An Electrodynamic Theory of the Non‐adiabatic Effects in Rate Processes for Molecules Adsorbed on Metals

We present a theory which computes the role of the electronic excitations in a metal substrate in dynamic processes involving adsorbed molecules. We use a model in which the molecular skeleton has effective charges whose magnitude and position varies when the nuclei of the molecule move. These moving charges couple to the electrons in the metal and excite them; as a result the molecule loses energy. The rate of such energy loss affects the vibrational line‐width and the fluorescence lifetime of the molecule, the van der Waals interaction between adsorbed molecules and the motion of the molecule at the surface. We show how these effects can be discussed in a unified way in terms of an electromagnetic theory. We emphasize that for obtaining reasonable numerical results we must replace phenomenological Maxwell equations with a microscopic theory that takes into account the non‐locality of the electron response to moving charges and the continuous nature of the interface.