Spectral diffusion induced by energy transfer in doped organic glasses: Delay-time dependence of spectral holes

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Abstract
Quantitative aspects of the ET!SD process have been investigated by means of time-resolved hole-burning experiments on free-base chlorin (H2Ch) in polystyrene ~PS! presented here. The ''effective'' homogeneous linewidth G hom 8 was determined as a function of delay time t d (10 25 210 3 s), temperature ~1.2 to 4.2 K! and concentration ( c51310 25 to 6310 3 M), at various excitation wavelengths within the S 1 S 0 0-0 band. G hom 8 as a function of temperature was found to obey the relation G hom 8 5G 0 81aT 1.3 , characteristic for glasses, and we present an analysis of the residual linewidth G 08 and the coupling constant a. In this analysis we determined ~i! the separate contributions to G 08 arising from the fluorescence lifetime, ET, and ET!SD, ~ii! the separate contributions to a arising from ''pure'' dephasing, ''normal'' SD, and ''extra'' spectral diffusion caused by ET!SD. The contributions of ET!SD to G 08 and a prove to be proportional to the concentration and to the logarithm of the delay time ( }c log td). © 1999 American Institute of Physics. @S0021-9606~99!53001-8#