Nitrogen oxide γ-band emission from primary and secondary streamers in pulsed positive corona discharge

Nitrogen oxide γ-band emissions (A² Σ⁺→X² Π) from primary and secondary streamers are observed in O₂/N₂ and NO/N₂ pulsed positive corona discharges with the aim of investigating the production of NO molecules and N₂(A³ Σ_u⁺) metastables in these primary and secondary streamers. The spatial distribution of the NO-γ emission shows that the NO-γ emission is mostly observed in the secondary streamer propagation area of the O₂/N₂ discharge. That is, NO molecules are mainly produced in the secondary streamer in the O₂/N₂ discharge. On the other hand, in the NO/N₂ discharge, the NO-γ emission is observed in the primary streamer propagation area. This result indicates that N₂(A³ Σ_u⁺) metastables are mostly produced in the primary streamer because the NO-γ emission is observed following the process NO(X² Π)+N₂(A³ Σ_u⁺)→NO(A² Σ⁺)+N₂(X² Σ_g), where NO(X² Π) is distributed uniformly in the background gas in the NO/N₂ discharge.