third body

https://doi.org/10.1351/goldbook.T06361
A species, other than the reactant itself, which brings about the energization of a molecule that can undergo a @[email protected] process, or brings about a combination reaction between atoms or radicals. In the latter case a third body is also called a @[email protected]
Source:
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 189 [Terms] [Paper]