Comment on the classical theory of the rate of isomerization.

The classical theory of the rate of unimolecular isomerization developed by Gray and Rice is extended in two ways. First, an improved state dependent approximation to the system separatrix is introduced. Second, a systematic approximation for the rate of intramolecular energy transfer in one isomer is introduced. These new approximations considerably improve the accuracy of the prediction of the rate of isomerization. Indeed, using the analysis described in this paper, the calculated rates of isomerization as a function of energy for the model system studied by Gray and Rice are in excellent agreement with the exact rates obtained from trajectory calculations. [ABSTRACT FROM AUTHOR]