Nature of excited 0(+) states in Sm-154

Lifetimes of the 0(2)(+) and 2(gamma)(+) states in Sm-154 were measured usi ng the Doppler-shift Attenuation Method following Coulomb excitation. The e xperiment employed the gamma-ray detector array YRAST Ball at Yale Universi ty in conjunction with an array of photo-electric cells. Sm-154 was identif ied as one of the few deformed nuclei where the first excited Of state is t he beta-vibration of the ground state. The 0(3)(+) level has no collective decay to the ground state band and is interpreted as a spherical shape coex isting state based on its decay properties and calculations in the framewor k of the interacting boson model (IBM) and geometric collective model (GCM) . (C) 1999 Elsevier Science B.V. All rights reserved.