Spectroscopic diagnostics of barrier-discharge plasma in mixtures of cadmium diiodide vapor with gases

The spectral characteristics of the emission of atmospheric-pressure gas-discharge plasma in mixtures of cadmium diiodide vapor with gases (Ne, Ar, Kr, Xe, and N₂) were investigated along with the time characteristics of the voltage and current. The gas-discharge plasma was produced and excited by a barrier discharge at a repetition rate of sine voltage pulses of up to 140 kHz. The discharge emission was analyzed in the spectral range 200–900 nm with a high resolution (0.05 nm). Radiation from exciplex CdI(B-X) molecules and excimer I₂* molecules was revealed, as well as the atomic lines of cadmium, iodine, and inert gases. In a mixture with xenon, radiation from exciplex molecules XeI(B-X, B-A) was also found. This radiation prevailed in the spectra at mixture temperatures up to 150°C. The further increase of the temperature leads to the prevalence of the CdI(B-X) radiation. It was found that the most intense CdI(B-X) radiation is observed in mixtures CdI₂/Xe(N₂)/Ne. Regularities in the spectral characteristics of the emission of the gas-discharge plasma are discussed.     

Characteristics of a high-frequency barrier discharge in mixtures of mercury diiodide vapor with gases

The spectral and electric characteristics of atmospheric-pressure high-frequency barrier discharge plasma based on mixtures of mercury diiodide with neon and admixtures of argon, xenon, and nitrogen are analyzed. A repetition rate of sinusoidal voltage pulses of about 100 kHz is used both to produce the gas discharge plasma and to excite the components of the working mixture. The radiation of the discharge in the range 200–900 nm is analyzed with a high resolution. It is found that, in the range 400–900 nm, the system of bands of excimer molecules HgI(B → X) emits 85% of the barrier discharge radiation. It is established that the radiation intensity of HgI(B → X) molecules is maximal in the mixture HgI₂/Xe/Ne = 0.6/10/90 kPa. In this mixture, UV radiation of molecules XeI(B → X) and XeI(B → A) is observed. The regular features of the spectral and electric characteristics of the gas discharge plasma are discussed. An atmospheric-pressure high-frequency barrier discharge in mixtures of mercury diiodide with gases is of interest for use in a selective (Δλ = 438–446 nm) excilamp with a cylindrical working aperture.     

Optical characteristics of barrier discharge plasma based on mixtures of cadmium diiodide vapors with gases

The spectral, integrated, and working life characteristics of the radiation from atmospheric pressure gas discharge plasma based on multicomponent mixtures (cadmium diiodide with helium and small admixtures of molecular nitrogen and xenon) are analyzed. A pulsed barrier discharge (pulse repetition rates 5000, 5500, and 6000 Hz; pulse duration ～150 ns) is used both to produce the gas discharge plasma and to excite the components of the working mixture. Visible radiation is detected from excimer molecules of cadmium monoiodide and cadmium, xenon, and krypton atoms. Regular features are found in the variations of optical plasma characteristics with pumping pulse repetition rate and with component and quantitative mixture composition.     

Optical characteristics of barrier discharge plasma based on mixtures of mercury diiodide and dibromide vapors with gases

We analyze the spectral, integrated, and durability characteristics of radiation from atmospheric-pressure gas-discharge plasma based on multicomponent mixtures (mercury diiodide and dibromide with helium and small admixtures of molecular nitrogen and xenon). We produced the gas-discharge plasma and excited the components of the working mixture by a pulsed (pulse repetition rates 500, 2000, and 4000 Hz; pulse duration ～150 ns) barrier discharge. Visible radiation was detected from excimer molecules of mercury monoiodide and monobromide, nitrogen and helium molecules, and helium and mercury atoms. Patterns were found in the variations of optical plasma characteristics with pumping pulse repetition rate and with component and quantitative mixture composition.     

Radiation spectra of a spark discharge in mixtures of inert gases with HCl and SF6

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 50, No. 4, pp. 556–559, April, 1989.     

