited by

a harmonic electric field of the form E(t) Eo e-it, the equation of motion is given by


mr + myr + mwor = qE(t) (2.77)


The second term models the energy loss mechanism of the oscillating dipole. Note that

the resonant frequency wo is a transverse oscillator frequency that is coupled to the

transverse electric field. Inserting a solution of the form r = ro e-it into Eq. 2.77 yields

q 1
r 2 E (2.78)
m LCQ LC) 17LCj

If there are N oscillators per unit volume, the resonant contribution to the macro-

scopic polarization is
Nq2 1
P Nqr Nq2 1 E. (2.79)
m LCo2 LC2 i

Note that the isotropic medium is assumed here. Then, the susceptibility arising from

the oscillator is
Nq2 1
S 2 (2.80)

The total polarization is given by


Ptotal = eE =(- Xo)E (2.81)


where X, is the background susceptibility that arises from the polarization due to all

the other oscillators at higher frequencies.

The dielectric function is determined from Eq. 2.10:

2
w(h) = d, + (2.82)

where we have defined the high frequency limit of E(cw) as


co = 1 + 47rX, ,


(2.83)







and the plasma frequency up as

2 4Nq (2.84)

Note that the subscript oo should be understood as contributions above a certain

resonance. Separating the real and imaginary parts, we obtain



2 2 _2
( 2)2 + (7U)2(

C2(Uw) ( > + c> 7 (2.86)

From these equations, it is straight forward to see that Cl gradually increases from the

value co + /wu0 as frequencies increase toward wo, and peaks at wo 7/2. It takes

sharp negative slope, passing through Co at w0, and bottoms at Uo + 7/2. As frequencies

increase further, it finally approaches the high frequency limit of C~. As mentioned

briefly in the earlier section of this chapter, the frequency for which Ci(w) = 0 is labelled

as ul at which electromagnetic waves are coupled to the longitudinal component of

the oscillator. Compared with el, C2 has a simple bell shape with a strong peak at Uo

and the full with at half maximum given by 7. Note that both ei and C2 vary on the

frequency scale of 7, and the damping of the oscillator has the effect of broadening. It

is in general that material is highly absorbing near the resonance, for obvious reason,

strongly reflecting between wo and wl, and transparent at frequencies further .li. from

the resonance where ei does not vary strongly.

Eq. 2.82 can be generalized to an arbitrary number of different oscillators as
2
~({) + Y3 (2.87)


where uj, 7j, and ,pj are the resonant frequency, damping constant, and plasma

frequency of the oscillator of type j, respectively. The plasma frequency is defined by


2 4 'j (2.88)

where Ny, qj, and mj are the number density, effective charge, and effective mass of the

oscillator of type j, respectively. These vales must be appropriately chosen to account





27

for the different oscillators. For example, in the case of a phonon, up is the ion plasma

frequency with q and m as the effective charge and the reduced mass of the particular

lattice vibration mode.

A corresponding quantum mechanical version of Eq. 2.87 can be written as


(w) =e + f (2.89)


where we have introduced a oscillator strength fj in order to account for the strength

of the response of different transitions to the perturbing electric field. In the quantum

picture, Lj is the transition frequency between two states which are separated in energy

by hyj, and 7j is the uncertainty (or width) in energy of the initial and final states

of transition. The oscillator strength fj is related to the probability of a quantum

mechanical transition, which can be calculated using Fermi's golden rule.10 It satisfies a

sum rule

1 (2.90)

The oscillator strength provides us an explanation for the different absorption strength

in different transitions.

2.5.2 Free Carrier Response and Drude Model

The equation of motion given in Eq. 2.77 can also be used to derive the dielectric

response of free carriers of charge q and effective mass m* by taking the restoring force

term zero (i.e., w O 0):
m*
m*v+- = qE(t), (2.91)
T



10 Fermi's golden rule shows that the transition rate between two states is proportional
to the square of a matrix element and also to a density of states for both the initial and
final states. The oscillator strength and absorption coefficient are related to the quan-
tum mechanical transition rate.





28

where we have expressed the damping constant 7 as a reciprocal of the collision time r

that characterizes loss of momentum of carriers due to scattering.11 This is a simple

equation based on the Drude model. Inserting a solution of the form v = vo e-i into

Eq. 2.91 yields
qr 1
v q E (2.92)
m* 1 iur

For N free carriers per unit volume, the current density is then

Nq2r 1
j Nqv = E = aE (2.93)
m* 1 iUr

Thus, the ac conductivity based on the Drude model is


oD(0) (2.94)
1 iU-

where co is the dc conductivity defined as

Nq2-
-o = (2.95)
m*

The real and imaginary parts are


JDo1 (2.96)
1 + W2r2

D2 o (2.97)
1 + U2,-T2

From Eq. 2.14, the dielectric function for the free carriers is given by

2
ED (W) =1 (2.98)
L) + iLL/'T




11 A typical value of r for a metal or doped semiconductor is in the range ~ 10-14
10-13 seconds, which correspond to ~3000 cm-1 and ~300 cm-.





29

where ucpD is the Drude plasma frequency defined by12

2 47rNq2
SPD (2.9

Eq. 2.98 is obviously the same expression as Eq. 2.82 with wo = 0, 7 = -1, and c 1.

Note that Eq. 2.98 assumes that only free carriers contribute to the dielectric function.

When other processes at higher frequencies give contributions, the unity should be

replaced by c,. The real and imaginary parts are
2 2
D1 1 (2.100)

D2 (2.101)
w(1 + Uw22)

In the limit of low frequency where w ;< T- is satisfied, we can obtain following

relations:


CD1 DT2 (2.102)

eD2 opDT/U 47 ro/w; >> CD1 (2.103)

n t (rc 2/2)1/2 (2.104)

S t 1 2/n 1 (2w/7ao)1/2 (2.105)


Eq. 2.105 is known as the Hagen-Rubens relation. From the second expression we can

find the absorption coefficient:


a =- (2.106)
c c



12 The Drude plasma frequency ucpD is related to the dc conductivity and carrier mo-
bility p as ao = ~Di-/4r Nqp. The mobility (a ratio of the carrier drift velocity to
the field) is given by p q-r/m*. For metals, ao is (nearly) independent of temperature
assuming that r does not (or only weakly) vary with temperature, and is used to char-
acterize metals. For semiconductors, on the other hand, their carrier densities can be
varied by changing the temperature or the dopant concentration. Therefore, the mobility
is more convenient quantity to characterize semiconductor since the carrier density is
taken out.








or the skin depth:
2 c
S- (2.107)
a y2w7a7o0
Therefore, the skin depth is inversely proportional to the square root of dc conductivity

and frequency. This implies that a material with higher dc conductivity allows shorter

penetration of ac fields for a given frequency.

As another limiting case, consider an undamped free carrier system like a perfect

conductor. In this special case, the Drude width -1 = 0 and the dielectric function is

real and given by


CD1 oo (2.108)

eD2 DI = 0 (w / 0) (2.109)


Here we have used c. just for the purpose of generality. This equation tells us that

CD < 0 for frequencies below the plasma edge (u < wUpD/ /-g). Then, the complex

refractive index N is purely imaginary and thus the reflectance J is 1 in this frequency

range and the system suddenly becomes transparent above the plasma edge.13 This,

so-called a plasma reflection, happens without loss of energy since there is no resistive

current (i.e., cUD = 0) associated with this free carrier response.

In real materials, the damping T-1 has a non-zero value which may be deduced

from dc conductivity or other measurements. The effect of the damping may be small

but results in slightly less reflectance as well as broadening of the plasma edge. The

reflectance may be even lower and have structures due to other absorption processes

such as interband transitions. If other processes occurs near the plasma edge, sharp

onset of transmission may not be observed.



13 For metals, c, t 1 and the reflectance is very high for frequencies up to UcpD. For
semiconductors, on the other hand, c. can be large and as a result the plasma edge at
wpD//-- is lower than UpD.








2.5.3 Drude-Lorentz Model

When both the Drude and the Lorentz types of dielectric response is observed in a

spectrum, the total dielectric function can be expressed as the sum of various different

processes that cause a polarization:
2 2
(w) 2 2 i 7 a)+3 w -2 +i (2.110)
SJ U1- tjU U J

This relation is called the Drude-Lorentz model, and can be used in fitting the experi-

mental reflectance data for extracting optical parameters. Unlike the KK-methods, the

fitting data with the model function can be employ,, 1 in a finite frequency range as long

as we have a well defined background contribution co beyond the measured frequency

range.

2.5.4 Sum Rules

In 2.5.1, we introduced the notion of oscillator strength f. Using quantum

mechanics, it can be shown that the total absorption by all transitions for the whole

frequency range is constant, and can be expressed by the f-sum rule:


ja 1 (a)) dw y- f. (2.111)


This tells that the total are under the real part of the conductivity is independent of

temperature, phase transition, photo-excitations, and so on. There exist several other

sum rules, but we will not discuss them here.

The sum rule is often applied to a certain process. If only free carriers are con-

cerned, Eq. 2.111 is rewritten as


SUai( )dw ) (2.112)

This is an exceptionally useful equation to see how the spectral weight shifts into the

delta function at zero frequency as a superconductor experiences phase transition.















CHAPTER 3
FOURIER SPECTROSCOPY

3.1 Introduction

A spectrometer is an instrument that is designed to yield spectral information

contained in the electromagnetic waves under study. There exist several types of

spectrometers used for a number of research fields. Figure 3-1 shows the classification

of spectrometers. Of all, the scanning two-beam interferometric types are probably the

mainstream instrument now owing to their various advantages which will be explained

shortly.

The monochrometer spatially separates the individual frequency components

by means of a dispersive element such as prism or diffraction grating. An individual

frequency component is selected by a slit, and its intensity is sequentially sampled. A

power spectrum is produced after measuring over all frequencies of interest. Although

this type of instrument is still used commonly, especially for near infrared and visible

spectroscopy, they have met with several limitations. The main difficulty comes from

their slow scanning process. Because the monochrometer measures each frequency

individually, it takes a long time (typically 10 minutes or more depending on the

signal to noise as well as resolution) to complete a single scan. The interferometric


Dispersing Prism spectrometer
spectrometer
(monochrometer) Diffraction spectrometer
Michelson interferometer
(amplitude separation)
Spectrometer-
Twin-beam interferometer-- Lamellar grating interferometer
(wavefront separation)
Interference Martin-puplett interferometer
spectrometer -(polarization separation)
(interferometer)
Fabry-Perot interferometer
Multi-beam interferometer--
-- Etalon

Figure 3-1: Classification of spectrometers.








techniques were developed to overcome some of the limitations encountered with

dispersive instruments.

The interferometer is an instrument that can divide the incoming beam of light

into two paths and then recombine the two beams after a (optical) path difference (or

retardation) has been introduced. These recombined beams produce interference and

the resulting signal is detected. The measured signal as a function of path difference,

called an interferogram, is the Fourier transform of the power spectrum of the incident

light. Thus it can be inverse-Fourier transformed to yield the power spectrum. However,

because of the fact that the detected signal must be treated mathematically before

obtaining meaningful spectrum, certain care must be taken to avoid introducing errors

into the spectrum.

Interferometric technique has two basic advantages over dispersive methods. The

fact that nearly alv-l- the total intensity hits the detector during the whole period of

measurement improves the signal-to-noise (S/N) ratio, particularly for weak radiation

sources. This is known as the throughput (or Jacquinot) advantage. The interferometer

measures all frequency components simultaneously. This leads to considerable multiplex

(or Fellgett) advantage allowing quick data acquisition and higher S/N.

