  The energy of the charge-exchange Anti-analog Giant Dipole Resonance (AGDR)
has been calculated for the 208Pb isotope using the state-of-the-art fully
self-consistent relativistic proton-neutron quasiparticle random-phase
approximation based on the Relativistic Hartree-Bogoliubov model. It is shown
that the AGDR centroid energy is very sensitively related to the corresponding
neutron-skin thickness. The neutron-skin thickness of 208Pb has been determined
very precisely by comparing the theoretical results with the available
experimental data on E(AGDR). The result DR(pn)= 0.161(42) agrees nicely with
the previous experimental results.
