Characteristics of OH* Generation in Pin-to-Electrolyte Discharges

The locations of excited hydroxyl radical [OH (A-X), in short OH*] generation are observed using the highspeed images in low-voltage-driven pin-to-electrolyte discharges. A comparison of the emission from the plasma and OH* reveals that the generation site of OH* is depending on the electrolyte polarity. It implies that the difference of OH* properties with polarity can be due to the OH* generation pathways on the electrolyte surface and in the plasma volume, corresponding to the humidity, the electron temperature, and the quenching rate.