Study of high spin states in ⁶²Ni with GRETINA at ANL

High spin states in ⁶²Ni were populated in a fusion evaporation reaction with a 190 MeV ⁴⁸Ca beam on an isotopically enriched ¹⁸O target at Argonne National Laboratory. The de-exciting gamma rays were detected by GRETINA (Gamma-Ray Energy Tracking In-beam Nuclear Array), which consisted at that time of 12 modules positioned to cover polar angles between 70⁰ and 170⁰. The spins and parities of excited levels were established using angular distribution and polarization asymmetry measurements. This allowed us to identify excited states formed by nucleon excitations within the fp shell and those involving neutron excitations into the g_9/2 orbital.

Two additional rotational bands have been added to the two existing rotational bands. The excitations within the fp shell and those with one neutron excited into the g_9/2 orbital were found to be consistent with large-scale shell model calculations. Deviations were, however, observed between the experimental results and the shell model calculations for high spin states, suggesting the importance of the two neutron excitations into the g_9/2 orbital not captured by the shell model calculations. These experimental results emphasized the need for refining the calculations to align with the suggested 2p-2h configurations of the states. Calculations using the Generator Coordinate Method were found to be more consistent with the 2p-2h excitations.



This work is supported by US NSF under Grant # PHY 2412808 (FSU) and the UD Department of Energy under Grant # DE-FG02-94ER40848 (UML) and DE-AC52-07NA27344 (LLNL)