Shape Coexistence in ^64,62Ni using the Nuclear Resonance Flourescence (NRF) Technique

Neutron-rich Ni isotopes have been attracting much attention on the account of a phenomenon known as shape coexistence, which has been observed in ⁶⁶Ni, doubly-magic ⁶⁸Ni (N = 40), and ⁷⁰Ni. The low-spin structures of the semi-magic ⁶⁴Ni and ⁶²Ni (Z = 28) isotopes are the latest to be investigated for shape coexistence.. The presence of this phenomenon in near closed-shell nuclei is indicative of the rapid change in structure that can happen with either the addition or removal of a few protons or neutrons, by which states associated with deformed shapes can be present at relatively low excitation energy beside the anticipated spherical ones. Finding proof of these shapes in ⁶⁴Ni and ⁶²Ni was stimulated by Monte Carlo shell-model (MCSM) calculations that account for these shapes in the heavier Ni isotopes and disclose the intricate landscape of coexisting shapes. A combination of four distinct measurements found evidence for shape coexistence in ⁶⁴Ni, one of these being a Nuclear Resonance Fluorescence (NRF) measurement carried out at TUNL’s High Intensity Gamma ray Source (HIGS). The work described here is part of the efforts to go beyond the results reported thus far by exploring the potential for additional physics from the NRF data. All the transitions observed in ⁶⁴Ni spectra generated with 8.7- and 8.95 - MeV beams and transitions observed in ⁶²Ni in spectra generated with 2.9 to 10.13 MeV beams are being analyzed for energy, intensity, anisotropy. Coincidence relationships are being explored as well as an important step toward a comprehensive investigation of shape coexistence in ⁶⁴Ni and ⁶²Ni.