Analysis of the Energy Dependence of the Isomer Ratio in theSn120(p,α)In117,117mReaction

Abstract

The method of Huizenga and Vandenbosch for calculating isomer ratios has been extended to reactions that constitute a small fraction of the total cross section. In particular, the method determines the effective distribution in $J$ for emission of particles $a$ brought about by competition between the emission of neutrons and particles $a$. The method is then applied to the reaction ${\mathrm{Sn}}^{120}(p,\alpha ){\mathrm{In}}^{117,117m}$, and values of $\sigma$, the parameter that characterizes the spin distribution, are extracted by comparison with experiment. The values of $\sigma$ obtained for proton bombarding energies of 12 and 18 MeV are 2.7 and 4.2, respectively, and do not depend strongly upon the value of $\sigma$ chosen for the neutron evaporation, but do depend strongly upon the fractional amount of direct interaction assumed. Similar values for $\sigma$ are obtained when competition is not considered. The energy dependence of $\sigma$ is discussed in the light of present theory.