Optical study of OH radical in a needle-plate DC corona discharge

State Key Laboratory of Materials Modification by Laser, Ion and Electron Beams, Dalian University of Technology, Dalian, 116024, P.R. China

Corresponding author: wangwenc@dlut.edu.cn

Received: 20 April 2006
Revised: 6 July 2006
Accepted: 7 February 2007
Published online: 21 March 2007

Abstract

In this study, the emission spectra of OH (A²Σ → X²Π, 0-0) and N₂ (C³Π_u → B³Π_g) emitted from the high-voltage DC (direct-current) corona discharge of N₂ and H₂O mixture gas in a needle-plate reactor are successfully recorded at one atmosphere. The relative vibrational populations and the vibrational temperature of N₂ (C, v') in negative DC corona discharge are determined. The effects of discharge voltage, input power and added oxygen on the relative populations of OH (A²Σ) radicals and N₂ (C³Π_u) molecules in negative DC corona discharge are investigated. It is found that the relative populations of OH (A²Σ) radicals and N₂ (C³Π_u) molecules increase with increasing the discharge voltage and the input power and decrease with increasing the added oxygen. The emission spectra produced by positive DC corona discharge are also studied for comparing with negative DC corona discharge. However, the emission spectrum of OH (A²Σ → X²Π, 0-0) is not obtained in positive DC corona discharge, only the emission spectrum of N₂ (C³Π_u → B³Π_g) is observed. The effects of discharge voltage and input power on the relative populations of N₂ (C³Π_u) molecules in positive DC corona discharge are also investigated. The relative populations of N₂ (C³Π_u) molecules increase with increasing the discharge voltage and the input power. The main involved physicochemical processes have been discussed.