Two-phonon excitations in 170Er

Recent experiments at the GEANIE/WNR facility and the University of Kentucky accelerator have yielded strong evidence for a two-gamma excitation in 170Er. This new case can be added to a handful of previously identified examples of two-gamma vibrations, all of them discovered in this decade. In this paper the experimental evidence for a two-phonon excitation 170Er is presented and the current state of understanding of these structures is reviewed in the context of this and other recent findings.