Medium spin excited levels in Br88 populated in fission of U235 induced by neutrons have been observed for the first time. The measurement of γ radiation following fission has been performed using the EXILL array of Ge detectors at the cold-neutron beam facility PF1B of the Institut Laue-Langevin (ILL), Grenoble. The ground state of Br88 is proposed to be 1-, changing the adopted (2-) value. The low-energy, newly observed levels are members of the πp3/2ν(d5/2)3 and πf5/2-1ν(d5/2)3 multiplets. A triplet of yrast levels observed at around 2 MeV is interpreted as being due to coupling of the g9/2 proton to the (d5/2)3, seniority 3 multiplet, supporting the presence of collective effects in Br88. The position of the g9/2 proton intruder in the Ni78 core is determined at 5.7 MeV above the f5/2 proton level. Shell-model calculations predict the same proton-neutron excitations proposed in Br88.
ASJC Scopus subject areas
- Nuclear and High Energy Physics