Neutron-Proton Interaction between States of Samelin Nuclear Shell Model

Talmi has suggested that the movement of the $g_{\frac{7}{2}}$ neutron state from the top to the bottom of its major shell between ${}_{40}{}^{}{}_{}{}^{}\mathrm{Zr}$ and ${}_{50}{}^{}{}_{}{}^{}\mathrm{Sn}$ is due to a strong attractive interaction between $g_{\frac{7}{2}}$ neutrons and $g_{\frac{9}{2}}$ protons which fill in this region, arising from the fact that both are $g$ states. Other evidence for this interaction is cited; e.g., the $h_{\frac{9}{2}}$ neutron state moves down several MeV in the region where the $h_{\frac{11}{2}}$ proton level fills ($Z=60-80\mathrm{}$), and the $f_{\frac{5}{2}}$ neutron level moves down considerably in the region where the $f_{\frac{7}{2}}$ proton state fills ($Z=20-28\mathrm{}$). Other evidence in support of this effect is presented; there is no apparent counter-evidence from nuclear level schemes.