Co low-energy structure via β decay including fast-timing measurements*

In neutron-rich nuclei near N = 40, the large energy separation of the νpf shell and the νg_9/2 single-particle state is responsible for a subshell closure that has long been investigated for its impact on other nearby neutron-rich nuclei. Just beyond the N = 40 subshell closure, nuclei exhibit a sudden onset of collectivity as protons are removed from the πf_7/2 single-particle state. This apparent fragility has been attributed to shape coexistence between spherical and prolate-deformed configurations. For ⁶⁸Co, a recent β-decay study at NSCL concluded that the lowest-energy populated state was attributed to a deformed configuration, extending the presence of shape coexistence to this nucleus. This work reports on ⁶⁸Co as determined from the analysis of new data from NSCL utilizing the selectivity of low-spin β decay from ⁶⁸Fe to populate ⁶⁸Co. An expanded schematic of the low-lying structure of ⁶⁸Co including half-life information, particularly for the low-lying states, will be presented.