Characteristics of negative corona discharge in the working media of atmospheric-pressure nitrogen lasers

We present the results of investigations of the electrical and optical characteristics of a negative-polarity corona discharge excited in systems of “pins-mesh” and “pins-plane” electrodes in a He/N₂ mixture at atmospheric pressure. In order that such a corona discharge could be applied in systems of electric pumping of the working medium of atmospheric-pressure N₂-lasers, the optimum conditions should be: the total pressure of the mixture ≤150 kPa and the nitrogen pressure ≤5 kPa. Uzhgorod State University, 46, Pidgirna St., Uzhgorod, 290000, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 6, pp. 837–840, November–December, 1997.     

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.     

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.     

Plasma emission spectra of working media of KrC1 and XeC1 electric-discharge lasers

Results of investigations of survey spectra of plasma emission of the working media of inert-gas-chloride electric-discharge lasers in the 200–600 nm range are reported. In the UV spectra, FeI lines, which are of interest for lasing with optical pumping of iron vapors by excimer molecules, were observed. In the visible spectrum, a number of HeI, KrI, and XeII lines are suggested for determination of electron density and investigation of the discharge instability on XeCl^* and KrCl^* molecules. Uzhgorod State University, 46, Pidgirna St., Uzhgorod, 294000, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 523–527, July–August, 1997.     

Laser on nitrogen-electronegative gas mixtures, pumped by inductive energy storage generator: Experiment and theoretical model

The advantages of inductive energy storage (IES) generators for increasing the pulse energy, power, and duration for nitrogen laser pumped by self-sustained transverse discharge have been experimentally demonstrated. A theoretical model is developed and the operation of IES-pumped laser on nitrogen-electronegative gas mixtures is numerically simulated. It is shown experimentally and theoretically that, adding electronegative gases, one can control the pulse shape of lasing on the C³II _u -B³II _g transition in nitrogen. The increase in the electric field strength in the laser gap in N₂-NF₃ and N₂-SF₆ mixtures produced 337.1-nm laser pulses consisting of two spaced peaks and 40–50-ns pulses close to rectangular. The increase in the laser active volume to 6 l (discharge cross section to 6×10 cm²) in N₂–SF₆ mixtures made it possible to obtain the maximum output energy (Q=110 mJ) and UV power (P _las =6 MW). In N₂-NF₃ mixtures, the laser pulse duration was up to ∼100 ns with an energy up to Q=30 mJ.     

A rapid-scan device for the determination of spectral line profiles in pulsed discharges

The results of a time-of-flight experiment are presented, in which the total cross-sections for 2–400 eV positrons on H₂, D₂, N₂, and CO were measured. Paper F7 presented at 3rd Internat'l. Conf. Positron Annihilation. Otaniemi, Finland (August 1973).     

The influence of vibrational excitation on the burning voltage of a pulsed electric discharge in HF laser working media

The burning voltages of an intermediate pressure self-sustained volume discharge (SSVD) in SF₆ and SF₆-C₂H₆ mixtures irradiated by a 10.6 μm pulse TEA CO₂ laser, have been measured on varying the laser fluences over a wide range. The delay between the voltage application and the laser pulse onset is 4 μs, and the laser pulse lasts ∼3 μs. The considerable rise observed in the discharge voltages with increasing absorbed specific laser radiation energy, is due to electron attachment to vibrationally excited molecules of SF₆. Different processes of relaxation of the vibrational energy stored in SF₆ molecules are analyzed and the relevant characteristic times are numerically assessed. The gas heating process owing to vibration-translation energy exchange is qualitatively described in terms of the “thermal explosion”. The relation between the “explosion” and delay times determines the peculiarities of electron attachment to vibrationally excited SF₆ molecules. The burning voltages of a submicrosecond non-irradiated SSVD in the above-mentioned media versus the specific electric energy deposited are also measured. They are compared to those of a laser-illuminated SSVD at commensurable specific laser energy depositions. It is concluded that electron attachment to the discharge-produced vibrationally excited SF₆ molecules is not capable of noticeably affecting the discharge voltages of a submicrosecond non-irradiated SSVD. PACS 42.55 Ks; 52.80     

Luminescence of mercurylike impurities in single-crystal CdWO4 compounds

The processes of crystallization by the method of liquid epitaxy are studied for the first time for single-crystal films of CdWO₄ doped with the mercurylike ions Bi³⁺ and Pb²⁺, which can be used as thin-film components of combined scintillators for monitoring α- and β-activities. It is shown that in comparison with their solidcrystal analogs, the special features of these films consist in a longwave shift of the integral luminescence spectrum that is caused by high concentrations of the radiating complexes (V_Cd-WO₆) with hv_max=2.05–2.15 eV and the “distorted” complexes (WO₆)^* in them. It is found that in the case of luminescence of single-crystal films CdWO₄:Pb, radiation of mercurylike centers (PbO₆) prevails with hv_max=2.87 eV, while in luminescence of CdWO4, radiation of centers (BiO₆) with hv_max=2.16 eV and of complexes (V_Cd-WO₆). Institute of Applied Physics, Iv. Franko Lvov State University, 49, General Chuprynka St., Lvov, 290044, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 65, No. 2, pp. 211–215, March–April, 1998.     

