Lifetime Measurements to Test the Coexistence of Spherical and Deformed Shapes inSe72

Mean lives of the $4^{+}$ or (${12}^{+}$) yrast states in ${}_{}{}^{72}{}_{}{}^{}\mathrm{Se}$ populated in the reaction ${}_{}{}^{58}{}_{}{}^{}\mathrm{Ni}({}_{}{}^{16}{}_{}{}^{}\mathrm{O}, 2p)$ were extracted from a line-shape analysis of the Doppler-broadened lines. The results strongly support the interpretation of the crossing of states built on near-spherical and deformed shapes in the yrast cascade. A least-squares fit of a collective Hamiltonian to the experimental data yielded a potential energy surface with spherical and strongly deformed prolate minima.