High-spin structures of55136Cs81

Abstract

Odd-odd ${}^{136}$Cs nuclei have been produced in the ${}^{18}\mathrm{O}+{}^{208}$Pb and ${}^{12}\mathrm{C}+{}^{238}$U fusion-fission reactions and their $\ensuremath{\gamma}$ rays studied with the Euroball array. The high-spin level scheme was built up to $\ensuremath{\sim}$4.7 MeV excitation energy and spin $I\ensuremath{\sim}16\ensuremath{\hbar}$ from the triple $\ensuremath{\gamma}$-ray coincidence data. The configurations of the three structures observed above $\ensuremath{\sim}$2 MeV excitation energy are first discussed by analogy with the proton excitations identified in the semimagic ${}^{137}$Cs${}_{82}$ nucleus, which involve the three high-$j$ orbits lying above the $Z=50$ gap, $\ensuremath{\pi}{g}_{7/2}$, $\ensuremath{\pi}{d}_{5/2}$, and $\ensuremath{\pi}{h}_{11/2}$. This is confirmed by the results of shell-model calculations performed in this work.