The evidence of the ion-ion potentials from heavy ion elastic scattering

From classical perturbation theory it is concluded that elastic scattering mainly determines the real part of the optical potential in a point slightly inside the distance of closest approach for a trajectory leading to the rainbow angle. With this rule the empirical evidence is compared to some ion-ion potentials given in the literature An empirical expression is given for the potential as well as for the radius of the Coulomb barrier. (Auth.)