Evolution of Nuclear Shell Structure due to the Pion Exchange Potential

Abstract

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 $\text{Lrb}\nu 1h_{9/2},\nu 1i_{13/2}$ in the N=82 isotones and between the proton ones $\text{Lrb}\pi 1g_{7/2},\pi 1h_{11/2}$ 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 resulting from pion correlations. It is shown that the inclusion of $\pi$-coupling plays a central role to provide realistic 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.

Comments: 4 pages and 4 figures