Shape-phase transitions in odd-mass γ -soft nuclei with mass A≈130

Abstract

Quantum phase transitions between competing equilibrium shapes of nuclei with an odd number of nucleons are explored using a microscopic framework of nuclear energy density functionals and a fermion-boson coupling model. The boson Hamiltonian for the even-even core nucleus, as well as the spherical single-particle energies and occupation probabilities of unpaired nucleons, are completely determined by a constrained self-consistent mean-field calculation for a specific choice of the energy density functional and pairing interaction. Only the strength parameters of the particle-core coupling have to be adjusted to reproduce a few empirical low-energy spectroscopic properties of the corresponding odd-mass system. The model is applied to the odd-A Ba, Xe, La, and Cs isotopes with mass A ≈ 130, for which the corresponding even-even Ba and Xe nuclei present a typical case of γ -soft nuclear potential. The theoretical results reproduce the experimental low-energy excitation spectra and electromagnetic properties, and confirm that a phase transition between nearly spherical and γ -soft nuclear shapes occurs also in the odd-A systems.

Shape transitions in odd-mass γ -soft nuclei within the interacting boson-fermion model based on the Gogny energy density functional

“…5 are, rather similar to those obtained within the relativistic framework based on the DD-PC1 [30] EDF (see, Ref. [29]).…”

“…In particular, the value of d (κ) used in Ref. [29] is significantly smaller (larger) than the one obtained in this work. To a large extent, these differences reflect the ones between the Gogny-D1M and DD-PC1 energy surfaces.…”

“…In order to better reproduce the ordering of the energy levels, we have assumed that the monopole strength parameter for the positive-parity states, denoted by A + 0 , is allowed to be j dependent, i.e., A + 0 ≡ A j . A similar assumption was made in the previous study [29].…”

High-spin structure in the transitional nucleus Xe131 : Competitive neutron and proton alignment in the vicinity of the N=82 shell closure

“…In the majority of cases, the theoretical investigations of such systems were carried out by means of the interacting boson model (IBM) [9,12,13], mean-field methods [2,14], or the cranked shell model (CSM) [15,16]. However, Xe isotopes have come within reach of advanced untruncated shell-model calculations, providing stringent tests of the predictive power and suitability of various nuclear potentials and models based on modern effective interactions in this region.…”

Shape phase transition and shape coexistence in the Bose-Fermi system

“…Shape phase transitions (SPTs) in odd-even nuclei have received some attentions in recent years [1][2][3][4][5][6][7][8][9][10]. Evidences of the spherical to prolate SPT and the associated shape/phase coexistence have been clearly identified in the odd Sm nuclei [8].…”