Prolate-to-oblate shape phase transitions in neutron-rich odd-mass nuclei

TL;DR

This paper studies shape phase transitions in neutron-rich odd-mass nuclei around mass 190, using a microscopic-interacting boson-fermion model informed by mean-field calculations, revealing a prolate-oblate transition with neutron number.

Contribution

It introduces a combined microscopic and phenomenological approach to describe shape transitions in odd-mass nuclei, extending previous studies on even-even systems.

Findings

Prolate-oblate shape transition observed as neutron number varies.

Calculated spectra and deformation parameters align with experimental data.

Transition pattern similar to neighboring even-even nuclei.

Abstract

We investigate the prolate-to-oblate shape phase transitions in the neutron-rich Pt, Os and Ir nuclei in the mass $A\approx 190$ region. The Hamiltonian of the interacting boson-fermion model, used to describe the odd-mass $^{185-199}$Pt, $^{185-193}$Os and $^{185-195}$Ir isotopes, is partially constructed by using as a microscopic input the results of constrained self-consistent mean-field calculations within the Hartree-Fock-Bogoliubov method with the Gogny force. The remaining few parameters are adjusted to experimental data in the odd systems. In this way the calculations reasonably describe the spectroscopic properties of the odd-mass systems considered. Several calculated observables for the odd-mass nuclei, especially the low-energy excitation spectra and the effective deformation parameters, point to a prolate-oblate shape transition as a function of the neutron number for all the isotopic chains considered and similar to the one already observed in the neighboring even-even systems.