The dynamical assumptions underlying the Slater and RRK classicalhyphen;mechanical theories of unimolecular reaction rates are investigated. The predictions of these theories for several nonlinear, triatomic, harmonically bonded molecular models are compared with the results obtained from the integration of the classical equations of motion. The accuracy of the smallhyphen;vibration and weakhyphen;coupling assumptions are found to break down at energies above about onehyphen;quarter of a bond dissociation energy. Nonetheless, the smallhyphen;vibration approximation predicts reaction frequencies in good agreement with the exact results for the models. The effects of rotation on intramolecular energy exchange are examined and found to be significant.
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