Enhancement of then−pinteraction in odd-odd nuclei

Abstract

A comprehensive study of the mass-data-based interaction energy of the last i proton(s) and the last j neutron(s) indicates that the last proton-neutron interaction energy ${\ensuremath{\epsilon}}_{1p\ensuremath{-}1n}$ in odd-odd nuclei is greater than half of the average value of the last proton-dineutron interaction energy ${\ensuremath{\epsilon}}_{1p\ensuremath{-}2n}$ in odd-Z nuclei and the last diproton-neutron interaction energy ${\ensuremath{\epsilon}}_{2p\ensuremath{-}1n}$ in odd-N nuclei, and the phenomenon of the enhancement of the $n\ensuremath{-}p$ interaction energy in odd-odd nuclei is universal. In proton rich nuclei, the enhancement is generally more remarkable than that in neutron rich ones. To one's surprise, the ${\ensuremath{\epsilon}}_{1p\ensuremath{-}1n}$ in some odd-odd nuclei near proton drip line is even greater than the average value of ${\ensuremath{\epsilon}}_{1p\ensuremath{-}2n}$ and ${\ensuremath{\epsilon}}_{2p\ensuremath{-}1n}.$ Additionally, it is found that ${\ensuremath{\epsilon}}_{1p\ensuremath{-}2n}$ in odd-Z nuclei is approximate to ${\ensuremath{\epsilon}}_{2p\ensuremath{-}1n}$ in odd-N nuclei with the same mass number A, which is equivalent to the Garvey-Kelson relation proposed long ago.