Abstract

A long-standing issue in surface science has been the role of electronic non-adiabaticity in the interactions of atoms and molecules with metal surfaces. The absence of any energy gap for electron-hole pair excitations of a metal substrate results in general of a breakdown of the adiabatic (Born-Oppenheimer) approximation for the electronic motion in response to ionic motion. A key question is whether this electronic non-adiabaticity is sufficiently strong to be important in dynamical processes at surfaces or not. The progress in the theoretical description of the electronic structure of adsorbates using density functional theory has made it possible to calculate the electronic non-adiabatic coupling for more or less realistic systems and we can now address this question in a more quantitative manner. A most elementary case is provided by electron-hole pair damping of adsorbate vibrations, whose theoretical treatment will be the starting point for this talk that will cover theory of electronic adiabaticity in transition state dynamics, hot-electron induced surface chemistry, chemically-induced electronic excitations upon adsorption of atoms and molecules, and exo-electron emission in vibrational de-excitation in scattering from surfaces?