A possible signature for single and double γ vibrations

The precise characterization of vibrational excitations of the β and γ type have remained unsettled in nuclear structure physics. One aspect of the mystery was due to the absence of observed multiple excitations. The authors have concentrated their search for K=4 (γγ) types of two-phonon vibrational excitations in the deformed A=150 region of nuclei. Their studies yielded 17 (K=4) bands, as well as a characteristic signature in their dynamic moments of inertia. In fact, there are six examples of nuclei where the dynamical moments of inertia are identical for the K=2 and the K=4 bands. A comparison of the data with predictions of various theoretical models is presented