Chemisorption
Ultra-high vacuum noble gas purification. Purification methods

Chemisorption is an exothermic adsorption phenomenon that enables reactive species (N₂ , O₂ , CO, CO₂ , C_xH_y, H₂S, etc.) from the gas phase to be fixed by sticking to the surface of an adsorbent. The energies involved in the formation of one or more strong chemical bonds (covalent bond, ionic bond, metallic bond) are of the order of 50 to 500 kJ · mol^–1, and give the reaction a hardly reversible character. These reactions take place on special adsorbents known as getters, and are described by the following equation, where "X" represents the gas particle and "*" an adsorption site: