The investigation of OH radicals produced in a DC glow discharge by laser-induced fluorescence spectrometry

Abstract

In this paper the OH radicals produced by a needle–plate negative DC discharge in water vapor, N2 + H2O mixture gas and He + H2O mixture gas are investigated by a laser-induced fluorescence (LIF) system. With a ballast resistor in the circuit, the discharge current is limited and the discharges remain in glow. The OH rotation temperature is obtained from fluorescence rotational branch fitting, and is about 350 K in pure water vapor. The effects of the discharge current and gas pressure on the production and quenching processes of OH radicals are investigated. The results show that in water vapor and He + H2O mixture gas the fluorescence intensity of OH stays nearly constant with increasing discharge current, and in N2 + H2O mixture gas the fluorescence intensity of OH increases with increasing discharge current. In water vapor and N2 + H2O mixture gas the fluorescence intensity of OH decreases with increasing gas pressure in the studied pressure range, and in He + H2O mixture gas the fluorescence intensity of OH shows a maximum value within the studied gas pressure range. The physicochemical reactions between electrons, radicals, ground and metastable molecules are discussed. The results in this work contribute to the optimization of plasma reactivity and the establishment of a molecule reaction dynamics model.

Effects of O2 addition on the plasma uniformity and reactivity of Ar DBD excited by ns pulsed and AC power supplies

“…Meanwhile, the amounts and kinds of the active species in plasmas are also critical important in many applications because those species participate physicochemical processes [23]. Usually, to improve the uniformity of atmospheric DBDs, the discharges need operate in inert gases, such as Ar and He, and there is lack of active and functional radicals for plasma-chemical processing.…”

The application of plasma technology for the preparation of supercapacitor electrode materials

“…31 Plasma generation and its role are performed in a variety of ways (Fig. 1b), 40 including dielectric barrier discharge (DBD), 41 glow discharge, 42 microwave discharge, 43 radio frequency discharge, 44 spark discharge, 45 corona discharge, 46 etc . Due to the different external control parameters (electrode structure, power supply, and type of working gas), the plasma characteristics generated by gas discharge are also different.…”

A comparative study on the spectral characteristics of nanosecond pulsed discharges in atmospheric He and a He+2.3%H2O mixture

“…to provide reactive species [10,11]. Among these gases, H 2 O in the vapor phase is an important reactive gas that adds to the gas mixture to produce hydroxyl radicals (OH), atomic oxygen and hydrogen, which plays a key role in the physicochemical processes [10,12,13].…”

“…Thus, the densities of electrons and active species in the configuration of two-pin electrodes are much higher than those in other electrode configurations. For example, in a plasma jet with a two annular electrode configuration, Yue et al reported that the OH density was measured up to ~1× 10 20 m −3 for discharges driven by a voltage of 5 kV [12]. However, with regard to pin-to-pin discharges, Verreycken et al reported that the OH density is at the level of 10 22 m −3 under similar applied-voltage conditions [16].…”