Particle decay of resonant state generated by direct reaction

Abstract

A framework is presented for studying two step reactions illustrated byA+a→B *+b, B*→C+c. In the first step, a direct reaction excites a resonant state (e.g., giant resonances or isobaric analog resonances), which decays by a particle emission in the second step. Feshbach's projection operator method is used to obtain a reaction amplitude, which consists of a compound part and a direct part. The latter corresponds to a knock-out process when the direct reaction is inelastic scattering. A compound part includes contributions from the direct decay of doorway states as well as the multistep decay. The statistical theory of precompound reactions is applied to this multistep decay and an explicit expression is given for the cross section.