Recoil saturation of the self-energy in atomic systems

Within the framework of the general self-energy problem for the interaction of a projectile with a many-body system, we consider the dispersion force between two atoms or between a charge and an atom. Since the Born-Oppenheimer approximation is not made, this is a useful approach for exhibiting non-adiabatic effects. We find compact expressions in terms of matrix elements of operators in the atomic displacement which are not limited by multipole expansions. 7 refs