Compound Inelastic Nucleon and Gamma-Ray Angular Distributions for Even- and Odd-Mass Nuclei

Abstract

The current theoretical and experimental status of angular distributions of inelastically scattered nucleons and succeeding $\gamma$ radiations on the basis of a compound-nucleus mechanism is reviewed, with special reference to symmetry, isotropy, and identity characteristics. Results of investigations using a fast computer to ascertain the influence of higher partial waves, multipole mixing, unobserved intermediate transitions, and the presence of additional exit channels are presented, together with an over-all survey of distribution systematics and tabulations of numerical parameters to assist in evaluation of differential cross sections by hand. The predictions for both proton and neutron inelastic scattering are discussed in detail and illustrated by analyses of experimental data for many nuclear spin sequences. In particular, it is shown for $\gamma$ distributions that the effect of cascades from higher levels upon the distribution structure and magnitude can be very appreciable. Also, the examination of the predicted behavior of ($n, n^{\prime }\gamma$) distributions near threshold has disclosed features deserving of further experimental and theoretical study. A set of recently measured ($n, n^{\prime }\gamma$) distributions for several heavy nuclei involving transitions between nuclear states of relatively high integer or half-integer spin is shown to compare well with the theoretical predictions when suitable account is taken of cascade and exit-channel contributions. It is concluded that there is a wide range of application of this theoretical approach to energy-averaged distributions, much of which remains yet to be exploited.