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1.
The production of excited xenon iodides and iodine dimers in the plasma of a longitudinal dc glow discharge is investigated. The discharge was ignited in iodine vapor and Xe/I2 mixtures at xenon pressures of P(Xe)=0.1–1.5 kPa and deposited powers of 10–100 W. The current-voltage characteristics of a glow discharge, the plasma emission spectra in the spectral range of 200–650 nm, and the intensities of spectral lines and molecular bands are studied as functions of the deposited power and the xenon partial pressure in a Xe/I2 mixture. It is found that the discharge plasma emits within the spectral range of 206–343 nm, which includes the 206-nm resonant line of atomic iodine and the XeI(B-X) 253-nm and I2(B-X) 343-nm molecular bands. The power deposited in the plasma and the xenon pressure P(Xe) are optimized to achieve the maximum UV emission intensity. The 7-W total UV power emitted from the entire surface of the cylindrical discharge tube is achieved with an efficiency of ≤5%. 相似文献
2.
Results are presented from the study of the electrical and optical characteristics of a transverse RF discharge in Xe/Cl2 mixtures at pressures of p≤400 Pa. The working mixture was excited by a modulated RF discharge (f=1.76 MHz) with a transverse electrode configuration (L≤17 cm). The emission spectrum in the spectral range of 210–600 nm and the waveforms of the discharge current, discharge voltage, and plasma emission intensity were investigated. The UV emission power from the discharge was studied as a function of the pressure and composition of a Xe/Cl2 mixture. It is shown that a discharge in a xenon-chlorine mixture acts as planar excimer-halogen lamp operating in the spectral range of 220–450 nm, which contains a system of overlapping XeCl(D, B-X; B, C-A) and Cl2(D′-A′) bands. Transverse RF discharges in Xe/Cl2 mixtures can be used to create a wideband lamp with two 50-cm2 planar apertures and the low circulation rate of the working mixture. 相似文献
3.
A. K. Shuaibov L. L. Shimon I. V. Shevera A. I. Dashchenko 《Plasma Physics Reports》2002,28(12):1060-1064
The spatial, electrical, and optical characteristics of a transverse glow discharge and a volume discharge with a spherical anode and plane cathode in low-pressure Xe/Cl2 mixtures are studied. It is shown that the transverse glow discharge in mixtures with a low chlorine content occupies most of the interelectrode gap and exists in the form of strata. As the total pressure (P≥300 Pa) and the partial chlorine pressure (P(Cl2)≥80 Pa) increase, a solitary plasma domain with a volume of 1–2 cm3 forms in the discharge gap. It acts as a selective source of UV radiation in the XeCl(D-X) 236-nm, Cl2 (D′-A′) 257-nm, and XeCl(B-X) 308-nm bands. In certain Xe/Cl2 mixtures, plasma self-oscillations in the frequency range 1–100 kHz are observed. The current of a low-pressure volume discharge with a spherical anode and plane cathode and the emission from it have both a dc and an ac component. The pressure and composition of the working mixture, as well as the average current of the volume discharge are optimized to attain the maximum emission intensity of the XeCl(D,B-X) bands. Low-pressure volume discharges in xenon/chlorine mixtures can be used as active media in low-pressure large-aperture planar or cylindrical excimer-halogen lamps emitting modulated or repetitive pulsed UV radiation. 相似文献
4.
V. P. Zimakov V. A. Kuznetsov N. G. Solovyov A. N. Shemyakin A. O. Shilov M. Yu. Yakimov 《Plasma Physics Reports》2016,42(1):68-73
The interaction of 1.07-μm laser radiation with plasma of a continuous optical discharge (COD) in xenon and argon at a pressure of p = 3–25 bar and temperature of T = 15 kK has been studied. The threshold power required to sustain COD is found to decrease with increasing gas pressure to P t < 30 W in xenon at p > 20 bar and to P t < 350 W in argon at p > 15 bar. This effect is explained by an increase in the coefficient of laser radiation absorption to 20?25 cm–1 in Xe and 1?2 cm–1 in Ar due to electronic transitions between the broadened excited atomic levels. The COD characteristics also depend on the laser beam refraction in plasma. This effect can be partially compensated by a tighter focusing of the laser beam. COD is applied as a broadband light source with a high spectral brightness. 相似文献
5.
