  Neutron and proton densities in the nuclear periphery are investigated within
(p,n) charge-exchange isobar transitions. For this purpose we have developed
parameter-free optical potentials with a detailed treatment of the in-medium
$t_{\tau}$ part of the effective interaction. Non local coupled-channel Lane
equations are solved to obtain the scattering observables. The use of
conventional proton and neutron densities significantly underestimates Fermi
(forward-angle) cross-sections in agreement with findings by various other
groups. However, we have found model-independent densities which provide a
remarkable improvement in the description of the quasielastic scattering
data.The densities obtained are consistent with recent measurements at CERN in
studies of the neutron-to-proton halo factor f(r)=Z$\rho_n/N\rho_p$ with
antiprotons. These findings provide an alternative way to investigate the
nuclear periphery, and may also help to solve the long-standing puzzle of the
underestimated Fermi cross section in (p,n) charge-exchange phenomena.
