A self-consistent approach to the ground state and lowest-lying negative-parity state in the barium isotopes

Abstract

The octupole degree of freedom in the 142–148Ba nuclei is investigated in a microscopic way. Our analysis is based on the constrained Hartree-Fock-plus-BCS theory as well as on the collective hamiltonian method, using different sets of mass parameters and zero-point energy corrections. The latter is able to restore the parity symmetry broken in the mean field approximation. In the numerical applications we use the Gogny force. From the mean field calculations we show octupole barrier heights, dipole moments and β 2,…, β 13 values along the constrained path. From the symmetry conserving calculations we display the 0 +−1 − splittings and wave functions as well as the E1 and E3 transition probabilities. The overall agreement with the available experimental data is very good. In the framework of a simple model we give an explanation of the onset of octupole deformation with increasing angular momentum.