Absolute Concentration of OH Radicals in Atmospheric Pressure Glow Discharges with a Liquid Electrode Measured by Laser-Induced Fluorescence Spectroscopy

The OH radical density and gas temperature in atmospheric pressure glow discharges with a liquid cathode or anode is measured with a laser-induced fluorescence (LIF) technique exciting the P 2 (3), Q 1 (4), and Q 1 (9) branches of the X 2 Π, ν''=0–A 2 Σ, ν'=3 transition. Glow discharge in contact with liquid is generated by positive and negative voltages at currents of 10–28.5 mA. The density of OH radicals linearly increases from 1.32 × 10 21 (water anode) and 1.3 × 10 21 m -3 (water cathode) to 8.95 × 10 21 and 1.78 × 10 22 m -3 , respectively, with the increase of the discharge current from 10 to 28.5 mA.