Reorientational motion of diphenylpolyenes in simple solvents as studied by depolarized light scattering and fluorescence anisotropy decay

摘要

The reorientational motion of diphenylpolyenes and related molecules in simple solvents is studied by depolarized light scattering and fluorescence anisotropy decay. The viscosity dependence of the reorientational correlation times obtained by the two techniques shows remarkable differences, although the Stokesndash;Einsteinndash;Debye equation applies to all data. The light scattering results are consistent with hydrodynamic models and slip boundary conditions. The reorientation about an axis perpendicular to the long molecular axis is monitored. With the fluorescence anisotropy decay measurements of the diphenylpolyenes on the other hand, a much smaller viscosity dependence is found. The influence of photophysical processes in the excited state on the fluorescence depolarization is discussed and it is shown that the fluorescence anisotropy measurements are sensitive to reorientation about a perpendicular axis as well as about the long molecular axis.