1 3 0 Ja n 19 99 Proton Single Particle Energy Shifts due to Coulomb Correlations

We show that the interplay between the Coulomb interaction and the strong interaction, which is enhanced in the nuclear surface, leads to a significant upward shift of the proton single–particle levels. This shift affects the position of the calculated proton drip line, a shift towards decreasing Z by several units. The same mechanism is responsible for significant corrections to the mass difference of the mirror nuclei (Okamoto–Nolen–Schiffer anomaly) and to the effective proton mass. PACS: 21.10.Sf Coulomb energies — 21.10.Dr Binding energies — 21.10.-k Nuclear energy levels The main part of the Coulomb energy in nuclei is given by the Hartree contribution and to a reasonable accuracy this can be computed as the energy of a uniformly charged sphere and is thus proportional to Z/A. There are a number of corrections, some of them rather subtle, arising from the interplay between the Coulomb and nuclear forces. The Okamoto–Nolen–Schiffer anomaly in the binding energy of mirror nuclei [1] is a case in point. In Ref. [2] we have shown that a specific many–body mechanism (described briefly below) leads to an enhancement of the Coulomb energy in the nuclear surface region and in this way one can account for the major part of this anomaly. This effect results in a systematic contribution to the nuclear binding energy, which scales as ∝ Z. We are going to demonstrate that the mechanism should be taken into account when calculating a number of nuclear properties. In this Letter we study the role of this new many–body effect on the single–particle proton energy levels, on the location of the proton drip line and on the proton effective mass. We shall operate within the density functional theory [3, 4, 5, 6]. The ground state energy of a nucleus E is given by a sum of two functionals (in the absence of pairing correlations): E = F0[ρπ(r), ρν(r)] + FCoul[ρπ(r), ρν(r)], (1)