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MO: Fachverband Molekülphysik

MO 24: Poster: Femtosecond spectroscopy

MO 24.8: Poster

Donnerstag, 17. März 2011, 16:00–18:00, P2

Femtosecond transient absorption with a deep-UV continuum probe — •Michael Foerster, Ulrike Selig, Johannes Buback, Patrick Nuernberger, and Tobias Brixner — Institut für Physikalische und Theoretische Chemie, Universität Würzburg, Am Hubland, 97074 Würzburg

The initial steps of many photochemical reactions evolve on an ultrafast time scale. With fs transient-absorption spectroscopy such dynamics can be investigated directly. The use of a continuum probe in combination with spectrally resolved detection allows for the simultaneous measurement of both sequential and concurrent processes and is well-established in the visible spectral range.

Here we present a setup for transient absorption at much shorter wavelength that combines the femtosecond time resolution of the frequency-doubled output of a commercial noncollinear OPA, tunable between 250 nm and 375 nm, with a broadband deep-UV probe. Focusing the third harmonic of a 1 kHz Titanium Sapphire regenerative amplifier into a moving CaF₂ plate produces a deep-UV continuum covering 235 - 360 nm. Data acquisition on a shot-to-shot basis is achieved by 1 kHz readout of the two-dimensional CCD camera of our spectrometer in combination with chopping the pump beam at 500 Hz.

We discuss constraints and potential of the experimental implementation, spectrally and temporally characterize the deep-UV continuum, and show exemplary time-resolved measurements.