Emission Spectra Of Discharge Research Articles

Monochromatization effect kinetic model for Penning gas mixtures emission mechanisms

The monochromatization effect (M-effect), which consists in the reduction of an electronegative-electropositive gas mixtures discharge emission spectrum to only a few or a single line, was largely explained in our previous published papers together with their generation mechanisms, namely the polar ion-ion recombination and the energy resonance condition. This paper presents a kinetic model for the M-effect based on the radiative and collisional processes which appear between 1s_2, 1s_3, 1s_4 and 1s_5 Paschen levels, in Penning gas mixtures, where this effect was observed to be the most powerful.

Spectral pyrometry of the objects with hot spots

Optical emission spectra of microwave discharges at the powder mixture surface are experimentally recorded, indicating spatial temperature nonuniformity the within the field of vision. Within the field of vision, the maximal and minimal temperature values calculated from the continuous spectrum (wavelength range 380–620 nm) differ by 20–25%. Modeling of the integral emission spectra of a heated surface with hot spots is performed. Spectral pyrometry of the objects with nonuniform temperature, when used within a narrow spectral interval, gives no possbility of determining the exact nature of the measured temperature because the temperature calculated from this spectrum may differ substantially from both averaged and maximal values. To determine the averaged and maximal temperature, it is necessary to significantly widen the recorded spectral interval.

Investigation on the effect of impurities in xenon based dielectric barrier discharge lamps

In any discharges, the existence of impurities could cause a severe change or bring a negative or positive effect to the discharge and plasma characteristics. The authors purposely added a few kinds of impurities and investigated their effect on the discharge. The common and typical impurities of H2, N2, CO2 and CH4 were applied in varying concentration percentages into a xenon dielectric barrier discharge lamp. Their discharge condition, emission spectra and electrical characteristics were studied. The plasma generation differs from one type of impurity to another. With two different concentrations of hydrogen applied, at 5% concentration it would stabilize the discharge and at 0.5% concentration it would cause an additional collision process where a strong peak of atomic lines was observed. Nitrogen with two types of concentration, i.e. 1% and 0.1%, exhibits two kinds of characteristics in emission spectroscopy. From the electrical parameters, the voltage across the gap shows the lamps with impurities have a higher value compared with the pure xenon lamp.

Discharges in Water and Applications to Wasted Water Treatment

Recently the electrical discharge in water has been used for the water treatment. In this study, various shape of electrodes were examined to observe and measure the electrical discharge phenomena in water. Both the Marx generator and the pulsed power generator were used to generate the discharge in water. The oscillation on the waveforms of both applied voltage and discharge current was observed using the pulsed power generator whose peak applied voltage was about 80-120 kV and its discharge repetition rate was about one pulse per thirty seconds although it wasn't observed on the waveforms in the practical use of the high voltage generator (peak applied voltage was about 30-40 kV) with high repetition rate of discharge (20-300 pulses per second). Bubbles were introduced into the discharge region of main electrode using the ejector and the generation of hydroxyl radicals (OH) was confirmed by the measurement of emission spectrum of discharge in water and the intensity of OH radicals increased with the ratio of G/L (where, G is gas flow rate and L is water flow rate). The hydrogen peroxide (H2O2) was also measured and this reactor system was applied for the de-color of water.

Formation of the continuous visible emission spectrum of pulsed discharge in cesium vapor

The formation of a continuous emission spectrum of pulsed discharge in high-pressure cesium vapor (P ≤ 1 bar) has been experimentally studied under conditions of increased power deposited in discharge. Experimental data well agree with the results of theoretical calculations. Physical mechanisms underlying the observed phenomenon are discussed. It is shown that, as the pumping current pulse amplitude is increased from 15 to 80 A, a discrete line spectrum transforms into the continuous spectrum. This is accompanied by an increase in the light yield (from 15 to 85 lm/W) and color-rendering index (from 86 to 98).