The aim of this work is to highlight, through numerical modeling, the chemical and the electrical characteristics of xenon chloride mixture in XeCl* (308 nm) excimer lamp created by a dielectric barrier discharge. A temporal model, based on the Xe/Cl2 mixture chemistry, the circuit and the Boltzmann equations, is constructed. The effects of operating voltage, Cl2 percentage in the Xe/Cl2 gas mixture, dielectric capacitance, as well as gas pressure on the 308-nm photon generation, under typical experimental operating conditions, have been investigated and discussed. The importance of charged and excited species, including the major electronic and ionic processes, is also demonstrated. The present calculations show clearly that the model predicts the optimal operating conditions and describes the electrical and chemical properties of the XeCl* exciplex lamp. 相似文献
6.
S. V. Avtaeva E. A. Sosnin B. Saghi V. A. Panarin B. Rahmani 《Plasma Physics Reports》2013,39(9):768-778
The influence of the chlorine concentration on the radiation efficiency of coaxial exciplex lamps (excilamps) excited by a dielectric barrier discharge (DBD) in binary Xe-Cl2 mixtures at pressures of 240–250 Torr is investigated experimentally and theoretically. The experiments were carried out at Cl2 concentrations in the range of 0.01–1%. The DBD characteristics were calculated in the framework of a one-dimensional hydrodynamic model at Cl2 concentrations in the range of 0.1–5%. It is found that the radiation intensities of the emission bands of Xe*2(172 nm) and XeCl* (308 nm) are comparable when the chlorine concentration in the mixture is in the range of 0.01–0.1%. In this case, in the mixture, the radiation intensity of the Xe*2 molecule rapidly decreases with increasing Cl2 concentration and, at a chlorine concentration of ≥0.2%, the radiation of the B → X band of XeCl* molecules with a peak at 308 nm dominates in the discharge radiation. The radiation efficiency of this band reaches its maximum value at chlorine concentrations in the range of 0.4–0.5%. The calculated efficiencies of DBD radiation exceed those obtained experimentally. This is due to limitations of the one-dimensional model, which assumes the discharge to be uniform in the transverse direction, whereas the actual excilamp discharge is highly inhomogeneous. The influence of the chlorine concentration on the properties of the DBD plasma in binary Xe-Cl2 mixtures is studied numerically. It is shown that an increase in the Cl2 concentration in the mixture leads to the attachment of electrons to chlorine atoms and a decrease in the electron density and discharge conductivity. As a result, the electric field and the voltage drop across the discharge gap increase, which, in turn, leads to an increase in the average electron energy and the probability of dissociation of Cl2 molecules and ionization of Xe atoms and Cl2 molecules. The total energy deposited in the discharge rises with increasing chlorine concentration due to an increase in the power spent on the heating of positive and negative ions. The power dissipated by electrons decreases with increasing chlorine concentration in the working mixture. Recommendations on the choice of the chlorine content in the mixture for reducing the intensity of VUV radiation of the second continuum of the Xe*2 excimer without a substantial decrease in the excilamp efficiency are formulated. 相似文献
7.
Investigation of the mechanism for rapid heating of nitrogen and air in gas discharges 总被引:1,自引:0,他引:1
N. A. Popov 《Plasma Physics Reports》2001,27(10):886-896
A rapid heating of nitrogen-oxygen mixtures excited by gas discharges is investigated numerically with allowance for the following main processes: the reactions of predissociation of highly excited electronic states of oxygen molecules (which are populated via electron impact or via the quenching of the excited states of N2 molecules), the reactions of quenching of the excited atoms O(1 D) by nitrogen molecules, the VT relaxation reactions, etc. The calculated results adequately describe available experimental data on the dynamics of air heating in gas-discharge plasmas. It is shown that, over a broad range of values of the reduced electric field E/N, gas heating is maintained by a fixed fraction of the discharge power that is expended on the excitation of the electronic degrees of freedom of molecules (for discharges in air, ηE?28%). The lower the oxygen content of the mixture, the smaller the quantity ηE. The question of a rapid heating of nitrogen with a small admixture of oxygen is discussed. 相似文献
8.
