An improved form of
Rice–Ramsperger–Kassel
(RRK) theory in which account is taken of the way in which the various normal-
mode vibrations and rotations contribute to reaction, and allowance is made for the zero-point
energies. In this theory the energy

in an energized molecule is classified as either active,

, or inactive,

.
The rate depends upon

,
where

is the density of states having energy between

and

, and

is the sum of the active quantum states of the
activated complex. This extension of RRK theory brings it in line with
transition-state theory.
Source:
PAC, 1996, 68, 149
(A glossary of terms used in chemical kinetics, including reaction dynamics (IUPAC
Recommendations 1996))
on page 186
Cite as:
IUPAC. Compendium of Chemical Terminology, 2nd ed. (the "Gold Book"). Compiled by
A. D. McNaught and A. Wilkinson. Blackwell Scientific Publications, Oxford (1997).
XML on-line corrected version: http://goldbook.iupac.org (2006-) created by M. Nic,
J. Jirat, B. Kosata; updates compiled by A. Jenkins. ISBN 0-9678550-9-8.
https://doi.org/10.1351/goldbook.