Crossover from nonclassical to classical chemical kinetics in an initially separated [Formula Presented] reaction-diffusion system with arbitrary diffusion constants

The asymptotic long-time properties of the reaction front formed in a reversible reaction-diffusion process [Formula Presented] with initially separated reactants are investigated. The case of arbitrary nonzero values of the diffusion constants [Formula Presented] of the components A, B, C and the initial concentrations [Formula Presented] and [Formula Presented] of A and B is considered. The system is studied in the limit of [Formula Presented] where g is the backward reaction rate constant. In accordance with previous work, the dynamics of the reaction front is described as a crossover between the “irreversible” regime at times [Formula Presented] and the “reversible” regime at times [Formula Presented] It is shown that through this crossover the macroscopic properties of the reaction front, such as the global rate of C production, the motion of the reaction zone center, and the concentration profiles of the components outside the reaction front, are unchanged. The concentration profiles of the components inside the reaction zone are described by quasistatic equations. The results of the theoretical consideration are confirmed by computing the mean-field kinetics equations.