vibrational distribution functions in radio-frequency and nanosecond-pulsed plasma jets*

The N₂ vibrational distribution functions (VDFs) play an important role in the plasma applications such as NO and NH₃ synthesis in the medical and agricultural field, respectively. A deep understanding of the N₂ VDF formation is necessary for optimization of the NO and NH₃ production. A radio-frequency (RF) atmospheric pressure He/N₂(v<58)/O₂(v<41) plasma jet and a near atmospheric pressure nanosecond (ns)-pulsed N₂(v<58) plasma jet are investigated by a zero-dimensional volume-averaged model coupled with a two-term Boltzmann equation solver. The model calculations are validated against the measured nitric oxide density in the RF jet, the measured electron density and vibrational level densities (v<5) in the ns-pulsed jet. It is predicted that N₂ VDF (v>12) plays a more important role in the NO production at higher power values in the range of 0.5-2.0 W of the RF plasma jet (i.e. the COST-Jet). In the subsequent study of the ns-pulsed jet, the influence of diverse theoretical approaches calculating the Vibrational-Vibrational (V-V) and Vibrational-Translational (V-T) rate coefficients on the simulated N₂ VDFs is revealed. In addition, it is predicted that the simulated N₂ VDFs are sensitive to the probabilities of the neutral wall reaction N₂(v) + wall → N₂(v-1).