Fundamental Aspects of the Adsorption and the Desorption of Gases at Solid Surfaces under Illumination

Abstract

The interaction of electromagnetic radiation with a solid can manifest itself in a variety of ways, but essentially the absorption of a photon generates an excited state of the solid. Similarly the interaction of a gaseous molecule with the surface of a solid will depend critically upon the chemical nature of the molecule in question and upon the chemical and the physical nature of the solid with which it is interacting. When an equilibrium is established between the gas and the solid, there will be a proportion of the molecules located in an adsorbed layer, held at the surface by either weak or strong bonding forces. Under illumination with radiation of a wavelength that is absorbed by the solid, the equilibrium, which is established thermally in the dark, will be displaced in one direction or the other causing a net photoadsorption or photodesorption of molecules.