Long-time spectral diffusion induced by short-time energy transfer in doped glasses: concentration-, wavelength- and temperature dependence of spectral holes

We discovered a remarkable effect: spectral diffusion (SD) induced by energy transfer (ET), here called ET→SD. The `effectiveʹ homogeneous linewidth Γhom′ of the S1←S0 0–0 band of free-base chlorin (H2Ch) in polystyrene (PS) was followed as a function of concentration and excitation wavelength by hole-burning. The results cannot simply be explained by Försterʹs ET mechanism: (1) the increase of Γhom′ towards the blue is larger than expected and follows an S-shaped curve; (2) Γhom′ increases linearly with concentration; and (3) the holes are Lorentzian. A model is proposed which predicts that Γhom′ should increase with delay time, even at T→0. This is confirmed by experiments.