S. N. Polukhin A. M. Dzhamankulov A. E. Gurei V. Ya. Nikulin E. N. Peregudova P. V. Silin 《Plasma Physics Reports》2016,42(12):1127-1133
The velocities of the plasma jets formed from Ne, N2, Ar, and Xe gases in plasma focus facilities were determined by means of laser-optical shadowgraphy of the shock waves generated at the jet leading edge. In spite of the almost tenfold ratio between the atomic weights of these gases, the outflow velocities of the plasma jets formed in experiments with these gases differ by less than twice, in the range of (0.7–1.1) × 107 cm/s under similar discharge conditions. The energies of the jet ions were found to vary from 0.7 keV for nitrogen to 4 keV for xenon. 相似文献
9.
The parameters of a repetitive volume discharge in CF2Cl2 (CFC-12) and its mixtures with argon at pressures of P(CF2Cl2)≤0.4 kPa and P(Ar)≤1.2 kPa are studied. The discharge was ignited in an electrode system consisting of a spherical anode and a plane cathode by applying a dc voltage Uch≤1 kV to the anode. The electrical and optical characteristics of a volume discharge (such as the current-voltage characteristics; the plasma emission spectra; and the waveforms of the discharge voltage, the discharge current, and the total intensity of plasma emission) are investigated. It is found that, by shunting the discharge gap with a pulsed capacitor with a capacitance of C0≤3.5 nF, it is possible to control the amplitude and duration of the discharge current pulses, as well as the characteristics of the pulsed plasma emission. The increase in the capacitance C0 from 20 to 3500 pF leads to a significant increase in the amplitude and duration of the discharge current pulses, whereas the pulse repetition rate decreases from 70 to 3 kHz. The glow discharge exists in the form of a domain with a height of up to 3 cm and diameter of 0.5–3.0 cm. The results obtained can be used to design an untriggered repetitive germicidal lamp emitting in the Cl2(257/200 nm) and ArCl (175 nm) molecular bands and to develop plasmachemical methods for depositing amorphous fluorocarbon and chlorocarbon films. 相似文献
10.
Catherine Tetreau Yves Blouquit Eugene Novikov Eric Quiniou Daniel Lavalette 《Biophysical journal》2004,86(1):435-447
Evidence for ligand migration toward the xenon-binding cavities in myoglobin comes from a number of laser photolysis studies of MbO2 including mutants and from cryo- and time-resolved crystallography of MbCO. To explore ligand migration in greater detail, we investigated the rebinding kinetics of both MbO2 and MbCO under a xenon partial pressure ranging from 1 to 16 atm over the temperature range (293–77 K). Below 180 K xenon affects to a significant, but minor, extent the thermodynamic parameters for rebinding from the primary docking site in each Mb taxonomic substate. Above 200 K the ligand migrates to the proximal Xe1 site but when the latter is occupied by xenon a new kinetic process appears. It is attributed to rebinding from transient docking sites located on the path between the primary and the secondary docking site of both ligands. Ligand escape exhibits a more complicated pattern than expected. At room temperature O2 and CO escape appears to take place exclusively from the primary site. In contrast, at T ≈ 250 K, roughly 50% of the CO molecules that have escaped from the protein originate from the Xe1 secondary site. 相似文献
11.
N. A. Dyatko Yu. Z. Ionikh A. V. Meshchanov A. P. Napartovich 《Plasma Physics Reports》2018,44(3):334-344
The memory effect (the dependence of the dynamic breakdown voltage U b on the time interval τ between voltage pulses) in pulse-periodic discharges in pure argon and the Ar + 1%N2 mixture was studied experimentally. The discharge was ignited in a 2.8-cm-diameter tube with an interelectrode distance of 75 cm. The measurements were performed at gas pressures of P = 1, 2, and 5 Torr and discharge currents in a steady stage of the discharge of I = 20 and 56 mA. Breakdown was produced by applying positive-polarity voltage pulses, the time interval between pulses being in the range of τ = 0.5–40 ms. In this range of τ values, a local maximum (the anomalous memory effect) was observed in the dependence U b (τ). It is shown that addition of nitrogen to argon substantially narrows the range of τ values at which this effect takes place. To analyze the measurement results, the plasma parameters in a steady-state discharge (in both pure argon and the Ar + 1%N2 mixture) and its afterglow were calculated for the given experimental conditions. Analysis of the experimental data shows that the influence of the nitrogen admixture on the shape of the dependence U b (τ) is, to a large extent, caused by the change in the decay rate of the argon afterglow plasma in the presence of a nitrogen admixture. 相似文献
12.
