Prompt $\gamma$-ray cascades in neutron-rich nuclei around doubly magic ${}^{132}\mathrm{Sn}$ have been studied at Eurogam II using a ${}^{248}\mathrm{Cm}$ fission source. Here we report results for the four-valence-proton $N=82\mathrm{}$ nucleus ${}^{136}\mathrm{Xe}$ and for its $N=83\mathrm{}$ neighbor ${}^{137}\mathrm{Xe}.$ For both nuclei, the yrast level spectra have been considerably extended, and empirical nucleon-nucleon interactions have been used to assign probable shell model configurations. The ${}^{136}\mathrm{Xe}$ level energies are compared with those calculated using different sets of proton-proton interaction matrix elements, both diagonal and nondiagonal, obtained by fitting experimental data for other $N=82\mathrm{}$ isotones.

• Received 21 December 1998

DOI:https://doi.org/10.1103/PhysRevC.59.3066