Spectroscopic Method for Determination of N2(A3 Σu) Metastable Density in Atmospheric Pressure Non-Equilibrium N2 Plasmas

Summary form only given. N₂ meta-stable species such as N₂(A³Σ_u) are very important in plasma treatments because of their high-energy contents, which make plasmas more sustainable and chemically reactive. However, direct measurements of these meta-stable species are not easy. In this study, a spectroscopic method to determine the N₂ metastable density has been developed by using a simple collisional-radiative model (CR model) with several molecule-molecule reactions included. The N₂ (A³Σ_u) metastable density can be calculated from the density ratio of N₂(C³Π_u)/N₂(B³ Π_g) by using the CR model. Governing equations for the model have some terms related to molecule-molecule reactions that depend on vibrational temperatures, which can be determined from the measured spectrum of N₂ second positive system by comparing with the simulated spectra. In addition, the density ratio of N₂ (C³Π_u)/N₂(B³Π _g) can be evaluated from the emission intensity ratio of N ₂ second positive system/N₂ first negative system. By measuring these spectra, the N₂ metastable density is successfully determined through both the vibrational temperature and the density ratio of N₂(C³Π_u)/N₂ (B³Π_g) without knowing electron temperature and electron density