Improved measurement of the 02+→01+E0 transition strength for Se72 using the SPICE spectrometer

Abstract

The selenium isotopes lie at the heart of a tumultuous region of the nuclear chart where shape coexistence effects grapple with neutron-proton pairing correlations, triaxiality, and the impending proton drip line. In this work, a study of $^{72}\mathrm{Se}$ by internal conversion electron and $\ensuremath{\gamma}$-ray spectroscopy was undertaken with the SPICE and TIGRESS arrays. New measurements of the branching ratio and lifetime of the ${0}_{2}{}^{+}$ state were performed, yielding a determination of ${\ensuremath{\rho}}^{2}(E0;{0}_{2}{}^{+}\ensuremath{\rightarrow}{0}_{1}{}^{+})=29(3)$ milliunits. Two-state mixing calculations were performed that highlighted the importance of interpretation of such $E0$ strength values in the context of shape coexistence.