The stable states picture of chemical reactions. I. Formulation for rate constants and initial condition effects

The stable states picture (SSP) of chemical reactions is used to derive flux time correlation function (tcf) formulas for reaction rate constants. These formulas, which apply to both gas phase and condensed phase reactions, are interpreted in terms of the flux out of an internally equilibrated stable reactant and the ensuing irreversible flux into a stable product. The determination of the rate constants by dynamics in an intermediate region lying between these stable states is illustrated for a simple model of barrier crossing in liquids. Generalized rate constant expressions which hold when internal nonequilibrium in the stable states is important are derived and discussed. The SSP approach is also used to derive tcf expressions for short time initial condition effects which carry information on reactive dynamics beyond that contained in rate constants. As an illustration, it is shown how the SSP formulation provides a starting point for the resolution of primary and secondary recombination in liquid state photodissociation reactions.