Microscopic aspects of $\gamma$-softness in atomic nuclei

TL;DR

This paper investigates the microscopic origins of gamma-softness in atomic nuclei using a triaxial projected shell model, demonstrating how quasiparticle excitations influence nuclear shape fluctuations, with detailed analysis of the nucleus $^{104}$Ru.

Contribution

It introduces a microscopic framework based on the triaxial projected shell model to explain gamma-softness, linking quasiparticle coupling to shape fluctuations in nuclei.

Findings

Successfully reproduces experimental energies and E2 matrix elements for $^{104}$Ru.

Shows quasiparticle excitations drive the transition from gamma-rigid to gamma-soft shapes.

Elucidates gamma-soft nature through shape invariant analysis of E2 matrix elements.

Abstract

The microscopic origin of the $\gamma$-softness (fluctuations in the triaxiality parameter $\gamma$ of the nuclear shape) observed in atomic nuclei is studied in the framework of the triaxial projected shell model approach, which is based on the deformed mean-field picture with multi-quasiparticle configuration space. It is demonstrated that the coupling to quasiparticle excitations drives the system from a $\gamma$-rigid to a $\gamma$-soft pattern. As an illustrative example for a $\gamma$-soft nucleus, a detailed study has been performed for the $^{104}$Ru nucleus. The experimental energies and a large sample of measured $E2$ matrix elements available for this nucleus are reproduced quite accurately. The shape invariant analysis of the calculated $E2$ matrix elements elucidates the $\gamma$-soft nature of $^{104}$Ru.