Fission of Bismuth with 15- and 22-Mev Deuterons

Radiochemical studies of bismuth bombarded with 15- and 22-Mev deuterons give evidence of fission product species, clearly distinguishable from species arising from activation of target impurities. The massyield curve of fission products from bismuth bombarded with 22-Mev deuterons is unlike the double-humped curves of the heavier elements ($Z>~90$) excited to comparable energies: it is single humped, symmetric about mass 103.5 and quite narrow. The width of the curve at half-maximum is only 17 mass units. The cross sections for fission of bismuth by 20-Mev deuterons is estimated to be about 1×{}10^-29 cm², and for 15-Mev deuterons about 4×{}10^-31 cm². The competition between fission and neutron evaporation in high-energy fission is discussed.