Spin-Isospin Giant Resonances and the Neutron Skin of Nuclei

The self-consistent relativistic proton-neutron quasiparticle random phase approximation (PN-RQRPA) has been employed in the analysis of charge-exchange modes: isobaric analog states (IAS) and Gamow-Teller resonances (GTR). A particularly interesting application is the study of the relation between the neutron skin of nuclei and the difference of excitation energies of the GTR and IAS. In addition to important information on basic nuclear structure, effective isovector interactions, and neutron-rich matter for astrophysical applications, the determination of neutron density distributions is crucial for the analysis of atomic parity-violating experiments. Detailed PN-RQRPA calculations of nuclear properties of a sequence of Sn isotopes, have shown that the isotopic dependence of the energy spacings between the GTR and IAS provides a measure of the evolution of the difference between the radii of the neutron and proton density distributions