Search for Isospin-Symmetry Breaking in the A=62 Isovector Triplet

The assignment of the first 2(+) state in Ga-62 has long been debated, due to its implications in triplet energy difference systematics in this mass region. An experiment has been performed at the IFIN-HH 9-MV Tandem accelerator using the ROSPHERE array in a mixed configuration of LaBr3(Ce) and HPGe detectors, as well as an additional array of liquid scintillator neutron detectors. Excited states in 62Ga were populated through a 2n fusion-evaporation channel and an anisotropy ratio was obtained from neutron-filtered HPGe statistics of transitions observed at different angles. A 2(+) state has been confirmed at an excitation energy of 978.1(1) keV. Theoretically, the interplay between isospin-symmetry breaking and shape-coexistence effects in the A = 62 isovector triplet is self-consistently treated within the beyond-mean-field complex excited Vampir variational model with symmetry projection before variation using an effective interaction obtained from a G matrix based on the charge-dependent Bonn CD potential adding the Coulomb interaction between the valence protons. Results are presented on Coulomb energy differences, mirror energy differences, triplet energy differences, and the superallowed Fermi beta decay of the ground state of Ge-62 and Ga-62.