Stokes shift definition

Fig. 1.6. Strategy for the choice of a fluorescent probe. Av, , and t are the Stokes shift, quantum yield and lifetime, respectively (see definitions in Chapter 3).

Fig. 3.3. Definition of the Stokes shift. Examples of Stokes shift benzoxazinone derivative (BOZ 7) and rhodamine 6G.

The definition of the spectral density [Eq. (15)] allows to connect the various correlation functions relevant to spectral broadening and spectral diffusion. For example, the fluorescence Stokes shift function S(t) can be written as... 

Figure 5.8. Stokes shift a) definition and b) dependence on the difference in equilibrium geometries of ground and excited states. Shown is the probability distribution in various vibrational levels, which is proportional to the square of the vibrational wave function (adapted from Philips and Salisbury, 1976).

Stokes shift. We conclude this section by discussing the implications of the presence of a Stokes shift. By definition, the Stokes shift corresponds to the energy separation between the 0-0 peaks in absorption and emission. There is actually much confusion in the literature indeed, some authors associate the Stokes shift to the separation between the most intense peaks, even if they differ from the 0-0 bands others have incorrectly claimed that the absence of a Stokes shift indicates an absence of relaxation in the excited state, even when clear vibronic effects are observed. 

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