Inelastic proton scattering from Pt isotopes and the interacting boson model

Inelastic proton scattering has been used to measure the d\ensuremath{\sigma}/d\ensuremath{\Omega} and ${\mathit{A}}_{\mathit{y}}$ angular distributions for several low-lying collective states in $^{194,196}\mathrm{Pt}$ using 647 MeV polarized protons with special emphasis on the excitation of the ${4}^{+}$ states below 2 MeV. The data have been analyzed in the framework of the coupled-channels scheme using the program ecis. Large E4 transition strengths to the ${4}^{+}$ states in both nuclei are found in sharp contrast with the predictions of the interacting boson model with only s (L=0) and d (L=2) bosons. It is found that although the E2 properties of these nuclei are consistent with the interacting boson model (sd) predictions, higher degrees of freedom, e.g., g (L=4) bosons, need to be invoked in order to get a reasonable agreement with the measured E4 properties.