Spectrally- and time-resolved fluorescence emission of indole during solvent relaxation: a quantitative model

Relaxation of polar solvents around excited fluorescent solutes results in a continuous time-dependent red shift in the fluorescence spectrum. Static heterogeneous broadening can also produce time-variant fluorescence spectra. The two effects can be distinguished by a quantitative model of fluorescence during homogeneous electrostatic relaxation. The model describes the evolution of the instantaneous spectrum and the time variation of the intensity observed at any fixed wavelength. The model is in good agreement with the experimental data obtained using a solution of indole in anhydrous glycerol at 4 nm spectral and 65 ps temporal resolution.