Changes in rotational characters of one- and two-phonon $\gamma$-vibrational bands in $^{105}$Mo

TL;DR

This paper investigates the rotational behavior of one- and two-phonon gamma-vibrational bands in the odd-A nucleus $^{105}$Mo, revealing how their character changes with spin and explaining the absence of signature splitting in the one-phonon band.

Contribution

It applies a particle-vibration coupling model to $^{105}$Mo to elucidate the rotational character changes and the reasons behind the observed spectral features, especially in the context of strong Coriolis effects.

Findings

The model reproduces the observed yrast bands well.

The rotational character change from low to high spin is clarified.

The reason for the absence of signature splitting in the one-phonon band is explained.

Abstract

The $\gamma$ vibration is the most typical low-lying collective motion prevailing the nuclear chart. But only few one-phonon rotational bands in odd-$A$ nuclei have been known. Furthermore, two-phonon states, even the band head, have been observed in a very limited number of nuclides not only of odd-$A$ but even-even. Among them, that in $^{105}$Mo is unique in that Coriolis effects are expected to be stronger than in $^{103}$Nb and $^{105}$Nb on which theoretical studies were reported. Then the purpose of the present work is to study $^{105}$Mo paying attention to rotational character change of the one-phonon and two-phonon bands. The particle-vibration coupling model based on the cranking model and the random-phase approximation is used to calculate the vibrational states in rotating odd-$A$ nuclei. The present model reproduces the observed yrast zero-phonon and one-phonon bands well. Emerging general features of the rotational character change from low spin to high spin are elucidated. In particular, the reason why the one-phonon band does not exhibit signature splitting is clarified. The calculated collectivity of the two-phonon states, however, is located higher than observed.