Rate Self quenching

The self-quenching rate constant of 21 x 10 cm /molecule s that was measured in these studies is unusually large (69). Quenching by various gases and collision induced rotational transitions have also been measured (68,69). The quenching cross sections by He and Ar in a supersonic jet increase at very low temperature (70), indicating the formation of collision complexes. ... 

The quantum yield of fluorescence of many fluorescent substances in solution decreases with increasing concentration. In some cases, e.g., with aqueous solutions of thionine and Methylene Blue, this selfquenching is due to formation of stable dimers in equilibrium with the monomer.78 In other cases, e.g., with solutions of anthracene, perylene, and coronene in solvents such as benzene, chloroform, and kerosene, Bowen and co-workers have shown that quenching takes place by collision17 the self-quenching rate constants obtained are very close to those given in Table I (see also ref. 19). 

An important aspect of the photophysics of the Pt(diimine)(dithiolate) photochemistry that has received increasing attention is the ability of the excited-state complexes to undergo self-quenching. Initial work by Connick and Gray (111) showed that the lifetime of the complex Pt(bpy)(bdt) (bdt = benzene-1,2-dithiolate, 31) decreased with increasing solution concentration. The bimolecular self-quenching rate constant, calculated from a Stem-Volmer quenching analysis, was found to be 9.5 x 109 A/-1 s-1 in acetonitrile and 4 x 109 M 1 s 1 in chloroform. However, no evidence of excimer formation... 

The 13 = 0 level of the D state is not predissociative, making the anomalously large self-quenching rate constant previously reported rather... 

Self-Quenching Rate Constants for Some Vibronic States of NO"... 

The zero pressure lifetimes and the self-quenching rate constants k, of fluorescence and phosphorescence are given in Table 6 (Kuttner et ai, 1977b). The difference in the zero pressure lifetimes of fluorescence and phosphorescence for the two isotope species is due to the normal deuterium... 

Fig. 30. Self-quenching rate for high- and low-quenching materials. Points for YAG and NdPP taken from Kaminskii (1978).

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