Hydrodynamical model for high-energy dipole vibrations in nuclei far from the beta-stability line

Abstract

The model for describing the isoscalar and isovector dipole giant resonance energies in nuclei with a neutron (or proton) halo or skin is presented. The realistic density distribution of the halo/skin, exponentially decaying with increasing radius, is taken into account. The proton and neutron density oscillations in the core part of the nucleus are described by the hydrodynamic equations of continuity and Euler. The proton and neutron density oscillations in the core part of the nucleus are coupled to both the proton and neutron core radii vibrations as well as the density fluctuation inside the neutron (or proton) halo/skin using the boundary conditions on the free surface. The pressure of the neutron (proton) matter related to the density oscillation in the halo/skin is evaluated using the Skyrme energy-density functional. Simple formulas are obtained for calculating the energies of dipole vibrations in nuclei with the halo/skin. It is found that the excitation energies of the isoscalar dipole resonances in the nuclei with halo/skin are smaller than those in the nuclei without halo/skin. The excitation energies of the isovector dipole resonances are weakly dependent on the halo/skin characteristics. The influence on the excitation energies of the dipole resonances of the halo/skin properties is discussed. The transition densities of the resonances are considered.