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 π-exchange potential is studied in detail. The energy differences between the neutron orbits {ν1h9/2, ν1i13/2} in the N=82 isotones and between the proton ones {π1g7/2, π1h 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 π-coupling plays a central role to provide substantial isospin dependence of the energy differences. In particular, the tensor part of the π-coupling has an important effect on the characteristic isospin dependence observed in recent experiments. © Europhysics Letters Association.