A Detailed Formulation of Kinetic Processes. II. The Role of Collision Processes

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Abstract
A detailed treatment is given of the activational processes occuring in both unimolecular and bimolecular processes. Such a treatment leads very naturally to the postulate of two critically energized species, one related to the products and one to reactants. In the case of unimolecular isomerizations it is shown that the properties of either one or both of these species may dominate the rate of the nonequilibrium reaction rate expression, and the form of the rate expression is given in terms of the Slater theory of unimolecular reactions. In the case of unimolecular decompositions, only the complex corresponding to reactants is important, whereas in the inverse case of association reactions only that for the products is of importance. Both of these types of reactions have the same form of pressure dependence in the steady-state concentration region. The above considerations apply even when the reactions are not reversible. That is, the critically energized complex related to products is still of importance in determining the reaction rate. In the case of bimolecular and higher order processes, a detailed investigation shows that the activational processes are always maintained at their equilibrium values, and there is no region in which the rate constants will show a significant dependence on concentration of inert gas.