On direct nucleon decay of the giant dipole resonance and photonucleon reactions

A semimicroscopical approach is proposed to describe the partial cross sections of the photonucleon reactions proceeding via the giant dipole resonance and the branching ratios for the direct nucleon decay of this resonance. The approach is formulated in two steps. The first (microscopical) one consists in the use of the continuum-RPA for calculating the energy, partial nucleon and radiative widths of those 1− collective particle-hole states (doorway states), which exhaust most of the classical sum rule. The second step concerns the coupling of the doorway state to complex configurations. It is phenomenologically taken into consideration with the use of a statistical assumption. Applications of the approach are given.