Berlin 2014 – scientific programme

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MO: Fachverband Molekülphysik

MO 5: Posters 1: Electronic Spectroscopy, Photochemistry, Femtosecond Spectroscopy

MO 5.26: Poster

Monday, March 17, 2014, 16:30–18:30, Spree-Palais

Two Photon Absorption in Organic Molecules — •Baidaa Hamed — FU-Berlin

We have applied a combination of two techniques to measure two-photon absorption (TPA)cross-sections and TPA-spectra of organic molecules in solution. One method is based on the measurement of the change in the transmittance. The sample scanned along the focused pump-beam. By another approach, we used the same pump configuration, but we measured the efficiency of fluorescence induced due to TPA. As a pump source we used Ti-sapphire laser providing 150 fs pulses at 780 nm and at a repetition rate of 1 kHz. The laser was used to carry the measurements (0,3 -5 mW power), or to pump an home-built optical parametric amplifier(OPA) tunable in the range of 1050-1400 nm. Tested measurements and a calibration of our system were done by measuring TPA cross-sections at 780 nm in Rhodamine 6G, Coumarin 47 and corroles dissolved in methanol at typical concentration of 6 mM/l. Fitting the transmittance and fluorescence efficiency versus the sample position and the pump-beam intensity enables to determine TPA cross-section. We have done preliminary measurements in some photosensitizer molecules, which are important for photodynamic therapy. This research is in progress.