Excited states in ${}^{139}\mathrm{Xe},$ populated in the spontaneous fission of ${}^{248}\mathrm{Cm},$ were studied by means of prompt-$\gamma$ spectroscopy, using the EUROGAM2 multidetector array. Spins and parities of excited levels were determined experimentally. New information was also obtained for the ${}^{141}\mathrm{Ba}$ nucleus. These data and a reevaluation of the data available in the literature on ${}^{141}\mathrm{Ba}$ and ${}^{143}\mathrm{Ce}$ show that the near-yrast structures of the ${}^{139}\mathrm{Xe},$ ${}^{141}\mathrm{Ba},$ and ${}^{143}\mathrm{Ce}$ nuclei are similar to that in the heavier $N=85\mathrm{}$ isotones. The presence of strong octupole correlations in the ${}^{139}\mathrm{Xe}$ and ${}^{141}\mathrm{Ba}$ nuclei, reported in another recent study, is not supported by the present work. The observed excitations in the $N=85\mathrm{}$ isotones are interpreted as being due to quadrupole and octupole vibrations coupled to the valence-neutron levels.

• Received 29 November 2000

DOI:https://doi.org/10.1103/PhysRevC.66.044302