Rotational inertia of superdeformed nuclei: Intruder orbitals, pairing, and identical bands

The phenomenon of identical bands is studied by analyzing the distributions of fractional changes in the dynamical moments of inertia of pairs of bands in superdeformed (SD) nuclei. These distributions are found to exhibit a peak with a centroid at nearly zero. Their widths increase in going from the SD bands in the mass A similar to 150, to the SD bands in the mass similar to 190, and to the normally deformed bands in the rare-earth region. Consequently, there exists a significant excess of identical bands in SD nuclei compared to the normally-deformed nuclei at low spins. This difference may be attributed to the weaker pairing correlations and the stabilizing role of intruder orbitals on the structures of SD bands.