Properties of low-lying states in Co65 from lifetime measurements

The low-energy structure of Co-65 was studied by means of gamma(-) and fast-timing spectroscopy at the ISOLDE/CERN facility. The known level scheme of Co-65 populated following the beta(-) decay of Fe-65 was expanded. The experimental results were compared with large-scale shell-model calculations. The measured long lifetime of the (1/2(1)(-)) level confirms its nature as a highly collective state with proton excitations across the Z = 28 gap and neutrons across the N = 40 subshell.