The Optical Diagnosis Of OH Radical Produced In Dielectric Barrier Discharge And DC Glow Discharge

The emission spectroscopy and laser-induced fluorescence techniques have been used to diagnose the OH radicals produced by dielectric barrier discharge at atmospheric pressure and DC glow discharge at low pressure respectively. The main results presented in the dissertation have been summarized as follows:1.The emission spectra of OH (A²âˆ‘→X²âˆ0-0) and N₂⁺ (B²âˆ‘_u⁺→X²âˆ_g⁺ 0-0) emitted from dielectric barrier discharge of N₂ and H₂O mixture gas in a needle-plate electrode reactor configuration were successfully recorded at atmospheric pressure. The relative vibrational populations and the vibrational temperature of N₂ (C, v' ) were determined. For the emission intensity of OH(A²âˆ‘→X²âˆ0-0) has been exactly gotten by subtracting the emission intensity of theâ–³v = +1 vibration transition band of N₂ (C³âˆ_u→B³âˆ_g) from the overlapping spectra, we use the following way to get the precise emission intensity of OH (A²âˆ‘→X²âˆ0-0): firstly, to obtain the relative vibration population and the vibration temperature of N₂(C, v') by the emission intensity of theâ–³v = -3 andâ–³v = -4 vibration transition band of N₂ (C³âˆ_u→B³âˆ_g), finally, the emission intensity of OH(A²âˆ‘→X²âˆ0-0) exactly obtained by subtracting the emission intensity of theâ–³v = +1 vibration transition band of N₂(C³âˆ_u→B³âˆ_g from the overlapping spectra. The effects of peak- peak voltage, discharge frequency, electrode gap and the N₂ flow rate on the emission intensities of OH(A²âˆ‘→X²âˆ0-0) and N₂⁺ (B²âˆ‘_u⁺→X²âˆ‘_g⁺ 0-0) are also investigated. It is found that when the peak-peak voltage and the discharge frequency are increased, the emission intensities of OH(A²âˆ‘→X²âˆ0-0) and N₂⁺ (B²âˆ‘_u⁺→X²âˆ‘_g⁺ 0-0) enhance correspondingly; the emission intensity of OH(A²âˆ‘→X²âˆ0-0) and N₂⁺ (B²âˆ‘_u⁺→X²âˆ‘_g⁺ 0-0) could hardly be influenced by increasing the N₂ flow rate, when the electrode gap increased, the emission intensity of OH(A²âˆ‘→X²âˆ0-0) and N₂⁺ (B²âˆ‘_u⁺→X²âˆ‘_g⁺ 0-0) enhance first, then decrease rapidly, with a maximum at 3mm approximately.2.Laser-induced Fluorescence Technique was used to determine the fluorescent spectrum of OH (A²âˆ‘→X²âˆ0-0) produced by a high-voltage negative dc glow discharge in a plate-plate reactor configuration at low pressure in water vapor, nitrogen-water vapor mixture, and helium-water vapor mixture, respectively. Particular attention has been paid to the influence of the discharge voltage and the pressure on the OH (A²âˆ‘→X²âˆ0-0) fluorescent intensity. Being strong and less disturbed by the ambient fluorescence branch, the Q1 (1)-Branch of OH (A²âˆ‘→X²âˆ0-0) fluorescence spectrum can reflect the whole change of OH (A²âˆ‘→X²âˆ0-0) fluorescence spectrum intensity, therefore, it's necessary for us to investigate the influence of discharge parameters on the Q1 (1)-Branch. It is found that the fluorescence spectrum intensity of Q1 (1) could hardly be influenced by increasing the discharge voltage, while decreases with increasing the applied discharge pressure in water vapor system; the fluorescence spectrum intensity strengthens with increasing the discharge voltage, while decreases rapidly with increasing the pressure in N₂/H₂O vapor system, with a maximum at 110 Pa approximately; the fluorescence spectrum intensity enhances with increasing the discharge voltage, while decreases quickly with increasing the pressure in He/H₂O vapor system, with a maximum at 180Pa approximately.