  Nolinear Absorption of CT TFF+ aggregates in PMMA matrix was studied with
resonant excitation around 800 nm in the femtoseconds regime with the Z-Scan
technique with 100 Hz pulse repetition rate. The saturated absorption profiles
were fitted with a prepared formula based on steady state rate equations for a
homogeneous ensemble of two levels systems, thin samples and quasi
monochromatic field without the usual assumption of low saturation regime. The
lifetime of the CT state, with the use of this model was estimated in hundred
of fs, of the same order of magnitude of the exciting pulse.
