Shape coexistence in Se72 investigated following the β decay of Br72

The structure of Se72 was investigated following the ε/β ⁺ decay of Br72 produced in the Ni58(O16, pn) reaction at 50 MeV. Using a beam chopping system, off-beam γ-ray decay data was collected with an array of clover Ge detectors. γ-γ coincidence measurements provided a significant modification of the prior level scheme, and γ-γ angular correlation measurements allowed spin determinations and multipole mixing ratio extraction. The new information on the non-yrast states was combined with previous in-beam data to investigate the issue of shape coexistence by comparing to various configuration mixing approaches. Clear evidence for shape coexistence is found, with a ground state of modest, or slightly oblate, deformation and a well-deformed prolate shape that would lie at an unperturbed excitation of 875 keV. The shape mixing is near complete at low spin.