Attainment of Statistical Equilibrium in Excited Nuclei

Abstract

The usual interpretation of high-energy nuclear reactions entails a two-step mechanism: (1) a first step, which includes the emission of knock-on particles in an intranuclear cascade generated by the incident particle, followed by (2) the "evaporation" of particles from the residual excited nucleus, which is assumed to be at statistical equilibrium. If the independent-particle model with residual two-body interaction is taken as a description of the residual excited nucleus, the assumption in the second step requires that the nonequilibrium distribution of nucleons and holes that are produced in the fast step approach the equilibrium distribution before more particles leave the nucleus. This requirement has been investigated and shown to be valid by numerically solving a Boltzmann-like master equation for a Fermi-gas system.