Influence of Ar, Ne, Xe, and CCl4 impurities on luminescence kinetics of Cd II ions (5s22D5/2-5p2P3/2 transition, λ = 441.6 nm) in He-Cd mixture

The luminescence kinetics of the Cd II ion at a wavelength of 441.6 nm has been studied experi-mentally in a high-pressure He-Cd mixture in the presence of Ar, Ne, Xe, and CCl₄ impurities. Cadmium ions were excited through the bombardment of a cadmium foil heated up to 240°C by a pulsed electron beam with an electron energy of 150 keV, a pulse duration of 3 ns, and a current of 500 A. The constants of collisional quenching of the Cd II 5s ^{2 2} D _5/2 level by Ar, Ne, and Xe atoms and CCl₄ molecules and the integral luminescence quenching constants of this level in the helium medium by these impurity gases have been determined. The constants of collisional quenching appeared to be 8.1 × 10⁻¹² (Ar), 1.2 × 10⁻¹² (Xe), 1.5 × 10⁻¹³ (Ne), and 1.8 × 10⁻¹⁰ cm³/s (CCl₄, for λ = 325 nm), while the integral constants were found to be, respectively, 4.1 × 10⁻¹¹, 3.4 × 10⁻¹¹, 9.5 × 10⁻¹², 1.4 × 10⁻⁹ cm³/s for Ar, Ne, Xe, and CCl₄ at a buffer gas pressure of 1 atm. Original Russian Text ? A.I. Miskevich, Liu Tao, 2009, published in Optika i Spektroskopiya, 2009, Vol. 107, No. 1, pp. 45–49.     

Investigation of the plasma of a 308-nm XeCl excimer light emitter based on an inert-gas-CCl4 mixture

Results are presented from optical measurements of the plasma of a transverse volume discharge in He(Ar)/Xe/CCl₄(HCl) mixtures (at pressures of P=10–100 kPa) that are used in excimer lamps emitting the XeCl 308-nm band. Emission spectra in different stages of the formation and degradation of the active medium, as well as temporal and resource characteristics of the emitter, are studied. The main products of decomposition of CCl₄ molecules that are detected by the plasma emission are C* atoms and C ₂ ^* and CN* radicals. The operating resource of the XeCl emitter is found to be (3–5)×10⁴ pulses and depends strongly on the pressure and composition of the active medium. The duration of the emission pulse at a wavelength of λ=308 nm is 200–300 ns.     

The viscosity and diffusion coefficients of eighteen binary gaseous systems

The paper reports accurate measurements of the viscosity of the eighteen binary gaseous systems: CF₄ with He, Ne, Ar, N₂, CO₂, CH₄; SF₆ with He, Ne, Ar, N₂, CO₂, CH₄, CF₄ and O₂ with He, Ne, CO₂, CF₄, SF₆. The measurements were performed in a high-precision oscillating-disk viscometer at atmospheric pressure and in the temperature range 25–200°C for the systems containing CH₄ or SF₆ and in the temperature range 25–400°C for the remainder. The reported viscosities are believed to be accurate to within ±0.1% at room temperature and to within ±0.2% at 400°C.It is shown that the data conform to the extended law of corresponding states developed by Kestin, Ro and Wakeham despite the complexity of some of the component gases. The standard deviation between the experimental values and those calculated from the law of corresponding states is only 0.3% which is commensurate with the uncertainty in the experimental results.Binary diffusion coefficients derived from the mixture viscosity data are also presented; they have an estimated uncertainty of ±2%.     

Performance study of the KrCl discharge laser with liquid chlorine donors

The effects of liquid chlorine donors (BCl₃ and CCl₄) on the output energy and the efficiency of a KrCl laser (222 nm) are investigated. Maximum laser energies of 230 mJ (3.3 J/l) in pulses of 16 ns duration were obtained from a 0.035% BCl₃/10.1% Kr/89.8% Ne mixture at a total pressure of 2600 Torr, and at a specific power loading of about 24 MW/cm³, a power conversion efficiency of 0.86% was obtained. These figures are reduced by a factor of two when He is used as buffer gas. Much weaker laser emissions were obtained when CCl₄ was used as a chlorine donor.     

