CONCENTRATION QUENCHING AND DEPOLARIZATION OF RHODAMINE 6G IN THE PRESENCE OF FLUORESCENT DIMERS IN POLYVINYL-ALCOHOL FILMS

Nonradiative energy transport in a concentrated system of rhodamine 6G in polyvinyl alcohol films is studied. Concentration changes in absor ption and fluorescence spectra evidence the presence of rhodamine 6G f luorescent dimers. The results of concentration quenching and depolari zation agree with the hopping theory of forward energy transport up to intermediate concentrations. At the highest concentrations, the exper imental quantum yield is higher than the theoretical one and no repola rization effect is found at room temperature. These discrepancies are explained by the formation of fluorescent dimers which are imperfect t raps for excitation energy. This conclusion is supported by measuremen ts at elevated temperature. (C) 1997 Elsevier Science B.V.