Observation of ground-state OH by LIF technique in DC nozzle-to-plate positive streamer coronas

In this study, the planar 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 at 282 nm was used. The two-dimensional OH distribution in the DC corona discharge in air/H₂O/Ar mixture was measured. The obtained results showed that the ground-state OH radical is generated mainly in the filamentary part of the streamers. The spontaneous emission of OH molecules excited by the streamer plasma was also recorded and compared to the LIF signal used for the detection of the ground-state OH molecules.