Spectroscopic Method for Determination of N<sub>2</sub>(A<sup>3 </sup>Σ<sub>u</sub>) Metastable Density in Atmospheric Pressure Non-Equilibrium N<sub>2</sub> Plasmas

Abstract

Summary form only given. N2 meta-stable species such as N2(A3Σu) 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 (A3Σu) metastable density can be calculated from the density ratio of N2(C3Πu)/N2(B3 Πg) 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 (C3Πu)/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(C3Πu)/N2 (B3Πg) without knowing electron temperature and electron density