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K: Kurzzeitphysik

K 11: Poster

K 11.2: Poster

Mittwoch, 29. März 2006, 17:45–19:00, Flure

Optimization of spectral coverage and resolution in femtosecond pump probe spectroscopy — •Cord Elsner, Uli Schmidhammer, Christian Schriever, Stefan Lochbrunner, and Eberhard Riedle — LS für BioMolekulare Optik, Ludwig-Maximilians-Universität München

Pump probe spectroscopy of the dynamics in complex quantum mechanical systems like molecules calls for a temporal and spectral resolution as high as possible. To optimize the bandwidth of the excitation pulses we developed a noncollinearly phase matched optical parametric amplifier (NOPA) with a variable spectral width. The chirp of the seed continuum is increased with dispersive material resulting in a reduced temporal overlap with the blue pump pulses in the nonlinear crystal of the amplifier stage. By varying the amount of dispersive material we can generate nearly Fourier transform limited pulses between 20 fs and 80 fs. For probing we implemented a CaF₂ based whitelight source pumped by the Ti:sapphire fundamental, which provides a usable continuum down to 300 nm. By coordinated scanning of the motorized delay stage and the monochromator we can correct for the intrinsic group delay dispersion of the whitelight during the scan of a transient spectrum to within ± 50 fs. This leads for UV and visible excitation to a time resolution of better than 100 fs over the whole spectral range of 300 nm to 720 nm.