Proton-neutron quadrupole interactions: an effective contribution to the pairing field

We point out that the proton-neutron energy contribution, for low multipoles (in particular for the quadrupole component), effectively renormalizes the strength of the pairing interaction acting amongst identical nucleons filling up a single-j or a set of degenerate manyj shells. We carry out the calculation in lowest-order perturbation theory. We perform a study of this correction in various mass regions. These results may have implications for the use of pairing theory in medium-heavy nuclei and for the study of pairing energy corrections to the liquid drop model when studying nuclear masses. ∗Postdoctoral fellow of the Fund for Scientific Research-Flanders (Belgium) †Visiting postdoctoral fellow of the Fund for Scientific ResearchFlanders (Belgium) ‡Present address: EP-ISOLDE, CERN, CH-1211 Geneva, Switzerland