Observation of N2(A³SIGMA+u) Metastable in Pulsed Positive Corona Discharge Using Laser-Induced Fluorescence

Relative density and spatial distribution of N₂(A³Sigma_u ⁺) metastables are measured in pulsed positive corona discharge using laser-induced fluorescence (LIF) under atmospheric pressure. The vibrationally ground state N₂(A³Sigma_u ⁺, v"=0) is excited to N₂(B³Pi_g, v"=4), then the fluorescence from (B³Pi_g, v"=4) to (A³Sigma_u ⁺,v"=1) is detected. The discharge occurs between a 12-mm point-to-plane gap in nitrogen or oxygen-nitrogen mixture. It is shown that the spatial distribution of N₂(A³Sigma_u ⁺) metastables is approximately uniform between the discharge gap. It indicates that N₂(A³Sigma_u ⁺) is mainly produced in the primary streamer channel, not in the secondary one. It is observed that, as well known, the decay rate of N₂(A³Sigma_u ⁺) density after discharge increases with O₂ concentration. The rate constant of N₂(A³Sigma_u ⁺)+O₂ is estimated to be 2.6times10^-2 cm³/s.