Optical characteristics of the plasma of a transverse volume discharge in Cl2 and He/Cl2 mixtures

Results are presented from a study of UV and VUV emission from the plasma of a transverse volume discharge in chlorine and a He/Cl₂ mixture. In the wavelength range Δλ=140–300 nm, the Cl₂(D′-A′) band with an edge at 258 nm and the Cl ₂ ^* band with edge at λ=195 nm are found to be dominant. It is shown that, in the pressure range [Cl₂]=0.1–2.0 kPa, the intensity of emission with λ≤195 nm is higher than the intensity of the Cl₂(D′-A′) band. At [Cl₂]≥2 kPa, emission in the 258-nm band is dominant.     

Subnormal glow discharge in a Xe/Cl2 mixture in a narrow discharge tube

Electrical and optical characteristics of a subnormal glow discharge in a short (L=10 cm) discharge tube with an inner diameter of 5 mm are investigated. The dependences of the discharge current-voltage characteristic, the energy deposition in the discharge, the plasma spectral characteristics in the 130-to 350-nm wavelength range, the emission intensities of the XeCl(D-X) 236-nm and XeCl(B-X) 308-nm bands, and the total emission intensity in the range 180–340 nm on the pressure and composition of the Xe/Cl₂ mixture are studied. Two modes of glow discharge are shown to exist: the low-current mode at a discharge current of I _ch ≤2 mA and the high-current mode at I _ch >2 mA. The transition from one mode to another occurs in a stepwise manner. The increase in the chlorine content causes the discharge voltage and the energy deposition in the plasma to increase. At low pressures of the Xe/Cl₂ mixture (P≤0.7 kPa), stationary strata form in the cathode region. The lower the discharge current, the greater the volume occupied by the strata. This longitudinal discharge acts as a powerful source of continuous broadband emission in the range 180–340 nm, which forms due to overlapping the XeCl(D, B-X) and Cl ₂ ^* bands with edges at λ=236, 308, and 258 nm. The intensity of the 236-nm band is at most 20% of the total intensity of UV radiation. The maximum power of UV radiation (3 W at an efficiency of 8%) is attained at a xenon partial pressure of 250–320 Pa and a total pressure of the mixture of 2 kPa.     

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

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-H₂O mixture in the spectral range 130–190 nm. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 6, pp. 831–833, November–December, 2006.     

Continuous frequency tuning of a picosecond neodymium-glass laser in the UV and VUV

The results of an investigation of continuous frequency tuning of a neodymium laser in the UV and VUV ranges are reported. Generation of the sum frequency of second harmonic radiation and the radiation from a parametric light generator in the UV region (338–366 nm) is achieved. The optimal conditions for tuning UV radiation in the range 113.5–117.0 nm in third-harmonic generation processes in xenon and its mixtures with other gases are investigated. A third-harmonic generation efficiency of ∼5×10⁻⁴ and a tuning range >2600 cm⁻¹ are obtained in the VUV range investigated. Zh. Tekh. Fiz. 68, 82–89 (May 1998)     

Longitudinal rf discharge in Xe/Cl<Subscript>2</Subscript> mixtures

Results are presented from the studies of the electrical and emission characteristics of the low-temperature plasma of a longitudinal rf (f₀=1.76 MHz) discharge in Xe/Cl₂ mixtures at pressures of 100–800 Pa. The discharge was ignited in a cylindrical quartz tube with an inner diameter of 1.4 cm and interelectrode distance of 3.0 cm. The discharge emission within the spectral range of 190–670 nm is studied. The dynamics of the discharge current and discharge emission at different pressures and compositions of a Xe/Cl₂ mixture are investigated. It is shown that a discharge in a Xe/Cl₂ mixture acts as a wideband excimer-halogen lamp with a cylindrical output aperture emitting in the spectral range of 220–320 nm. The broad plasma emission spectrum is formed due to the overlap of the XeCl(D, B-X; B, C-A) bands that are broadened at low working-gas pressures. The composition of the working mixture is optimized to achieve the maximum power of the wideband UV plasma emission. Longitudinal rf discharges in low-pressure Xe/Cl₂ mixtures are of interest for developing small-size wideband (Δλ=220–450 nm) cylindrical-aperture lamps, whose efficiency can, on average, exceed the efficiency of conventional hydrogen lamps by more than one order of magnitude.     