Spectroscopic diagnostics of carbon and aluminum laser-produced plasmas

VUV emission spectra of plasmas produced by focusing laser radiation with intensity of 10¹⁰–10¹¹ W/cm² on carbon and aluminum targets were studied. Using the partial local thermodynamic equilibrium model for an electron density exceeding 10¹⁷ cm^?3, the spectroscopic diagnostics and the analysis of ion composition of plasmas were carried out. The electron temperatures determined for carbon and aluminum plasmas from the ratio of intensities of ionic lines were found to be 8±3 eV and 11±4 eV, respectively. Stark broadening of aluminum lines was measured and parameters of electron broadening were determined. Using the spatially resolved measurement of Stark line broadening, the spatial density distribution and the law of electron gas expansion were found. The electron gas in the hot region of size 5 mm with an average density of (5±2) 10₁₇cm ^?3 experienced one-dimensional expansion according to the law 1/z ^1.1 with increasing distance z from the target.     

VUV lamp based on mixtures of inert gases with water molecules pumped by a pulsed-periodic capacitive discharge

The spectral characteristics of the emission in the 140-315 nm range from pulsed-periodic capacitive discharges in mixtures of water vapor and helium and argon are described. In the VUV the most intense bands have maxima at λ = 156.0, 180.3, and 186.0 nm, and in the region of 300–315 nm, at λ = 312.1 and 313.4 nm. The brightness of the emission from the capacitive discharge plasma is optimized with respect to the partial pressures of helium, argon, and water vapor. The electron kinetic coefficients of discharges in argon and water vapor mixtures are calculated for E/N = 1–1000 Td.     

Study of the glow discharge in inert gases with water vapor

The behavior of the water vapor concentrations and fragments in wet plasma is studied. The results of plasma-chemical modeling are compared with the results of direct measurements of water molecule dissociation in plasma.     

Energy exchange in high-pressure discharge plasmas excited in diatomic gases

The energy loss that electrons sustain in inelastic collisions in high-pressure discharge plasmas excited in molecular gases is strongly affected by the vibrational temperature of the molecules and the temperature of the neutral gas. The theoretically computed average fractional energy loss due to collision with a gas molecule is far higher than the respective experimental values available at present. The energy exchange occurring between the various components of a discharge plasma is also influenced to a considerable degree by the processes of electronic and molecular vibrational de-excitation.The author wishes to extend his thanks to Prof. Dr. V. Truneek, CSc., for valuable comments, to Mr. R. Nekuda for the preparation of the diagrams, and to Mr. J. Dvoák for the automatic computer programme of the calculations.     

Spectroscopic diagnostics for an electrical discharge plasma in a liquid

We conducted spectroscopic studies of an electrical discharge plasma in a liquid, used for synthesis of nanosized particles of metals and their compounds. From the intensity ratio of the copper lines, we estimated the electron temperature, and from the Stark broadening of the hydrogen lines H _α we determined the electron density in the electrical discharge plasma. Information about the concentration of copper atoms in the discharge was obtained from analysis of the spectra in the region of resonance lines of copper. We carried out a comparative analysis of the plasma parameters for spark and arc discharges in water, ethanol, and air. Based on the equation of state for an ideal plasma, taking into account the Debye correction, we estimated the pressure in the plasma channel.     

Density dependence of electric properties of binary mixtures of inert gases

A computational study of the density dependence of the refractivity and dielectric constants, the electric-field induced second harmonic generation (ESHG) hyperpolarizabilities and of the Kerr constants of binary mixtures of helium, neon and argon is presented. Potentials and interaction properties of the homonuclear A₂ and heteronuclear AB dimers (A,?B=He, Ne, Ar) are taken from a previous study [J. López Cacheiro, B. Fernández, D. Marchesan, S. Coriani, C. Hättig, A. Rizzo. Molec. Phys., 102, 101 (2004)]. Dispersion coefficients for the second virial coefficients allow for the determination of the density dependence at any frequency far from the lowest resonance. Fully quantum mechanical results are presented and a comparison with the corresponding classical estimates is discussed. Deep minima are predicted to occur in the ESHG second virial coefficient curve drawn as a function of the molar fraction of one of the components in binary mixtures of He/Ar and Ne/Ar. This phenomenon, observed over a wide range of temperatures, should be easily verifiable experimentally.     

