Effects of Bias on the Kinetics of A+B->C with Initially Separated Reactants

The effects of a constant field on the early-time kinetic behavior of the A+B→C reaction-diffusion system with initially separated reactants are analyzed. This is in order to account for the pressure effect resulting from the injection of the reactants on both sides of the experimental capillary. The kinetics at early times depends on the magnitude of the field relative to the reaction rate constant, in a suitable set of units. An approximate solution is given for the case in which the effect of the reaction is smaller than that of the bias. We show that the production rate of C is initially proportional to t12 with a crossover to proportionality to t, a behavior which has been experimentally observed. The converse case, in which the effect of the bias is smaller than that of the reaction, has been studied numerically, and exhibits effects of bias only in the long-time limit.