Emission properties of a pulsed-periodic barrier discharge initiated in helium-iodine and argon-iodine mixtures

The subject of investigation is the emission properties of a pulsed-periodic barrier discharge initiated by submicrosecond pulses (f = 40–1000 Hz) in He-I₂ and Ar-I₂ mixtures. The investigation is carried out in the spectral range 200–400 nm at a pressure of the working medium of 1–100 kPa and an iodine partial pressure of 130–200 Pa. The dependence of UV emission from the plasma of the barrier discharge at the 342 nm I₂(D′ → A′) band and the iodine atom spectral line at 206.2 nm on the argon and helium partial pressures, excitation pulses repetition rate, and charging voltage of the capacitor of a short high-voltage pulse modulator is optimized. The contribution of the 206.2 nm I* spectral line to the UV emission of the barrier discharge is estimated.     

Source of far and vacuum ultraviolet radiation based on a transverse high-frequency discharge

We present the results of an investigation of a short-wavelength radiation source (Δλ = 130–350 nm) with excitation by a transverse high-frequency (f = 1.76 MHz) discharge based on a mixture of argon and chlorine (p = 100–500 Pa). We have studied the spectral characteristics of the plasma, the oscilloscope traces of the voltage, the current and emission of the discharge, the dependence of the power of the emission on the electrical power of the discharge, and also the pressure and partial composition of the Ar/Cl₂ mixture. The UV-VUV source emits in a system of broadened and overlapping ArCl(B/X), Cl₂(D′/A′), and Cl**₂ molecular bands. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 74, No. 5, pp. 648–651, September–October, 2007.     

An electric discharge emitter operating simultaneously in the 308 [XeCl(B-X)], 258 [Cl2(D′-A′)], 236 [XeCl(D-X)], 222 [KrCl(B-X)], 175 [ArCl(B-X)], and 160 [H2(B-X)] nm bands

An experiment to optimize an ultraviolet (UV)-vacuum ultraviolet (VUV) multiwave emitter using chlorine molecules and chlorides of heavy inert gases is reported. The emitting medium was an Ar-Kr-Cl₂ or an Ar-Kr-Xe-Cl₂ (HCl) mixture kept at a pressure ranging from 1 to 30 kPa. Excitation was effected by means of a transverse volume discharge with spark preionization. Emission spectra were examined. The dependences of the emission intensity on the total pressure of the medium, partial pressures of its components, charging voltage, and number of discharge pulses were studied. It is demonstrated that such a discharge emits simultaneously in the 308, 258, 236, 222, 175, and 160 nm bands due to the transitions XeCl(B-X), Cl₂(D′-A′), XeCl(D-X), KrCl(B-X), ArCl(B-X), and H₂(B-X), respectively. It was established that the respective intensities are close to each other if the partial pressures are as follows: P _Ar=10–20 kPa; P _{Kr, Xe}=0.4–0.6 kPa; P _Cl2=0.2–0.4 kPa, P _HCl=0.08 kPa, and P _H2=0.5–1.0 kPa. It was found that the addition of H₂ to the medium decreases the intensities of the excimer bands, increases the emission resource (to 10⁴ pulses or higher), and expands the operating wavelength range. The last-named effect is due to Lyman H₂ bands (at 158–161 nm).     

