Proton hole states in neutron rich Pd nuclei

The ($\overrightarrow{t}, \alpha$) reaction at 17 MeV triton energy has been used to study proton hole states in targets of ${}_{}{}^{106,108,110}{}_{}{}^{}\mathrm{Pd}$. The results indicate that for the residual nuclei, ${}_{}{}^{105,107,109}{}_{}{}^{}\mathrm{Rh}$, the ground states have a spin of ${\frac{7}{2}}^{+}$, in contrast to the lighter Rh nuclei, and are not of single-particle character. Coupled-channels analysis indicates a possible particle-vibration character for these ground states. A strong neutron-proton interaction may be evident from the level systematics of Rh nuclei as the ground state spins change between $N=58\mathrm{}$ and $N=60\mathrm{}$ (${}_{}{}^{103}{}_{}{}^{}\mathrm{Rh}$ and ${}_{}{}^{105}{}_{}{}^{}\mathrm{Rh}$).