5.3-DAY ELEMENT 61
G. W. Parker
P. M. Lants
M. G. Inghram
D. C. Hess, Ir.
R. J. Hayden
Argonne National Laboratory
This document consists of 1 page.
Date Declassified: May 28, 1947
This document is for official use
Its issuance does not constitute authority
for declassification of classified copies
of the same or similar content and title
and by the same author (s).
Technical Information Division, Oak Ridge Directed Operation
Oak Ridge, Tennessee
Digitized by the Internet Archive
with funding from
University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation
5.3-DAY ELEMENT 61
By G. W. Parker, P. M. Lantz, M. G. Inghram, D. C. Hess, Jr., and R. 7. Hayden
A sample of fission 61, shown by mass spectrographic analysis to be predominantly mass 147
(61 isotopes of other masses were present to less than one part in two thousand), was irradiated by
slow neutrons in the Clinton pile. After bombardment, a 5.3-day 61 activity was found to be present.
The cross section for this reaction was approximately 60 x 10- cm2. The radiations from this
sample, as determined by absorption curves, were a ca. 2.5 Mev and a 0.8 Mev 7. This is prob-
ably the same activity observed by Law, Pool, Kurbatov, and Quill."'2 They observed it as formed
by Nd(p,n), Nd(d,n), and Nd(a,p). The second of these reactions is incompatible with our determina-
tion of the mass of this isotope.
To verify that the reaction involved was actually (n,v) and hence that the mass of the 5.3-day
element 61 was 148, a portion of the sample was analyzed by means of a mass spectrograph.3 After
separation, active isotopes were found at masses 147 and 148. To verify that the activity at mass
148 had a half-life of 5.3 days, the following technique was used: The photographic plate upon which
the separated isotopes were deposited was placed successively against various parts of a larger pho-
tographic plate for times calculated to give equal intensity in the 148 position if its half-life were
5.3 days. Five exposures were taken for successive times of 33.2 hours, 40.7 hours, 52.3 hours,
72.3 hours, and 122 hours. Upon development, this large plate showed equal blackening at mass 148
and increasing blackening for successive transfers at mass 147. Thus the mass of the 5.3-day ele-
ment 61 is 148.
1. Law, Pool, Kurbatov, and Quill, Phys. Rev. 59: 936 (1941).
2. Kurbatov and Pool, Phys. Rev. 63: 463 (1943).
3. Inghram, M. G. and R. J. Hayden, Phys. Rev. 71: (1947).
UNIVERSITY OF FLORIDA
ff1111111 111111 II II111 II!I II!11111 111111IIIl IliY1111111
3 1262 08909 7090