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Femtosecond pump-probe spectroscopy of conjugated polymers: Coherent and sequential contributions

1992; American Physical Society; Volume: 68; Issue: 16 Linguagem: Inglês

10.1103/physrevlett.68.2456

1092-0145

Wayne B. Bosma, Shaul Mukamel, B. I. Greene, S. Schmitt‐Rink,

Spectroscopy Techniques in Biomedical and Chemical Research

We report femtosecond pump-probe difference absorption experiments on polydiacetylene-para-toluene sulfonate. Theoretical analysis using a three-mode Brownian oscillator model for the nuclear dynamics reveals spectral diffusion in this conjugated polymer; this effect cannot be accounted for using the optical Bloch equations. Sequential (pump first) time ordering is dominant for resonant excitation, whereas experiments utilizing an off-resonant pump are dominated by nonsequential time orderings of the pump and the probe; the latter represent coherent (Raman-type) processes.