New features of collective nuclear rotation at very high frequency in Sb109

Three rotational bands have been discovered in the nucleus Sb109 that extend in angular momentum to ≃81/2ħ. The rotational frequency at the highest spins reaches ħω≃1.4 MeV, the highest frequency so far observed in a heavy nucleus. With increasing frequency the collective moments of inertia of all three bands smoothly diminish to unexpectedly low values, scrJ(2)∼13ħ2 MeV-1, approximately one-third the rigid-body value, and, contrary to expectations, the moments of inertia become nearly equal to one another and to those of rotational bands in the core nucleus Sn108.