Rotational bands in deformed odd-odd nuclei

In-beam γ-ray studies of deformed odd-odd nuclei in the neutron-deficient Re region produce simpler spectra than expected. Almost all of the deexcitation feeds through a few rotational bands based on high-Ω proton and/or neutron states (K itself is not necessarily large). A similar phenomenon is found with high-spin bands in the near-closed-shell Sb nuclei. This can be explained on the basis of highly-aligned single-particle states being most efficient at sharing large amounts of angular momentum with the collective core modes: Once locked into such states, the nucleus tends to deexcite through related, highly-aligned states, thus picking out a select subset of possible states. In addition, such odd-odd nuclei tend to have multi-particle states at lower energies than other nuclei, often with the particles forming a sort of oblate girdle about the prolate core - these can be thought of as oblate-parallel pseudo-rotational bands. Very-heavy-ion beams are necessary to bring in enough angular momentum to excite much in the way of high-spin collective modes in these odd-odd nuclei