Model for photonuclear reactions at intermediate energies

In the present paper we discuss photonuclear reactions for photon energies E_γ>50 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 (γ, n) and (γ, p) and for a strong relative suppression of the reactions (γ, pp) and (γ, nn) compared to (γ, np). This solves the standing problems of photonuclear reactions at intermediate photon energies. We present numerical calculations for the reactions (γ, p) and (γ, n) on ⁴He 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.NUCLEAR REACTIONS ⁴He(γ, p), ⁴He(γ, n) E=50-140 MeV; calculated σ, σ(θ).