Odd-even staggering in the neutron-proton interaction and nuclear mass models

In this paper we study odd-even staggering of the empirical neutron-proton interaction between the last neutron and the last proton, denoted as δV1n-1p, and its consequence in the Garvey-Kelson mass relations (GKs) and nuclear mass models. The root-mean-squared deviations of predicted masses respectively for even-A and odd-A nuclei by using two combinatorial GKs suggest a large odd-even staggering of δV1n-1p between even-odd and odd-even nuclei, while the odd-even difference of δV1n-1p between even-even and odd-odd nuclei is much smaller. The contribution of the odd-even staggering of δV1n-1p between even-A and odd-A nuclei in deviations of theoretical δV1n-1p values of the Duflo-Zuker model and the improved Weizsacker-Skyrme model are well represented by an isospin-dependent term. The consideration of this odd-even staggering improves our description of binding energies and one-neutron separation energies in both the Duflo-Zuker model and the improved Weizsacker-Skyrme model.