On the line intensity ratios of prominent Si II, Si III, and Si IV multiplets

Line intensities of singly, doubly and triply ionized silicon (Si II, Si III, and Si IV, respectively) belonging to the prominent higher multiplets, are of interest in laboratory and astrophysical plasma diagnostics. We measured these line intensities in the emission spectra of pulsed helium discharge. The Si II line intensity ratios in the 3 s3 p 22 D–3 s 24 p 2 P o , 3 s 23 d 2 D–3 s 24 f 2 F o , and 3 s 24 p 2 P o –3 s 24 d 2 D transitions, the Si III line intensity ratios in the 3 s3 d 3 D–3 s4 p 3 P o , 3 s4 p 3 P o –3 s4 d 3 D, 3 s4 p 3 P o –3 s5 s 3 S, 3 s4 s 3 S–3 s4 p 3 P o , and 3 s4 f 3 F o –3 s5 g 3 G transitions, and the Si IV line intensity ratios in the 4 p 2 P o –4 d 2 D and 4 p 2 P o –5 s 2 S transitions were obtained in a helium plasma at an electron temperature of about 17,000 ± 2000 K. Line shapes were recorded using a spectrograph and an ICCD camera as a highly-sensitive detection system. The silicon atoms were evaporated from a Pyrex discharge tube designed for the purpose. They represent impurities in the optically thin helium plasma at the silicon ionic wavelengths investigated. The line intensity ratios obtained were compared with those available in the literature, and with values calculated on the basis of available transition probabilities. The experimental data corresponded well with line intensity ratios calculated using the transition probabilities obtained from a Multi Configuration Hartree–Fock approximation for Si III and Si IV spectra. We recommend corrections of some Si II transition probabilities.

Physical and chemical processes in gas-discharge plasma during the deposition of nanocarbon films

The relationship of the parameters of activated methane-hydrogen mixture with the phase composition and structural features was determined for carbon films, which were precipitated from this mixture. Optical emission spectra of dc discharge were studied in conditions of the growth of different nanocarbon films. The peculiarities of the space intensity distribution of radiation corresponding to carbon C2 dimers are shown.

Atmospheric pressure barrier torch discharge and its optimization for flexible deposition of TiO 2 thin coatings on various surfaces

This paper reports on the preparation of titanium (IV) oxide films via the improved atmospheric pressure barrier torch discharge (BTD) deposition. This approach is a modification of the atmospheric pressure glow discharges (APGDs) ranking among plasma enhanced chemical vapor deposition (PECVD) techniques. These methods are based on plasma–chemical reactions of the precursors' vapors occurring in the active plasma environment. The layers are produced in terms of heterogeneous recombination reactions of the high active species on the supporting surface. The major treated topic comprises the influence of the used support on the physical properties of the layers. A set of three different supports was used including quartz slides (non-conducting, dielectric), silicon discs (semi-conducting) and polished Ni sheets (conducting). Crystallographic structure, surface roughness, surface wettability and the film thickness were assessed and used as a set of physical properties to be discussed and compared for each of the films and mutually. In parallel the qualitative analysis of the emission spectra of the barrier torch discharge during the deposition process was also presented. Different conductive connection of plasma stream with the substrate crucially influences the temperature of this substrate. It has a direct effect mainly on the crystallinity and morphology of the films and also on the plasma parameters. This knowledge might be used as a tool for the optimization of deposition conditions. Photocatalytic functionality of the layers was quantified in a simple test based on the photocatalytic oxidation of Rhodamine B (C 28H 31ClN 2O 3) under UV radiation.

Ar gas discharge lamp with heated LiF window: A monochromatized light source for photoemission

We present a simple, inexpensive, and highly effective method for monochromatizing the vacuum ultraviolet light emitted from an Ar gas discharge for use, e.g., in photoemission experiments. By using a slightly heated window of LiF acting as low-pass filter, the emission spectrum of the Ar gas discharge is reduced to the Ar line at 11.62eV (106.7nm). The performance of the low-pass filter is demonstrated by photoemission measurements on Cu(111). Furthermore, we compare our light source with an unmonochromatized He gas discharge, which represents the most widely used laboratory photon source in photoemission.

DC-excited discharges in vapour bubbles in capillaries

DC-excited discharges in vapour bubbles in capillaries are studied. A bubble is generated in a capillary filled with a NaCl solution due to Joule heating. The fluid columns on either side of the bubble serve as electrodes for the electrical discharges inside the bubble. The electrical breakdown (corresponding to a corona-to-spark transition) of quasi-static vapour bubbles is discussed. The breakdown electrical field decreases with bubble length. For larger bubbles, the reduced electrical field is smaller than the electrical field where electron attachment equals ionization, indicating that the discharge is a surface discharge. Linear translation of bubbles in the cathode direction, coinciding with intense discharges inside the bubbles, is observed and can be explained by asymmetric heating due to the plasma. The optical emission spectrum of a vapour bubble discharge consists of excited hydroxyl, hydrogen and sodium emission. A delay in the range of 0.1 s is observed between the emission of hydroxyl and sodium. The sodium emission is most intense on the anode side of the bubble where orange anode spots are visible.

