Gas Release from Solids

Summary

All the gas could be pumped from a vacuum chamber in a very short time if it were located in only the volume of the chamber. This chapter discusses the mechanisms of gas evolution from solid surfaces and explains how they affect the pumping rate and ultimate pressure in vacuum chambers. Gas is dissolved in and adsorbed on solids. This gas release, collectively referred to as outgassing, is actually a result of several processes. Gases and vapors released from the surface are a result of vaporization, thermal desorption, diffusion, permeation, and stimulated desorption. Gas diffusion to the interior wall of a vacuum system followed by desorption into the chamber contributes to the system outgassing. Thermal desorption is the heat‐stimulated release of gases or vapors previously adsorbed on the interior walls of the system.