Deformation of rare-earth nuclei with Skyrme forces

Abstract

The possibility of different deformations for the protons and neutrons in 154Sm, suggested by analyses of (p,p') data, is examined by means of Skyrme-HF calculations in the Sm and Er isotopes. Two different versions of the Skyrme force give essentially identical results, in spite of markedly different surface asymmetry and nuclear compressibility characteristics. Constrained calculations, with either a single constraint on the matter density (quadrupole moment) or separate constraints on the protons and neutrons, illustrate a very strong coupling between proton and neutron deformations. Indeed, proton and neutron deformations are found to follow each other very closely even when the relative strengths of the proton and neutron spin-orbit potentials are altered in opposite senses, or when the proton and neutron pairing interaction strengths are varied separately. Generally the protons have larger quadrupole moments per particle, while for the hexadecapole mode the neutron deformation per particle is greater-contrary to the conclusions drawn from analysis of (p,p') data.