Unexpected5/2−spin of the ground state in147Ba: No octupole deformation in ground states of odd-ABa isotopes

Abstract

The ${}^{147}$Ba nucleus has been studied in prompt $\ensuremath{\gamma}$-ray spectroscopy using the EUROGAM2 Ge array. Spin and parity of the ground state has been determined to be $5/{2}^{\ensuremath{-}}$. The unexpected, $5/{2}^{\ensuremath{-}}$ ground state results from interaction with other negative-parity configurations. A new ground-state band has been established in ${}^{147}$Ba and some previously reported levels have been arranged into a $3/{2}^{\ensuremath{-}}$ band, which may correspond to the $3/{2}^{\ensuremath{-}}$[532] configuration. The new spin assignments in ${}^{147}$Ba suggest that the theoretical predictions of static octupole deformation in the ground state of ${}^{147}$Ba may not be be valid. No candidates for parity doublets have been found in ${}^{147}$Ba. Instead, an octupole band built on the ground state has been proposed.