3.2 Fourier Transform Interferometry

3.2.1 General Principles

The general principle of interferometry can be understood by considering a simpli-

fied Michelson interferometer [21, 22, 23], which is shown schematically in Figure 3-2.



Consider that a monochromatic plane wave of the form


Es = Eo Ci(27vx-t)


(3.f)















Source C


Beam splitter
(r(wo), t(wo))


1 M1 (r,(o), #(o))


. x/2 (M
SM2 (ro(o), 2(o))
(Movable)


V Detector

Figure 3-2: A schematic view of a simplified Michelson interferometer. The light travels
to the beam-splitter with its amplitude reflectivity r and transmissivity t. The partially
reflected beam travels toward the fixed mirror (\! I) that has the reflectivity ri and
introduces phase shift 1. The partially transmitted beam travels a variable distance
toward the movable mirror (\ 2) with r2 and 2. The beams are recombined at the
beam-splitter after a optical path difference x has been introduced, and half of the total
beam returns to the source, and the other half proceeds to a detector. A sample can be
place between interferometer and the detector.


is incident on the beam-splitter from the source. Here, v is the wavenumber.1 This

beam-splitter partially reflects the beam toward the fixed mirror M1, and transmits

the rest toward the movable mirror M2.2 After travelling their respective paths, the

two beams are recombined at the beam-splitter, and the resultant beam proceeds

to a detector. If the beam-splitter has the amplitude reflectance r and amplitude

transmittance t,3 the resulting field emerging from the interferometer toward the



1 The wavenumber is defined as v = 1/A = 2rk = w/2rc.
2 Here for simplicity, we will assume that both M1 and M2 are equivalent perfect
reflectors. The amplitude reflectivity is a complex number which can be expressed as
r = r/E, = r(ow)|ei K), where E, is the reflected field, Ei is the incident field, and Q(w)
is the phase shift. For a perfect mirror, r| = 1 and Q = r.

3 For an ideal beam-splitter, r = t = 2-1/2. They are both frequency dependent.


2 -7r







detector is a superposition of fields from two beams which is given by

ED ri .,,, L- t) + Ci(2V 2- t)] (3.2)


where xi and x2 are the total distances of respective beam's optical path (see Fig-

ure 3-2). Since the energy reaching the detector is proportional to EDES, the time

averaged detector signal can be written as

S(x) = -lo(v)[1 + cos(2vx)] (3.3)
2

where we have defined the optical path difference, x = x2 x, the beam-splitter

efficiency, c = 4|rt|2, and the source intensity, lo(v). This expression may be simplified

to

S(x) = f(v)[1 + cos(27vx)] (3.4)

where f(v) is an arbitrary spectral input that depends only on v. S(x) is the detector

signal for a monochromatic source. The cosine term gives the modulation on the

detector signal as a function of x.

As mentioned earlier, with the interferometric technique all frequency components

are measured simultaneously. Eq. 3.4 can be generalized for a polychromatic source by

integrating it over all frequencies:


S(x) f ()[1 + cos(27vx)]dv (3.5)

At x = 0, the detector signal reaches its maximum value of

S(0) 2 f(v)dv (3.6)

This position corresponds to the zero optical path difference (or ZPD) where all

frequency components interfere constructively. As x -- o, on the other hand, the

coherence of the modulated light is completely lost, and the cosine term in Eq. 3.5 goes

to zero. Therefore, the detector signal oscillates around an average value:

S(oo) f (v)dv =S( (3.7)
n 2







The interferogram is the cosine modulation part of the detector signal:

F(x) = S(x) S(o) = f(v) cos(27vx)dv (3.8)

This is the cosine Fourier integral of the desired spectrum f(v) which can be recovered

by taking the inverse Fourier transform:

f(v) = 4 F(x) cos(27vx)dx (3.9)


3.2.2 Finite Retardation and Apodization

So far in our calculation, it was assumed that the spectrum is obtained after the

Fourier transform (FT) of the interferogram measured with an infinitely long optical

path difference (retardation). In practice the interferogram can not be measured

to infinite retardation, and it must be truncated. This type of truncation can be

manipulated mathematically by multiplying the complete interferogram by a truncation

function G(x) which vanishes outside the range of the data acquisition. Thus the actual

function which is transformed is the product of the interferogram and the truncation

function.

Now according to the convolution theorem, the FT of the product of two functions,

i- F(x) and G(x), is the convolution of the FT of each function, f(v) and g(v), where

the convolution is defined by

f(v) *g() f(v')g( v')d' (3.10)

Hence, the calculated spectrum is the true spectrum convolved with the FT of the

truncation function.

In order to examine the effect of truncation, consider multiplying an interferogram

F(x) with the boxcar function G(x) which is defined by

(1 if x\ < L
G(x) = if < L (3.11)
0 if x > L,






















Vv 1/
-1/L-


V cm


v,-1/2L v +1/2L

Figure 3-3: The sine function convolved with a single spectral line of wavenumber V1. L
is the maximum retardation.

where L is the maximum retardation. The FT of F(x) is the true spectrum f(v), while

the FT of G(x) is the sine function:


FT[G(x)] = 2Lsn(27 L) 2L sinc(27wL) (3.12)
27rvL

When the sine function is convolved with a single spectral line of wavenumber

v1, the resultant spectrum is the sine function centered about v1, which is shown in

Figure 3-3. Thus the effect of convolution is to smooth out the narrow feature. The

single spectral line shape as a result truncation is sometimes called the instrument line

shape (ILS) function.

It can be shown that the first zeros on either side of v1 occur at v1 1/2L. Thus,

two spectral lines separated by 1/L are completely resolved. Thus the resolution is

limited by the maximum path difference on the interferogram. The value of 1/L (in

cm-1) is often used as a quick estimate of spectral resolution. The full width at half

maximum (FWHM) is sometimes used as an alternative estimate of resolution.








The sudden cutoff with the boxcar function introduces side lobes near sharp

features in the spectrum.4 Thus, it is desirable to use a weighted truncation function

that cuts off the interferogram in gentler fashion. This process, known as apodization,

reduces the ringing at the expense of a further reduction in resolution. For example, the

Happ-Genzel [24] is a simple apodization function given by


Gi(x) 0.54 + 0.46cos(7x/L) (3.13)


where L is still the maximum retardation. The FT of the Happ-Genzel is


FT[Gi(x)] 2L sinc(27vL) 0.54 (46(2v2 L)2 (3.14)


Again, convolution of this function with a single spectral line of wavenumber v1 is the

resultant spectrum which is shown in Figure 3-4 together with the FT of the boxcar

(i.e., since function). This figure clearly demonstrates that the use of a gentler truncation

function suppresses the side lobes while the resolution is reduced. The FWHM of the

spectrum using the Happ-Genzel and the boxcar are 0.91/L and 0.61/L, respectively.

Some of other popular apodization functions are the Norton-Beer (weak, medium,

strong) [25] and the Blackman-Harris (3-term, 4-term).5 Very nice discussion about

apodization functions can be found in Griffiths [22].

3.2.3 Sampling

In the use of a computer for data acquisition, the analog signal must be converted

to digitized data sets (i.e., A/D conversion) before any sort of manipulation can take

place. For this reason, the interferogram is sampled at small, equally spaced discrete

retardation, and the Fourier integral, Eq. 3.9, is approximated by a sum. This discrete



4 The first minimum drops off below zero by 22' of the height at central maximum.
The secondary maxima are also relatively large. These side lobes give rise to oscillation
which may appear as spurious features especially in the neighborhood of sharp spectral
features.

5 Personally, I start with the Norton-Beer (medium) apodization function first, and
try others if ceratin improvement has to be made depending on the spectral features.









- --.. FT [Boxcar]
FT [Happ-Genzel]


"* : VI
- '# < 1 1
" ,-' I1/LT -*. "


V cm


v,-1/2L v +1/2L

Figure 3-4: The FT of the Happ-Genzel (HG) apodization function convolved with a
single spectral line of wavenumber v1. L is the maximum retardation. For comparison,
the FT of the boxcar sincec function) convolved with the same single line is shown. The
FWHM of the spectrum for the HG and the boxcar cases are 0.91/L and 0.61/L, respec-
tively. Note that the side lobes in the spectrum are suppressed by using the HG at the
cost of resolution.

nature can be handled mathematically by using the Dirac delta comb defined by


Im(x)= 6(x an) (3.15)
12=-00

The Dirac delta comb is just a series of 6 functions at the integers. It has following

properties:


II(x + m) = U(x) (periodic), (3.16)

S(ax) (x= -) (scaling), (3.17)

i1(ax)T 0
FT[(axr)] (11 w Ci2'n/a (Fourier transform), (3.18)


iI(z) F(x) = F(n)6 (z- n) (sampling), (3.19)
) n=-

III(x)* F(x) > F(x- ) (replication). (3.20)
n=-oo








(A) f
max
!imax .. .. ......


0 A 2 v cm

Av=1/Ax
(B)


I 0 I I o
1- v cm
max

Figure 3-5: The relation between spectrum replication and sampling rate. (A) Proper
choice of sampling rate such that the true spectrum is confined to one-half of the repli-
cation period (i.e., vmx < Av/2). In this situation, the periodic replicas do not overlap
and no error is introduced by sampling. (B) Improper choice of sampling rate. Overlap-
ping with .,I]i i ent replicated spectrum causes spurious result in the spectrum.

If the continuous (or analog) interferogram F(x) is sampled at intervals Ax, the

sampled (or digitized) interferogram F'(x) is given by

F'(x) II ( x) F(x) = x F(nAx)(x nAx) (3.21)


Then, the spectrum derived from the FT of F'(x) is

f'(7) -U f (V) f= ( nA), (3.22)
n=-oo

where Av = 1/Ax and f(v) = FT[F(x)].
Eq. 3.22 is the spectrum we actually obtain as data which is comprised of periodic
replicas of our desired spectrum f(v) with period Av. This replication, which obviously

arises from the sampling of the analog interferogram, raises an important issue of the
sampling frequency, which is peculiar to discrete sampling. Figure 3-5 illustrates the
relation between replication and sampling rate. As in the figure (B), if the highest

frequency, ,max, of the true spectrum exceeds the folding frequency, Av/2, then two
.,.li i:ent replicated spectra overlap, and too-high frequencies appear falsely at lower





41







Figure 3-6: The red curve of above-Nyquist frequency appears to possess the same set of
data points as the black curve of below-Nyquist frequency.


frequencies causing spurious result in the obtained spectrum. This is because higher

frequency waves can be drawn additionally through the same sampling points taken for

lower frequency waves as illustrated in Figure 3-6. This effect, known as spectral folding

or aliasing, can be prevented by insuring the condition:


Vmax <- (3.23)
2

or

Ax < An (3.24)
2

These conditions state that the highest frequency needs to be sampled at least twice per

wavelength, which is just the Nyquist sampling criterion. Therefore, it is experimentally

important either to ensure digitizing an interferogram at a high enough sampling rate

or to limit the range of frequency input to the detector using optical and/or electronic

filters. The responsivity of the detector often works as a kind of low-pass filter.

