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 MDDC - 1145 
 
 UNITED STATES ATOMIC E NERGY COMMISSION 
 
 SOME EXCITATION FUNCTIONS OF ALPHAS AND DEUTERONS ON BISMUTH 
 
 by 
 
 E. L. Kelly and E. Segre 
 
 University of California 
 
 This document consists of 2 page. 
 Date of Manuscript: June 18, 1947 
 
 Date Declassified: July 15, 1947 
 
 This document is for official use. 
 
 Its issuance does not constitute authority 
 
 for declassification of classified copies 
 
 ul iiic sctme ui bluiiiiir cuuieid and liile 
 
 and by the same author(s). 
 
 Technical Information Division, Oak Ridge Directed Operations 
 Oak Ridge, Tennessee 
 
SOME EXCITATION FUNCTIONS OF ALPHAS AND DEUTERONS ON BISMUTH 
 
 By E. L. Kelly and E. Segre 
 
 Asa part of a systematic investigation of excitation functions, the absolute cross sections for the 
 reactions (Qf,2n), (a,3n), (d,p), (d,n), and (d,3n) on bismuth will be presented. See graphs. The tech- 
 nique used is the usual one of bombarding stacked foils, with some improvement of the definition of 
 energy and measuroment of current. The improvements consisted of a collimating slit system that 
 produced a beam of 2 per cent straggling or less, and a means of continuously recording the beam 
 current during bombardment of the stack of foils. The (a,3n) reaction on Bi leading to the formation 
 of At^'° has been identified. At^'° has a half-life of 8.3 hr, decaying by K-capture to Po"°, accompa- 
 
 nied by emission of 1.0-Mev gamma rays. 
 per cent, if it exists. 
 
 Branching decay of At by alpha emission is less than 1 
 
 The integrated mass stopping power of Bi, Cu, Ag, Ta, Tl, and U have been redetermined with 
 respect to Al, using 36-Mev alphas. The tabulated results are listed in Table 1. 
 
 The unexpected rise of the (d,n) cross section above 13 Mev is taken to indicate the presence of 
 the (d,2n) reaction. An attempt will be made to disentangle the (d,2n) cross section and identify the 
 resulting product. 
 
 Table 1. 
 
 Substance 
 
 Energy range 
 
 Integrated mass stopping 
 power relative to aluminum 
 
 Cu 
 Cu 
 
 Ag 
 Ag 
 
 Ta 
 Ta 
 
 Bi 
 
 Th 
 Th 
 
 U 
 U 
 
 36-28 
 27-15 
 
 36-28 
 27-15 
 
 36-28 
 27-15 
 
 36-6 
 
 36-28 
 
 97 -IS 
 
 36-28 
 27-15 
 
 0.801 
 0.781 
 
 0.671 
 0.650 
 
 0.548 
 0.516 
 
 0.488 
 
 0.505 
 
 n 477 
 
 0.487 
 n.472 
 
 MDDC - 1145 
 
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 MDDC - 1145 
 
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 ENERGY OF BOMBARDING ALPHAS IN Mev 
 
 Figure 1 
 
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 ENERGY OF BOMBARDING DEUTERONS IN Mev 
 
 20 
 
 Figure 2 
 
UNIVERSITY OF FLORIDA 
 
 3 1262 08907 9783