Gamma ray emission from multistep compound reactions

The multistep compound formalism of Feshbach, Kerman, and Koonin has been extended to include γ ray emission. By allowing the first few simple preequilibrium bound states to decay via electromagnetic transitions rather than particle emission, the large number of high-energy γ rays observed in the experimental data can be understood. It is assumed that single-particle and hole transitions lead to the emission of γ rays, and radial matrix elements for such transitions are estimated by exploiting the inverse process, photoabsorption. Reactions of 14 MeV neutrons with 59Co, 93Nb, and 181Ta are analyzed and it is found that between twenty and fifty percent of cross sections for high-energy γ ray emission can be accounted for by the multistep compound mechanism. (author). 27 refs, 3 figs