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MO: Molekülphysik

MO 23: Femtosecond Spectroscopy

MO 23.4: Vortrag

Samstag, 5. März 2005, 14:45–15:00, HU 2091

A compact laser flash photolysis technique compatible with ultrafast pump-probe setups — •Stefan Roth¹, Uli Schmidhammer¹, Alexander Tishkov², Eberhard Riedle¹, and Herbert Mayr² — ¹LS für BioMolekulare Optik, Ludwig-Maximilians-Universität München — ²Department Chemie, Organische Chemie, Ludwig-Maxilimians-Universität München

Photoinduced chemical reaction cycles can display time scales from few femtoseconds to milliseconds. We can readily monitor the femtosecond and picosecond regime with state of the art light pulses. Laser Flash Photolysis classically provides an effective method up to the ns timescale. The recent development of pulsed diode lasers and high power light emitting diodes (LEDs) open the route to a miniaturized laser flash photolysis system that is fully compatible with the femtosecond setup.

Instead of a high power lamp laser diodes or LEDs at various wavelengths in the visible and NIR are used as monitoring beam. These small sized semiconductor devices are positioned in an ultrafast pump-probe setup substituting the femtosecond white light or single wavelength probe. The sample is excited in both setups with fully tunable femtosecond pulses.

To demonstrate the versatile options of the system, we investigate the photoinduced chemistry of benzhydryl cations with the nitrite ion. The photodissociation takes some 100 fs while the combination is detected with 500 ps (for diode lasers) to few nanosecond resolution. In this way the full reaction cycle can be monitored with identical excitation conditions.