$\beta$ decay and evolution of low-lying structure in Ge and As nuclei

TL;DR

This paper models shape evolution and beta-decay properties of Ge and As nuclei around mass 70-80 using nuclear density functional theory, revealing shape coexistence and matching experimental data.

Contribution

It introduces a comprehensive framework combining density functional theory and particle-core coupling to study shape and decay properties in this nuclear region, including shape coexistence and decay rates.

Findings

Rapid shape evolution from gamma-soft oblate to prolate shapes.

Shape coexistence around neutron sub-shell closure N=40.

Reasonable agreement with experimental spectra and decay rates.

Abstract

A simultaneous calculation for the shape evolution and the related spectroscopic properties of the low-lying states, and the $\beta$-decay properties in the even- and odd-mass Ge and As nuclei in the mass $A\approx70-80$ region, within the framework of the nuclear density functional theory and the particle-core coupling scheme, is presented. The constrained self-consistent mean-field calculations using a universal energy density functional (EDF) and a pairing interaction determines the interacting-boson Hamiltonian for the even-even core nuclei, and the essential ingredients of the particle-boson interactions for the odd-nucleon systems, and of the Gamow-Teller and Fermi transition operators. A rapid structural evolution from $\gamma$-soft oblate to prolate shapes, as well as the spherical-oblate shape coexistence around the neutron sub-shell closure $N=40$, is suggested to occur in the even-even Ge nuclei. The predicted low-energy spectra, electromagnetic transition rates, and $\beta$-decay $\log{ft}$ values are in a reasonable agreement with experiment. The predicted $\log{ft}$ values reflect the structures of the wave functions for the initial and final nuclei of $\beta$ decay, which are, to a large extent, determined by the microscopic input provided by the underlying EDF calculation.