Search for the origin of wobbling motion in the $A\approx 130$ region: The case of ${}^{131}$Xe

Abstract

In-beam ${\hat{I}}^3$-ray spectroscopy of ${}^{131}$Xe has been carried out to study the structure of the intruder $\hat{I}½h_{11/2}$ band. Excited states were populated via an $\hat{I}\pm$-induced fusion-evaporation reaction at E${}_{\hat{I}}\pm =38$ MeV. Inspection of ${\hat{I}}^3{\hat{I}}^3$-coincidence data resulted in the identification of a new rotational sequence. Based on the systematics of excitation energy, assigned spin-parity, decay pattern, and the electromagnetic character of the inter-band $\hat{I}”I=1$ ${\hat{I}}^3$-transitions, this sequence is proposed as the unfavoured signature partner of the $\hat{I}½h_{11/2}$ band. The structure of this band is further illuminated in the light of the triaxial particle rotor model (TPRM). The possibility of wobbling excitation in $N=77$ Xe-Ba-Ce isotones has been explored in a systematic manner.