EMPIRICAL PROTON-NEUTRON INTERACTIONS NEAR CLOSED SHELLS - A SIMPLE SHELL-MODEL APPROACH

We point out that the proton-neutron residual interaction is able to a ccount for the recently observed properties in the empirical interacti on energies between the last odd proton and neutron in nuclei adjacent to closed shells. Using zero-range forces, the specific difference be tween the average particle-particle and particle-hole interaction matr ix elements is the major factor. We extend the arguments to cover also nuclei with two valence proton and two valence neutron configurations outside of a closed shell (we treat both two-particle two-particle, t wo-hole two-hole, and two-particle two-hole situations). Here we deriv e the particular binding energy contribution due to the proton-neutron interaction and give applications to heavy nuclei.