Multiwave excimer lamps using XeF/XeCl/KrF/KrCl molecules

Results are presented of an investigation of the spectral and temporal characteristics of an electricdischarge excimer lamp emitting simultaneously on the 351 nm XeF, 308 nm XeCl, 249 nm KrF, and 222 nm KrCl transitions. The He/Kr/Xe/SF₆/HCl working mixtures were excited in a transverse discharge with ultraviolet spark preionization at a total pressure of 25–100 kPa. In order to obtain the same brightness the concentration ratio [Kr]/[Xe] for the excimer molecular transitions was 8/0.8 kPa, and that for the halogen-containing molecules was [SF₆]/[HCl][=[0.06–0.12]/[0.08–0.16] kPa. The duration of the radiation pulses for the excimer molecular transitions at atmospheric pressure was 100–200 ns and when the total mixture pressure was reduced to 250 kPa, this was doubled or trebled. The service life of the spontaneous radiation for B-X transitions in excimer molecules was 10⁵ pulses. Zh. Tekh. Fiz. 68, 64–67 (December 1998)     

Observation of simultaneous ν1(SF6) + ν3(NF3) and ν2(SF6) + ν3(NF3) transitions enhanced by the resonance dipole-dipole interaction with the ν1 + ν3 and ν2 + ν3 states of the SF6 molecule

IR spectra of the solution of SF₆ molecules in liquid NF₃ at 84 K have been recorded. In a solvent transmission window of 1500–1750 cm⁻¹, two wide absorption bands with pronounced peaks in the high-frequency part are observed. The profile of these bands is explained by the influence of the resonance dipole-dipole (RDD) interaction of the states of the simultaneous transition ν₁(SF₆) + ν₃(NF₃) and ν₂(SF₆) + ν₃(NF₃) with the states (ν₁ + ν₃) and (ν₂ + ν₃) of the SF₆ molecules, respectively. The use of three isotopic modifications ³²SF₆, ³³SF₆, and ³⁴SF₆ has allowed us to vary the resonance detuning and thus to change the strength of the RDD interaction. With the liquid near the melting point being represented as a close-packed cubic crystal, the profile was calculated and its spectral characteristics were determined. The frequencies of the main peaks coincide with the experimental values accurate to the error.     

电激励脉冲HF激光SF_6/C_2H_6工作气体的放电特性

研究了电激励脉冲HF激光工作介质SF6/C2H6混合气体的放电特性。通过对放电等离子体荧光图像和放电波形的测量,分析比较了不同条件下放电稳定性、剩余电压、能量沉积效率等特性参数的变化情况。实验结果表明:混合气体的放电过程存在主放电、剩余电压维持和电弧放电3个阶段,各阶段的放电特性有所差异;提高充电电压有利于放电能量的有效沉积,也会使不稳定的电弧放电提前;增加C2H6原子分数能起到抑制电弧放电的作用;混合气体总压的增加会导致剩余电压的提高以及辉光放电的能量沉积效率的降低;最佳的能量沉积出现在电弧放电阶段与辉光放电阶段即将融合的临界状态。     

Study of ion–solvent interactions and activation energy of LiBr in DMSO,H<Subscript>2</Subscript>O and DMSO–H<Subscript>2</Subscript>O mixtures at various temperatures

The Jones–Dole B coefficients of the electrolyte Lithium bromide (LiBr), reference salts tetra butyl ammonium tetra phenyl borate (BU₄NBPh₄), tetra butyl ammonium bromide (BU₄NBr), and potassium chloride (KCl) in dimethylsulfoxide (DMSO), water, and DMSO–water mixtures were obtained at different temperatures range from 25 to 45 °C For this, the relative viscosities were measured for Lithium bromide (LiBr) and reference salts in DMSO, water, and DMSO–water mixtures at above-mentioned temperatures. The B coefficients of these electrolytes were behaved as structure makers in DMSO, while in H₂O and DMSO–H₂O mixtures, the B-coefficient values were less positive showing the weak structure-making effect. Ionic viscosity B coefficients allow us to assess the behavior of ions in the solvent mixtures. In this study it was observed that all the values of ionic B coefficient of (Li⁺) were positive and small showing the weak structure-making effects. It was also observed that Br⁻ ions maintain negative B coefficient values in all DMSO–H₂O mixtures, except in 60% DMSO mole fraction. From this it can be concluded that Br⁻ ion behaved as a structure breaker in water and in all DMSO–H₂O mixtures except in 60% DMSO mole fraction mixtures. The low B _± values of alkali metal ions and Br⁻ ions in water are due to the breakdown of the tetrahedral structural of water and the formation of strongly structured solvated ion. It is also observed that the values of the energy of activation of the flow for LiBr are greater in DMSO–water mixtures and in pure water than in DMSO. This may be due the presence of a network of hydrogen bonds which cause the hindrance in the flow of the solution of LiBr in DMSO–water mixtures and in pure water than in DMSO.     

