Fundamental Atomic-Scale Issues/Processes Pertinent to Dynamics at Surfaces
John William Gadzuk
An introduction to some basic concepts and building blocks that facilitate the understanding of atomic scale dynamics at surfaces is presented. The focus is mainly towards processes defined in terms of both nuclear and electronic involvement. Reduction of the general quantum dynamics problem into something tractable is taken up first within the Born-Oppenheimer separation of fast and slow variables. The role of non-adiabatic processes is of special importance in condensed matter systems owing to the continuum of electron-hole pair excited states and this is a continuing theme throughout this introductory chapter. The basis for the commonly invoked trajectory model is examined. A paradigm-establishing example of a curve-hopping, diabatic transition model for the simple process of sticking is used to illustrate several points involving molecule-surface collisions. Surface processes involving significant dynamic charge transfer are dealt with taking advantage of both some unlikely similarities with fundamental processes triggered in core level spectroscopies and also the many modern advances in understanding the role of electron friction in condensed phase chemical dynamics. The importance of electron-resonance-enhanced dynamics is taken up and illustrated with a simple, generic, classical model for resonance-enhanced processes here applied to bond-breaking/desorption. This introduction concludes with some final historical thoughts.