Structure of 60,62Fe and the onset of νg9/2 occupancy

Level structures in 60,62Fe34,36 and adjacent nuclei were studied with Gammasphere using the reaction of a 430-MeV 64Ni beam on a 55-mg/cm2 thick 238U target. High-spin level schemes were deduced from singly- and doubly-gated prompt coincidence events. Levels populated in the β decay of 60,62Mn isomers were studied in singly- and doubly-gated delayed coincidences. Spin and parity assignments were deduced from angular correlations of γ rays observed in both nuclei, leading to firm positive-parity yrast assignments up through 8+ in 62Fe. The observed levels for 60Fe up to ∼3.5 MeV compare well with pf shell-model calculations available in the literature. Calculations performed in a limited pfg basis exhibit reasonable agreement for the 2+, 4+, and 6+ levels in 62Fe. However, theoretical descriptions that include the newly identified negative-parity levels in 62Fe require a much larger basis, necessarily including g9/2 neutrons, as well as improved interactions leading to negative-parity levels.