Berlin 2005 – scientific programme
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MO: Molekülphysik
MO 31: Ultrafast Photochemistry
MO 31.7: Talk
Monday, March 7, 2005, 12:00–12:15, HU 2091
Photon-echo and transient grating measurements with tunable 8 fs pulses from a NOPA — •Peter Baum1, Jaroslaw Sperling2, Franz Milota2, Harald F. Kauffmann2, and Eberhard Riedle1 — 1LS für BioMolekulare Optik, Ludwig-Maximilians-Universität München — 2Institut für Physikalische Chemie, Universität Wien
The dynamics of solvation crucially determines many chemical and physical processes in the condensed phase. Time-resolved photon-echo and transient grating experiments on molecular solutes provide concise information about the electronic phase decay and the spreading of population gratings due to solute-solvent interactions. Such third-order nonlinear time domain probes of solvation yield access to the frequency fluctuation correlation function and thus allow to extract static and dynamics components from linear absorption spectra.
To match the pulse spectrum to the sample absorption and to resolve the fastest time scales, extremely short and widely tunable visble pulses are needed. We present successful photon echo and transient grating experiments with 8 to 20 fs pulses from a 1 kHz NOPA. A crucial point in photon-echo experiments is the elimination of satellite pulses. We use ZAP-SPIDER [1] to fully characterize and optimize the pulse shape and obtain Fourier-limited pulses.
Results on several spectrally and chemically distinct two-level model dyes are discussed. The dynamics in polar solvents reflect the rigidity and the degree of conformational freedom. Larger molecules seem to become more independent of the bath, in particular if the solvent is less polar. The data is further compared to that obtained from a soluble conjugated polymer, where the nonlinear response reflects a distribution of conformational subunits.
[1] P. Baum, S. Lochbrunner, and E. Riedle, Opt. Lett. 29, 210 (2004)