Berlin 2005 – scientific programme

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P: Plasmaphysik

P 14: Poster: Niedertemperaturplasmen / Plasmatechnologie 6, Diagnostik 4

P 14.18: Poster

Saturday, March 5, 2005, 14:45–16:45, Poster HU

Electric field measurements by Doppler-free spectroscopy in hydrogen — •Minja Gemisic Adamov, Andreas Steiger, and Joachim Seidel — Physikalisch-Technische Bundesanstalt Berlin

Direct measurements of local electric field strengths in low-density plasmas are possible by Doppler-free two-photon spectroscopy, based on the Stark splitting of the atomic resonance lines. For this purpose, an advanced pulsed UV-laser tuneable around 205 nm is used which provides both the high peak power needed for two-photon excitation and the high spectral resolution required to resolve hyperfine splitting. Hydrogen is suitable because of the simplicity of its spectra and its presence in most low density plasmas. In this experiment atomic hydrogen is produced by thermal dissociation in a small cell filled with hydrogen gas. In the homogeneous electric field between two parallel electrodes, the Stark-splitting of the 1S-3S, 3D transition is detected by an opto-galvanic signal and the Balmer-a fluorescence. For comparison, both signals induced by two-photon excitation at 205 nm are measured simultaneously.