Abstract
The ๐ฝ-decaying states of 70,72Co were studied at the National Superconducting Cyclotron Laboratory using the VANDLE neutron time-of-flight array. The (6โ,7โ)โข๐ฝ-decaying state in 70Co is near-spherical with a lifetime of 113ยฑ7 ms, and the low-spin (1+,2+)โข๐ฝ-decaying state is postulated to be the prolate deformed ground state with a lifetime of 508ยฑ7 ms. Both decay predominantly to the bound states of 70Ni. For the first time neutron-emissions from neutron unbound states from both the (6โ,7โ) and (1+,2+)โข๐ฝ decays were measured. Even with the low statistics data, we were able to disentangle the neutron emission from both decays, which enabled a determination of ๐ฝ-decay strength above the neutron separation energy of 70Ni. Neutron emission probabilities were measured to be 7.1ยฑ1.5% and 9.4ยฑ1.7%, respectively, for the (6โ,7โ) and (1+,2+) decays. The decay pattern of the 70Co is driven by neutron ๐5/2 to proton ๐7/2 Gamow-Teller transformation. The observed population of neutron unbound states is attributed to the conversion of ๐1/2 and ๐3/2 neutrons to ๐3/2 and ๐1/2 protons excited across the ๐=28 closed shell.
