Microscopic description of even-even nuclei in the mass A = 130 region

Abstract

We present a systematic study of even-even nuclei in the mass A = 130 region using a microscopic nuclear structure model, in which the nuclear wave functions are approximated by linear combinations of number- and spin-projected zero-quasiparticle and two-quasipartile determinants obtained from a self-consistent Hartree-Fock-Bogoliubov mean field. With a fixed hamiltonian, being a slightly renormalized Brueckner G-matrix based on the Bonn potential the model is able to reproduce the main trends of empirical energy and electromagnetic properties of the transitional, soft nuclei in the region. The empirical nature of the crossing ( πh 11 2 ) 2 and ( vh 11 2 ) 2 superbands in Ce and Ba isotopes, respectively, is confirmed. The calculations suggest a particular interpretation of the negative-parity bands observed for 128Ba and 124Xe. Furthermore a rich variety of empirically unknown excited 2 q.p. bands with positive parity is predicted to exist throughout the region. We suggest an empirical method to deduce the low-end termination of such bands based on comparisons of microscopic electric quadrupole moments to those of the rotation model. The model fails to account for the low-lying quasi-gamma bands in Ce and Ba isotopes but indicates a strong contribution of proton 2 q.p. excitations for this band in Xe isotopes.