Band structures inCs129

Abstract

The $^{122}\mathrm{Sn}(^{11}\mathrm{B},4n)$ fusion-evaporation reaction at ${E}_{\mathrm{lab}}=60$ MeV was used to populate excited states in $^{129}\mathrm{Cs}$, and the deexcitations were investigated using in-beam $\ensuremath{\gamma}$-ray spectroscopic techniques. The level scheme of $^{129}\mathrm{Cs}$ is established up to \ensuremath{\sim}8 MeV excitation energy and 47/2 \ensuremath{\Elzxh} spin. The observed band structures are interpreted for their configurations in the framework of cranking model calculations and systematic of the neighboring ${}_{55}$Cs isotopes. A negative-parity $\ensuremath{\Delta}I=1$ coupled band has been assigned the $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}({h}_{11/2}){}^{2}$ configuration as solution of the tilted-axis cranking, which coexists with the $\ensuremath{\pi}{h}_{11/2}$ yrast band resulting from the principal-axis cranking. A new band has been identified as a $\ensuremath{\gamma}$-vibrational band built on the $\ensuremath{\pi}{h}_{11/2}$ orbital. A pair of strongly coupled positive-parity bands exhibiting similar features have been assigned different unpaired three-quasiparticle configurations involving the $\ensuremath{\pi}{h}_{11/2}\ensuremath{\bigotimes}\ensuremath{\nu}{h}_{11/2}$ component. The previously identified unfavored signature partners of the $\ensuremath{\pi}{d}_{5/2}$ and $\ensuremath{\pi}{g}_{7/2}$ bands are reassigned as $\ensuremath{\gamma}$ vibrations of the core coupled to the $\ensuremath{\pi}{g}_{7/2}$ single-particle configuration, and the favored signature of the $\ensuremath{\pi}{d}_{5/2}$ band, respectively.