The coexistence of possible magnetic and chiral rotation in $^{129}\mathrm{Cs}$ and $^{131}\mathrm{La}$: a microscopic investigation

TL;DR

This study uses microscopic calculations to reveal the coexistence of magnetic and chiral rotation modes in $^{129}$Cs and $^{131}$La, showing shape coexistence and transitions between different rotational regimes.

Contribution

It introduces a microscopic investigation demonstrating the coexistence of magnetic and chiral rotations on identical quasiparticle configurations in specific nuclei.

Findings

Coexistence of magnetic and chiral rotation in $^{129}$Cs and $^{131}$La.

Predicted deformation parameters for different rotational modes.

Experimental data for specific bands are well reproduced.

Abstract

A microscopic investigation of the rotational properties in $^{129}\mathrm{Cs}$ and $^{131}\mathrm{La}$ was carried out using the three-dimensional tilted axis cranking covariant density functional theory (3DTAC-CDFT). The calculations reveal the coexistence of magnetic and chiral rotation built on identical qusiparticle configurations $\pi {h}_{11/2}^{1}\otimes \nu {h}_{11/2}^{-2}$ in $^{129}\mathrm{Cs}$ and $^{131}\mathrm{La}$, establishing a new type of shape coexistence. The calculations predict the deformation parameters for magnetic rotation in $^{129}\mathrm{Cs}$ ($\beta\approx0.23$, $\gamma \approx41^\circ$) and $^{131}\mathrm{La}$ ($\beta \approx0.25,$ $\gamma \approx42^\circ$), along with those for possible chiral rotation in $^{129}\mathrm{Cs}$ ($\beta \approx0.20,$ $\gamma \approx29^\circ$) and in $^{131}\mathrm{La}$ ($\beta \approx0.20,$ $\gamma \approx27^\circ$). The energy spectra, the relation between the spin and the rotational frequency, and the reduced $M1$ and $E2$ transition probabilities are obtained with the various configurations. The experimental characteristics of band B8 in $^{129}\mathrm{Cs}$ and band 13 in $^{131}\mathrm{La}$ are well reproduced. Moreover, a distinctive rotational mode transition is uncovered in this work, progressing from the principal-axis rotation to the planar rotation and finally to the chiral rotation, as the rotational frequency evolves through different regimes.