《Biophysical journal》2022,121(23):4635-4643
Protein interiors contain void space that can bind small gas molecules. Determination of gas pathways and kinetics in proteins has been an intriguing and challenging task. Here, we combined computational methods and the hyperpolarized xenon-129 chemical exchange saturation transfer (hyper-CEST) NMR technique to investigate xenon (Xe) exchange kinetics in maltose-binding protein (MBP). A salt bridge ~9 Å from the Xe-binding site formed upon maltose binding and slowed the Xe exchange rate, leading to a hyper-CEST 129Xe signal from maltose-bound MBP. Xe dissociation occurred faster than dissociation of the salt bridge, as shown by 13C NMR spectroscopy and variable-B1 hyper-CEST experiments. “Xe flooding” molecular dynamics simulations identified a surface hydrophobic site, V23, that has good Xe binding affinity. Mutations at this site confirmed its role as a secondary exchange pathway in modulating Xe diffusion. This shows the possibility for site-specifically controlling xenon protein-solvent exchange. Analysis of the available MBP structures suggests a biological role of MBP’s large hydrophobic cavity to accommodate structural changes associated with ligand binding and protein-protein interactions. 相似文献
13.
G. S. Voronov G. M. Batanov M. S. Berezhetsky Yu. F. Bondar’ V. D. Borzosekov I. Yu. Vaphin D. G. Vasilkov S. E. Grebenshchikov I. A. Grishina L. V. Kolik E. M. Konchekov N. F. Larionova A. A. Letunov V. P. Logvinenko D. V. Malakhov A. I. Meshcheryakov E. I. Pleshkov A. E. Petrov K. A. Sarksyan S. N. Satunin N. N. Skvortsova V. D. Stepakhin N. K. Kharchev Yu. V. Khol’nov O. I. Fedyanin V. A. Tsygankov V. A. Kurnaev I. V. Vizgalov V. A. Urusov A. Antipenkov R. Pearce L. Worth 《Plasma Physics Reports》2012,38(9):708-717
Results of testing of a possible method for location of water microleakages in the cooling system of the first wall and vacuum chamber of ITER are presented. The method consists in spectroscopic detection of the emission lines of atoms and ions of the Xe additive dissolved in water. These lines are excited when the water with dissolved Xe contacts the plasma. The high electron cyclotron resonance heating (ECRH) power deposited in a relatively small plasma volume in the L-2M stellarator (P = 0.5 MW, V = 0.24 m3, and the specific heating power ??2 MW/m3) makes it possible to achieve plasma parameters close to those in the edge plasma of ITER for different operating modes, including the H-mode with an edge transport barrier. In test experiments, several lines of Xe ions were revealed suitable for detection of xenon in plasma with parameters close to those in the edge plasma of ITER at leakage rates at a level of ??10?6 Pa m3 s?1 and spatial resolution of ??0.5 cm. 相似文献
14.
15.
Abstract The thermodynamic stability of clathrate hydrates I and II encaging xenon or argon has been investigated by examining the temperature dependence of the dissociation pressure. The evaluation of the stability is made based on the generalized van der Waals and Platteeuw theory developed by Tanaka and Kiyohara [J. Chem. Phys. 98, 4098 (1993)]. In the new treatment, the free energy of formation of hydrates in equilibrium with ice is calculated by taking the coupling of the host lattice vibrations with guests into consideration. The predicted dissociation pressures of Xe and Ar hydrates agree well with experiments in higher temperature range. A poor agreement between experiment and calculation for Ar clathrate hydrate at low temperature is improved by the use of a quantum mechanical partition function for a harmonic oscillator in evaluating the free energy difference between ice and empty hydrate. 相似文献
16.
V. N. Babichev A. V. Dem’yanov N. A. Dyatko A. F. Pal’ A. N. Starostin A. V. Filippov 《Plasma Physics Reports》2017,43(5):515-532
Emission of xenon excited by a 120-keV electron beam at gas pressures of 100, 200, 500, and 760 Torr nm was studied experimentally and theoretically. More than 30 spectral lines were identified in the wavelength range of 750–1000 nm. A self-consistent kinetic model is developed to calculate the emission intensity of xenon atoms in the near IR range. The model includes balance equations for the number densities of electrons, ions and excimer molecules; equations for the populations of electron levels; and the Boltzmann equation for the low-energy part of the electron energy distribution function with a source of slow electrons. Excitation and ionization rates of xenon by the beam electrons and the energy spectrum of slow electrons are calculated by the Monte Carlo method. It is shown that, under these conditions, the main mechanism of xenon atom excitation is dissociative recombination of Xe3 + ions. 相似文献
17.
