Evidence for Coexistence of Spherical and Deformed Shapes in ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$

We report evidence for an excited $K^{\pi }=0^{+}$ rotational band in ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ and its mixing with vibrational states. The mean life of the 937-keV $0^{+}$′ state was measured to be 22.8±1.4 nsec, yielding $B\left(E2\mathrm{}\right)=36\mathrm{}\pm 7$ single-particle units for the 75-keV $0^{+}$′ → $2^{+}$ transition. From in-beam, $\gamma$-ray spectroscopy following the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, 2p)$, a strong $\gamma$-ray cascade was observed from an yrast band of levels $0^{+}$, $2^{+}$,... to spin ${12}^{+}$ in ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$.