Kinetics of diffusion-limited catalytically activated reactions: An extension of the Wilemski-Fixman approach

We study the kinetics of diffusion-limited catalytically activated A + B → B reactions taking place in three-dimensional systems, in which an annihilation of diffusive A particles by diffusive traps B may happen only if the encounter of an A with any of the B s happens within a special catalytic subvolumen: these subvolumens being immobile and uniformly distributed within the reaction bath. Suitably extending the classical approach of Wilemski and Fixman [ J. Chem. Phys. 58 , 4009 ( 1973 ) ] to such three-molecular diffusion-limited reactions, we calculate analytically an effective reaction constant and show that it comprises several terms associated with the residence and joint residence times of Brownian paths in finite domains. The effective reaction constant exhibits a nontrivial dependence on the reaction radii, the mean density of catalytic subvolumens, and particles' diffusion coefficients. Finally, we discuss the fluctuation-induced kinetic behavior in such systems.