Nature of excited 0+ states in 154Sm

Lifetimes of the 02+ and 2γ+ states in 154Sm were measured using the Doppler-shift Attenuation Method following Coulomb excitation. The experiment employed the gamma-ray detector array YRAST Ball at Yale University in conjunction with an array of photo-electric cells. 154Sm was identified as one of the few deformed nuclei where the first excited 0+ state is the β-vibration of the ground state. The 03+ level has no collective decay to the ground state band and is interpreted as a spherical shape coexisting state based on its decay properties and calculations in the framework of the interacting boson model (IBM) and geometric collective model (GCM).