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

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 $\ddot{I}€h_{11/2}^1\otimes \hat{I}½h_{11/2}^{-2}$ 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 ${}^{129}\mathrm{Cs}$ (${\hat{I}}^2\approx 0.23$, ${\hat{I}}^3\approx 41^{\circ }$) and ${}^{131}\mathrm{La}$ (${\hat{I}}^2\approx 0.25,$ ${\hat{I}}^3\approx 42^{\circ }$), along with those for possible chiral rotation in ${}^{129}\mathrm{Cs}$ (${\hat{I}}^2\approx 0.20,$ ${\hat{I}}^3\approx 29^{\circ }$) and in ${}^{131}\mathrm{La}$ (${\hat{I}}^2\approx 0.20,$ ${\hat{I}}^3\approx 27^{\circ }$). 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.

11 pages, 9 figures