Single-particle and collective excitations in Ni 62

Background: Level sequences of rotational character have been observed in several nuclei in the A = 60 mass region. The importance of the deformation-driving pi f(7/2) and nu g(9/2) orbitals on the onset of nuclear deformation is stressed. Purpose: A measurement was performed in order to identify collective rotational structures in the relatively neutron-rich Ni-62 isotope. Method: The Mg-26(Ca-48,2 alpha 4n gamma)Ni-62 complex reaction at beam energies between 275 and 320 MeV was utilized. Reaction products were identified in mass (A) and charge (Z) with the fragment mass analyzer (FMA) and gamma rays were detected with the Gammasphere array. Results: Two collective bands, built upon states of single-particle character, were identified and sizable deformation was assigned to both sequences based on the measured transitional quadrupole moments, herewith quantifying the deformation at high spin. Conclusions: Based on cranked Nilsson-Strutinsky calculations and comparisons with deformed bands in the A = 60 mass region, the two rotational bands are understood as being associated with configurations involving multiple f(7/2) protons and g(9/2) neutrons, driving the nucleus to sizable prolate deformation.