We point out that the proton-neutron residual interaction is able to account for the recently observed properties in the empirical interaction energies between the last odd proton and neutron in nuclei adjacent to closed shells. Using zero-range forces, the specific difference between the average particle-particle and particle-hole interaction matrix 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, two-hole two-hole, and two-particle two-hole situations). Here we derive the particular binding energy contribution due to the proton-neutron interaction and give applications to heavy nuclei.

• Received 22 December 1993

DOI:https://doi.org/10.1103/PhysRevC.49.2499