Shape coexistence inSe72investigated following theβdecay ofBr72

Abstract

The structure of {sup 72}Se was investigated following the {epsilon}/{beta}{sup +} decay of {sup 72}Br produced in the {sup 58}Ni({sup 16}O, pn) reaction at 50 MeV. Using a beam chopping system, off-beam {gamma}-ray decay data was collected with an array of clover Ge detectors. {gamma}-{gamma} coincidence measurements provided a significant modification of the prior level scheme, and {gamma}-{gamma} 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.