Frankfurt 2006 – scientific programme

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MO: Molekülphysik

MO 42: Excitation and Coherence Decay

MO 42.3: Talk

Wednesday, March 15, 2006, 14:30–14:45, H12

Xanthone in Water — Fast Intersystem Crossing and Intense Fluorescence — •Björn Heinz¹, Bernhard Schmidt¹, Christopher Root¹, Helmut Satzger¹, Franz Milota², Beat Fierz³, Thomas Kiefhaber³, Wolfgang Zinth¹, and Peter Gilch¹ — ¹Department für Physik, Ludwig-Maximilians-Universität, Oettingenstr. 67, D-80538 München, Germany — ²Institut für Physikalische Chemie der Universität Wien, Währingerstraße 42, A-1090 Wien, Austria — ³Division of Biophysical Chemistry, Biozentrum, University of Basel, Klingelbergstraße 50/70, CH-4056 Basel, Switzerland

Due to their efficient intersystem crossing (ISC) aromatic carbonyl compounds are of great importance in photophysics and photochemistry. They, for instance, serve as triplet sensitizers and thereby allow to access triplet states of molecules with low inherent ISC yields. Because of its rigid and symmetric structure the carbonyl compound xanthone has been thoroughly studied by various spectroscopic techniques. In most solvents (non-polar and polar) the fluorescence quantum yield is very low (∼ 10⁻⁴) in accordance with short ISC times. In water this yield is as high as 0.05. Still, a fast ISC process is observed. We propose a delayed fluorescence scheme to account for these observations. The scheme will be underscored by time resolved fluorescence and absorption measurements. The schemes allows to extract energetic information on the triplet states not accessible heretofore.