Emission characteristics and parameters of gas-discharge plasma in mixtures of heavy inert gases with chlorine

The ultraviolet (UV) radiation from longitudinal glow-discharge plasma in three- and four-component mixtures of argon, krypton, and xenon with chlorine has been investigated. The total radiation of Ar, Kr, and Xe monochlorides and chlorine molecules in the spectral range 170–310 nm has been optimized with respect to the composition and the pressure of gas mixtures, as well as the discharge current. The mean output power, the electric power of discharge, and the efficiency of a broadband low-pressure exciplex halogen lamp have been determined. Parameters of the glow discharge in Ar-Kr-Cl₂ and Kr-Xe-Cl₂ mixtures have been simulated numerically. The electron energy distribution functions have been determined through the solution of the Boltzmann kinetic equation. These functions have been used to calculate the plasma parameters, namely, electron transfer characteristics, specific losses of discharge power for electronic processes, and ionization and attachment coefficients.     

Properties of the dielectric barrier discharge in mixtures of methane with helium

The influence of the chemical composition of the feeding gas mixtures CH₄-He on the physical properties of dielectric barrier discharge was investigated experimentally as well as theoretically. Certain changes in the shape of charge-voltage characteristics (Lissajous figures) were observed when the content of He was varied within the range 0–90%. An increase of the He concentration was found to cause monotonous but not linear decrease of the ignition voltage as well as of the burning voltage of the discharge. Measurements of the burning voltage were used to estimate the characteristic energy of electrons in the mixtures under consideration. These estimates were compared with experimentally determined values of the energy consumption for the synthesis of C₂H₂, C₂H₄ and C₂H₆, respectively. It was demonstrated that the observed dependencies of the energy consumption upon He content can be explained taking into consideration the influence of the chemical composition of feeding gas mixture upon the characteristic energy of electrons in the dielectric barrier discharge. Dedicated to Prof. Jan Janča on the occasion of his 60th birthday. The work was supported by the Sonderforschungsbereich 198 “Kinetik partiell ionisierter Plasmen”.     

微波脉冲氮气等离子体发射光谱测量

通过发射光谱测量和拟合不同的微波脉宽和气压下C波段微波放电的氮气等离子体振动温度、转动温度和电子激发温度。气压在266～400 Pa时,等离子体的振动温度为(2700100) K,电子激发温度为(0.32 0.015) eV,转动温度随脉宽增加而上升,实验中测得的最大转动温度为370 K。偏离266～400 Pa时,振动温度和电子激发温度同时出现了下降的趋势,而转动温度出现了上升的趋势。这意味着电子激发温度和振动温度具有很强的关联性。     

微波脉冲氮气等离子体发射光谱测量

通过发射光谱测量和拟合不同的微波脉宽和气压下C波段微波放电的氮气等离子体振动温度、转动温度和电子激发温度。气压在266~400Pa时,等离子体的振动温度为(2700±100)K,电子激发温度为(0.32±0.015)eV,转动温度随脉宽增加而上升,实验中测得的最大转动温度为370K。偏离266~400Pa时,振动温度和电子激发温度同时出现了下降的趋势,而转动温度出现了上升的趋势。这意味着电子激发温度和振动温度具有很强的关联性。     

Formation of monochlorides of heavy inert gases in a high-frequency transverse discharge plasma

Emission characteristics of a high-frequency transverse discharge plasma in mixtures of argon and xenon with chlorine molecules are presented. It is shown that the discharge in xenon-chlorine mixtures is a source of broadband radiation in the spectral region 220–450 nm, while in argon-chlorine mixtures, it emits in the region 150–270 nm. Double mixtures with a partial pressure of inert gases ranging within 300–400 Pa and a chlorine partial pressure of 30-40 Pa are found to be optimal. The mean output discharge power ranges within 15–50 W.