First experimental test of X(5) critical-point symmetry in theA~130mass region: Low-spin states and the collective structure ofCe130

Abstract

Excited, low-spin states in $^{130}\mathrm{Ce}$ are populated in the ${\ensuremath{\beta}}^{+}/\ensuremath{\epsilon}$ decay of $^{130}\mathrm{Pr}$ and studied through off-beam \ensuremath{\gamma}-ray spectroscopy at the Yale moving tape collector. New coincidence data lead to the construction of a substantially revised level scheme. The low-lying states of $^{130}\mathrm{Ce}$ are compared with the predictions of the X(5) critical-point model and the X(5)-${\ensuremath{\beta}}^{4}$ model, and the latter is found to give better agreement with the data in terms of energies. Discrepancies in the relative $B(E2)$ values in $^{130}\mathrm{Ce}$ and the geometrical models suggest that the \ensuremath{\gamma} degree of freedom may play an important role in this mass region.