A possible mechanism for a bimolecular process catalyzed at a solid surface. It is assumed that two molecules are adsorbed on adjacent sites and that a reaction takes place via an activated complex on the surface to yield the products of the reaction. This mechanism was suggested by the US chemist Irving Langmuir (1881–1957) in 1921 and developed by the British chemist Sir Cyril Hinshelwood (1897–1967) in 1926. Some bimolecular reactions at surfaces are in agreement with the predictions of this model. See also Langmuir-Rideal mechanism.