The existence of two-y-phonon excited states in rare-earth nuclei remains a contentious issue in nuclear structure. While examples of single-phonon γ-vibrational states are prevalent in even-even deformed nuclei, identifying two-phonon excitations is challenging due to strength fragmentation and competing non-collective states. Although states with a strong two-phonon contribution are predicted by the collective model of Bohr and Mottelson, experimental evidence remains scarce, with only six cases reported in rare-earth nuclei. While pproperties of these states are largely in agreement with predictions from the model, their rarity challenges its validity. This work presents an overview of a Coulomb-excitation investigation into the low-lying states of 162Dy, which exhibits two Kπ = 4+ states suspected to be a splitting of the two-y-phonon contribution. Analysis methods for determining reduced transition matrix elements (If∥Eλ∥Ii), a key indication of collectivity, are presented. A new particle-detector array under development to enhance the Coulomb-excitation capabilities at the Australian Heavy Ion Accelerator Facility is also discussed.
Perissinotto et al. (Wed,) studied this question.