Triplet–triplet annihilation in viscous solutions as an example of non-Fickian diffusion

Abstract

Diffusion-controlled triplet–triplet annihilation is analyzed in terms of non-Fickian diffusion. The description is based on the second Fick’s law with a time-dependent diffusion coefficient. We introduce the time-dependent diffusion coefficient because of the interaction of two associated relaxation phenomena: first-order decay and diffusion-controlled annihilation. The equation for the time-dependent rate parameter $k_{2A}(t)$ obtained from the model proposed is compared with the standard Smoluchowski expression. The new equation is applied for the evaluation of the kinetic data of the diffusion-controlled triplet–triplet annihilation of anthracene. The limits of the applicability of the proposed model are discussed.

© 2005 Optical Society of America

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