First identification of excited states in Ba117 using the recoil- β -delayed proton tagging technique

Abstract

Excited states have been observed for the first time in the neutron-deficient nucleus $^{117}\mathrm{Ba}$ using the recoil-decay tagging technique following the heavy-ion fusion-evaporation reaction $^{64}\mathrm{Zn}$($^{58}\mathrm{Ni}$, 2p3n)$^{117}\mathrm{Ba}$. Prompt $\ensuremath{\gamma}$ rays have been assigned to $^{117}\mathrm{Ba}$ through correlations with $\ensuremath{\beta}$-delayed protons following the decay of $A=117$ recoils. Through the analysis of the $\ensuremath{\gamma}\ensuremath{-}\ensuremath{\gamma}$ coincidence relationships, a high-spin level scheme consisting of two bands has been established in $^{117}\mathrm{Ba}$. Based on the systematics of the level spacings in the neighboring barium isotopes, the two bands are proposed to have $\ensuremath{\nu}{h}_{11/2}[532]5/{2}^{\ensuremath{-}}$ and $\ensuremath{\nu}{d}_{5/2}[413]5/{2}^{+}$ configurations, respectively. The observed band-crossing properties are interpreted in the framework of cranked shell model.