Following the above arguments, it is quite obvious that measurements of narrow

frequency range require smaller number of sampling points. If the number of points

is too small, the spectral shape may not be well defined. In such case, we can add

extra zero-valued data points at the end of the interferogram keeping the same sample

spacing. This technique, known as zero filling, effectively produces larger number

of spectrum points per resolution element. Since the points added are zero-valued,

spectrum resolution will not increase. It merely provides a smoother spectral line shape.

3.2.4 Phase Error and Correction

Until this point, we have assumed that the interferogram is perfectly symmetric

about the ZPD. In a real experiment, however, there often exists a phase error that

must be included to describe the actual measured (i.e., .,i-ii ". i ic) interferogram. It







mainly results from sampling errors, electronic filtering, and optical effects from various

parts of instrument optics as well as a sample. The effect of such error is to distort the

ILS function from the symmetric since function to an ..i-mmetric shape. This could lead

to negative spectrum or slight shift of sharp features. Therefore, it is important to have

schemes that could correct faulty effects from a calculated spectrum.

When the phase error is included, the interferogram given by Eq. 3.8 is modified

to6

F(x) f (V)e-i(2-vx-dv = [fv ()ei]e- i2XFdv (3.25)

where 0 is the phase error (or phase spectrum) which can be frequency dependent. Note

that here we used the exponential notation for simplicity. Then, the the calculated

spectrum through the inverse complex FT is

f() =(V)ei F(x, -7dx. (3.26)


Hence, the ..ivmmetric interferogram yields a complex spectrum. The real part of the

spectrum, Re[f(v)], and the imaginary part of the spectrum, Im[f(v)], can be computed

by the cosine FT and the sine FT of the interferogram measured symmetrically on either

side of the zero retardation point (or centerburst), respectively. Our aim is to find the

phase error, 0, from which we apply some sort of phase correction scheme to determine

the true spectrum of interest, which is f(v) in Eq. 3.26.

Here we explain the simplest way to achieve the phase correction. First, we take

an interferogram between -L1 < x < L2 where x = 0 corresponds to the centerburst.

Since it is only required to calculate 0 at very low resolution, the distance L1, which

is determined by the phase resolution setting, can be smaller than the distance, L2,



6 The phase error is added to the phase angle of the interferogram as cos(2rvx 0) =
cos(27vx) cos 0 + sin(27vx) sin 0. The FT of a truncated sine wave is an odd function.
Thus, the added sine component is responsible for the ..i-, ii, I iir shape of an interfero-
gram, and the its FT causes distortion of the ILS function.





43

required to attain the desired resolution (I/L2).7 From the short double-sided region of

the interferogram (-Li < x < L1), the phase spectrum can be found from


(v) = arctan (m[f(f( (3.27)
Re[f(v)])

Having calculated 0, the complex spectrum, f(v) may be corrected by multiplying it by

e-io cos 0 i sin 0 such that


f(v/)corrected f()ei e-io = f () (3.28)

In this way the recovered spectrum may be corrected for errors incurred as a result of

.,i-v,,ii. 1 i1. s in the measured interferogram.

There are several phase correction modes available among which the method

developed by Mertz is the most commonly used one. More detailed discussion of phase

correction methods can be found in various papers [26,27,28].

3.2.5 Step-Scan and Rapid-Scan Interferometers

There are in general two different kinds of interferometers depending on its scanner

(movable mirror) movements: step-scan interferometers and rapid-scan interferometers.
In step-scan interferometers, the scanner starts from its reference position, and steps

to equally spaced sampling positions. At each sampling position, the scanner is held

stationary and the detector output signal is integrated. The stepping continues until

the desired resolution has been achieved. Compared with rapid-scan interferometers,

step-and-integrate systems have unavoidable down time while moving to the next

sampling point and waiting for the scanner to be stable before actually starting data

acquisition. In addition, the fact that it takes longer time to complete single scan

makes step-and-integrate systems prone to be sensitive to slow variations in the source

intensity which could degrade spectrum especially at low frequency. Further, the



7 Typically the phase resolution is set to have 4 to 8 times lower than the spectral res-
olution. If the double-sided acquisition mode is used (i.e., L1 = L2), the phase resolution
setting is completely ignored for obvious reason.








systems generally require to use a chopper, and thus lose another half of the signal after

the interferometer. These characters makes step-scan technique rather inefficient, and in

general rapid-scan method is superior and adopted by the most of recent instruments.

In rapid-scan interferometers, the scanner moves at constant and sufficiently high

velocity. When a signal of a particular frequency v is sent as input to an interferometer,

it is modulated at a frequency v' which is related to the moving mirror velocity v as

V/ -v vv (3.29)
c A

where v' and v are in Hz, A in cm, v in cm/s, and v in cm-1. Hence, in order to be

able to analyze the signal at the detector it is necessary to know the scanner velocity

accurately. It can be calculated by measuring the modulated frequency of a laser

input with known wavelength. If a Helium-Neon (He-Ne) laser at 632.8 nm is used, for

example, its typical modulated frequency,8 -v- 10 kHz, corresponds to 0.6328 cm/s for

the scanner velocity.

Now, having a continuous source as input, all frequency components are modulated

(typically in the kHz range) according to Eq. 3.29. Since these modulation frequencies

are in the audio range, they can be easily amplified and filtered electronically. A low-

pass filter eliminates noise of much higher frequency than the modulation frequency

of the shortest wavelength in the spectrum and prevents aliasing. A high-pass filter,

on the other hand, may be used to force slow background modulation, such as source

fluctuation, to below its cutoff.

Another important factor in rapid-scan systems is the determination of the correct

time to start data acquisition. The position of the centerburst of continuous source

can be used as a reference point. This information is essential for data collection, since

the method of analysis relies on the cumulative addition (co-adding) of a number of




8 Some of modern instrument, such as Bruker IFS66v/S, can set the modulated fre-
quency of He-Ne laser to as fast as 200 kHz, which calculates to 12.66 cm/s of the scan-
ner velocity.





45

interferograms. Co-addition is a technique which improves the signal-to-noise (S/N)

ratio. Corresponding data points must be sampled at the same path difference on every

successive scan. The zero crossing points of the laser interferogram may be used as a

reference point to start and tri -. -.-r the sampling of analog data from the detector. The

signal increases linearly since it is ah--,v- coherent. Noise occurs randomly, thus the

signal increases faster than the noise. This process, called signal averaging, increases

the S/N ratio as square root of the number of scans co-added. Therefore, in order to

increase the S/N by a factor of 2, the number of scans must be increased by a factor of

4.

3.3 Polarization Modulation

Up to this point of this section, we have been talking about interferometers of

amplitude separation type which use a partially transmitting and partially reflecting

beam-splitter with Michelson configuration. Despite clear advantages over dispersive

type of monochrometer, amplitude separation interferometers also exhibit some difficul-

ties especially for very far infrared. The main difficulty of this type is the low efficiency

and limited spectral range of thin-film dielectric beam-splitters such as Mylar which is

mostly used for far infrared. In order to overcome such disadvantages, different types of

interferometers were developed. One of them is a lamellar grating interferometer. Rather

than separating amplitude of incident light, a lamellar grating separates wavefront of

incident light. The efficiency of lamellar grating beam-splitter is nearly independent of

frequency and can be very high. Although the lamellar grating uses different method

to separate light from film beam-splitter, both are still intensity modulation type of

interferometers. We will not discuss the lamellar grating interferometer further, but

interested readers are encouraged to read several papers about this topic [22, 29].

There is another type of interferometer which is commercially available these d v-

It is the polarizing interferometer based on a concept by Martin and Puplett [30]. It

has similar configuration as Michelson, but uses rather unique approach to produce

modulation of incident light. A schematic diagram of polarizing (or Martin-Puplett)

interferometer is shown in Figure 3-7. Light from an unpolarized (or polarized) source is







M1





Unpolarized >- /B
(or polarized) M2
source /

P1 v M -

P2


"7 Detector

Figure 3-7: A schematic view of a Martin-Puplett interferometer. The collimated light
is linearly polarized at a polarizer P1 and travels to a polarizing beam-splitter B which
is aligned at an angle of 450 with respect to the plane of polarization after P1. The
beam-splitter separates two polarization components sending one component toward a
fixed rooftop mirror Ml and the other toward a movable rooftop mirror M2. On reflec-
tion, the polarization of each beam is rotated by 900, and two beams are recombined
at the beam-splitter. At the beam-splitter, the initially transmitted beam is completely
reflected, and initially reflected beam is completely transmitted. The recombined beam
heads to the second analyzing polarizer P2 and the beam is linearly polarized after P2
with an amplitude varying periodically with path difference.

linearly polarized at a polarizer P1 in the plane at ceratin orientation. It is then divided

into two polarization components by a polarizing beam-splitter B which is typically a

free-standing fine wire grid (or a grid on Mylar film). This type of beam-splitter has

been shown to have almost frequency independent and high efficiency of nearly 10(I' .

from effectively zero frequency up to roughly 1/2d (cm-1), where d (cm) is the spacing

of the wires [31]. The gird reflects the component of the incident light parallel to the

direction of the wires and transmit the component normal to the direction of the wires.

When the beam-splitter is oriented with the wire grids at an angle of 450 with respect to

P1, the incident polarized light is equally split sending one component to a fixed mirror

Ml and the other to a movable mirror M2. Both M1 and M2 are the 900 rooftop mirrors

which rotate the plane of polarization by 900 on reflection. Therefore, when two beams

come back to the beam-splitter, the one reflected initially is transmitted completely, and





47

(a) (b) (c)


Io

2 -------------------^------ ^AAAAV VAAA/^_





Figure 3-8: Interferograms produced by a polarizing interferometer. (a) The interfero-
gram for parallel P1 and P2. (b) The inverted interferogram for crossed P1 and P2. (c)
The difference of (a) and (b), which is obtained by polarization modulation technique.
Note that the mean level of the interferogram is automatically eliminated.

the one transmitted initially is reflected completely. No beam is sent to the direction of

the source. The combined beam finally passes through the second polarizer P2 with its

polarization axis either parallel or perpendicular to that of Pl.

As M2 moves, a phase difference is introduced between two beams. For a monochro-

matic source, the initially linearly polarized beam is elliptically polarized after recombi-

nation at the beam-splitter with an ellipticity varying periodically with increasing path

difference. At the ZPD, the recombined beam has the same polarization as the incident

beam on the beam-splitter. After P2, the beam is plane polarized with an amplitude

that varies periodically with path difference in the same way as in a Michelson inter-

ferometer. Assuming an unpolarized source, the intensity at the detector is given by



I (x) = [1 + cos(27vx)] (3.30)

or

Ii(x) = [l cos(2vx)] (3.31)
2

where Jo is the intensity of the linearly polarized beam incident on the beam-splitter.

The case III is for parallel P1 and P2, and I_ is for crossed P1 and P2. For a source of

continuous spectrum, the output intensity yields an typical interferogram except that of

Ij is inverted (see Figure 3-8).





48

The complementary nature of the interferograms for the two orientations of one

polarizer with respect to the other can be utilized to introduce polarization modulation.

This is usually done by keeping P1 fixed and by dynamically switching the orientation

of P2 using a polarizing chopper.9 Then, by using standard Lock-in technique, the

detected signal is the difference between II and 1L, which is given for a monochromatic

source as

I(x) = I (x) I (x) = o cos(27vx) (3.32)

Thus, the phase modulation technique eliminates the mean level of the interferogram

which could introduce errors due to spurious fluctuations (see Figure 3-8). This and

wide range high efficiency of a polarizing beam-splitter makes the Martin-Puplett

interferometer advantageous for very far infrared measurements. One of spectrometers

we used is the polarization modulation type. Details of the specific instrument will be

discussed in C'! pter 6.


























