A rotational band based on the proton ${\mathit{h}}_{11/2}$ orbital has been observed to high spin (79/2ħ) and high rotational frequency (ħω≃1.0 meV) in the nucleus ${}_{51}{}^{113}{}_{}{}^{}\mathrm{Sb}$. The measured transition quadrupole moment is ${\mathit{Q}}_0$=4.4±0.6 e b, consistent with an axial prolate deformation of ${\mathrm{\beta }}_2$≃0.32. A large interaction strength (360±60 keV) has been measured for the rotational alignment of ${\mathit{h}}_{11/2}$ neutrons which, together with a considerable delay in the crossing frequency (Δħω≃0.09 MeV), is construed as the first direct evidence of a large high-j proton-neutron interaction.

• Received 30 October 1992

DOI:https://doi.org/10.1103/PhysRevLett.70.1065