Stuttgart 2012 – wissenschaftliches Programm
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P: Fachverband Plasmaphysik
P 13: Poster: Niedertemperaturplasmsen
P 13.13: Poster
Dienstag, 13. März 2012, 16:30–19:00, Poster.III
Time dependent density of metastable nitrogen molecules in barrier discharges — •Sebastian Nemschokmichal and Jürgen Meichsner — Institute of Physics, University of Greifswald
Barrier discharges at atmospheric pressure are typically filamentary, but under certain conditions a diffuse mode exists, e.g. in pure nitrogen. One reason for the diffuse mode might be the existence of metastables, which can release electrons in the volume or at surfaces by Penning-processes. For a better understanding of the interaction between plasma particles and surfaces a new discharge configuration has been developed with a BSO crystal and a glass plate as dielectrics (1 mm gap width) to investigate the density of metastables together with surface charges and discharge development.
This contribution focuses on the behaviour of the metastable A3Σu+,v=0 state of the nitrogen molecule, whose density has been measured by laser induced fluorescence spectroscopy (LIF). The absolute calibration has been done by the comparison with Rayleigh scattering. Typical densities are about 3× 1013 cm−3 at 500 mbar in the filamentary mode in pure nitrogen. By focussing and triggering the laser with the driving voltage it was possible to determine the density of metastables phase resolved each 0.2 mm in front of the dielectrics. The measurements show a larger density in front of the anode. Furthermore, the maximum of the density has a delay of several microseconds with respect to the appearance of microdischarges.