microscale atmospheric-pressure plasma jets: Validation with a focus on NO density*

Reactive oxygen and nitrogen species produced by atmospheric-pressure plasma jets are of importance in biomedical applications, e.g., nitric oxide (NO) for wound healing. The jets are investigated by zero-dimensional (volume-averaged) and pseudo-one-dimensional (plug-flow) models, coupled with the Boltzmann equation under the two-term approximation to self-consistently calculate the electron energy distribution function. The simulation results are validated against a wide variety of measurements in He, N₂, He/O₂, He/N₂ and He/N₂/O₂ plasmas. The NO density is determined as a function of the gas mixture ratio, helium flow rate and absorbed power. A larger hypothetical “effective” rate coefficient value is necessary for the reactive quenching N₂(A³Σ, B³Π; v=0) + O(³P) → NO + N(²D) in the simulations to better capture the NO density measurements at low power. This indicates that in this quenching the species N₂(A³Σ, B³Π; v>0) and multiple higher N₂ electronically excited states also play an underlying role in NO production at low power. The sensitivity of the simulated plasma properties to the N₂(v) and O₂(v) resolutions, the wall reaction probabilities and the synthetic air impurity levels is uncovered.