CH spectroscopic observables in He–CH₄and N₂–CH₄atmospheric pressure dielectric barrier discharges

In this paper we report on a spectroscopic study on CH observables including laser induced fluorescence (LIF) on CH and emission spectroscopy on the CH Ger¨ o band. Direct observation by LIF has been found to be very difficult, both because of technical difficulties and an overall low CH density in the discharge. Analysis of CH(A) emission shows that it is due to CH4 dissociative excitation processes, by He(2 3 S) in He‐based mixtures, and by electron impact in N2‐CH4. The analysis of spectra evidences the need for more precise knowledge on the collision quenching of electronically excited states and on the electron energy distribution function. (Some figures in this article are in colour only in the electronic version)