Much of the usefulness of fluorescence in biology derives from the fact that an electronically excited molecule has different reactivity than its ground-state parent. Light absorption not only increases the energy content of a molecule but also significantly alters its physical and chemical properties. The absorbing molecule is transformed into a new species capable of undergoing a variety of photoreactions during its life span of several nanoseconds. When a photoreaction proceeds adiabatically,1 i.e. if the photoreaction yields electronically excited products, then the possibility of observing dual, multiple or continuous fluorescence exists.2 The degree of complexity of this fluorescence depends on the number of excited products generated and on their relative quantum efficiencies. This number in turn depends on the reactivity of the parent excitation and on the nature of the local solvent environment, which includes the availability of reaction partners as well as more generalized bulk properties such as polarity, viscosity and polarizability.
KeywordsFluorescence Decay Spectral Position Electronic Relaxation Solvent Relaxation Solvent Cage
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