Evidence for the existence of two-phonon collective excitations in deformed nuclei

Abstract

For the first time, definite evidence for the existence of two-phonon collective states in deformed nuclei has been established through the measurement of the absolute transition rate for the decay of the double-\ensuremath{\gamma} ${\mathit{K}}^{\mathrm{\ensuremath{\pi}}}$=${4}^{+}$ vibration in $^{168}\mathrm{Er}$.