Transition probabilities in 154Gd: Evidence for X(5) critical point symmetry

Lifetime measurements in 154Gd were performed by means of the recoil distance Doppler-shift method. Excited states of 154Gd were populated via Coulomb excitation with a 32S beam at 110 MeV delivered by the FN tandem accelerator of the University of Cologne. The determined transition probabilities as well as the low-spin level scheme of 154Gd demonstrate a good agreement with the predictions of the critical point symmetry X(5). Comparison of specific experimental observables for the N=90 rare earth isotones with the calculations of the X(5) model clearly show that 154Gd is one of the good examples of the realization of the X(5) dynamical symmetry. In addition, the experimental data are compared to fits in the framework of the IBA and the general collective model