FLUORESCENT DIMERS OF RHODAMINE 6G IN CONCENTRATED ETHYLENE-GLYCOL SOLUTION

Aggregation of rhodamine 6G in concentrated ethylene glycol solutions is studied as a function of temperature. The measurements of absorptio n and fluorescence spectra evidence that the system of interest consis ts of two fluorescent species: monomers and dimers. Strong overlaps be tween all absorption and fluorescence hands in this system enable forw ard and reverse energy transport between monomers and dimers. The quan titative analysis of the effect of nonradiative energy transport (NET) on the fluorescence spectra as well as on the fluorescence quantum yi elds of monomers and dimers explains the temperature and concentration regularities observed. In particular, it is shown that in the concent rated solution the calculated monomer quantum yield is underrated comp ared to that measured, if the reverse NET is neglected. The lack of in formation on the value of the dimer quantum yield does not allow for f ull analysis of the forward and reverse NET in the system. However, it is shown that if that quantum yield is determined as the best fit par ameter, an excellent agreement between the experimental and calculated values is obtained.