Five-valence-proton N=82 isotone 137Cs

Yrast excitations in the N=82 isotone 137Cs have been identified for the first time in thick-target γ-ray coincidence measurements for the system 232Th+136Xe using the Gammasphere array. The 137Cs nuclei were produced in deep inelastic one-proton-transfer reactions. By-products of the main investigation were two well-developed rotational bands which were identified in heavy reaction partner products complementary to 137Cs and are tentatively assigned to the little studied nucleus 231Ac. There was no difficulty in placing the 11 observed 137Cs transitions in a yrast level scheme extending to an Iπ=(31/2-) level at 5494 keV. Interpretation was also straightforward, since the experimental level energies are in close agreement with results of shell model calculations performed earlier using empirical single particle energies and interaction matrix elements derived from experimental data for other N=82 isotones. copyright 1999 The American Physical Society