The Z = 82 shell closure in neutron-deficient Pb isotopes

摘要

Recent mass measurements show a substantial weakening of the binding-energy difference δ_(2p)(Z, N) = E(Z - 2, N) - 2E(Z, N) + E(Z + , N) in the neutron-deficient Pb isotopes. As δ_(2p) is often attributed to the size of the proton magic gap, it might be speculated that reduction in δ_(2p) is related to a weakening of the spherical Z = 82 shell. We demonstrate that the observed trend is described quantitatively by self-consistent mean-field models in terms of deformed ground states of Hg and Po isotopes.