9 We can keep P2 and rotate P1 just as well. If we have a polarized input source,
however, P1 should be aligned such that the most light can go through, and use P2 for
the polarization modulation. There is also a technique called a double polarization mod-
ulation which uses two polarizing choppers for P1 and P2 [32,33].













CHAPTER 4
SUPERCONDUCTIVITY

4.1 Introduction

In 1911, soon after successfully liquifying helium in 1908, Kammerlingh Onnes

discovered that the electrical resistance of mercury suddenly drops to an unmeasur-

ably small value when it is cooled below 4.2 K [34]. This phenomenon was named as

superconductivity. In subsequent years, many more metals and metallic alloys were

found to be superconducting when cooled to below a certain critical temperature T,.

In 1933 Meissner and Ochsenfeld demonstrated another basic property of supercon-

ductor, perfect diamagnetism, which is known as the Meissner effect [35]. In 1935,

F. London and H. London developed a purely phenomenological description through

a modification of an essential equation of electrodynamics in such a way to explain

the Meissner effect [36]. They pointed out that superconductivity is a fundamentally

quantum mechanical phenomenon that is observed on a macroscopic scale, with an

energy gap between superconducting and normal state. Another phenomenological

theory was also developed by Ginzburg and Landau in 1950 [37]. Then, finally in 1957,

Bardeen, Cooper, and Schrieffer proposed a microscopic theory of superconductivity as

a phenomenon where electrons form pairs and an energy gap develops in the electronic

density of states around Fermi energy [38]. This so-called BCS theory remains as a valid

microscopic explanation for many simple superconductors (BCS superconductors).

A breakthrough in superconductivity research occurred in 1986 when Bednorz and

Miller found a copper oxide compounds of the Ba-La-Cu-O system which superconducts

at a substantially higher temperature (T, ~ 30 K) than previously known [39]. With

their work, a new era of superconductivity opened in this class of materials (high-T,

superconductors) which differs from conventional BCS superconductors. Now we know

various materials that have T, above the boiling point of liquid nitrogen (77 K).







The microscopic theory of superconductivity can not be described in the language

of the independent electron approximation, and relies on formal techniques.1 It is quite

extensive and highly specialized. Consequently, we will limit our survey of the theory

to qualitative descriptions of some of the in i.' concepts within the framework of BCS

theory. Details of the subject can be found in many places [40, 41, 42, 43, 44]. In the

following section, we will merely summarize a few basic properties of superconductors.

In C'!I pter 7, we will provide brief theoretical background for the infrared properties

of superconductors and the effects of localization on superconductivity, based on the

work by Mattis and Bardeen [45], and by Maekawa and Fukuyama [46], respectively. In

C'!I pter 8, we will discuss theory of nonequilibrium superconductivity.

4.2 Fundamentals of Superconductivity

4.2.1 Fundamental Phenomena

Vanishing DC Resistance

Of all the characteristics of superconductors, the absence of any measurable DC

electrical resistance is the most striking phenomenon. Above a critical temperature T, a

bulk superconducting specimen behaves completely as normal metal with DC resistivity

generally given by

p(T) po + BT (4.1)

where the first term arises from impurity and defect i ii. 1 ii.- and the second term

from phonon scattering. Below Tc, the metal becomes superconducting with no dis-

cernible DC resistivity (zero DC resistivity), and current flows in it without any



1 The second quantization description of many-body system is used to describe the
BCS theory, including the energy of the BCS ground state, giving the energy gap result-
ing from the electron pairing.





51

Table 4-1: Transition temperatures for several superconductors. Some of high-T, materi-
als are also listed.
Element Te(K) Compound Te(K) High-To T (K)
Mo 0.92 NiTi 10 Bao.75La4.25Cu505(3-y) 30
Al 1.2 NbN 15.2 La2_-SrCuO4 38
In 3.4 Nb3Sn 18.1 YB2C307 92
Hg 4.1 Nb3Ga 20.3 Bi2Sr2CaCu202 85
Pb 7.2 Nb3Ge 23.2 Bi2Sr2Ca2Cu3010 110
Nb 9.2 MgB2 39 HgBa2Ca2Cu30s 133


dissipation of energy. The transition of a bulk material is usually abrupt, and hap-

pens at very low temperature.2 Table 4-1 lists the transition temperatures of several

superconductors. The fact that there is no measurable resistivity allows us to pass large

current through a superconductor, and in turn, to create large magnetic field. However,

if the current density exceeds a critical current J,, a superconductor reverts to a normal

conductor (Silsbee effect). J, is related to whether the magnetic field created by the

current exceeds the critical field He above which superconductivity is destroyed. In an

AC electric field, superconductors at finite temperature no longer exhibit zero resistivity.

The resistivity increases with frequency. However, at temperatures well below T~, the

resistivity is still negligible provided that the frequency is not too large (< A/h, where

A is the energy gap.). 7.2.1 describes the response of superconductors in AC fields.

Meissner Effect

A superconductor expels magnetic flux, and hence acts like a perfect diamagnet.

This is another peculiar phenomenon of superconductivity known as the Meissner effect

(or Meissner-Ochsenfeld effect). Having p = 0 in the Maxwell equations for a perfect

conductor, we find OB/Ot = 0, and thus the magnetic flux is expected to remain

unchanged within the specimen. In superconducting state, however, we find not only

B = constant, but also B = 0, and the field penetrating the specimen (provided that



2 The thermal energy kBTc corresponding to the transition temperature is on the or-
der of a few meV or less. This is much smaller than the energy scale such as the Fermi
energy EF (~ 10 eV) and the Debye energy huoD (~ 0.1 eV) of the most of metals.








it is not too strong) prior to making the transition to superconducting state will be

expelled from the interior. A simple explanation for this effect is that the impinging

magnetic field induces shielding currents on the surface of a superconductor, which

are just enough to cancel the field in the interior. Since the superconductor has zero

resistivity, the currents (i.e., supercurrents) will persist even after the field stopped

changing. The distance which the supercurrents form a finite sheath into the specimen

is called the London penetration depth AL. Magnetic flux can also penetrate the same

distance into the material. For many simple, pure metals, this penetration depth is on

the order of 500 A. As mentioned above, if the field gets too large, however, the material

will eventually lose its superconducting state.

Magnetic Flux Quantization

It is another property of superconductors that the magnetic flux passing through

any area enclosed by a supercurrent in a closed loop can only take on values of integral

multiples of the so-called flux quantum (or fluxoid):

he
40 2.0679 10-7G cm2 (4.2)
2e

where h is Planck's constant, c is the speed of light, and e is the elementary charge.

This flux quantization is a consequence of that the complex order parameter Q(r) =

i', '|. (introduced in the Ginzburg-Landau theory) is a single-valued function, and thus

its phase must change by 27 times an integer.

A similar effect occurs when a type II superconductor (refer to 4.2.3) is placed

in a magnetic field. At sufficiently high field strengths, some of the magnetic field may

penetrate the superconductor in the form of thin threads of material that have turned

normal. Each thread is in fact the central region ("core") of vortex of the supercurrent,

and carries a single flux quantum.

Josephson Effects

When two superconductors are in weak contact (e.g., separated by a thin insulating

oxide barrier (10 20 A), a normal conducting lv-r (100 1000 A), or a constriction),





53

Cooper pairs could tunnel from one to the other giving rise to a characteristic current

through the so-called Josephson junction.

When there is no voltage drop across the junction, a DC current will be generated,

given by

I = l sin (4.3)

where po is a constant phase difference (i.e., relative phase) of the BCS irn ivi-body

states in two superconductors, and Ic is the maximum current that can pass through the

junction before driving it to a resistive state. This is called the DC Josephson effect.

When a DC voltage U is applied between the junction, the relative phase pO evolves

with time as
2eU
(t) = (0) t (4.4)

This gives rise to an AC current given by


I = Isin[(0) t] (4.5)


with
2eUT
2e= (4.6)

This is called the AC Josephson effect. Interesting interference phenomena arise when

two Josephson junctions are connected in parallel. These can be used for a very sensitive

magnetic field senor, known as the SQUID.

These are the effects where the characteristic high coherence of the Cooper pairs

becomes particularly evident.

Isotope Effect

When a constituent atom of a superconducting material is replaced by its isotope,

the critical temperature often changes with atomic mass M in accordance with the

relation


M'T = constant ,


(4.7)





54

where a = 1/2 for the simplified BCS model. As will be shown later, the simple BCS

theory predicts that Tc is proportional to the Debye frequency LcD (hD is a measure

of the typical phonon energy), and thus this is expected since the Debye frequency is

proportional to the square root of the atomic mass for a simple metal.

4.2.2 Thermodynamic Properties

The transition of a metal from its normal state to its superconducting state is a

thermodynamic phase transition. Therefore, some sort of changes may be expected in

thermodynamic quantities as a specimen makes its transition. The electronic part of

specific heat, for example, increases discontinuously at T, from the linear temperature

dependence observed in normal state (T > Tc), and then at very low temperatures sinks

to below the value of the normal phase. At temperatures well below T,, the specific heat

decreases exponentially.

In thermodynamics, we can use a free energy F(T) to describe the stability of a

system at a given temperature. Naturally, the system tends to change its state toward

the lower free energy, and becomes stable at a minimum of the free energy. Below the

transition temperature, the free energy in the superconducting phase F, is reduced

below that in the normal phase F, (i.e., F, < F,) due to the condensation of Cooper

pairs, and thus the system naturally becomes superconducting. The critical temperature

is the temperature where F, crosses over F,.

As mentioned earlier, superconductivity is destroyed with a sufficiently large

magnetic field. When the amount of work has to be done to establish the magnetic field

of the screening currents that cancels the field in the interior becomes larger than the

reduction of free energy by turning into a superconducting phase, it is energetically

advantageous for a specimen to revert back to normal, allowing the field to penetrate.

The difference in free energy between normal and superconducting states is related to

the critical field He as

F (T)- F,(T) H(T) (4.8)
87








Thus, from He, we can calculate the free energy difference. Then using Eq. 4.8, we

can deduce a series of thermodynamical properties including the difference in entropy

between two phases, the latent heat of the transition, and the discontinuity in the

electronic specific heat. The latent heat of the transition L vanishes for the transition

in zero field, and thus the superconducting transition in zero field is of the second

order. When a magnetic field is present, however, there is a latent heat, and the nature

of the transition changes to the first order. The difference (F, Fn)T=o is called the

condensation energy.

4.2.3 Types of Superconductor

Superconductors are categorized as being one of two types: type I and type II. Type

I superconductors are mostly the simple (nontransition) metals and metalloids with low

T,. The BCS theory explains these superconductors quite well. Type II superconductors,

in contrast, are more complex (transition metals, intermetallic compounds, high-Tc,

and etc.), and often have a higher T,. One of the main difference between two types

of superconductors is the manner in which penetration occurs with increasing external

magnetic field strength. It generally depends also on the shape of the specimen, but

the clear distinction can be demonstrated with the simplest geometry of a long cylinder

(diameter > penetration depth) with its axis parallel to the applied field.

