Angular-Momentum Distributions of Residual Nuclei in Compound-Nuclear Reactions

Abstract

A classical vector model is used to determine the changes which occur in the distribution functions for the angular momentum of nuclei when particles and photons are evaporated from these nuclei. Closed-form expressions are derived for angular-momentum distributions after a sequence of evaporations. It is found that at higher excitations one must expect the average angular momentum of a nucleus to decrease by a relatively small amount per evaporation. The mean-square angular momentum will increase or decrease depending on the ratio of the nuclear angular momentum to the equipartition value appropriate to the nuclear excitation. General expressions are given for the angular distributions of the evaporations. Some of the difficulties of applying statistical models to emissions at low excitation energies are briefly discussed.