In this chapter we focus on a series of phenomena that occur as a result of the interaction between the chaotically moving gas particles and the surrounding solid surface (e.g. the walls of the enclosure). This interaction, together with the ability of solids to bind and store gas particles, is the major obstacle for obtaining extremely low pressures. On the other hand, gas-solid interactions also form the basis for different pump principles in vacuum technology.
Topics to be discussed are: physical adsorption, gas-surface interaction potential (Lennard-Jones), adsorption and desorption rate, residence time, dynamic equilibrium between adsorption and desorption, adsorption models and isotherms (Langmuir, BET), mobile versus localized adsorption, surface migration, porous materials and their ability to capture large quantities of gas, chemisorption, condensation, absorption, diffusion, permeation and outgassing of solid materials.