Type I

With the applied field below a critical field [H < Hc(T)], magnetic flux does not

penetrate the bulk of the type I cylindrical material, thus showing complete Meissner

effect (B = 0). When the applied field exceeds H,(T), the entire specimen becomes nor-

mal, and the field penetrates completely (B = H). This type of behavior is particularly

evident in the magnetization curve M(H). We know that the magnetic field inside any

material satisfies Eq. 2.18. Therefore, up to He, -47M increases in proportion to the

external field H. Then, at He it abruptly vanishes except for the very small diamagnetic

and paramagnetic effects of normal metals.





56

With more complex geometries, the fields at some macroscopic portions of specimen

necessarily exceed H,, and therefore, the sample exhibits an intermediate state with

some parts being normal while the rest li.ii;; superconducting.

Type II

For type II superconductors, there are three distinct phases depending on the

strength of the applied field. Below a lower critical field H~i(T), there is no flux pene-

tration just as for type I material. When the applied field exceeds an upper critical field

H,2(T), there is complete flux penetration, and the specimen becomes totally normal.

However, when the applied field is in between H~I(T) and H,2(T), there is a partial pen-

etration of flux into the specimen developing a rather complicated microscopic structure

of both superconducting and normally conducting regions. This phase is known as the

mixed state (or Shubnikov phase). The flux penetrates in the form of thin filaments

(referred as vortex lines). In the core of a filament, the field is high and the material is

normal. Each filament is surrounded by a superconducting screening current and en-

closes exactly one flux quantum o4. Current flows through the superconducting regions

and thus the material still has zero resistance. The vortex lines repel one another due

to the magnetic force between them, and thus they arrange themselves into an ordered

array of a triangular lattice. With increasing external field, the distance between the

vortex lines becomes smaller, and at H,2 they overlap completely. The magnetization

curve of type II superconductors is quite different from that of type I. Up to H,1, -47M

rises linearly with the applied field H just like type I. At H,1 partial penetration begins,

and the magnetization decreases monotonically with increasing field until it vanishes

completely at H,2. In contrast to the behavior of type I, the transition is not abrupt.

4.2.4 Length Scales

London Equation and Penetration Depth

In an effort to describe the observed behavior of the Meissner effect correctly, F.

and H. London -,ir.-. -1. '1 a condition (known as the London equation) that the local

magnetic field h(r) and the current density carried by superconducting electrons j,(r)








satisfy3

Vx j, h, (4.9)
mc

where m is the effective mass of the superconducting electrons, and N, is the super-

conducting electron density (or superfluid density).4 This purely phenomenological

equation, together with the Maxwell equation V x h = 47j,/c yields

h
A L

2j i, (4.11)
AL

where the length scale AL, known as the London penetration depth, is defined by


AL(T) 4 2t)2 1 (4.12)


Eqs. 4.10 and 4.11 allow us to calculate the distribution of fields and currents within a

superconductor. For the simplest geometry of a semi-infinite superconductors occupying

the half space z > 0, the solutions of these equations decay exponentially showing

that both magnetic fields and currents in superconductors can exist only within a liv.

of thickness AL of the surface. Therefore, the London equation implies that when a

superconductor is in an external magnetic field, the surface current flows in a thin -1v- r

and keeps the interior field-free; i.e., the Meissner effect.

Coherence Length

The London equation (Eq. 4.9) assumes that the current density j,(r) at one

point r is related to the field h(r) (or the vector potential A(r)) at the same point.



3 Fields and currents are assumed to be weak and slowly varying on the length scale
of the coherence length of the superconductor.

4 The London brothers incorporated the two-fluid model of Gorter and Casimir [47].
The model separates the total density of conduction electrons N into a density of su-
perconducting electrons N, superfluidd density) and a density of normal electrons N,
(normal fluid density) such that N N= N + NV, Ns -- N as T -- 0, and N, = N when
T > T,. They assumed that only the superfluid participates in a supercurrent while the
normal fluid remain inert at T < Tc.







Thus, the London equation is a local equation. However, it is more general to assume

that j,(r) at one point r will depend on the vector potential A(r') at all neighboring

points r'. In order to describe this non-local effects, Pippard modified the London

equation, and introduced a length scale 1o, such that Ir r'i| < o [48]. This distance

o is one of fundamental lengths characterizing a superconductor, and is referred

to as the coherence length. In one context, it is used for the distance over which

the density of superconducting electrons N, varies significantly (from zero to full

thermodynamic value). In another context, it is used as the spatial extent of the pair

wave function (i.e., the size of a Cooper pair). In pure materials well below Te, however,

both coherence length definitions have the same value; using the uncertainty principle,

Pippard estimated the coherence length to be

hvu
o = (4.13)


where vU is the Fermi velocity, and Ao is the energy gap around the Fermi surface in

the superconducting state at absolute zero. Note that the Pippard's coherence length is

independent of temperature.

In the London model, it was assumed that the density of superconducting electrons

N, would have the full thermodynamic value right from the surface (i.e., 0o = 0). Since

j, and h vary on a scale AL, we might expect that the London's model is valid only for

AL > o0. In fact, this is the case, and Pippard's non-local model reduces to the London

model in such a limit. The materials that satisfy this condition (AL > 0) are the type

II superconductors, and Eq. 4.12 accurately calculate the penetration depth for the type

II.

In type I materials, on the other hand, the penetration depth is much shorter

than the coherence length (AL < o). Thus, Ns does not reach its full value over the

penetration depth. This implies that not all of the electrons within the thickness o

from the surface contribute to the screening currents. For these materials the London

equation is inadequate. In order to calculate the penetration depth in the type I

materials more accurately, the Pippard's non-local model has to be used, and a rigorous







calculation gives

A 0.62A0o (4.14)

Consequently, the field penetrates type I materials deeper than the London value.

Ginzburg-Landau Theory

Another phenomenological approach proposed by Ginzburg and Landau (GL)

describes superconductivity in terms of a complex order parameter &(r) = &|(r)|e ,

whose magnitude |I(r) is a measure of the superconducting order at position r below

Tc [37, 49]. The order parameter ) is zero above T, and increases continuously as the

temperature falls below Tc. The physical significance of &(r) was not clear at the time

the GL theory was developed, but now we can interpret it as a wave function of a

particle of mass m*, charge q, and density N*, which are given by

m* = 2m (4.15)

q 2e, (4.16)

N* = |12 = ,/2 (4.17)

where m, e, and Ns are the effective electron mass, electron charge, and superfluid

density, respectively.

In the GL formalism, two temperature dependent characteristic lengths are intro-

duced: the coherence length (T) and the penetration depth A(T). The GL coherence

length defines the length scale over which Q(r) varies, and is given by

h h2 1/2
( 2T) 2 1) (4.18)

where a is a temperature dependent coefficient in the 12 term of the free energy

(See [40]). It is closely related to the Pippard coherence length o defined in Eq. 4.13. In

weak fields, the GL penetration depth is given by

( *C 2 1/2
A(T) 2q12 (4.19)
47q 21 b0


where ',, is the equilibrium order parameter well inside the material.







For a pure material near Tc, the microscopic calculation in the BCS approximation

gives


(T) 0.74(o 1- 12 (4.20)

A(T) --/(0) (-- (4.21)
V2 Tj

Since both diverges in the same way as T To, it is practical to form their ratio


K = A (4.22)
A(T)

The ratio K is known as the Ginzburg-Landau parameter of the material. For a pure

material, this is given by

S=0.96 A ) (4.23)

The difference in the behavior of two types of superconductors in a magnetic field

depends on whether the creation of interfaces between normal and superconducting

regions is energetically favorable, or not. Penetration of magnetic field reduces the field

energy penalty implicit in the Meissner effect. Thus, a material with large A favors

interfaces. Large coherence length means a greater extent of the superconducting state.

Therefore, with the associated energy gain from the superconducting condensation

energy, a large opposes interfaces. Interfacial energy changes sign at =t 1//2. When

V < 1/v2, the material is the type I, while r > 1//2, the material is the type II. In the

limit of r > 1, the GL theory reduces to the London theory.

Electron Mean Free Path

Another important length scale characterizing a superconductor is the electron

mean free path I in the normal state due to elastic scattering by disorder. In the

presence of disorder, we can define an effective coherence length (1), which is valid at

absolute zero,
1 1 1
S+ 1- (4.24)
(1) o I *
Depending of the size of 1 relative to o, we can think of two limiting cases concerning

the purity of a superconductor: clean limit and dirty limit [44]. Up to this point, we







have concerned only pure materials, and the mean free path has p1l i, d no role on

determining the characteristic length scales. In reality, however, the actual values of

both coherence length and penetration depth are somewhat modified from the values

defined above by mean free path effects.

In the clean limit (1 > co), Eq. 4.24 gives


(1) =o (4.25)

Thus, the coherence length and the penetration depth we discussed above can be used

without any modification.

In contrast, Eq. 4.24 gives for the dirty limit (1 < o),


(1) 1 (4.26)

Thus, the coherence length at absolute zero is completely determined by the mean free

path, the length that governs the transport properties of the material in the normal

state. In this limit, the relationship between current and magnetic field (i.e., vector

potential), and in turn, magnetic penetration depth are modified. Note that the London

penetration depth AL given in Eq. 4.12 is an expression for pure metals. The dirty limit

expression of the magnetic penetration depth is [40]

A AL( 1 (1 o). (4.27)

Thus, A increases as I becomes shorter. At temperatures near T,, the coherence length

and the penetration depth in the dirty limit are given by [40]
/ T\ 1/2
(T) 0.85(ol)/2 (4.28)

A(T) 0.62AL ( 1 (4.29)

Thus, the GL parameter for a dirty material is given by

S0.75AL(0) (4.30)
1








Consequently, as the mean free path becomes shorter, the coherence length becomes

smaller than that given in Eq. 4.13 and penetration depth becomes longer than the

London's defined in Eq. 4.12. In fact, it frequently happens that alloying a pure type I

superconductor transforms it into a type II superconductor. Many of superconductors in

the form of thin films, not to mention those in amorphous form, are in the dirty limit.

4.2.5 BCS Theory

In 1957, Bardeen, Cooper, and Schrieffer (BCS) proposed a microscopic theory

of superconductivity (now known as the BCS theory) [38]. A central result of the

BCS theory is the existence of an energy gap between the electron system in the

superconducting ground state and the excited states. Here, we will only describe the

underlying ideas, assumptions, and 1 i i"r predictions associated with the theory,

without any rigorous mathematical details.

Cooper Pairs

The ground state (T = 0 K) of a non-interacting Fermi gas of electrons corresponds

to the situation where all electron states with wave vector k within the Fermi sphere

(with EF h2k2/2m) are filled and all states outside are empty. If a pair of electrons

is added in states just above EF, the total energy of the system should increase by the

kinetic energy of the pair. However, Cooper recognized that if there is an attractive

interaction between the electrons, no matter how weak it is, they will form a bound

state, and adding a pair of electrons may reduce the total energy (kinetic plus potential

energy).5 Thus, the normal state becomes unstable to the formation of these paired

bound states [50].



5 Note that these two additional electrons are prevented from individually having
energy less than EF by the Pauli exclusion principle.





63

Since electrons have a repulsive Coulomb interaction,6 the attractive force must,

in theory, come from some interaction between the electrons that is mediated by some

other mechanism inherent in the material. Cooper argued that continuous exchange of a

virtual phonon between electrons occupying states kl and k2 provides a mechanism for

a weak attraction that results in the reduction of total energy.7 The probability of the

energy-reducing phonon exchange processes is maximum for the case ki = -k2 = k. It

is therefore sufficient to think that electrons with equal and opposite wave vectors form

a pair. This so-called Cooper pair can be represented by a two-particle wave function

given by

(ri, r2) akik-(r-r2), (4.31)
k
which is symmetric in spatial coordinates (ri, r2) upon exchange of electrons 1 and 2.

