Hannover 2003 – scientific programme

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MO: Molekülphysik

MO 1: Elektronische Überg
änge

MO 1.5: Talk

Monday, March 24, 2003, 15:00–15:15, B 302

Observation and Characterization of Nonlinear Processes in Organic Samples by Excited State Absorption (ESA) Spectroscopy — •David v. Seggern, Christian Spitz, and Ralf Menzel — Universität Potsdam, Institut für Physik, Am Neuen Palais 10, 14469 Potsdam

In this talk we report the investigation of a biester-substituted biphenylpyrene derivate (Py-C) by time resolved pump and probe laser spectroscopy.

Compounds like Py-C are known to show intramolecular charge transfer (ICT) following optical excitation. It is assumed that after excitation an equilibrium is built up between the locally excited (LE) state with the excitation energy staying in the phenylpyrene part of the molecule, and the ICT state with the charge having passed over to the biester phenyl part. Because of the strong polarity of the ICT state the effect is strongly solvent dependent. If LE and CT states show different absorption bands, their population should be detectable by transient optical absorption measurements [1].

Our investigations show the solvent dependency of the equilibrium constant kCT,LE and an increase of the absolute values of the excited state cross sections with increasing solvent polarity.

The ESA method is compared to traditional fluorescence techniques.

[1] C. Spitz, D.v. Seggern, G. Grunwald, R. Menzel Biomedical Nanotechnology Architectures and Applications, Darryl J. Bornhop et al. (eds.) Proceedings of SPIE 4626 (2002), 493