Evolution of nuclear shell structure due to the pion exchange potential

The evolution of nuclear shell structure is investigated for the first time within density-dependent relativistic Hartree-Fock theory and the role of pi-exchange potential is studied in detail. The energy differences between the neutron orbits {v1h(9/2),v1i(13/2)} in the N = 82 isotones and between the proton ones {pi 1g(7/2), pi 1h(11/2)} in the Z = 50 isotopes are extracted as a function of neutron excess N - Z. A kink around Z = 58 for the N = 82 isotones is found as an effect of pion correlations. It is shown that the inclusion of pi-coupling plays a central role to provide substantial isospin dependence of the energy differences. In particular, the tensor part of the pi-coupling has an important effect on the characteristic isospin dependence observed in recent experiments. Copyright (c) EPLA, 2008.