Reflection symmetry of the near-yrast excitations in145Ba

Abstract

Excited states in ${}^{145}$Ba, populated in spontaneous fission of ${}^{248}$Cm, have been studied by means of $\ensuremath{\gamma}$ spectroscopy, using high-fold $\ensuremath{\gamma}$ coincidences measured with the EUROGAM2 array of Ge detectors. The 507.7-keV level, which has been assigned in this work spin and parity 9/2${}^{+}$, belongs to the ${i}_{13/2}$ intruder band. We have identified in ${}^{145}$Ba a new 9/2${}_{2}^{\ensuremath{-}}$ level at 346.3 keV and a band on top of it. The negative parity indicates that it is not due to an octupole excitation. The position of the 5/2${}^{\ensuremath{-}}$ ground state, relative to the positive-parity band, could be reproduced by calculations with a reflection-symmetric potential and we do not observe a parity doublet to the ground state. Therefore we conclude that octupole excitations in ${}^{145}$Ba are most likely due to octupole vibrations coupled either to the reflection-symmetric ground state or to the ${i}_{13/2}$, decoupled neutron configuration.