Spectroscopic investigation of the plasma of a high-current diffuse discharge in He/Ar/CF2Cl2(CCl4) mixtures

Survey emission spectra in the region of 190–600 nm and time and service-life characteristics of a transverse nanosecond discharge in He/Ar/CF₂Cl₂(CCl₄) mixtures at a pressure of 10–100 kPa are investigated. In the emission spectra, excited products of the decomposition of freons—C₂(A−X), CN(B−X), Cl ₂ ^* , C^*, Cl^*, and Cl^+*— and the emission of ArF at λ=193 nm are revealed. The emissions of Cl ₂ ^* at λ=258 nm and ArF at λ=193 nm were the most intense. The discharge in the He/Ar/CF₂Cl₂ mixture is a multiwave emission source with λ=258 nm Cl ₂ ^* 193 nm ArF, and probably, 175 nm Arcl. It is of interest for applications in UV-VUV-range pulse photometry. The duration of the emission on Cl ₂ ^* , ArF, ArI, ClI, and ClII transitions in the discharge in the Ar/CF₂Cl₂ mixture (P=10–20 kPa) was 200–300 nsec. With adding He and increasing pressure to 100 kPa the duration of the emission decreased by a factor of 1.5–2. The basic mechanisms of the formation of Cl₂, ArF, and CN(B) molecules in the transverse-discharge plasma are considered. Uzhgorod State University, 46, Pidgirna Str., Uzhgorod, 294000, Ukraine. Translated from Zhurnal. Prikladnoi Spektroskopii, Vol. 66, No. 2, pp. 241–246, March–April, 1999.     

Output characteristics and parameters of the plasma from a gas-discharge low-pressure ultraviolet source using helium-iodine and xenon-iodine mixtures

The output characteristics and parameters of the plasma of a powerful gas-discharge source of UV radiation are studied. The UV source uses He-I₂ and Xe-I₂ mixtures and is excited by a longitudinal glow discharge. The pressure of the gas mixtures is varied from 100 to 1500 Pa, and the discharge power falls into the range 15–250 W. The source (lamp) emits in the spectral interval 200–390 nm, which covers the spectral line of the iodine atom at 206.2 nm, the spectral band of XeI(B-X) with a maximum at 253 nm, and the spectral band of with a maximum at 342 nm. For He(Xe)-I₂ mixtures at a pressure of 800–1000 Pa (this pressure range is near-optimal according to our experimental data), the electron energy distribution functions and the electron kinetic coefficients as functions of parameter E/N (E is the electric field strength, and N is the particle concentration in the discharge) are calculated. The calculated plasma parameters are used in the qualitative analysis of key electronic processes in the plasma of an exciplex halogen UV source and will be subsequently employed in numerical simulation of the process kinetics and output characteristics of a UV source based on helium-iodine or xenon-iodine mixtures.     

RF exciplex halogen source of UV radiation on an argon-xenon-chlorine mixture

An exciplex halogen source of UV radiation that is excited by an rf transverse discharge is studied experimentally. The active medium of the source is an Ar-Xe-Cl₂ mixture kept at a low pressure (100–1000 Pa), and its working spectral range is 220–450 nm. The radiation spectrum contains 235 nm XeCl(D-X), 257 nm Cl₂(D′-A′), 306 nm XeCl(B-X), 390 nm XeCl(C-A), and 430 nm XeCl(B-A) lines. The results of optimization of the UV power as a function of the pressure, Ar-Xe-Cl₂ mixture composition, and excitation power are reported.     

Optical characteristics of a repetitively pulsed low-pressure discharge in a krypton-freon-12 mixture

Results of a study of the plasma radiation of a repetitively pulsed discharge in a Kr/CF₂ Cl₂ mixture (P≤1.5 kPa) in the 130–300 nm spectral range are presented. Spatial, spectral, and temporal characteristics of the discharge are studied in a spherical anode-plane cathode system, in which the repetitively pulsed mode is established due to the evolving instability of the glow discharge. It is demonstrated that a discharge of this type can be used for the development of a repetitively pulsed low-pressure bactericidal lamp which emits in the band system of KrCl (222 nm) and Cl₂ (257, 200 nm) in the 180–270 nm spectral range.     

