Rice–Ramsperger–Kassel (RRK) theory

https://doi.org/10.1351/goldbook.R05390
A theory of @[email protected] gas reactions in which the rate with which the energized reactant molecule breaks down is treated as a function of the energy \(\varepsilon\) that it contains. The theory assumes that the rate is proportional to the number of ways of distributing \(\varepsilon\) among the internal @[email protected] of the reactant molecule, in such a manner that the critical energy \(\varepsilon_{\text{c}}\) is localized in one particular degree of freedom.
Source:
PAC, 1996, 68, 149. (A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC Recommendations 1996)) on page 185 [Terms] [Paper]