Heidelberg 1999 – wissenschaftliches Programm

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MO: Molekülphysik

MO V: HV V

MO V.1: Hauptvortrag

Donnerstag, 18. März 1999, 12:00–12:30, PA1

Cavity Ring Down Spectroscopy of Transient Molecules — •Harold Linnartz — Institute for Physical Chemistry, Univ. of Basel, Switzerland

Transient molecules belong to the chemically most reactive species. This high reactivity, however, also complicates systematic spectroscopic studies, as it is hard to generate large abundances under laboratory controlled conditions. A very sensitive and generally applicable technique is presented here that overcomes these problems. The method is based on cavity ring down spectroscopy in a pulsed slit nozzle, incorporating a discharge in a high pressure supersonic expansion. Cavity ring down spectroscopy is immune to pulse-to-pulse fluctuations in the laser power and the very long absorption pathlengths (up to 100 km) make this technique ideal to study unstable species. The latter are generated in a supersonic slit nozzle expansion, providing a Doppler free environment and combining high molecular densities and relatively large absorption pathlengths with an effective adiabatical cooling. The method is demonstrated with rotationally resolved spectra of electronic transitions of astrophysically relevant carbon chain radicals.