3.3. Three-body reaction

There are several reactions in the atmosphere, where a third „non-reactive” compound is involved. A three-body reaction is a reaction of two species A and B to yield one single product species AB. This reaction requires a third body (M) to stabilize the excited product AB* by collision:






The third body M could be any inert molecule (in the atmosphere, generally N2 and O2) that can remove the excess energy from AB* and eventually dissipate it. We can write the overall (net) reaction as


to emphasize the need for a third body.