Effect of nuclear deformation on the electric-dipole strength in the particle-emission threshold region

Abstract

The role of nuclear deformation in the photoabsorption cross section in the tail region of the electric giant dipole resonance (GDR) is studied in terms of a deformed oscillator model and a Nilsson-plus-random-phase-approximation model. It is found within the framework of these approaches that extra electric dipole strength is generated at energies below the GDR maximum if the nuclear system is spatially deformed. This is important in the prediction of stellar photodisintegration rates, knowing that an extra strength can affect these rates even below the particle separation energies through the so-called \ensuremath{\gamma} process. Because the nuclear deformation is governed by shell effects, this extra strength does not directly correlate with the neutron excess.