Detailed low-spin spectroscopy of Ni-65 via neutron capture reaction [Detailed low-spin spectroscopy of Ni65 via neutron capture reaction]

An extended investigation of the low-spin structure of the Ni-65 nucleus was performed at the Institut Laue-Langevin, Grenoble, France, via the neutron capture reaction Ni-65(n, gamma) Ni-65, using the Fission Product Prompt Gamma-Ray Spectrometer High-Purity Ge array. The level scheme of Ni-65 was significantly expanded, with two new levels and 87 newly found transitions. Angular correlation analyses were also performed, allowing us to assign spins and parities for a number of states and to determine multipolarity mixing ratios for selected y transitions. The low-energy part of the experimental level scheme (up to about 1.4 MeV) was compared with Monte Carlo shell-model calculations, which predict spherical shapes for all states, apart from the 9/2(+) and the second excited 1/2(-) states of oblate deformation.