We investigate the correlation between integrated proton-neutron interactions obtained by using the up-to-date experimental data of binding energies and the $N_{ \rm p} N_{ \rm n}$, the product of valence proton number and valence neutron number with respect to the nearest doubly closed nucleus. We make corrections on a previously suggested formula for the integrated proton-neutron interaction. Our results demonstrate a nice, nearly linear, correlation between the integrated p-n interaction and $N_{ \rm p} N_{ \rm n}$, which provides us with a firm foundation of the applicability of the $N_{ \rm p} N_{ \rm n}$ scheme to nuclei far from the stability line.
Categories: nucl-th