Projected shell model analysis of tilted rotation

The study of high-angular-momentum phenomena has provided a deep understanding of the motion of nucleons in a rotating mean field. It is known that this motion is strongly perturbed by the Coriolis interaction in the high- j intruder orbitals and, for instance, shows up in the form of the backbending phenomenon at high angular momenta @1,2#. The conventional interpretation of the backbending is in terms of a crossing of the s band with the ground-state band @3#. The s band has two quasiparticles coupled to low-K and orbiting around the rotational axis. ~‘‘K’’ is the projection of the total angular momentum along the symmetry axis!. The s band requires less collective rotational energy to generate angular momentum and becomes energetically favored at higher spins as compared to the ground-state band. For a partially rotation-aligned state formed from a twoquasiparticle ~2-qp! excitation, the total K quantum number of the state can be obtained either by the addition or subtraction of the V quantum numbers of the individual quasiparticles. We thus can have two kinds of couplings: a 2-qp state with a larger total K ~high-K! and a state with a smaller K ~low-K!. We can discuss two situations according to the shell filling: in the lower half of the intruder subshell, both individual quasiparticle states have small V numbers and the total K numbers for both of the coupling schemes are relatively small. Therefore, they both can contribute to the s band. However, when we move to the upper half of the subshell, both of the individual quasiparticle states have larger V numbers. The coupling in this case will lead to two 2-qp states with very different total K values—one is small and