Pion-nucleon correlations in finite nuclei in a relativistic framework: Effects on the shell structure

摘要

The relativistic particle-vibration coupling (RPVC) model is extended by the inclusion of isospin-flip excitation modes into the phonon space, introducing a new mechanism of dynamical interaction between nucleons with different isospin in the nuclear medium. Protons and neutrons exchange by collective modes which are formed by isovector pi and rho-mesons, in turn, softened considerably because of coupling to nucleons of the medium. These modes are investigated within the proton-neutron relativistic random phase approximation (pn-RRPA) and relativistic proton-neutron time blocking approximation (pn-RTBA). The appearance of isospin-flip states with sizable transition probabilities at low energies points out that they are likely to couple to the single-particle degrees of freedom and, in addition to isoscalar low-lying phonons, to modify their spectroscopic characteristics. Such a coupling is quantified for the shell structure of Sn-100,Sn-132 and found significant for the location of the dominant single-particle states. (C) 2016 The Author. Published by Elsevier B.V. This is an open access article under the CC BY license.