Spectroscopic Observation of the Resonance-Stabilized 1-Phenylpropargyl Radical

The gas-phase laser-induced fluorescence (LIF) spectrum of a 1-phenylpropargyl radical has been identified in the region 20,800-22,000 cm(-1) in a free jet. The radical was produced from discharges of hydrocarbons including benzene. Disregarding C2, C3, and CH, this radical appears as the most strongly fluorescing product in a visible wavelength two-dimensional fluorescence excitation-emission spectrum of a jet-cooled benzene discharge. The structure of the carrier was elucidated by measurement of a matching resonant two-color two-photon ionization spectrum at m/z = 115 and density functional theory. The assignment was proven conclusively by observation of the same excitation spectrum from a low-current discharge of 3-phenyl-1-propyne. The apparent great abundance of the 1-phenylpropargyl radical in discharges of benzene and, more importantly, 1-hexyne may further underpin the proposed importance of the propargyl radical in the formation of complex hydrocarbons in combustion and circumstellar environments.

Mechanism for generating stimulated VUV emission of the Xe*Kr dimer in a dc capillary discharge

The emission spectrum of a dc capillary discharge in krypton with a small (≤0.1%) xenon impurity has been experimentally studied in the 115-850-nm range. It is shown that most of the radiation energy is concentrated in a narrow VUV spectral band adjacent to the 146.96-nm resonance line of xenon and belonging to the heteronuclear Xe*Kr molecule. The power of the narrow-band VUV radiation and its angular dependence have been measured. A conclusion is drawn that the appearance of the narrow-band VUV radiation represents amplified spontaneous emission caused by transillumination of the broad-band amplifying medium by a narrow-band "seed."

Emission characteristics of plasma of a transverse volume discharge in mixtures of helium, argon, and krypton with sulfur hexafluoride

The emission characteristics of the plasma of repetitively pulsed spontaneous UV-VUV radiation sources on the basis of ArF* (193 nm) and KrF* (249 nm) molecules, and the products of decomposition of sulfur hexafluoride molecules pumped by a transverse volume discharge in a mixture of inert gases with sulfur hexafluoride molecules have been investigated. The discharge emission spectra in the range of 190–780 nm at the low-current and high-current stages of the transverse discharge, the time characteristics of the voltage across the electrodes, the pump current, and the emission of excimer molecules and the products of decomposition of sulfur hexafluoride have been studied. It is shown that, in the gas-static operation mode of the radiator at the number of discharge pulses smaller than 103, the 193-nm ArF* and 249-nm KrF* bands are main in the emission spectrum. Upon further operation of the radiator, a spectral continuum is formed on the basis of sulfur molecular bands in the range 260–550 nm.

Influence of methane on the capacitively coupled hydrogen discharge

In this work the mixture of hydrogen and a small amount (0–1.5 %) of methane was studied. The measurements were carried out in a low-pressure (5 Pa) capacitively coupled radio frequency (RF) discharge. Positive ions and neutral particles were detected by Plasma Process Monitor PPM 421 (Balzers). Optical emission spectra of active discharge were measured by spectrometer Triax 550 Jobin-Yvon Spex.

Spectroscopic investigation of the bipolar pulsed discharge in water-air mixture

Emission spectrum of the bipolar pulsed discharge in water-air mixture has been measured in the near-ultraviolet (UV) region using an Inspectrum 300 charge-coupled device (CCD) spectrograph. Effects of several parameters including peak-to-peak voltage, pulse repetitive frequency, etc., on the relative UV radiation intensity have been investigated. Experimental results show that bipolar pulsed discharge in water-air mixture emits strong UV radiation. The emission spectrum of the discharge has a wide range. The applied peak-to-peak voltage, pulse repetitive frequency, and air flow rate have positive effect on the relative intensity of the second positive band of nitrogen at 337.1 nm. However, solution conductivity has negative effect

Temperature determination of N2 discharge plasma by computational simulation of its emission spectra

The emission spectra of N2 hollow cathode and pulsed discharges were investigated and computational simulations have been made for the determination of the rotational and vibrational temperatures. A calibration curve was obtained by rotational simulation and was applied to study the space-resolved temperature in the pulsed discharge plasma. The rotational temperature was found to decrease rapidly along the radial axis of the plasma. The vibrational temperature in the pulsed discharge plasma was estimated by spectral simulation and was found to be more than three times higher than the rotational temperature.

