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P: Fachverband Plasmaphysik

P 15: Poster: Diagnostik

P 15.16: Poster

Wednesday, April 1, 2009, 17:30–19:30, Foyer des IfP

Electric field measurements in near-atmospheric pressure nitrogen and air based on a four-wave mixing scheme — •Sarah Müller¹, Tsuyohito Ito², Kazunobu Kobayashi³, Dirk Luggenhölscher¹, Uwe Czarnetzki¹, and Satoshi Hamaguchi³ — ¹Institut für Experimentalphysik V, Ruhr-Universität Bochum, 44780 Bochum — ²Frontier Research Base for Young Researchers, Osaka University, Osaka, Japan — ³Center for Atomic and Molecular Technologies, Osaka University, Osaka, Japan

Electric fields are measured for the first time in molecular nitrogen at atmospheric pressures. Measurements are performed in either pure nitrogen or air. The laser spectroscopic technique applied here is based on a CARS-like four-wave mixing scheme originally developed for measurements in molecular hydrogen by Ochkin and Tskhai in 1995. The technique is ideal for the investigation of microdischarges at atmospheric pressures. The frequencies of two focussed laser beams in the visible are tuned to match the energy difference between the two lowest vibrational levels in nitrogen. The presence of a static electric field then leads to the emission of coherent IR radiation at this difference frequency. The signal intensity scales with the square of the static electric field strength. In parallel to this process also anti-Stokes radiation in the UV by the standard CARS process is generated. Normalization of the IR signal by the UV signal provides a population independent measurement quantity. Experimental results at various pressures and electric field strengths are presented.