Shape coexistence in 72Se investigated following the β decay of 72Br.

The structure of 72Se was investigated following the ϵ/β+ decay of 72Br produced in the 58Ni(16O, 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. [ABSTRACT FROM AUTHOR]