Eight superdeformed rotational bands have been observed in the ${}_{}{}^{149}{}_{}{}^{}\mathrm{Gd}$ nucleus. Several excited bands have partners in neighboring nuclei which differ by up to four nucleons, with nearly identical dynamic moments of inertia and quantized γ-ray phasing. These observations cannot be easily explained by theoretical models including an intrinsic scaling with mass of the moment of inertia. A paired backbend and an interaction due to an accidental degeneracy between two superdeformed levels have also been observed.

• Received 23 April 1993

DOI:https://doi.org/10.1103/PhysRevLett.71.688