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MO: Molekülphysik

MO 11: Femtosekundenspektroskopie IV: molekulare Dynamik

MO 11.6: Talk

Wednesday, March 6, 2002, 17:45–18:00, HS 15/E07

A novel technique to determine femtosecond fluorescence lifetimes — •Peter Gilch, Qingrui An, and Wolfgang Zinth — Sektion Physik, Ludwig-Maximilians-Universität München, Oettingenstr. 67, D-80538 München

The determination of fluorescence lifetimes in the femtosecond regime relies on optical gates. In the techniques currently employed, optical Kerr gating and fluorescence up-conversion, the fluorescence emission of a sample induced by a pump pulse is imaged onto a non-linear medium. There the interaction of the fluorescence light with a second laser pulse responsible for the optical gating takes place. In the novel technique presented here pump and gate beams cross in the sample.

A non-linear Raman process (Raman loss) involving fluorescence photons and gate photons serves as the optical gate. The solvent of the fluorophore constitutes the Raman active material. The practicability of the approach is demonstrated by lifetime measurements on several fluorophores. It is shown that the technique can be employed in the interesting time window from ∼ 100 fs to a few picoseconds. Advantages of this technique as compared to conventional procedures are discussed.