Spectroscopic studies of back-discharge

Different forms of low current back-discharge in air at atmospheric pressure with fly ash used as a dielectric barrier are discussed in the paper. The discharge was characterized in terms of optical emission spectra and current-voltage characteristics. The discharge emission spectra in the wavelength range of 200÷540 nm have been measured to investigate behavior of the species present in the fly ash when back-discharge is initiated. In normal conditions the emission spectra are dominated by atmospheric components (molecular nitrogen, atomic oxygen and nitrogen) but atomic lines due to chemical composition of the fly ash were also identified.

Enhancement of Etch Rate by the Addition of O2 and Ar in Chemical Dry Etching of Si Using a Discharge Flow of Ar/CF4 and CF4/O2 Gas Mixtures

The chemical dry etching of Si in a fast discharge flow was studied using a low-power (80 W) microwave discharge of Ar/CF4/O2 mixtures. The variation of etch rate was measured as a function of the O2 or Ar flow rate in order to determine the effects of the addition of O2 and Ar. The maximum etch rate was about 3600 Å/min at the Ar, CF4 and O2 flow rates of 2500, 100 and 10 sccm, respectively. This etch rate was larger than those obtained without the addition of O2 by a factor of 8 and without the addition of Ar by a factor of 23. Auger and XPS spectra of Si substrates and emission spectra of discharges were measured in order to examine the effects of the addition of O2 on the Si surface and discharge. The marked enhancement of the etch rate at low O2/CF4 flow ratios below 10% was explained by an increase in the F concentration and a decrease in the concentrations of carbons and CFn (n=1,2). The decrease in the etch rate at high O2/CF4 flow ratios above 10% was attributed to the formation of SiO2 on the substrate. The marked enhancement of the etch rate by the addition of Ar was explained by the generation of active Ar species which enhance [F] and [O] in the discharge flow.

High-Lying Rotational Levels of Water: An Analysis of the Energy Levels of the Five First Vibrational States

As a continuation of the work carried out on the ground and (010) vibrational states of water (R. Lanquetin, L. H. Coudert, and C. Camy-Peyret, 1999, J. Mol. Spectrosc.195, 54–57), rotational energy levels for these two states are revisited here and new accurate rotational energy levels are considered for the three next vibrational states, that is, the (020), (100), and (001) states. Experimental rotational energies, along with their uncertainties, are retrieved through analyses of already published data sets and of discharge and flame emission spectra. The maximum value of J for the obtained levels is 25 for the ground state, 21 for the (010) state, and 20 for the three next states. Based on the bending-rotation Hamiltonian approach (L. H. Coudert, 1997, J. Mol. Spectrosc.181, 246–273), a new theoretical approach is proposed to calculate rotational energies in the five interacting vibrational states under consideration and is used to carry out an analysis of the experimental energies. Comparisons with other existing energy level data sets are also presented.

Analysis of the 1–v″ Progression of the 3A Band System (c3Π–a3Π) in the 13C16O Molecule Spectrum

The 1–0, 1–1, and 1–2 bands of the 3A system of 13CO (c3Π–a3Π) have been recorded for the first time, in the form of discharge emission spectra photographed at high resolution. Preliminary rotational analysis suggests that the v = 1 level of the c3Π state is perturbed in a fashion similar to the v = 0 level, previously observed by Dabrowski et al. (1987. I. Dabrowski, M. Vervolet, and D. C. Wang, Can. J. Phys. 65, 1171–1177). Rotational combination differences from the 1720 measured lines have been used to obtain rotational constants for the v = 0–2 levels of the a3Π state, using the Hamiltonian of Brown et al. (1979. J. M. Brown, E. A. Calbourn, J. K. G. Watson, and F. D. Wayne, J. Mol. Spectrosc. 74, 294–318). and the least squares formalism of Curl and Dane (1988. J. Mol. Spectrosc. 128, 406–412), as modified by Watson (1989. J. Mol. Spectrosc. 138, 302–308). Term values for the c3Π, v = 1 level have then been obtained from the line frequencies, and a set of effective rotational constants for the c3Π (v = 1) level of 13CO has been derived.