The exclusive reaction of pion quasi-elastic knockout from nucleon <Emphasis Type="Italic">p(e,e′ π)B</Emphasis> to various states of the final baryon-spectator <Emphasis Type="Italic">B</Emphasis> and the quark models for the pion cloud of nucleon

The pion momentum distributions (MDs) in four channels of virtual decay p→B+π, B = N, Δ, N _1/2-(1535), N _1/2+(1440) are calculated in two models, the microscopic model of ³ P ₀ scalar q−q fluctuation with the pion as a composite q−q-system and the chiral semi-microscopic model of πq interaction with the pion as a structureless Goldstone boson. The results of the above models are similar for the baryon states B = N, Δ, N _1/2-(1535) but are rather different for the Roper resonance N _1/2+(1440) which corresponds to excitation of two oscillator quanta in the nucleon. The experimental investigation of pion MDs by means of the reaction of quasi-elastic knockout of pion by an electron of a few GeV energy p(e, e′ π)B may be very suitable for Jefferson Laboratory, Virginia (JLab).     

Determination of Trace Mercury by Solid Substrate-Room Temperature Phosphorimetry Quenching Method Based on Catalytic Effect of Hg2+on Formation of the Ion Association Complex [Sn(XO)6]4+·[(Fin)4]

A new method for the determination of trace mercury by solid substrate-room temperature phosphorimetry (SS-RTP) quenching method has been established. In glycine-HCl buffer solution, xylenol orange (XO) can react with Sn⁴⁺ to form the complex [Sn(XO)₆]⁴⁺. [Sn(XO)₆]⁴⁺ can interact with Fin⁻ (fluorescein anion) to form the ion associate [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which can emit strong and stable room temperature phosphorescence (RTP) on polyamide membrane (PAM). Hg²⁺ can catalyze H₂O₂ oxidizing the ion association complex [Sn(XO)₆]⁴⁺·[(Fin)₄]⁻, which causes the RTP to quench. The ΔIp value is directly proportional to the concentration of Hg²⁺ in the range of 0.016–1.6 fg spot⁻¹ (corresponding concentration: 0.040–4.0 pg ml⁻¹, 0.40 μl spot⁻¹), and the regression equation of working cure is ΔIp=10.03+83.15 m Hg²⁺ (fg spot⁻¹), (r=0.9987, n=6) and the detection limit (LD) is 3.6 ag spot⁻¹(corresponding concentration: 9.0×10^–15 g ml⁻¹, the sample volume: 0.4 μl). This simple, rapid, accurate method is of high selectivity and good repeatability, and it has been successfully applied to the determination of trace mercury in real samples. The reaction mechanism for catalyzing H₂O₂ oxidizing the ion association complex ([Sn(XO)₆]⁴⁺·[(Fin)₄]⁻) SS-RTP quenching method to determine trace mercury is also discussed.     

Electrical and optical characterization of pulsed plasma of N<Subscript>2</Subscript>–H<Subscript>2</Subscript>

This paper considers the electrical and optical characterization of glow discharge pulsed plasma in N₂/H₂ gas mixtures at a pressures range between 0.5 and 4.0 Torr and discharge current between 0.2 and 0.6 A. Electron temperature and ion density measurements were performed employing a double Langmuir probe. They were found to increase rapidly as the H₂ percentage in the mixture was increased up to 20%. This increase slows down as the H₂ percentage in the gas mixture was increased above 20% at the same pressure. Emission spectroscopy was employed to observe emission from the pulsed plasma of a steady-state electric discharge. The discharge mainly emits within the range 280–500 nm. The emission consists of N₂ (C-X) 316, 336, 358 nm narrow peaks and a broad band with a maximum at λ_max = 427 nm. Also lines of N₂, N₂ ⁺ and NH excited states were observed. All lines and bands have their maximum intensity at the discharge current of 0.417 A. The intensities of the main bands and spectral lines are determined as functions of the total pressure and discharge current. Agreement with other theoretical and experimental groups was established.     

