Singlet fluorescence

Thus we see that we have three processes which can compete for deactivation of the excited singlet fluorescence, internal conversion, and intersystem crossing. If we increase the rate of the latter by adding a heavy atom, this should result in a decrease or quenching of the fluorescence intensity ... 

The overlap integrals J (v) which are essential for a Forster long-range dipole-dipole transfer mechanism 56> were obtained from the benzaldehyde phosphorescence spectrum and the absorption spectra of the fluorescers used. A linear relation was observed between the square root of the overlap integrals and the number of excited singlet fluorescer molecules produced per molecule of benzaldehyde triplet, which is a strong argument for the essential role of the proposed transfer mechanism. 

Time constants of monomer singlet fluorescence of PS in cyclohexane at room teperature... 

A i and A are prefactors of first and second components, respectively, and r are relaxation times of monomer singlet fluorescence for first and second components, respectively. 

The time evolution of the triplet character, L(t), may be determined by time-resolved measurements of absorption at wavelengths corresponding to the T-T transitions from initially populated (unrelaxed) Tj levels (Ashpole et ai, 1971). It has been shown that for collision-free naphthalene and 1-methylnaphthalene, the T-T absorption builds up with the rate constant of the singlet (fluorescence) decay (Soep et ai, 1973). Similar results have been obtained for acridine, where the fluorescence decay and triplet induction time are of the order of lOpsec (Hirata and Tanaka, 1977) (see Fig. 16). 

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