LONG-TIME SPECTRAL DIFFUSION-INDUCED BY SHORT-TIME ENERGY-TRANSFER INDOPED GLASSES - CONCENTRATION-DEPENDENCE, WAVELENGTH-DEPENDENCE AND TEMPERATURE-DEPENDENCE OF SPECTRAL HOLES

We discovered a remarkable effect: spectral diffusion (SD) induced by energy transfer (ET), here called ET --> SD. The 'effective' homogeneo us linewidth Gamma(hom)' of the S-1 <-- S-0 0-0 band of free-base chlo rin (H(2)Ch) in polystyrene (PS) was followed as a function of concent ration and excitation wavelength by hole-burning. The results cannot s imply be explained by Forster's ET mechanism: (1) the increase of Gamm a(hom)' towards the blue is larger than expected and follows an S-shap ed curve; (2) Gamma(hom)' increases linearly with concentration; and ( 3) the holes are Lorentzian. A model is proposed which predicts that G amma(hom)' should increase with delay time, even at T --> 0. This is c onfirmed by experiments. (C) 1998 Elsevier Science B.V. All rights res erved.