Model for photonuclear reactions at intermediate energies

Abstract

In the present paper we discuss photonuclear reactions for photon energies ${E}_{\ensuremath{\gamma}}g50$ MeV. We show in detail how the different processes concerning the nucleon-nucleon interactions enter the transition matrix. Explanations are given for the similar behavior of ($\ensuremath{\gamma}, n$) and ($\ensuremath{\gamma}, p$) and for a strong relative suppression of the reactions ($\ensuremath{\gamma}, \mathrm{pp}$) and ($\ensuremath{\gamma}, \mathrm{nn}$) compared to ($\ensuremath{\gamma}, \mathrm{np}$). This solves the standing problems of photonuclear reactions at intermediate photon energies. We present numerical calculations for the reactions ($\ensuremath{\gamma}, p$) and ($\ensuremath{\gamma}, n$) on $^{4}\mathrm{He}$ from 50 to 140 MeV photon energy and show in detail how the different physical processes numerically enter the total cross sections and angular distributions. Over-all good agreement with the experiments is achieved.