Determination of N₂(A³ _u ) metastable density produced by nitrogen streamers at atmospheric pressure: 1. Design of diagnostic method

Abstract

A new method based on time-resolved UV-VIS spectrometry was developed to determine absolute densities of N 2 (A 3 + u ) metastable species produced by nitrogen streamers at atmospheric pressure. The method originates with the correlation of N 2 (C 3 u ), N 2 (C 5 u ) and NO(A 2 + ) state populations with N 2 (A 3 + u ) state evolution. The diagnostic procedure is based on predicting emissions controlled by N 2 (A 3 + u ) species through the pooling and resonant energy transfer reactions in high-purity nitrogen with well-defined trace quantities of NO. A simple analytical tool to evaluate the N 2 (A 3 + u ) concentration is provided using synthetic NO-γ , N 2 -second positive (2.PG) and N 2 -Vegard-Kaplan (VK) band emission spectra. The application of the method requires tracking post-discharge formation of the N 2 (C 3 u , C 5 u ) states and inferring time evolution of N 2 (A 3 + u ) species from emission intensities of the N 2 -2.PG and N 2 -Herman infrared (HIR) systems. Simultaneously, the post-discharge evolution of the NO(A 2 + ) state has to be monitored through the NO-γ system. The concentration of N 2 (A 3 + u ) metastables can finally be evaluated from relative emission intensities of pre-selected NO-γ , N 2 -2.PG and N 2 -VK bands.

Detection of metastable excited molecules N2(A3Σu+) in an atmospheric pressure nitrogen discharge by Raman scattering

“…Measurement methods with a minute amount of NO mixed into N 2 and using the luminescence of NO and the energy transfer associated with collisions between N 2 (A 3 Σ u + ) and NO have also been reported [23,24].…”

LIF diagnostics in volume and surface dielectric barrier discharges at atmospheric pressure

“…The modeling of the OODR process at atmospheric pressure is an hopeless task, so that the possibility to deduce absolute densities of the metastable relies upon a calibration strategy. We adopted in [1] the method proposed in [17] by which the metastable density is proportional to the ratio of SPS and NO-γ emission intensities and to the NO density in the post-discharge. We then selected a condition, the post-discharge of a diffuse APTD in pure N 2 , in which the LIF sampled volume is the same homogeneous volume from which the emissions come out (note that this is not true in a filamentary discharge).…”

Advances in the optical diagnostics of kinetic processes in atmospheric pressure dielectric barrier discharges

“…The selected condition was the post-discharge of an APTD in pure N 2 , in which we proved that reactions (3) and (4) hold simultaneously. It was then possible to apply the method proposed in [19], by which the metastable density is proportional to the ratio of SPS and NO-γ emission intensities and to the NO density. The proportionality constant contains various terms, among which the ratio k 1 /k 2 of the rate coefficients of reactions (3) and (4).…”

“…The proportionality constant contains various terms, among which the ratio k 1 /k 2 of the rate coefficients of reactions (3) and (4). We introduced two major improvements with respect to [19]. First, NO density was measured by LIF instead of being presumed on the basis of known small NO additions to the gas feed.…”