Nucleon escape widths of the giant dipole resonances in spherical nuclei

Abstract

The proton and neutron escape widths for the various giant resonances in 54Mn, 56Fe, 60Ni, 72Ge, 74As, 90Zr and 106Ag have been calculated. The giant resonances are described in the Dynamic Collective Model (DCM) where giant resonance phonons are coupled with surface quadrupole vibrations. The initial states are given by the collective wavefunctions of the DCM while the final states are particle-hole states which are coupled to surface phonons. Up to two surface phonons have been considered in the final states. The particle wavefunctions are computed in a Saxon-Woods potential obtained from low-energy neutron scattering. All partial widths for protons and neutrons are represented in tables. The total widths are represented together with the dipole strengths for the various giant dipole resonances in figures. Typical total widths are varying between 0.5 and 1.5 MeV. In general the total escape widths for those giant resonances which are at higher energies are larger than for those at lower energies. Formulas for the angular distributions of the escaping nucleons in terms of the various partial widths are furnished.