EFFECTS OF SOLVENT DYNAMICS ON FAST REACTION PATTERNS IN FLUIDS

The effects of solvent dynamics on fast reaction patterns in fluids ar e discussed in terms of the stochastic renewal theory with a fractal s et of renewal moments which results from the use of Kohlrausch (1863) function to describe the structural relaxations in the reaction system . The dispersive patterns of reaction kinetics are evident when the ti me scale of reaction, zeta, approaches that of structural relaxations, tau. In the limit zeta << tau, corresponding to suppressed internal r earrangements in reaction system for ultrafast reactions, the reaction patterns are ''solid-like'', or dispersive, following from modelling of kinetics in statically disordered systems. When the time scale of r eaction is long compared to that of relaxation, zeta >> tau, the class ical patterns of reaction kinetics, ''liquid-like'', are shown to be v alid. However, for fast reactions of highly reactive species, i.e. for those with local reaction probability (when two reactants collide) P --> 1, the reaction rate constant, k, depends on tau as k similar to t au(alpha-1) where 0 < alpha < 1 is the dispersion parameter used in re action modelling in the statically disordered system. If relaxations i n reaction system are driven and/or damped solely by thermal motions o f solvent molecules through friction, tau similar to eta, one has the viscosity dependence of the rate constant k similar to eta(-alpha) for a = alpha-1. Only for low local reaction probability one recovers k = const. following from the usual theories of reaction kinetics.