Term: indirect reaction
https://doi.org/10.1351/goldbook.I03011

Definition:
A chemical process in which the reactive complex has a lifetime that is longer than its period of rotation is called an indirect reaction (in contrast to a direct reaction). In a molecular-beam experiment the products of such reactions are scattered at random with reference to the centre of mass of the system. Indirect reactions are also called complex-mode reactions. (They are sometimes called complex reactions, but this usage is not recommended in view of the danger of confusion with composite reactions, which occur in more than one step).

Related Terms:
1) reactive complex (http://doi.org/10.1351/goldbook.R05182).
2) lifetime (http://doi.org/10.1351/goldbook.L03515).
3) composite (http://doi.org/10.1351/goldbook.CT07545).
4) direct reaction (http://doi.org/10.1351/goldbook.D01773).
5) molecular-beam (http://doi.org/10.1351/goldbook.M03982).
6) complex-mode reactions (http://doi.org/10.1351/goldbook.C01206).

Source: PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 168 (https://doi.org/10.1351/pac199668010149)

Citation: 'indirect reaction' in IUPAC Compendium of Chemical Terminology, 5th ed. International Union of Pure and Applied Chemistry; 2025. Online version 5.0.0, 2025. https://doi.org/10.1351/goldbook.I03011

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