DISPERSIVE ELECTRONIC-ENERGY TRANSFER IN AN ORGANICALLY DOPED XEROGELGLASS

Time-resolved fluorescence depolarization measurements have been used to probe the wavelength dependence of optical energy transfer between quinizarin-aluminum chromophores in an aluminosilicate sol-gel glass. The optical energy transfer rate at low temperature is found to depend on the optical excitation energy due to inhomogeneous broadening of t he absorption band. In contrast, energy transfer at room temperature i s found to be nearly dispersionless, indicating significant vibronic c ontributions to the homogeneous absorption line shape at higher temper atures. The dispersive energy transfer observed at low temperature is analyzed using an energy trap model.