Effect of energy transfer on the kinetics of the decay and anisotropy of luminescence of prodan molecules

The temporal characteristics of the decay and polarization of luminescence of prodan solutions with different concentrations, excited by a picosecond laser radiation, are studied. The kinetics of the emission decay and polarization depend on the spectral range of luminescence recording and on the luminophore concentration and reflect the relaxation processes (leading to a long-wavelength shift of the entire emission band) and, in the case of sufficiently high concentrations, nonradiative energy transfer between the prodan molecules. It was found that the evolution of luminescence anisotropy in a diluted solution depends on the recording wavelength, which allowed us to calculate the average times of the Brownian rotational diffusion for prodan in glycerol, whose maxima were determined to be about 40 ns in the spectral region near 520 nm and to decrease to 14 and 17 ns at the edges of the emission region at 450 and 560 nm, respectively.