Improved measurement of the $0_2^{+}\to 0_1^{+}$ E0 transition strength for ${}^{72}$Se 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 dripline. In this work a study of ${}^{72}$Se by internal conversion electron and ${\hat{I}}^3$-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 $\ddot{I}{}^2(E0;0_2^{+}\to 0_1^{+})=29(3)$ milliunits. two state mixing calculations were performed that highlighted the importance of interpretation of such $E0$ strength values in the context of shape-coexistence.