Crystal structure and physical properties of the new 2D polymeric compound bis(1,5-diaminotetrazole)dichlorocopper(II) 总被引:1,自引:0,他引:1
Pavel N. Gaponik Alexander S. Lyakhov Oleg A. Ivashkevich Jan Reedijk 《Inorganica chimica acta》2005,358(8):2549-2557
Two new coordination complexes, Cu(datz)Cl2 and Cu(datz)2Cl2, where datz is 1,5-diaminotetrazole, have been obtained by the reaction of copper(II) chloride with datz. For one of them, Cu(datz)2Cl2, the crystal structure, magnetic susceptibility and thermal properties are reported. For the other compound only spectroscopic and thermal properties are presented. In Cu(datz)2Cl2 the Cu atoms were found to be octahedrally coordinated. Equatorial positions are occupied by two chloride anions and two tetrazole ligands via their N4 donor atoms. Surprisingly, the amino groups at the N1 atom of the tetrazole ring of nearby molecules are in axial positions. Each copper atom is linked with four others through the datz molecules to form 2D polymeric networks parallel to the yz plane. Magnetic properties of Cu(datz)2Cl2 and the data of quantum-chemical calculations of molecular electrostatic potential and energies of hydronation of nitrogen atoms for datz using MP2/6-31G* and B3LYP/6-31G* levels of theory are in agreement with the structural data obtained. 相似文献
18.
The photochemical reactions between OCSe and Cl2 or Br2 isolated in solid argon at cryogenic temperatures were studied by means of FTIR spectroscopy. The OCSe?Cl2, OCSe?Br2 and SeCO?Br2 molecular complexes were identified by the shifts of the OCSe IR absorptions on complexation, and also by the IR activation of the Cl-Cl vibration in the first adduct. The hitherto unknown ClC(O)SeCl and BrC(O)SeBr molecules were formed upon UV-Vis irradiation of the matrix. The former was firstly obtained in the anti form, and subsequently photochemically transformed into the thermodynamically more stable syn conformation, while only the syn rotamer of BrC(O)SeBr was produced. The characterization of the novel species through their IR spectra was supported by the comparison with results of quantum chemical calculations. 相似文献
19.
The properties of noble gas systems can be greatly extended by heterogeneous mixtures of elements. The geometrical structures and energies of mixed Ar–Kr–Xe clusters were investigated using ternary Lennard-Jones (TLJ) potential. For the Ar19Kr n Xe19, Ar19Kr19Xe n , and Ar n Kr19Xe19 (n?=?0–17) clusters investigated, the results show that only two minimum energy configurations exist, i.e., polytetrahedron and six-fold pancake. The inner core of all these clusters is composed mainly of Ar atoms, and Kr and Xe atoms are distributed on the surface with well mixed pattern for polytetrahedral and segregate pattern for six-fold pancake configurations. The relative stability property of Ar–Kr–Xe clusters with a certain composition is discussed. Moreover, the role of heterogeneity on the strain was investigated, and reduced strain energies in Ar–Kr–Xe clusters were studied to find possible ways of reducing strain. The results showed that the strain energies were affected mainly by Ar–Ar, Ar–Kr, and Xe–Xe bonds. Figure
Investigation of the structures of Ar19Kr n Xe19, Ar19Kr19Xe n , and Ar n Kr19Xe19 (n?=?0–17) clusters reveal the existence of only exist two minimum energy configurations, i.e., polytetrahedron and six-fold pancake. Furthermore, reduced strain energies in Ar–Kr–Xe clusters were studied for the possible ways of reducing strain. 相似文献
20.
V. E. Levashov K. N. Mednikov A. S. Pirozhkov E. N. Ragozin 《Plasma Physics Reports》2004,30(2):149-153
The interaction of a noble gas jet (Xe, Kr, He) with a laser plasma at a distance of ~1 cm from a solid target (Mg, (CH2)n, LiF, or CF4) was studied for the first time. The line spectra that were excited in the course of charge exchange of multicharged ions with noble gas atoms in the interaction region were recorded. A clean (debris-free) soft X-ray source excited by laser pulses focused into a xenon jet was designed and investigated. 相似文献