PARAMETRIZATION OF CHEMICALLY-ACTIVATED REACTIONS INVOLVING ISOMERIZATION

Parametrization of theoretical rate coefficients for chemically-activa ted reactions involving isomerization of activated complexes was exami ned. The theoretical rate coefficients were computed for chosen test r eaction systems by using the Rice-Ramsperger-Kassel-Marcus theory. The low- and high-pressure-limit rate coefficients were found to be propo rtional to [M](i), where [M] is the bath gas density and i identifies a specific reaction channel. Several parametrization approaches to the pressure dependence of the rate coefficients were tested. The formula s based on a falloff broadening factor and the generalized interpolati on between the pressure Limits produced generally large errors. Modifi cations were introduced that improve the accuracy of these previously suggested formulas. The most promising parametrization formula discove red in the present study contains only three temperature-dependent adj ustable parameters and demonstrates a high level of accuracy, with max imum errors below 1% for most cases tested, including bath chemically- activated and unimolecular reactions.