TIME-RESOLVED FLUORESCENCE DEPOLARIZATION OF DODCI IN ETHYLENE GLYCOL: EFFECT OF ORIENTATIONAL CORRELATION ON ELECTRONIC EXCITATION TRANSPORT

$^{1}$ D. E. Hart, P. A. Anfinrud, and W. S. Struve, J. Chem. Phys. 86, in press. $^{2}$ D.L. Huber, D. S. Hamilton, and B. Barnett, Phys. Rev. B16, 4642 (1977). $^{3}$ C.R. Gochanour, H.C. Andersen, and M.D. Fayer, J. Chem. Phys. 70, 4254 (1979).Author Institution: Department of Chemistry and Ames Laboratory - USDOE, Iowa State UniversityIn an earlier fluorescence depolarization study of singlet excitation transport in glycerol solutions of DODCI [1], physically large discrepancies were observed between experimental fluorescence profiles and profiles calculated from current transport theories [2,3]. Artifacts arising from fluorescence self-absorption, excitation trapping by dye aggregates, and solvent reorganization were ruled out as sources of these discrepancies. In this work, the study was repeated for DODCI in ethylene glycol, a far less viscous solvent than glycerol. The orientational diffusion of DODCI was characterized in this solvent at low concentration, and its contribution to fluorescence depolarization at higher concentrations was separated from the contribution arising from excitation transport. Analysis of the fluorescence profiles then yields close agreement with transport theories. These results strongly suggest that the discrepancies observed in glycerol are caused by orientational correlation (nonrandomness) in the more viscous solvent