LIF imaging of OH radicals in DC positive streamer coronas

In this study, the LIF detection of the hydroxyl (OH) radicals was performed in a nozzle-to-plane electrode system having an electrode gap of 30 mm during the steady-state positive streamer corona discharge at atmospheric pressure. For monitoring the ground-state OH radicals, OH transition [A2 Σ+(v′ = 1) ← X2Π(v″ = 0)] at 282 nm was used. The time relationship between the regular streamer coronas, laser pulse, OH fluorescence and laser-induced streamer was measured. The time dependence of OH radicals between the successive streamers was measured for the evaluation of OH dynamics when the discharge was in a steady-state condition. The two-dimensional OH distribution in the DC streamer corona discharge was observed. The obtained results showed that the ground-state OH radicals were generated mainly in the filamentary part of the streamers. It was found that LIF detectable amount of ground-state OH radicals stayed in the region where streamers propagate during the steady-state DC positive streamer corona in open air.