Reconciling deformation parameters from fusion with those from Coulomb excitation

The effects of deformation on sub-barrier fusion were first demonsrated almost fifteen years ago. Since that first analysis, it has become generally accepted that quadrupole deformation parameters deduced from fusion are significantly lower than those deduced from Coulomb excitation. Following a detailed analysis of the excitation function for ${}_{}{}^{154}{}_{}{}^{}\mathrm{Sm}$${+}^{16}$O we find the excitation function is best fitted with deformation parameters which are consistent with Coulomb excitation data when a sufficiently complete model is used. The shape of the deduced barrier distribution strongly favors the inclusion of a positive hexadecapole moment.