Identification of excited states and collectivity in Se88

The γ decays of excited states in the very neutron-rich nucleus Se88 have been observed following the neutron-induced fission of U235. The measurement was performed using the EXILL array of Ge detectors at the PF1B cold-neutron beam facility of the Institut Laue-Langevin, Grenoble. The level scheme of Se88 was established using γ-γ-γ coincidences. A low (21+) energy hints at the onset of quadrupole deformation, and the identification of possible members of a (22+) band provide evidence for γ vibrations. Shell-model calculations using a Ni78 core reproduce the decay scheme well. Equivalent deformation and B(E2) values have previously been predicted for Se88 using pseudo-SU(3), shell-model, and beyond mean-field frameworks implying that interactions between particles in the πf5/2p and νsd orbits are mostly responsible for the collectivity present.