Signature inversion in odd-oddRh114: First identification of high-spin states in very neutron-richRh114and application of the triaxial projected shell model

Abstract

High-spin excited states in the very neutron-rich nucleus $^{114}\mathrm{Rh}$ have been studied by examining the prompt $\ensuremath{\gamma}$ rays emitted in the spontaneous fission of $^{252}\mathrm{Cf}$ with the Gammasphere detector array. A high-spin level scheme of $^{114}\mathrm{Rh}$ has been established for the first time with 13 new levels. The level scheme is proposed to be built on a ${7}^{\ensuremath{-}}$ state. The existence of a relatively large signature splitting and an yrare band show features which may indicate triaxial deformation. The phenomenon of signature inversion has been observed in $^{114}\mathrm{Rh}$ at $I=12 \ensuremath{\hbar}$. The observed signature inversion of $^{114}\mathrm{Rh}$ is interpreted successfully in terms of the triaxial projected shell model. Theoretical calculations suggest that the negative-parity, yrast band of $^{114}\mathrm{Rh}$ has the two-quasi-particle configuration of $\ensuremath{\pi}{g}_{9/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$, consistent with the systematics of odd-odd Rh isotopes. The signature inversion at spin $12 \ensuremath{\hbar}$ may be attributed to the change of rotational mode, from quasi-particle aligned rotation at low spins to collective rotation at high spins.