Fluorescence-based investigation of the Janossy effect anomalous wavelength dependence

In order to explain the wavelength dependence of the "Janossy effect" observed in certain dye-doped liquid crystals, we investigated the fluorescence emitted by 1,8-diamino 4,5-dihydroxy 3,6-diisopentyl anthraquinone dye dissolved in different hosts. We measured the lifetime tau(e), rotational time tau(r), initial anisotropy r(0) and fluorescence quantum yield Phi of photo-excited dye molecules versus excitation-light wavelength lambda. The only significant lambda-dependence observed was that of the quantum yield Phi, which showed a marked increase with lambda. Phi(lambda) appears to be well correlated with the Janossy effect. These results rule out several proposed explanations for the Janossy effect wavelength dependence and suggest a simple alternative explanation.