The range of summation is confined to

h2k2
EF < < EF + Lj+ D (4.32)
2m

ak is the probability amplitude for finding one electron in state k and the other in -k.

Since the states k < kF are already occupied, the Pauli principle requires ak = 0 for

k < kF. Because the Pauli principle applies to both electrons, the spin part of the whole

wave function must be antisymmetric. Therefore, a Cooper pair must be imagined as an

electron pair in which the two electrons ahv--, occupy states with opposite wave vectors

and opposite spins (k T, -k 1), (k' T, -k' 1), an so on.8



6 Screening reduces the natural Coulomb repulsion between two electrons, leading to
an effective interaction which is relatively short range compared with the unscreened
Coulomb potential.

7 Originally, the phonon-mediated attractive interaction was proposed by Frohlich in
1950 [51].

s This pair state is sometimes referred as an s-wave, spin-singlet pairing state
(i.e., L 0 and S 0).








BCS Ground State

The formation of a Cooper pair leads to an energy reduction. In a real material,

many more electrons participate in the Cooper pairing to achieve a new lower-energy

ground state. Because a Cooper pair is composed of two fermions with opposite spin,

it may be considered as a single entity that obeys Bose-Einstein statistics. Thus, at

T = 0 K, all Cooper pairs condense into an identical two-electron state even though the

individual electrons are being scattered continually between single electron states. The

Pauli principle limits the states into which the two interacting electrons, which make up

the pair, may be scattered.

In order to calculate the ground state (T = 0 K), BCS made several assumptions

for simplicity. First of all, just like Cooper did, the BCS theory is based on the free

electron approximation. Thus, the Fermi surface is spherical. They also simplified the

net attractive interaction between electrons by expressing the matrix element that

describes scattering of the electron pair from (k 1, -k 1) to (k' 1, -k' 1) and vice versa

as9

Vk' -V/L3 for l D (4.33)
0 otherwise ,

where V is a positive constant, L3 is the volume of the system, h;D is the Debye energy,

and ( is the kinetic energy relative to the Fermi level, which is defined as

h2k2
h= Ek. (4.34)
2m

Further, they approximated the BCS ground state vector of the many-body system

of all Cooper pairs by the product of the identical pair state vectors. With all the

assumptions, they deduced the ground state energy of the superconductor, and showed



9 In some materials (e.g., Hg and Pb), the electron-phonon interaction is very strong.
In such case, the net interaction between electrons is quite complex and even retarded.
Since phonons are the origin of the coupling, the phonon structure of each material will
also influence the matrix element. The extension of the BCS theory to strong-coupling
superconductors is known as the strong-coupling theory [44].








E E

electron-like
thermal
quasiparticles

E,+Ao EF+A(T)

E, N(E)/N(O) E, > N(E)/N(O)
E,-A(T)
EF+Ao

hole-like
thermal
quasiparticles
N,(T)~exp(-2A,/kT)
(a) (b)

Figure 4-1: (a) Density of states in BCS ground state (at T = 0 K) relative to that in
normal state. A gap of 2Ao is developed around the Fermi level. The shaded region are
the states occupied by superconducting electrons. Note that no states are lost in the
phase transition. (b) Corresponding density of states at finite temperature (T < Tc).
Cooper pairs are thermally broken creating quasiparticles (or normal electrons) above
the gap, and the gap 2A(T) is smaller than the ground state value.


that the energy density of superconducting ground state is reduced from that of normal

state by N(0)A2/2, where N(0) is the single-spin electronic density of states at the

Fermi energy, and A is a half of the energy gap developed in the density of states

around the Fermi level at absolute zero. The energy gap is given by the solution to

1 D d -1 D
N(-O)V J WD d sinh-1 (. (4.35)


In the weak-coupling limit (i.e., N(O)V < 1),10 we find


A = 2h De-1/N()V (4.36)


Figure 4-1(a) shows the corresponding density of states in the vicinity of the Fermi

level. Note that it requires a minimum energy of 2A to break up a Cooper pair and

create two uncorrelated electrons. It is this gap that gives rise to the superconductor's

zero resistivity.


10 Empirically, the weak-coupling limit is justified when N(O)V < 0.3.









1.0


0.8-


S0.6-


0.4-


0.2-


0.0
0.0 0.2 0.4 0.6 0.8 1.0
T/ T
C
Figure 4-2: Temperature dependence of the gap as a function of temperature in the
BCS approximation.

BCS Predictions

At temperatures above T = OK, thermally excited phonons become available to

scatter electrons in a Cooper pair. Thus, there is a finite probability of finding electrons

in the states above the gap 2A (see Figure 4-1). These excited electrons are called

quasiparticles. As the temperature increases, pair-breaking is progressively enhanced,

and finally Cooper pairs cease to exist at Tc. In a meantime, the gap 2A shrinks as T

increases, and completely closes at Tc. In the framework of the BCS theory, one can

deduce the temperature dependence of the gap A(T) as the solution to

1 [hwD T ]t [
t 1"( 24f ( 4.37)
N(O)V o 2 + A2

where f(E) is the Fermi function. Note that for T = 0, f(E) is zero (E being positive),

and one recovers Eq. 4.35. This equation defines an implicit relation between A and T,

and numerical analysis yields A(T) as shown in Figure 4-2. As the figure shows, the gap

develops quickly as the temperature is lowered below Tc, and opens up almost fully by a

half of T,. It is also convenient to remember that the result of numerical analysis can be







approximated by
A(T) cos (T ) (4.38)
A(0) 2 T,
At temperatures near Tc, the value of the gap can be approximated by

A(T) T \1/2
A() 174) 1 (4.39)
A (0) T,

By setting A = 0 in Eq. 4.37, an equation for T, is determined by

1 rfv^D t
V T tanh (4.40)
N(0)V o 2kBT,

For hwD > kBTc, numerical calculation yields


kBT 1.4De-1/N()V (4.41)

Then, by comparing Eq. 4.36 with Eq. 4.41, one can find the relationship between the

ground state gap Ao[= A(0)] and T, in the weak-coupling limit as

2Ao
2 = 3.52 (4.42)
kBTC

which is free from parameters such as V and wD.11 This relationship agrees quite well

(within about 10 percent with tunnelling experiments [52]) for the weakly coupled

superconductors. For those strong-coupling superconductors (e.g., Hg and Pb), the ratio

is larger than 3.52. For example, the ratio for Hg and Pb were experimentally found to

be 4.6 and 4.3, respectively. The strong-coupling theory [44] provides better agreement.

At finite temperature, the quasiparticle-occupation of the excited one-electron states

E = ((2 + A2)1/2 obeys Fermi statistics. Therefore, the density of quasiparticles at a



11 The Debye temperature OD (hence, Debye frequency UwD) may be deduced from
specific heat measurement, but the matrix element V is difficult to calculate precisely.
Therefore, parameter-free expression are desired.







function of temperature is given by


Nq = fka f(E)N( )d 2N(0) (4.43)
ka -O J0 + exp( +A2l2BT)

4.2.6 Eliashberg Formalism

In the BCS theory, the dynamic interaction induced among electrons by phonon

was crudely represented by using a dimensionless constant N(O)V as the strength of

electron-electron interaction and the Debye energy hwD as the maximum phonon energy;

the details of the electron-phonon coupling was not considered at all. Even though

the theory was quite successful for weak-coupling superconductors, it failed to treat

strong-coupling superconductors accurately. Eliashberg took a more general approach to

the electron-phonon coupling by taking into account the retarded nature of the phonon-

induced interaction and by properly treating the damping of the excitations [44, 53, 54,

55].

The Eliashberg theory starts with two nonlinear coupled equations for the gap A

and the renormalization factor Z, which replace the BCS gap equation. In the Eliash-

berg equations, two parameters, p* and A, are introduced, where p* is known as the

Coulomb pseudopotential (or the renormalized Coulomb interaction parameter) which

describes a residual repulsive screened Coulomb interaction [56], and A is known as the

electron-phonon coupling constant12 which is related to the attractive interaction. The

constant A is defined by

A 2 QFQd (4.44)
Jo
where a2(Q) is the effective electron-phonon interaction, and F(Q) is the phonon density

of states with Q the frequency of the exchanged phonon. In the Eliashberg theory,



12 The parameter A is also known as mass-renormalization (or mass-enhancement)
parameter because the effective electron mass is modified by the electron-phonon in-
teraction as Z = 1 + A = m*/m. Superconductors are characterized according to the
magnitude of A, weak-coupling (A < 1), intermediate coupling (A < 1), strong coupling
(A > ).







a2(Q)F(Q) (the electron-phonon spectral density) is an important function that contains
all the relevant information about the electron-phonon interaction that gives rise to the
effective attractive interaction between electrons around the Fermi energy. In principle,
superconducting tunnelling measurements provide direct information on a2 ()F(Q).
For a simple model of a metal, a2(Q)F(Q) can be approximated at low frequencies by
the quadratic form bQ2, where b is a constant characteristic of a given material. For the
strong-coupling superconductors, a2 ()F(2)) shows significant low frequency structure.
From the Eliashberg equations, McMillan developed a much more quantitative
equation for T, than the BCS result (Eq. 4.41) [57]. The McMillan formula improved
later by Allen and Dynes is given by [58]

1kBTC -hexp rA + 02A) (4.45)
ksT, = exp (4.45)
1.2 A- p(1t+0.62A) '

where Qin is a characteristic phonon frequency defined by [58]

n,11 = exp +j2 In(Q) ,2() d (4.46)

Also from the Eliashberg equations, the ratio 2Ao/kBTc is expressed approximately
by [55]
2kB = 3.53 1 + 12.5 n n( ) (4.47)
kWT, 0n 2Tc
where 01, hQ= i/kB. This equation includes strong-coupling corrections in terms of the
parameter T1c/O1, and the universal BCS value is recovered for T1/01n 0. It shows
excellent agreement with experiment.













CHAPTER 5
SYNCHROTRON RADIATION AND PUMP-PROBE TECHNIQUE

5.1 Synchrotron Radiation

5.1.1 Introduction

It is well known that an accelerated charged particle emits electromagnetic radia-

tion [9]. Synchrotron radiation is radiation emitted by a charge moving at relativistic

speed. It is a very stable, high flux, broadband light source. In addition, it has peculiar

properties such as polarization, pulsed time structure, angular collimation, and small

source size. It was first identified as a technical problem in accelerator physics, but its

properties make synchrotron vital for various fields of science.

Synchrotron facilities available around the world are based on the use of an

electron storage ring, a closed, high-vacuum chamber with a number of circular arc

and straight segments. In this section the theory and properties of synchrotron radiation

are summarized in particular for an electron making a circular trajectory at a dipole

bending magnet section of a storage ring. Synchrotron radiation from so-called insertion

devices, such as wigglers and undulators placed at straight segments, will not be

discussed here [59,60].

5.1.2 Radiated Power from a Bending Magnet

For a single nonrelativistic (v < c) accelerated particle with charge e, the total

instantaneous radiated power is given by Larmor formula:

2 e2
P = 3 112 ,(51)
3 C3

where v is the acceleration of electron.

