Rotational bands near the Z=50 closed shell: 51111Sb

Rotational states have been identified in 15111Sb for the first time. Three decoupled (ΔI=2) bands extending to over 1 MeV in rotational frequency have been observed. At the highest frequencies, the scrJ(2) moments of inertia for these three bands are seen to decrease steadily to unexpectedly low values; this is interpreted as evidence for a novel form of band termination. One of these bands is interpreted as being based on the πh11/2 orbital coupled to a deformed [(πg9/2)-2 direct-product(πg7/2)]0+ state of the 15010Sn core. The interaction strength for the alignment of a pair of h11/2 neutrons has been extracted and compared with calculations. Two possible quasiparticle configurations are discussed for the other decoupled bands. Two strongly coupled (ΔI=1) bands have been identified and both shown to involve the [(πg9/2)-1 direct-product(πg7/2)2] configuration. A large number of spherical states have also been observed, which can be explained on the basis of valence protons coupled to spherical states in the 110Sn core