Term: Rice–Ramsperger–Kassel (RRK) theory
https://doi.org/10.1351/goldbook.R05390

Definition:
A theory of unimolecular gas reactions in which the rate with which the energized reactant molecule breaks down is treated as a function of the energy ɛ that it contains. The theory assumes that the rate is proportional to the number of ways of distributing ɛ among the internal degrees of freedom of the reactant molecule, in such a manner that the critical energy ɛc is localized in one particular degree of freedom.

Related Terms:
1) unimolecular (http://doi.org/10.1351/goldbook.M03989).
2) degrees of freedom (http://doi.org/10.1351/goldbook.D01572).

Source: PAC, 1996, 68, 149. 'A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)' on page 185 (https://doi.org/10.1351/pac199668010149)

Citation: 'Rice–Ramsperger–Kassel (RRK) theory' 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.R05390

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