Larmor formula can be generalized for arbitrary velocities by a series of Lorentz

transformations. For a particle of mass m in circular motion with velocity = v/c,

energy E, and radius of curvature (the bending radius) p, the relativistic (v C c)





71

generalization of the formula is [9,59,60,61]

2 e2c 4 4
P 44 (5.2)
3 p2

where 7 = E/mc2. The emitted power is proportional to the fourth power of the energy

and inversely proportional to the rest mass. This property explains why electrons are

used rather than other heavier charged particles such as protons. When electron travels

around a storage ring, it makes a circular trajectory and emits radiation only while it

experiences magnetic field at each bending magnet.1 Thus, the total time for it to have

radiative-energy loss per revolution is 27p//3c. Therefore, the radiative-loss per turn by

one electron is
4r e2
6E = 3 4 (5.3)
3 p
For a highly relativistic electrons ( -_ 1) Eq. 5.3 is expressed in practical units as2

[E(GeV)]4
6E(keV) 88.5 x Ge (5.4)
p(m)

The synchrotron radiation spontaneously emitted from _,rn' i electrons in random

distribution (as from a storage ring) is generally incoherent. Figure 5-1 schematically

shows this situation as well as coherent radiation which can be found for example in the

coherent telahertz emission from micro-bunched electrons or in the free electron lasers

(FEL). In incoherent case, the total radiated power by N electrons in the ring is simply

N6E/T where T is the period of electron circulation around the ring. Therefore, the

total power radiated by ring with ring current i is given by3


Pi,,g(kW) 88.5 [E(GeV) A) 26.5[E(GeV)]3B(T)i(A) (5.5)
p(m)



1 The bending radius p is related to the magnetic field B of the bending magnet,
which is given in practical units as p(m) 3.336E(GeV)/B(T). For the VUV ring with
E = 0.808 GeV and B = 1.41 T, the bending radius p is 1.91 m.
2 For the VUV ring, 6E ~ 20 keV per electron per revolution.

3 For the VUV ring, Pig, r 20 kW/amp of beam.








(a) Incoherent (b) Coherent







Eincoherent- N1/2Esingle Ecoherent NEsingle
P ~ NP P ~ N2P
incoherent NPsingle Pcoherent- single

Figure 5-1: (a) Incoherent radiation from N-electrons in random distribution,and (b)
coherent radiation from micro-bunched N-electrons.

(a) p<<1 (b) p~-1
A A
Acceleration


Bending
radius -

4---- \
Electron orbit




Figure 5-2: Angular distribution of radiation emitted from an electron moving along a
circular orbit.

This equation tells us that the total intensity delivered to each beamline is proportional

to the beam current, thus the current signal can be used to normalize measured spectra

in order to compensate time varying intensity due to decay of beam current.

5.1.3 Angular Collimation and Polarization

For an electron circulating at nonrelativistic speed, the angular distribution of

emission is a dipole pattern which extends to a large range of angles (see Figure 5-2).

For a relativistic electron, however, the radiation is strongly concentrated to a narrow

angular range around a direction tangential to the orbit as shown in Figure 5-2. The

divergence of the vertical angle i is roughly estimated from 7-1





73

The instantaneous power (in cgs units of erg/[sec rad cm]) radiated per unit

wavelength and per unit vertical angle according to the Schwinger theory [61] is given by

d2P(A, ), t) 27 e2 4 A 8 ( + 2 2 X2 2
3 p 7 '(1+} LK2/3(0) + x K 3(0) (5.6)
d~d 3273 3 A 1 + X2 I/

where X = 7', = Ac(1 + X2)3/2/2A, and the subscripted K's are modified Bessel

functions of the second kind. The parameter Ac is called critical wavelength that

characterizes the spectral output of particular storage ring which is given by4

Ac 47p/373 (5.7)

Half the total power is emitted as photons of wavelength shorter and half longer than Ac.

Eq. 5.6 is the basic formula for the calculation of the characteristics of the synchrotron

radiation.

The bending magnet radiation has a peculiar polarization property. The two terms

in the square brackets of Eq. 5.6 are associated with the parallel and perpendicular

components of the emitted power, respectively. At small vertical angles b the radiation

is predominantly polarized in the direction parallel to the electron's orbital plane, and at

S=- 0, it is completely linearly polarized. As the vertical angle increases, perpendicular

component starts showing up, but the parallel component is aliv-, the larger of two.

Both components are phase correlated, and as a consequence, the emission observed

above and below the electron's orbital plane (i.e., b / 0) is elliptically polarized. In

Figure 5-3 the normalized intensities of the parallel and perpendicular components are

plotted as a function of ) for the VUV ring of NSLS at three different photon energies.

This figure shows that the radiation is strongly concentrated at the critical wavelength,

but the vertical spread increases at longer wavelengths.



4 Alternative parameter used for the same purpose is the critical photon energy which
is given by hv = hc/A, 3hcy3/47p.





74

1.0 -,
\ dash://
08 solid: I
0.8
0. blue: 100 cm1
g ; green: 1000 cm-
a 0.6 -
S\ red: X
4 \c
-0
N 0.4


Z 0.2 ,

0.0
0 10 20 30 40
w [mrad]

Figure 5-3: Angular distribution of parallel and perpendicular polarization compo-
nents at three different photon energies. The critical wavelength of the VUV ring is 19.9
A (~ 5,000,000 cm-1).

5.1.4 RF Cavity and Pulsed Nature

The accelerating fields inside the RF cavity system periodically acts on the circulat-

ing electrons to restore the energy lost due to emission. Because the RF field oscillates,

only electrons arriving at a particular time receive the proper acceleration. This leads

to form electron bunches which are contained in regularly spaced, imaginary contain-

ers so-called "RF b,. I [21]. Therefore, the light produced by the synchrotron is

pulsed. This pulsed time structure of the synchrotron radiation was exploited in our

time-resolved measurements. For the ordinary linear spectroscopic experiments, the time

constant of common detectors are much longer than the pulse repetition period of the

radiation. For example, the most commonly used far infrared detectors is a bolometer.

It is a thermal detector with a typical time constant on the order of milliseconds. Thus

such a detector sees pulses just as steady-state source of light.

The maximum number of buckets is determined by the RF frequency Vrf of the

cavity and the time To (or circumference D) for an electron to make one revolution








around the ring, which is given by

Nmbax rp rf D
N1V x Vrf To Vf (5.8)


where v is the velocity of the electron. Any integral number of buckets smaller than

Nbnax can be filled with electrons arbitrarily.5

Within a bunch, electrons are distributed randomly, and there is a slight spread in

energy from that of the average electron which is travelling around the ideal electron

path at the reference center of the bunch. All electrons in a bunch are moving at the

same speed (v ~ c) and subject to the same Lorentz force while passing through a

bending magnet. However, the electron with slightly higher (lower) energy has larger

(smaller) mass. As a consequence, it has slightly longer (shorter) orbital length than

the reference orbit, and thus arrives later (earlier) than the reference electron. The

accelerating field acts to electrons in such a way to bring the energy of all electrons

closer to that of reference every time a bunch enters the cavity. Figure 5-4 schematically

illustrates the field found by electrons arriving at cavity at different times.

The RF system is designed to regain only the energy lost by radiation for the

reference electron, but more (less) energy for electrons arriving earlier (later). This

causes longitudinal oscillations about the center of the bunch, which is referred as

synchrotron oscillations.6

5.1.5 Beam Lifetime

Even though the electron energy is maintained by the RF system, the electrons

have a finite lifetime due to two 1, i i" mechanisms [59]: the scattering of electrons

by residual gas particles in the vacuum chamber and Touschek effect (discussed be-

low). Therefore, refilling of electrons are regularly scheduled every a few hours. As



5 For the VUV ring, Nba = 9.
6 Besides the synchrotron oscillations, electrons in a bunch make transverse (both hor-
izontal and vertical) oscillatory motion which are called the betatron oscillations. Pairs
of quadrupole magnets are used to focus electrons toward the reference orbital.








RF voltage RF voltage

-- RF system
Accelerating voltage 4th harmonic system
found by reference -- RF + 4th harmonic
electron


0 Time 0 \ Time








Figure 5-4: The accelerating voltage as a function of time. The time = 0 corresponds to
the arrival of the reference electron. The RF system is designed to regain only the en-
ergy lost by radiation for the reference electron, but more (less) energy for electrons ar-
riving earlier (later). The right hand side shows the effect of using the higher harmonic
cavity system used in conjunction with the main RF system in the effort to increase the
lifetime. The 4th harmonic system is shown here. Each bunch sees a flat voltage which
stretches the bunch length.


explained in the previous subsection, the electrons oscillate around the reference or-

bit while orbiting around the ring: betatron oscillations (transverse oscillations) and

synchrotron oscillations (longitudinal oscillations). The Touschek effect is caused by

the scattering between transversely oscillating electrons inside each bunch. This type

of electron-electron scattering converts part of the transverse momentum into longi-

tudinal momentum that modifies the time at which the electron enters the RF cavity.

Then, those electrons which gained large enough longitudinal momentum are no longer

properly accelerated, and can be lost from the bunch. The effect is more severe when

electrons are packed tighter. Right after electron injection, electron density is the high-

est. Therefore, the Touschek effect is the dominant lifetime limiting mechanism at the

early stage of beam current decay with time-dependent decay time. As the electron

density decreases, the scattering by residual gas particles starts to take over, and at this

time, the decay becomes exponential that is represented by a single characteristic decay

time.

A higher harmonic RF cavity can be used to flatten the potential in the main

RF bucket causing an increase in the bunch length with a consequent reduction of







intrabeam scattering and an improvement in the Touschek lifetime. Figure 5-4 shows

the effect of using the higher harmonic cavity system used in conjunction with the main

RF system in the effort to increase the lifetime.

5.1.6 Infrared Synchrotron Radiation

The Eq. 5.6 can be considerably simplified in the spectral range where wavelengths

A are much longer than the critical wavelength Ac. This condition (Ac/A < 1) is usually

satisfied in the entire infrared wavelengths for the most storage rings, and we can obtain

useful expressions valid for the infrared synchrotron radiation (IRSR) such as [62]

dP(A, t) 1W] (5.9)
= 8.6416 x 10-10iOpl/-7/3G (5.9)
dA cm
d2p(A, t) 5.2 x 10- 0ip2/3 -8/3H d c(5.10)
dA o rad cm

where p and A are both in cm, i (the ring current) in A, and 0 in mrad. The functions G

and H are defined as

G= 1 2.193 ) (5.11)

1 (p4/3
H [1 6.312 ) ]. (5.12)

For Ac/A < 1, G and H can be taken to be unity.

The vertical opening angle as a function of wavelength is given by

(A) 1.66188 (- G [rad] (5.13)

Note that T is twice of the angle defined for the angular divergence b (see Figure 5-2).

This is a useful expression when we determine the natural opening angle that is nec-

essary to collect the full-width at half-maximum of the power profile at a given wave-
length. Figure 5-5 shows T in the infrared spectral range as a function of wavenumber

using the VUV ring parameters.7



7 The U12IR's first mirror is capable of correcting light with 90 mrad of the vertical
opening angle.







1000






CO 100
E






1 10 100 1000 10000

Frequency [cm1]

Figure 5-5: The natural opening angle of IRSR using the VUV ring parameters.

