MDDC - 978 
 
 t 
 
 \ 
 
 UNITED STATES ATOMIC ENERGY COMMISSION 
 
 5.3 -DAY ELEMENT 61 
 
 by 
 
 G. W. Parker 
 P. M. Lantz 
 M. G. Inghram 
 D. C. Hess, Jr. 
 R. J. Hayden 
 
 Argonne National Laboratory 
 
 This document consists of 1 page. 
 Date Declassified: May 28, 1947 
 
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 Oak Ridge, Tennessee 
 
Digitized by the Internet Arcliive 
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 University of Florida, George A. Smathers Libraries with support from LYRASIS and the Sloan Foundation 
 
 http://www.archive.org/details/53dayelement6100usat 
 
5.3 -DAY ELEMENT 61 
 
 By G. W. Parker, P. M. Lantz, M. G. Inghram, D. C. Hess, Jr., and R. J. 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"" cm^. The radiations from this 
 sample, as determined by absorption curves, were a ca. 2.5 Mev jS ' and a 0.3 Mev y. This is prob- 
 ably the same activity observed by Law, Pool, Kurbatov, and Quill.'' ^ 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,y) 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.' 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. 
 
 REFERENCES 
 
 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). 
 
 MDDC - 978 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 08909 7090