Emission characteristics of a gas-discharge plasma of water vapor in the vacuum UV region of the spectrum

Abstract

We present the results of a study of emission from a low-density water vapor plasma in the vacuum ultraviolet (VUV) region of the spectrum. The plasma was formed in a longitudinal glow discharge. We have studied the spectral characteristics of the plasma and also the dependences of the relative energy characteristics of the hydroxyl (OH) emission band on the discharge current and the helium partial pressure in a He-H 2 O mixture in the spectral range 130-190 nm.

Global model of low-temperature atmospheric-pressure He + H2O plasmas

“…Low-temperature water-containing plasmas have been explored for many scientific interests and technological applications such as mercury-free ultraviolet light sources [5][6][7][8][9][10][11], sterilization [8,[12][13][14][15][16][17], surface modification [18][19][20][21], biomedical applications [22][23][24], air pollution control [25,26], and water treatments [27][28][29]. In most cases, however, the understanding of the chemical environment created in these plasmas is limited and the efficacies of the processes are unlikely to have reached their maximum.…”

Spectral characteristics of the emission from a barrier discharge plasma based on an Ar–H2O mixture in the UV spectral region

“…In a glow discharge lamp based on water vapor, when the water vapor pressure is greater than 0.5-1.0 kPa (pink discharge), the main bands in the emission spectrum of the plasma are bands with λ max = 286 and 306-315 nm. When the water vapor pressure decreases down to 50-150 Pa, the main bands in the emission spectrum become the bands at 180-186 nm and 156 nm in the vacuum UV region [5]. Under the operating conditions for this lamp, especially with increased water vapor content in the discharge tube, a significant portion of the water molecules may exist in the form of clusters of the (H 2 O) n type (where n = 2, 3, ...) [10], while the major decomposition products of the H 2 O molecules and their clusters are OH • radicals, negative OH -ions, clusters based on OH • radicals and hydrogen atoms.…”

“…Such a medium might be hydroxyl radicals, the A → X emission band of which (with main maximum at 309 nm) has already been used as the basis for design of some types of emitters [3,4]. Other OH • transitions in the vacuum UV range of the spectrum and also the conditions for their appearance in a glow discharge have been studied in [5]. Currently under development are various optical technologies in the area of environmental work, medicine, and microelectronics associated with use of spontaneous and stimulated UV emission sources [6,7].…”

Modeling of Gas Discharge in Water Vapor

“…At the same time, an increasing interest is drawn to UV emitters based on water vapor, because of the environmentally safe and inexpensive working medium that is used in them. Therefore, the research of the parameters of such radiation sources is challenging [3][4][5][6]. Their main advantage in comparison with mercury-containing lamps is the absence of mercury in the working medium so that there is no adverse effect to the environment in the course of their subsequent recycling.…”