Coupling of the giant dipole resonance to gamma vibrations

Existing photonuclear data for ${}_{}{}^{166}{}_{}{}^{}\mathrm{Er}$ are analyzed in the framework of both the dynamic collective model and the interacting boson approximation. In particular, the cross section for the inelastic scattering of photons populating the γ-vibrational band is reanalyzed in order to infer information about the coupling of the giant dipole resonance to γ vibrations in deformed nuclei. These data are found to be in agreement with the predictions of both models and therefore do not discriminate between them.