Some Considerations of Unimolecular Rate Theory. II. Aspects of the General Theory

Abstract

The rate constant for a unimolecular reaction is obtained in alternative ways from the Liouville equation supplemented by the strong collision assumption. The final expression for the rate constant explicitly includes the details of the interactions between the collision process and intramolecular processes. The ``new-approach'' formula, obtained by Slater on intuitive grounds, is recovered when the collisional relaxation time is evaluated from the kinetic theory collision constant. With this assumption, the rate constant is expressed in terms of the eigenvalue problem generated by the Liouville operator of the isolated molecule in its interesting states. This expression provides a basis for a perturbative evaluation of the rate constant. Statistical arguments are used to develop consistency theorems for checking experimental data. Reversible isomerization reactions are discussed, and a transmission coefficient which monotonically increases with pressure is deduced.