Aachen PK 2003 – wissenschaftliches Programm

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P: Plasmaphysik

P 4: Poster I

P 4.20: Poster

Montag, 17. März 2003, 17:45–19:15, Foyer

Excitation and Relaxation of C-Triplet State of Nitrogen in a N2/Ar dielectric barrier discharge — •Alexander Fateev, Igor Vinogradov, Mahmud Shakhatre, and Achim Lunk — Universitaet Stuttgart, Institut fuer Plasmaforschung, Pfaffenwaldring 31, 70569 Stuttgart, Germany

The second positive system of nitrogen molecule is widely used as a ”probe” for determination of a gas temperature in a low-temperature plasma. However, in the case of argon-nitrogen plasma, the emission spectrum reflects a non-Boltzmann distribution over rotational levels and cannot be used for identification of the gas temperature. This is well-known fact in the low-pressure plasma. We have also observed a non-Boltzmann distribution in the spectrum of second positive system in high-pressure plasma of dielectric barrier discharge. This is a new and unexpected fact because rotational relaxation at high-pressure conditions should be very fast. At high-pressure there are two major formation channels of C-triplet state of nitrogen: pooling reaction of two metastable nitrogen molecules and energy transfer in collisions of metastable argon atoms with nitrogen molecules in the ground state. The first channel gives a low rotational excitation, but the second one always goes to population of very high rotational levels that reflects the non-resonant nature of the process. The relaxation of low- and high- rotational levels is going quite different ways and in different time scale. The evidences of importance of each channel have been clearly demonstrated. The modeling of the rotational relaxation and the calculated rate constants will be discussed in detail.