Beyond Sphericity in a Semi-Magic Nucleus: Multiple-Shape Coexistence in $^{116}$Sn

Abstract

The study of nuclear shape evolution and coexistence provides key insight into the nuclear interaction, particularly in semi-magic systems expected to be spherical. A high-precision Coulomb-excitation measurement of $^{116}$Sn yields a comprehensive set of electromagnetic matrix elements, enabling the determination of quadrupole moments of the $2_{1,2,3}^+$ states and intrinsic deformations of the $0_{1,2,3}^+$ states. The results provide an unambiguous and direct proof of the rare phenomenon of multiple-shape coexistence, revealing a weakly deformed ground state incompatible with the spherical shape.