ISOMERIC CROSS-SECTION RATIOS FOR SOME (n,$gamma$) AND (/cap alpha/,XN) REACTIONS

Isomeric cross section ratios for several nuclear reactions in the medium mass region were measured. The cross section ratios of isomers produced by the thermal neutron irradiation of Se/sup 60/, Rh/sup 103/, Pd/sup 106/ TE/sup 128/ and Cs/s up 133/ were measured. Isomeric cross section ratios for the formation of the isomeric pair In/sup 110/ and In/sup 110m/, produced in the Ag/ sup 107/ ( alpha ,n) and the Ag/sup 109/ ( alpha ,3n) reactions were also measured at several energies of the incoming projectile. He ions were accelerated to a maximum energy of 43 Mev. The relative amounts of the isomers produced in the reactions were determined by scintillation counting. In the case of the In/sup 110/ isomers the efficiencies of the scintillation counter for detecting each isomer were measured, so that absolute cross sections as well as cross section ratios could be determined for these isomers. The isomeric cross section ratios were also calculated theoretically using a statistical model, in which angular momentum effects were included. By comparing experimentally measured cross section ratios for the formation of isomeric pairs to the calculated ratios, information about the dependence of the nuclear level density on angular momentum was obtained. (auth