Indication of a<i>mini-valence</i>Wigner-like energy in heavy nuclei

Certain double differences of binding energies can be constructed that exhibit the valence proton-neutron interaction. These double differences, known as $\ensuremath{\delta}{V}_{\mathit{pn}}(Z,N)$, show singularities in light $N=Z$ even-even nuclei (and $N=Z\ensuremath{-}1$ even-$Z$, odd-$N$ nuclei) due to uniquely large overlaps of the proton and neutron wave functions and the short-range residual interaction. It is suggested that a similar phenomenon appears, heavily muted, in heavy nuclei as well, when one considers valence nucleon numbers. It is proposed that it arises from the overall similarity of the sequences of orbits in different major shells, giving higher overlaps when the respective proton and neutron shells are approximately equally filled.

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