Inclusion of dynamics in the ion-metal surface interaction. I

Abstract

By identifying the self-energy of an ion in the presence of a semi-infinite metal as the ion-metal effective interaction, we obtain a quantum description of this interaction, which takes into account the dynamics of the metal, and which is therefore both non-local and retarded. Since a metal is characterized by the existence of excitations having energy arbitrarily close to zero, it is not obvious that an ion far outside a metal sees only the image force. We show in general that the ion self-energy reduces to the image potential far outside the metal if the ion is infinitely massive, i.e., in the classical limit. Our analysis provides a foundation for the calculation of corrections to the image potential for an ion of finite mass and velocity at arbitrary positions relative to a metal surface. In particular the response of a finite metal to an external charged particle can be decomposed into surface and bulk contributions.