5.1.7 Source Comparison

The Eq. 5.5 gives the total radiated power from a storage ring in all directions

integrated over entire spectral range. Although the total power certainly indicates

certain aspect of the output capability, it does not describes superiorities of synchrotron

radiation over conventional thermal sources. For a practical point of view, the spectral

brightness b is a more useful source quality parameter since it takes into account the

source size as well as the angular distribution of synchrotron radiation. The brightness

of a light source is defined as

b() C x (v) (5.14)

where C is a constant, F(v) is the flux of photons, S is the source area, and f is the

solid angle of emission. It is intuitively obvious that a source with smaller size and

divergence has higher brightness just like a light beam from a laser is brighter than

that from a flame of candle. A small source size allows optics to focus photons to a

diffraction-limited size, and small divergence minimizes the loss of photons even with

reasonably small optical components. Therefore, a brighter source has a marked effect







10-3
S- Synchrotron
S10 -4 Blackbody











1 10 100 1000 10000

Frequency [cmn]
10-





10a 8
1 10 100 1000 10000

Frequency [cm-1]

Figure 5-6: Spectral power calculated for a 2000 K blackbody source and synchrotron
radiation. For the synchrotron radiation, parameters for the VUV ring is used. This
shows the power advantage of the synchrotron radiation over the thermal source only in
the far infrared region.

on improving signal to noise ratio for various types of experiments such as microscopy

and surface science.

Figures 5-6 and 5-7 show calculated spectral power and brightness comparisons

between conventional thermal source and synchrotron radiation, respectively [21]. In the

plots, a blackbody source at temperature of 2000 K with its source size of 0.4 cm2 and

solid angle of 0.02 sr (f/3.5) is used. For the synchrotron radiation, the parameters of

the NSLS VUV ring are used.

Note that the synchrotron shows significantly lower output power than the thermal

source over most of the spectral range (between mid-IR and visible) where the globar is

commonly used (see Figure 5-6). The synchrotron has a power advantage only in the

very far infrared (< 100 cm-1). In terms of brightness, the synchrotron source has an

advantage over entire spectral range shown in Figure 5-7 over the thermal source, which

is obviously attributed to its small source size and angular collimation.







1 0 -1 ... . ... ... ...

10-2 ~ Synchrotron
E Blackbody
10-3

S10-4
10-5
4 10-6
(..

10-7
10-8

'O 10-9

1 10 100 1000 10000

Frequency [cm-1]

Figure 5-7: Spectral brightness calculated for a 2000 K blackbody source and syn-
chrotron radiation. For the synchrotron radiation, parameters for the VUV ring is used.
This shows the brightness advantage of the synchrotron radiation over the thermal
source in the entire spectral range.

5.2 Principle of Pump-Probe Studies

The pump-probe measurement is a valuable technique that determines the nonequi-

librium state of a system at various instants of time after some sort of stimulus has been

applied. The process is repeated for a wide range of time values to build up a complete

history of the sample's relaxation processes, namely the dynamics of the system. There

are av ii. i of excitation (pumping) methods commonly used that provide adequate en-

ergy density to create the desired density of excitations in the sample. Examples include

electrical current, electric field, magnetic field, or light pulses. Here we will discuss the

principle of the technique that uses near IR/visible laser pulses as excitation source and

synchrotron pulses as probe.

The purpose of this section is to provide a very simple idea of the technique

that would be helpful to know before going to the next chapter. The details of the

experimental technique are described in 6.6.








Spectrometer
Pump
(Laser)

^ Sample
Probe (IRSR) 1 2 3

Figure 5-8: Principle of the pump-probe experiment. (1)Laser pulse creates photoexci-
tations in sample, which subsequently evolve with time. (2)After time At, broadband
IR pulse arrives and is partially absorbed (or reflected) by excitations. (3) IR pulse ana-
lyzed with or without a spectrometer, extracting details of excitations at a time At after
their creation.

5.2.1 Laser-Synchrotron Pump-Probe Measurement

Synchrotron radiation is a broadband bright source of light. Most people exploit

its brightness and overlook its temporal structure of the light pulses. The pump-probe

technique developed at the National Synchrotron Light Source (NSLS) of Brookhaven

National Laboratory utilizes the pulsed nature of synchrotron source especially at far

infrared where it offers both brightness and power advantage over conventional thermal

sources [1]. The short pulses of laser light are used to illuminate a sample, and create

photoexcitations. These excitations in the sample begin to relax immediately after the

arrival of laser pulse, and can appear as changes in the sample's optical properties. The

synchrotron pulse arrives at the sample at some point in time At after the pump, and

in 1v.. -the sample's response (e.g., transmission or reflection) at a time At into its

relaxation process. The experiments are performed by fixing the time difference between

the laser (pump) and the synchrotron (probe) pulses, and then measuring a spectrum

in the normal way. A fast detector is not required. The entire process repeats at a high

repetition rate (10's of MHz) in a manner similar to using a synchronized strobe light to

freeze a particular moment of a repetitive process, allowing the slowly responding human

eye to view it. This way a complete spectrum that represents a momentary snapshot of

the sample's state for a particular At can be measured. Various time differences between

pump and probe thus produce a set of data as a function of time and energy providing

greater insight into the relaxation process of the system. Figure 5-8 shows the principle

of the experiment.





82

The measured temporal response S(At) in a pump-probe experiment is determined

by the sample's impulse response function (the quantity of interest) as well as the

duration of the pump and probe pulses. When the sample has a linear response, S(At)

is given as
/+00 ft'
S(At) = dt' dt"Ipb(t + At)pump(t")G(t") (5.15)

where Iprobe(t) and Ipump(t) are temporal intensity profiles of the probe and pump pulses,

respectively, and G(t) is the impulse response function of the sample. Note that the

expression assumes that there is no self-excitation by probe pulses. This condition is

easy to achieve in practice. We can either use much less intense probe pulses than the

pump pulse or limit the spectral range of the probe below some photon energy threshold

using an optical filter. For G(t) = 6(t), the expression becomes a cross correlation

of the probe and pump pulses that defines the minimum temporal resolution. Note

that the temporal resolution is independent of the sensitivity and response time of the

spectrometer and detector.

In our pump-probe experiment, we used picosecond pump pulse that has signifi-

cantly shorter temporal profile than the synchrotron probe pulse of the pulse width on

the order of 1 ns. Hence we can take Ipump(t) o6(t), and Eq. 5.15 can be rewritten as

p+00
S(At) o= o dt'Iprobe(t' + At)G(t') (5.16)

This shows that the measured response is a convolution of the synchrotron pulse shape

with the sample's response. The nature of damping in a storage ring leads to a Gaussian

like electron distribution within a bunch and thus a Gaussian shaped probe intensity

profile.

5.2.2 Interferometry Using Pulsed Source

When pulsed light source is used for an interferometer, a beam-splitter divides every

pulse into two pulses. As a scanner mirror moves, one of the pulse is d. 1 ,i, .1 in time

relative to the other, so that the light travelling toward sample and detector consists

of two pulses for every pulse incident of the beam-splitter. When the delay is shorter





83

than the pulse duration, the two pulses overlap temporally, and cause interference. This

situation is clearly the same as the case of a continuous source. Now, if we run high-

resolution measurements to resolve a narrow spectral feature, one may think that we

may encounter a situation where the scanner moves far enough that the delay exceeds

the pulse duration and two pulses no longer overlap. However, this is not the case [1,21].

A sample with a narrow absorption feature will automatically lengthen a short

pulse. The lengthened pulses will overlap to cause interference. The amount of length-

ening is equivalent to the path difference necessary to resolve the feature's absorption

width. A Fabry-Perot interferometer is a simple way to picture how a short pulse can be

lengthened by a resonance. Therefore, regardless of the sharpness of a feature, there is

no limit to the spectral resolution using short pulsed source.

We can also think of it in the following way. The first pulse is incident on the

sample. If there is a narrow absorption feature, the sample absorbs that particular

fourier component from the pulse, and the absorption mode ilnl for awhile (ring

down time determined by the narrowness of the absorption mode). The second pulse is

then incident on the specimen, and the same fourier component is absorbed. But if the

mode is already imgini; (from the first pulse), then the particular fourier component

of the second pulse may be at the wrong phase (the second pulse tries to drive atoms

in one direction, but they are already moving in the opposite direction due to the first

pulse). Varying the time-delay of the interferometer will bring the proper mode in and

out of phase. So interference is observed. Observable interference will occur as long as

the mode keeps ringing. This is consistent with the longer path difference necessary

to achieve a higher spectral resolution. This path difference can be much longer than

the original pulse. In this picture, the sample has a "memory" determined by the

narrowness of the relevant absorption features. It remembers for a time long enough to








span the time between the two original pulses. There are other v- -- to picture this, but

the result is the same.8

5.2.3 Advantage of Laser-Synchrotron Technique

There are other sources of light that may be useful as a probe. For example,

tunable pulsed lasers, free-electron lasers (FELs), optical parametric oscillators (OPOs),

coherent THz pulses from a biased semiconductors illuminated by a femtosecond laser

are possible probe sources. Even though these can have higher temporal resolution

than the synchrotron, they have either restricted spectral range or stability issues.

A synchrotron, on the other hand, is a broadband, bright, and stable source. These

properties make the synchrotron suitable for ordinary spectroscopy over a broad spectral

range. For the time-resolved study, the synchrotron can follow the system that relaxes

through a wide range of energies. As will be described in the following chapter, pulse

width and repetition frequencies (PRF) are somewhat adjustable for various relaxation

time scales. All of these properties act as advantages of using synchrotron as a probing

source even at the expense of temporal resolution. The fact that our pump laser

(Ti:Sapphire) is tunable in wavelength, PRF, and power, adds flexibility to our pump-

probe system that can be very useful to investigate the dynamics of systems with time

scales from t100 ps to ~100 ns.


8 The explanation given here is based on a conversation with G.L. Carr.













CHAPTER 6
EXPERIMENT

6.1 Introduction

Pump-probe timing experiments were performed at the National Synchrotron Light

Source (NSLS) to study low-frequency dynamics in solids. Synchrotron radiation is a

broadband pulsed source. We took advantage of this pulsed nature to observe the state

of materials excited by a laser which is also pulsed and synchronized to the synchrotron

radiation. The Vacuum Ultraviolet (VUV) ring at the NSLS has two infrared beamlines,

U10A and U12IR, dedicated for solid state physics study. These are two beamlines

used for both time-resolved and linear spectroscopy, described in this dissertation. This

chapter will start with a description of the NSLS facility focusing on the properties

of the VUV ring and beamlines. Spectrometers at U10A and U12IR and pump laser

system are three principal pieces of instrumentation, and will be described separately

in detail followed by brief descriptions of the other apparatus such as the cryostat, our

home-made sample chamber, superconducting magnet, detectors, and fiber optics. The

experimental setup and techniques will be discussed toward the end of the chapter.

6.2 National Synchrotron Light Source

6.2.1 General

The NSLS is a user facility funded by the U.S. Department of Energy. Two

separate electron storage rings, an X-Ray ring (2.8 GeV, 300 mA) and a VUV ring

(800 MeV, 1.0 A), provide intense light spanning the electromagnetic spectrum from

the infrared through x-rays. The properties of this light, and the specially designed

experimental stations, called beamlines, allow scientists in many fields of research

to perform experiments not otherwise possible at their own laboratories. The NSLS

currently has 56 X-Ray and 23 VUV operational beamlines for performing a wide range