Diffusion controlled reactions: experimental verification of the time-dependent rate equation

Abstract

The transient effect in a diffusion limited reaction is described by a time-dependent rate coefficient: k(t)=a+b exp(c²t)erfc(ct^½), where a, b, and c are expressed in terms of the diffusion coefficient (D), the encounter distance (R), and the absolute rate coefficient (k_a); and for ionic reactions, the Onsager length (r_c). Time resolved fluorescence quenching studies on cresyl violet-potassium iodide system in water confirm the validity of the above equation. The values of D and R obtained from the fluorescence quenching studies are in good agreement with the values inferred from other sources, and the value of k_a is reasonable.