Diffusion-corrected quenching rate

Figure 2. The logarithm of kqc (the diffusion-corrected quenching rate constant) vs. — (the reduction potential for the RuLs3 / RuLs2 couple) for quenching (left side, by Rh(4f4 -(CHs)ibpy)s3+ (24) and (right side, + by Euaq3 (22). (Copyright 1982, American Chemical Society.)...

Comparison with Eq. (a) shows that the diffusion-corrected quenching rate constant k (corr) is given by ... 

The quenching rate constants measured in fluid solutions need to be corrected for diffusional effects and for this reason it is useful to define a diffusion-controlled quenching rate constant kq. as follows ... 

This latter equation correctly predicts the rates at which 1-iodo-naphthalene quenches triplet naphthalene in several fairly viscous solvents.165 It also correctly predicts the rate at which 2,5-dimethyl-2,4-hexadiene quenches triplet valerophenone in cyclooctane if the ketone s triplet lifetime is the same as that estimated from quenching experiments and from the flash spectroscopically measured rate constant for diffusion-controlled quenching in benzene.183... 

For many purposes it is convenient to correct the ob rved quenching rate constant for the rate of diffusion together of the two reactants by using ... 

Figure 3.8. (a) The linear viscosity dependence of the inverse ionization rate in the reaction studied in Ref. 98. Bullets—experimental points solid line—fit performed with the generalized Collins—Kimball model, (b) The effective quenching radius for the same reaction in the larger range of the viscosity variation. Bullets—experimental points solid fine—fit performed with the encounter theory for the exponential transfer rate. The diffusion coefficient D given in A2/ns was calculated from the Stokes—Einstein relationship corrected by Spemol and Wirtz [100]. 

At s = 0 the concentration corrections in Eq. (3.667) become the rates of excitation quenching by any partner that does not belong to a given couple (reactant pair). These bachelors compete for an excitation with the reactants in a couple when they move apart for a while between successive recontacts. Similar results were obtained with the many-particle theory of diffusion-influenced reactions based on the revised superposition approximation and became known as MPK1 [51]. The authors were the first who managed to obtain concentration corrections to the IET result for the kinetics of reversible energy transfer. In a subsequent modification of their theory, named MPK3 [126], the same authors reached the full correspondence with MET. 

When the quenching reactions are rapid, the observed rate constant must be corrected for the effect of diffusion in order to obtain the activation controlled rate constant. The correction is made by applying... 

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