Aachen PK 2003 – wissenschaftliches Programm
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P: Plasmaphysik
P 4: Poster I
P 4.7: Poster
Montag, 17. März 2003, 17:45–19:15, Foyer
On the Chemical Reaction Kinetics of Molecular Plasmas Containing CH4 and N2 — •D. Loffhagen1, F. Hempel1, R. Röpcke1, and P.B. Davies2 — 1Institute for Low-Temperature Plasma Physics, 17489 Greifswald, Germany — 2Department of Chemistry, University of Cambridge, Cambridge CB21EW, U.K.
Low-pressure, non-equilibrium molecular plasmas are of growing interest in the field of plasma processing and basic research. But the plasma chemical processes in discharges of such plasmas are still not well understood. Tunable diode laser absorption spectroscopy in the mid infrared was used to investigate molecular concentrations in the ground state in microwave plasmas at a frequency of 2.45 GHz containing H2, N2, Ar and CH4. For varying N2 to H2 ratios NH3, HCN, C2N2, CH3, C2H2, C2H4 and C2H6 were measured under flowing and static discharge conditions. Among these species NH3 and HCN were identified to be final products of the reaction kinetic processes. They had the highest concentrations, while C2N2 was found to have the lowest one. The degree of dissociation of the precursor hydrocarbon CH4 varied between 15 and 93%. A model of the plasma chemical processes of 22 species concentrations was established including 30 electron impact dissociation processes and 78 chemical reactions. The comparison between theoretical and measured species concentrations shows a satisfactory agreement within the order of errors of measurements. Non-measured species concentrations are estimated and a basic reaction scheme for H2-N2-Ar-CH4 mixture plasmas is proposed.