Emission characteristics of a high-power glow discharge plasma in a mixture of inert gases with bromine and iodine vapor

The results of an investigation of the UV radiation from the plasma of a dc glow discharge in mixtures of inert gases with bromine and iodine molecules are presented. The current-voltage and spectral characteristics of a longitudinal glow discharge with a power of 10–250 W are studied. The power and the efficiency of the total UV radiation of the plasma, as well as the power of radiation at the spectral line of the iodine atom at 206.2 nm, are optimized as functions of the power deposited into the plasma and the composition of the gas mixture. In active media based on Kr-Br₂ mixtures, the molecular emission of the plasma was represented by bands at 207 (KrBr(B-X)) and 289 nm (Br ₂ ^* ), while, in He-Xe-I₂ mixtures, it was represented by bands at 253 (XeI(B-X)) and 342 nm (I₂).     

Optical characteristics of a transverse discharge in neon at atmospheric pressure

We present the results of investigation into radiation of a pulsed transverse discharge in neon at a pressure of 10–200 kPa. Survey spectra of plasma radiation, time characteristics of radiation, and the effect of small impurities of water vapors and air on the optical characteristics of a neon plasma were studied. We show that at a pressure of residual gases at a level of 10 Pa intense OH*, NO*, and N _* ² bands are observed in radiation of the plasma of a nanosecond transverse discharge in Ne against the background of continuous plasma radiation, and in the spectral region with λ>400 nm radiation was observed on the H_β 486.1 nm and NeI 585.3 nm lines, and (when P≥100 kPa) on the line at the 3s–3p-transitions of a Ne atom. The radiation intensity of the third continuum of neon increases with pressure and with energy contribution to plasma, with its maximum being located in the VUV spectral region (λ _max <200 nm). To whom correspondence should be adressed. Uzhgorod State University, 46, Pidgirna St., Uzhgorod, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 1, pp. 5–10, January–February, 1999.     

A Pulsed-Periodic, Low-Pressure Volume Discharge in Chlorine and in a Xenon/Chlorine Mixture

The electrical and optical characteristics of a self-initiated, low-pressure, pulsed-periodic discharge in chlorine and in a xenon/chlorine mixture are investigated. A volume discharge not bounded by dielectric walls was triggered in a spherical anode–plane cathode system of electrodes on supply of a constant positive-polarity voltage to the anode. The discharge existed in the form of a unit domain. The spatial, spectral (in the range 150–350 nm), and time characteristics (voltage, current, and photocurrent of total radiation of plasma in the spectral range 200–700 nm) of the volume discharge are investigated. Optimization of the pressure and of the structure of the working medium is carried out to obtain the maximum brightness of UV–VUV radiation of the bands of the Cl₂(D–A), Cl₂ ^**, and XeCl(D, B–X) molecules. The results obtained are of interest for being used in a pulsed-periodic, excimer-halogen low-pressure lamp.     

Multiwave electric-discharge radiator for the 175–258-nm region

The radiation spectra of plasma in the region of 130–350 nm and the intensities of the 175-nm ArCl, 193-nm ArF, and 258-nm Cl₂ bands produced in the transverse volume discharge on a mixture of Ar/CF₂Cl₂ = (1–15)/(0.008–0.150) kPa are investigated. The discharge is shown to be a multiwave source of UV-VUV radiation on transitions of ArCl, ArF, and Cl₂ molecules. The optimum content of Freon-12 molecules is 0.008–0.010 kPa and that of argon atoms 10–15 kPa. The ratio of the intensities of the ArCl (B-X) and ArF (B-X) bands is 10, which is approximately equal to the ratio of concentrations of [Cl⁻] and [F⁻] ions, which are formed in the reaction of dissociative electron attachment to CF₂Cl₂ molecules. The service life of a radiator with λ = 175 nm of ArCl on one mixture in a gas-static mode is not greater than 5·10³ pulses. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 67, No. 3, pp. 407–408, May–June, 2000.     

