Spatial distribution of OH radical density in atmospheric-pressure dc helium glow plasma in contact with electrolyte solution

The spatial distribution of OH radical density was measured in an atmospheric-pressure dc helium glow plasma produced between a nozzle anode and an electrolyte cathode. Laser-induced fluorescence imaging spectroscopy was applied to measuring OH density. To obtain the accurate distribution of OH density, we carefully examined the spatial distributions of collisional quenching frequency and rotational temperature. The distribution of OH radical density indicates that the surface of the electrolyte cathode works as the sink of OH radicals, suggesting the transport of OH radicals from the gas phase into the inside of the electrolyte.