Medium-spin states of the neutron-rich nucleus $^{87}$Br

International audienceMedium-spin excited states of the neutron-rich nucleus 87 Br were observed and studied for the first time. They were populated in fission of 235 U induced by the cold-neutron beam of the PF1B facility of the Institut Laue-Langevin, Grenoble. The measurement of γ radiation following fission was performed using the EXILL array of Ge detectors. The observed level scheme was compared with results of large valence space shell model calculations. The medium-spin level scheme consists of three bandlike structures, which can be understood as bands built on the π f 5/2 , π (p 3/2 + f 5/2), and π g 9/2 configurations. The behavior of the observed π g 9/2 band at high spins shows a considerable deviation from the shell model predictions. This deviation in this band is probably the result of an increased collectivity, which can be understood assuming that the π g 9/2 highj proton polarizes the core