Relative yields of the pairs 96gNb 95mNb and 96Nb 95Nb in fission of Pb, Bi, Th and U induced by 15–157 MeV protons

Abstract

The ratio between the fission yield of the high spin isomer and that of the low spin isomer has been measured for the isomeric pair 95 g Nb 95 m Nb a function of the irradiation energy and of the target used. For all the targets used, the isomeric yield ratio increases with increasing proton energy, and for given irradiation energy, the ratio is highest when lead is irradiated and lowest when uranium is irradiated. A simple statistical model calculation indicates that the spin of the primary fission fragment produced by the fission of uranium is very low for low bombarding energies. In the same experiments the ratio between the fission yields of 24 hr 96Nb and 95Nb has been measured.