Empirical pairing gaps and neutron-proton correlations

Analysis of various mass relations connected with neutron-proton correlations in atomic nuclei is carried out. On the example of $N = Z$ chain it is shown that for self-adjoint nuclei various formulas proposed in literature for $np$ pairing energy estimations lead to similar results. Significant differences between the calculation methods arise when nuclei with $N \ne Z$ are considered, which allows to show the complexity of neutron-proton correlations in different types of atomic nuclei and to make some assumptions on the correspondence of a mass ratio to the real effect of $np$ pairing. The Shell Model parametrization of binding energy makes it possible to arrive to additional conclusions on the structure of mass formulas and their interrelationships with one another.