High-Energy Fission of Bismuth. Proton Energy Dependence

Radiochemical studies of the fission of bismuth with protons of 75 Mev to 450 Mev have been performed. Radioactive products ranging from ${\mathrm{Cu}}^{61}$ to ${\mathrm{Cs}}^{131}$ were isolated and their cross sections were measured. Integration of the calculated cross section vs mass number curves for the various energies yielded values for the fission cross section which increase rapidly from a value of 0.016 b at 75 Mev to 0.12 b at 192 Mev, then more slowly to 0.20 b at 450 Mev. The most probable fission products decrease in mass and in neutron to proton ratio as the proton energy increases.