Diagnosis of OH Radicals in Air Negative Pulsed Discharge With Nozzle-Cylinder Electrode by Optical Emission Spectroscopy

OH radicals (A²Σ→ X²Π, 0-0) generated during air negative pulsed discharge are diagnosed in a nozzle-cylinder reactor by optical emission spectroscopy (OES). The nozzle high-voltage discharge electrode is put in the middle of the cylinder steel reactor which is grounded. The effects of the pulse repetition rate, the humidity of the air in the reactor, the outer diameter of the nozzle electrode, and the flow rate of the air through the reactor on the relative intensity of OH radicals´ (A²Σ→ X²Π, 0-0) OES were investigated. Results show that higher pulse repetition rate, lower flow rate of the air, or smaller diameter of the nozzle is helpful to get stronger relative intensity of OH radicals´ (A² Σ→ X²Π, 0-0) OES. To some extent, OH radicals´ ( A²Σ→ X²Π, 0-0) yield can be increased by increasing the humidity of the air; however, it will be decreased when the humidity is too high. In our experiments, the humidity of the air being 55% is the best.