Enhancement of VUV Emission from a Coaxial Xenon Excimer Ultraviolet Lamp Driven by Distorted Bipolar Square Voltages

Enhancement of vacuum UV emission (172 nm VUV) from a coaxial xenon excimer UV lamp (EUV) driven by distorted 50 kHz bipolar square voltages, as compared to that by sinusoidal voltages, is investigated numerically in this paper. A self‐consistent radial one‐dimensional fluid model, taking into consideration non‐local electron energy balance, is employed to simulate the discharge physics and chemistry. The discharge is divided into two three‐period portions; these include: the pre‐discharge, the discharge (most intense at 172 nm VUV emission) and the post‐discharge periods. The results show that the efficiency of VUV emission using the distorted bipolar square voltages is much greater than when using sinusoidal voltages; this is attributed to two major mechanisms. The first is the much larger rate of change of the voltage in bipolar square voltages, in which only the electrons can efficiently absorb the power in a very short period of time. Energetic electrons then generate a higher concentration of metastable (and also excited dimer) xenon that is distributed more uniformly across the gap, for a longer period of time during the discharge process. The second is the comparably smaller amount of “wasted” power deposition by Xe⁺₂ in the post‐discharge period, as driven by distorted bipolar square voltages, because of the nearly vanishing gap voltage caused by the shielding effect resulting from accumulated charges on both dielectric surfaces (© 2011 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Ultraviolet radiation sources on (H2O,D2O) water vapor

Emission characteristics of ultraviolet (UV) radiation from water vapor (H₂O, D₂O, and a mixture of H₂O and D₂O vapors) excited by pulse-periodic discharges with open electrodes, as well as electrodes outside the discharge tube (capacitive discharge), are presented. Radiation is studied in a spectral range of 175–350 nm. The emission characteristics of a UV radiation source based on vapors of ordinary and “heavy” water, as well as the results of optimization of brightness of radiation bands from the OH and OD radicals as functions of pressure and the composition of the He-H₂O and He-D₂O mixtures, are reported.     

Glow-discharge-pumped broadband ultraviolet lamp

The optical characteristics of a UV broadband lamp that was excited by a longitudinal glow discharge and operated on Kr—Br₂—I₂, Xe—Br₂—I₂, and Kr—Xe—Br₂—I₂ mixtures are investigated. The interelectrode spacing in the lamp is 10 cm, the inner diameter of a discharge tube being 14 mm. The current-voltage characteristics, the emission spectra of the plasma, and the dependence of the intensity of spectral lines (the amplitude of radiation bands) on the power that was pumped into the plasma based on mixtures of various compositions and pressures, as well as the radiation power in the spectral range from 200 to 390 nm, are studied. __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 72, No. 6, pp. 840–842, November–December, 2005.     

Emission characteristics of a glow discharge in a mixture of heavy inert gases with iodine vapor

The results of a systematic investigation of the emission characteristics of a low-pressure UV excimer-halogen lamp pumped by a longitudinal dc glow discharge are presented. The discharge was initiated in mixtures of heavy inert gases with iodine vapor at a total pressure of 100–2000 Pa and a power deposited into the plasma of 10–100 W. Current-voltage characteristics of the glow discharge and emission spectra of the plasma in the region of 190–360 nm are studied. The radiation intensity at the resonance line of the iodine atom (206.2 nm) and the intensity at the peaks of the XeI(B-X) (253 nm) and I₂(B-X) (342 nm) emission bands are analyzed as functions of the pressure and partial composition of the mixtures of Ar, Kr, and Xe with iodine vapor, as well as the electric power of the glow discharge. The most efficient gas mixtures are determined for an electric-discharge UV iodine vapor lamp with continuous-wave emission and a long service life before a change of the mixture is required.