Diffusion-influenced radical recombination in the presence of a scavenger.

The recombination reaction of radicals photolytically produced in solution proceeds via two distinguishable kinetic phases. At short times recombination between geminate radicals predominates, while at long times recombination between nongeminate radicals that have diffused away from their geminate counterparts to the bulk solution takes place. In most previous theories dealing with the effect of added scavenger molecules on the radical recombination reaction, only the geminate recombination phase has been considered. However, if the concentration of radical pairs generated is high, the interplay of bulk recombination in the dynamics needs to be considered. In the present paper, we formulate a theory that deals with the scavenging effect in both the geminate and bulk recombination phases within a unified framework. We show that the scavenger concentration CS and the scavenging rate coefficient kS have independent effects on the reaction, in general. In contrast, conventional theories involve these two quantities only as a product kSCS, usually in the form of a Laplace transformation variable. © 1996 American Institute of Physics. [ABSTRACT FROM AUTHOR]