Brunauer–Emmett–Teller Theory

A multilayer physisorption theory extending Langmuir's single‑layer concept to describe physical adsorption of gases on solid surfaces and providing an operational equation (the BET equation) used to determine the monolayer adsorbed gas volume vm and hence specific surface area from gas adsorption isotherms under specified experimental conditions (commonly cryogenic adsorbate like N2 at 77 K).