Rice–Ramsperger–Kassel–Marcus (RRKM) theory

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 $ɛ *$ in an energized molecule is classified as either active, $ɛ *active$ , or inactive, $ɛ *inactive$ . The rate depends upon $P ɛ *active N ɛ *$ , where $N ɛ *$ is the density of states having energy between $ɛ *$ and $ɛ * + d ɛ *$ , and $P ɛ *active$ 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