Level structure of92Moat high angular momentum: Evidence forZ=38,N=50core excitation

Abstract

In-beam $\ensuremath{\gamma}$-ray spectroscopic studies of the $N=50$ nucleus ${}^{92}\mathrm{Mo},$ up to spins of $J\ensuremath{\sim}18\ensuremath{\Elzxh}$ and ${E}_{x}\ensuremath{\sim}12 \mathrm{MeV},$ are reported using a heavy ion fusion reaction with a ${}^{28}\mathrm{Si}$ beam at an incident energy of 138 MeV on an isotopically enriched ${}^{74}\mathrm{Ge}$ target. Sixteen new transitions belonging to this nucleus have been observed and placed in the decay scheme using the conventional $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence data. The level scheme derived from these measurements is compared with shell model calculations. The presence of gamma rays with ${E}_{\ensuremath{\gamma}}\ensuremath{\sim}2 \mathrm{MeV}$ at $J\ensuremath{\sim}14\ensuremath{\Elzxh}$ is indicative of the breaking of the $N=50$ core. The occurrence of gamma rays with ${E}_{\ensuremath{\gamma}}\ensuremath{\sim}2 \mathrm{MeV}$ at low spins $(J\ensuremath{\sim}8\ensuremath{\Elzxh})$ indicates the excitation of protons across the $Z=38$ core. This is supported by large-basis shell model calculations. The deduced level scheme exhibits single-particle behavior up to the highest observed spins and excitation energies.