Intensitäten myonischer röntgenlinien in argon,in wasserstoff plus argon und in argon plus neon

Muonic X-ray spectra from Ar and H₂ + Ar have been measured with a high-pressure gas target. Strong differences between the observed intensities of corresponding lines were found for the two cases. The results are compared with cascade calculations. The ratio between Coulomb capture in Ar and in Ne for an Ar-Ne mixture (atomic ratio 1:1) was determined to be 1.11±0.14.     

Nonresonant third order hyperpolarizability of rare gases and N2 determined by third harmonic generation

The third order hyperpolarizabikity γ⁽³⁾₁₁₁₁(-ω₃;ω₁,ω₁,ω₁) of the rare gases He, Ne, Ar, Kr, Xe and of N₂ are determined by third harmonic generation involving picosecond light pulses of a Nd-glass laser. The results are compared with reported experimental and theoretical values.     

Anisotropic intermolecular forces. I. Rare gas—hydrogen chloride systems

Anisotropic potential energy surfaces for Ne.HCl, Kr.HCl and Xe.HCl are obtained by simultaneous least squares fitting to molecular beam spectra and rotational line broadening cross sections. A revised potential surface for Ar.HCl is also presented. The potentials are all very similar in shape, with the absolute minimum at the linear rare gas-HCl geometry in each case. The absolute well depths and well depth anisotropies increase steadily as the size of the rare gas atom increases.

The potentials should be reliable in the region of the absolute minimum and on the repulsive wall of the potential. The molecular beam spectra for Ne.HCl can be fitted only by a potential with a significant secondary minimum at the linear Ne.Cl-H geometry, but the existing data for the more anisotropic Ar, Kr and Xe systems are not sensitive to the presence of this potential feature. The potential surfaces for these systems have accordingly been constrained to have a similar secondary minimum near the linear rare gas-ClH geometry. Experiments which would provide further information on the intermolecular potentials are suggested and predictions of the results are made.     

Zersetzung von CCl4 im HF-Niederdruckplasma für plasmachemisches Ätzen von Aluminium

After a brief summary of decomposition processes occuring in a plasma etching reactor investigations of CCl₄-decomposition by gaschromatography and time resolved emission spectroscopy are described. The decomposition takes place in a plasma tube with external r.f. electrodes. The qualitative identification of decomposition products of CCl₄ shows few main products only quite in contrast to plasma decomposition of hydrocarbons. These are CCl₄, Cl₂, C₂Cl₄, C₂Cl₆ and glow polymers. The dependence of the product distribution on power density and flow rate gives some hints for a rapid decomposition mechanism. The time resolved emission spectroscopy bases on a two channel method using a reference signal of an Ar line to eliminate the changing plasma conditions during the decomposition process. The limits of application of this method are discussed. Investigations of CCl-, Cl₂- and Cl-intensity-time-functions also reveal the existence of a the rapid decomposition mechanism for which a dissociative electron attachment is supported giving rate constants in the expected order of magnitude.     

Polarization effects in ionizing thermal energy collisions of laser-excited Ne(3p 3 D 3) atoms with Ar atoms

