Polarization of fluorescence and bleaching of dyes in a high-viscosity solvent

The behavior of the degree of polarization of the fluorescence and transmission versus intensity of complex molecules in high-viscosity solvents has been studied. We show that, in the usual case, when the electronic transition can be represented as a linear oscillator, molecules excited at low field have an anisotropic distribution; then, at high field, the distribution becomes isotropic. So, the relation between the transmission of the solution with intensity differs significantly from the transmission versus intensity relation derived by using the mean value of the cross section.