Effects of N₂O and O₂ addition to nitrogen Townsend dielectric barrier discharges at atmospheric pressure on the absolute ground-state atomic nitrogen density

Abstract

Abstract Absolute ground-state density of nitrogen atoms N (2p 3 4 S 3/2 ) in non-equilibrium Townsend dielectric barrier discharges (TDBDs) at atmospheric pressure sustained in N 2 /N 2 O and N 2 /O 2 gas mixtures has been measured using Two-photon absorption laser-induced fluorescence (TALIF) spectroscopy. The quantitative measurements have been obtained by TALIF calibration using krypton as a reference gas. We previously reported that the maximum of N (2p 3 4 S 3/2 ) atom density is around 3 × 10 14 cm −3 in pure nitrogen TDBD, and that this maximum depends strongly on the mean energy dissipated in the gas. In the two gas mixtures studied here, results show that the absolute N (2p 3 4 S 3/2 ) density is strongly affected by the N 2 O and O 2 addition. Indeed, the density still increases exponentially with the energy dissipated in the gas but an increase in N 2 O and O 2 amounts (a few hundreds of ppm) leads to a decrease in nitrogen atom density. No discrepancy in the order of magnitude of N (2p 3 4 S 3/2 ) density is observed when comparing results obtained in N 2 /N 2 O and N 2 /O 2 mixtures. Compared with pure nitrogen, for an energy of ∼90 mJ cm −3 , the maximum of N (2p 3 4 S 3/2 ) density drops by a factor of 3 when 100 ppm of N 2 O and O 2 are added and it reduces by a factor of 5 for 200 ppm, to reach values close to our TALIF detection sensitivity for 400 ppm (1 × 10 13 cm −3 at atmospheric pressure).