THE PROTON-H11/2 INTRUDER ORBITAL - EVIDENCE FOR COLLECTIVITY AND A STRONG PROTON-NEUTRON INTERACTION

A rotational band based on the proton h11/2 orbital has been observed to high spin (79/2 HBAR) and high rotational frequency (HBARomega congruent-to 1.0 MeV) in the nucleus Sb-113(51). The measured transition quadrupole moment is Q0 = 4.4 +/- 0.6 e b, consistent with an axial prolate deformation of beta2 congruent-to 0.32. A large interaction strength (360 +/- 60 keV) has been measured for the rotational alignment of h11/2 neutrons which, together with a considerable delay in the crossing frequency (DELTAHBARomega congruent-to 0.09 MeV), is construed as the first direct evidence of a large high-j proton-neutron interaction.