Observation of excited states in the neutron-rich nucleus 89Br

Excited states of the neutron-rich 89Br have been observed for the first time. They were populated in cold-neutron induced fission of 235U at the PF1B facility of the Institut Laue-Langevin, Grenoble. The measurement of γ radiation following fission has been performed using the EXILL array of Ge detectors. The observed level structure looks similar to the yrast level structure of 87Br. Large valence space shell model calculations performed for 89Br confirmed this similarity. Comparison of the observed πg9/2 band with the results of the shell model calculations provides information on the evolution of collectivity in this region.