First-principle study on the structural and electronic properties of H2S and SO2 adsorption on Pd-doped MoS2 monolayer

The partial discharge in SF₆-insulated equipment produces characteristic decomposition products: SO₂ and H₂S. The characteristic decomposition products vastly speed up the process of discharge faults. Based on density functional theory (DFT) calculation, single layer Pd-doped MoS₂ (Pd-MoS₂) is adopted as the adsorbent to adsorb SO₂ and H₂S to ensure the operational stability of SF₆-insulated equipment. The adsorption energy, charge transfer and structure parameters of SF₆, H₂S, and SO₂ adsorption on the Pd-MoS₂ monolayer are analysed to find the most stable adsorption structure. The molecular orbital theory, total density of states and partial density of states are studied to analyse the adsorption mechanism. The results show that Pd-MoS₂ adsorbent possesses high catalytic activity and excellent adsorption performance to H₂S and SO₂ by strong chemical adsorption. This study is of great significance to ensure the operational stability of SF6-insulated equipment by removing these characteristic decomposition products.     

Importance of pre-ionisation for the non-chain discharge-pumped HF laser

The importance of pre-ionisation for the non-chain discharge-pumped HF laser is studied through experiments on an X-ray photo-triggered laser using mixtures of Ne, SF₆, and ethane. The discharge dynamic in Ne/SF₆ mixtures or pure SF₆, as well as the stabilisation effect induced by C₂H₆ and consequences for the laser performance, are investigated for pre-ionisation electron density values, n_eo, ranging from 10⁶ cm^-3 up to 10⁹ cm^-3, as well as for the so-called discharge self-breakdown mode. Without ethane, the minimum n_eo value which is needed to complete 100% homogeneous charge deposition in the plasma is a very sharply increasing function of the SF₆ pressure. This hinders performance optimisation when the molecule used to react with F-atoms, for instance H₂, has no effect on the discharge dynamic. The minimum ethane partial pressure that is needed to stabilise the discharge depends on n_eo, the pumping pulse duration, the deposited electric charge, and the SF₆ pressure. Discharges in Ne/SF₆ can be much more efficiently stabilised by addition of a small amount of ethane than by an increase of n_eo. A pre-ionisation density as low as 10⁶ cm^-3 is sufficient to achieve the maximum laser energy value, but total suppression of the pre-ionisation has a detrimental effect on the active medium homogeneity. Received: 30 May 2000 / Revised version: 9 October 2000 / Published online: 9 February 2001     

Modeling of a pump discharge for chemical non-chain-reaction HF lasers

A model of a pump discharge for a chemicalHF laser in aNe/SF ₆/C₂H₆ gaseous mixture excited with a self-maintained discharge is described. The results of numerical modeling are presented. It is shown that the density of positive and negative ions in the current maximum of such discharges exceeds the electron density by two orders of magnitude. Institute of High-Current Electronics of the Siberian Branch of the Russian Academy of Sciences. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 63–66, August, 1999.     

Optoacoustic gas analyzer based on a13C16O2 laser for multicomponent pollution of air

A computer-aided optoacoustic gas analyzer based on a continuous¹³C¹⁶C₂ laser for multicomponent pollution of atmospheric air is described. The analyzer has the ability to detect absorption of radiation by detected substances at the level of ∼1·10⁻⁹ cm⁻¹ at a time resolution of 30 sec. Results of an experiment on simultaneous detection of H₂O, CO₂, NO₂, NH₃, HNO₃, OCS, and C₂H₄ in the atmospheric air using 40 laser lines are presented. B. I. Stepanov Institute of Physics, National Academy of Sciences of Belarus, 68, F. Skorina Ave., Minsk, 220072, Belarus. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 66, No. 3, pp. 345–350, May–June, 1999.     

Radiation-induced radical ions in calcium sulfite

We have used EPR to study the effect of γ radiation on calcium sulfite. We have observed and identified the radiation-induced radical ions SO ₂ ⁻ (iso) with g = 2.0055 and SO ₂ ⁻ (orth-1) with g₁ = 2.0093, g₂ = 2.0051, g₃ = 2.0020, identical to the initial and thermally induced SO ₂ ⁻ respectively, SO ₃ ⁻ (iso) with g = 2.0031 and SO ₃ ⁻ (axial) with g_⊥ = 2.0040, g_∥ = 2.0023, identical to mechanically induced SO ₃ ⁻ . We have established the participation of radiation-induced radical ions SO ₃ ⁻ in formation of post-radiation SO ₂ ⁻ . __________ Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 73, No. 4, pp. 467–472, July–August, 2006.