Reversible and irreversible reaction fronts in two competing reactions system

A modeling of the non-equilibrium diffusion phenomena of the impurities in the semiconductors is based on the reaction-diffusion equations for local concentrations of the components. Through this approach a new feature, a reaction front, may be caused by reaction in diffusion profiles of the components. The asymptotic long-time properties of the reaction fronts in the system with initially separated components and two competing reactions: reversible A₁ + B ↔ C₁ and irreversible A₂ + B → C₂ are studied in this work. It is assumed that the backward constant of the reaction A₁ + B ↔ C₁ is small. The dynamics of the system is described as a cross-over between the "irreversible" regime for small times and the "reversible" regime for large times. It is shown that the "irreversible" regime is characterized by single reaction zone, in which both reactions occur. The two reaction fronts, reversible A₁+B ↔ C₁ and irreversible A₂ + C₁ → A₁ + C₂ appear in the "reversible" regime. Numerical computing of the mean-field kinetics equations confirms these asymptotic results. The experimental tests of the theoretical predictions relating to the diffusion phenomena in semiconductors are discussed.