Some analytic properties of the master equation for unimolecular reaction

Abstract

Necessary and sufficient conditions for the occurrence of strict Lindemann behaviour in thermal unimolecular reactions are presented; both strong-collision and weak-collision régimes are treated. For the strong-collision case, there is a simple connection between the shape of the fall-off curve and the specific rate constant function k ( E ), but there is no direct connection between the shape of the fall-off curve and the structure of the molecule. In the weak-collision case, strict Lindemann behaviour will occur only when bottleneck effects dominate, and as a prelude to the detailed examination of this problem, we derive the rate constant for a weak-collision master equation, valid for all pressures.