Mainz 2022 – wissenschaftliches Programm

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P: Fachverband Plasmaphysik

P 21: Atmospheric Pressure Plasmas II

P 21.5: Vortrag

Freitag, 1. April 2022, 15:00–15:15, P-H11

Vibrational excitation in a nanosecond discharge — •Jan Kuhfeld¹, Zoltan Donko², Nikita Lepikhin¹, Dirk Luggenhölscher¹, and Uwe Czarnetzki¹ — ¹Institute for Plasma and Atomic Physics, Ruhr University Bochum, D-44780 Bochum, Germany — ²Wigner Research Centre for Physics, Budapest, Hungary

Vibrational distribution functions of nitrogen are measured in a nanosecond discharge (200-250 ns, conducting electrodes) by coherent anti-Stokes Raman scattering (CARS). It is found, that for vibrational states with v<8 a two temperature distribution function is a very good approximation to the vibrational distribution. The excitation conditions for vibrational states are constant during most of the discharge pulse and agree very well with the excitation rates from the literature for the given electric field, which is measured by E-FISH (electric field induced second harmonic generation). The development of the vibrational states during the afterglow is compared to a state-to-state kinetic model, which is dominated by VV transfer and transport losses. Here too, good agreement was found for rates available in the literature. Additionally, Particle-in-Cell/Monte Carlo Collisions (PIC/MCC) simulations are performed for the same conditions as in the experiments. The results of these simulations are used to derive analytical models for the discharge. The models can explain the value of the reduced electric field in the plasma bulk (about 80% of the discharge volume), which favors vibrational excitation.