Diffusion-limited reactions in spherical cavities

We study a quenching reaction occurring at sinks within a spherical cavity and at the cavity surface. One may think of reactions at these two, distinct locations as two, coupled reactive channels. Reactions of the type D*+A→D+A are studied in the limit of nondilute A, present at both locations, and dilute D, present within the cavity. We use a Monte Carlo algorithm to compute mean rates, pseudo-first-order rates and branching ratios, and compare with results obtained by assuming that the two reactive channels operate in parallel. The ratio of activities of the two channels are varied; static and moving sinks are studied. We discuss an application to the determination of pore structure by NMR (nuclear magnetic resonance).