Using transverse and longitudinal excitation of a collimated metastable Ne(3s ³ P _2.0) beam with average velocities of 500, 800, and 1,200 m/s by means of a single mode dye laser on the²⁰Ne(3s ³ P ₂→3p ³ D ₃) transition, we have investigated ionizing collisions of polarized Ne(3s ³ P ₂) and Ne(3p ³ D ₃) atoms with Ar atoms. The product electrons were energy analyzed with high resolution (9–25 meV). The resulting Ne(3p ³ D ₃) electron spectra exhibit a strong dependence on the three types of laser polarization (π _∥,π_⊥, σ_?), chosen to prepare the excited atoms. In contrast, the Ne(3s ³ P ₂) spectra are only weakly dependent on polarization. Detailed model calculations have been carried out for the Ne(3p)+Ar cross sections, using computed excited-state potential curves, semi-empirical ionic potentials, and local autoionization width functions. A semiclassical closecoupling method is applied to describe the evolution of the polarized collision system in the coupled entrance channels. It is found that a single autoionization widthΓ(R) is not sufficient to describe the measured polarization effects properly. The dependence ofΓ on the initial and final state is expressed in terms of few reduced electronic transition matrix elements, which are determined by comparison of measured and calculated total cross sections and Ar⁺(² P _3/2)/Ar⁺(² P _1/2) branching ratios for ionizing collisions of the various Ne(3pJ=1,2,3) multiplet states with Ar. The matrix elements corresponding to Ar(3pσ)→Ne(2pσ) electron transfer during autoionization are found to dominate, but Ar(3pπ)→Ne(2pπ) transfer has also to be included. The resulting calculated electron spectra reproduce the measured polarization effects in a semi-quantitative way.     

Trends in atmospheric halogen containing gases since 2004

The changes in the atmospheric concentration of 16 halogenated gases in the atmosphere have been determined using measurements made by the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS). ACE-FTS has been used to measure the change in concentration between 2004 and 2010 of CCl₄, CF₄, CCl₃F (CFC-11), CCl₂F₂ (CFC-12), C₂Cl₃F₃ (CFC-113), CH₃Cl, ClONO₂, COF₂, COCl₂, COClF, CHF₂Cl (HCFC-22), CH₃CCl₂F (HCFC-141b), CH₃CClF₂ (HCFC-142b), HCl, HF and SF₆ between 30°N and 30°S. ACE-FTS measurements were compared to surface measurements made by the AGAGE network and output from the SLIMCAT three-dimensional (3-D) chemical transport model, which is constrained by similar surface data. ACE-FTS measurements of CFCs show declining trends which agree with both AGAGE and SLIMCAT values. There are problems with the ACE-FTS retrievals of CFC-113 and HCFCs, with work currently ongoing to correct these problems. At lower altitudes the volume mixing ratio (VMR) of these species increase with altitude. This is due to problems with the retrievals at high beta angle (the angle between the orbital plane and the Earth-Sun vector). Although some of the retrievals have problems, we are confident that the trends are generally reliable. The concentrations of HCFCs appear to be increasing with ACE-FTS, SLIMCAT and AGAGE all showing positive trends. ACE-FTS measurements of the decomposition products (COFCl and COCl₂) do not show any significant trends. SLIMCAT data show a negative trend for COFCl which corresponds to the decrease in CFC-11, its assumed major source, during this time. COF₂ measurements from ACE-FTS show an increasing trend, while SLIMCAT shows a decreasing trend again linked to its assumed production from CFCs. ClONO₂ is highly photosensitive, thus the ACE-FTS occultations have been divided into local morning and evening occultations. Evening measurements of ClONO₂ show a decreasing trend in VMR, while morning measurements show an increasing trend. The reason for this difference is not understood at this time. The SLIMCAT output used in this study was not saved as local sunrise and sunset: therefore, only 24 h mean fields are available for ClONO₂. These SLIMCAT data show a decreasing trend. SLIMCAT and ACE-FTS both show an increasing trend in the VMR of HF and a decreasing trend in the VMR of HCl. These results illustrate the success of the Montreal Protocol in reducing ozone depleting substances. The reduction in anthropogenic chlorine emissions has led to a decrease in the VMR of stratospheric HCl. The replacement of CFCs with HCFCs has led to an increase in the VMR of HF in the stratosphere. As chlorine-containing compounds continue to be phased out and replaced by fluorine-containing molecules, it is likely that total atmospheric fluorine will continue increasing in the near future.     

Pressure-broadened iodine-laser-amplifier kinetics and a comparison of diluent effectiveness

An iodine laser kinetic model is used to investigate inversion parameters in highly pressure-broadened amplifier systems using i-C₃F₇I as the parent compound and CO₂, N₂, He, Ne, Ar, Kr, and Xe as the diluent gas. These data are used to calculate a diluent merit function for diluent pressures P_d = 1–100 atm. The most effective choices for buffer gases are as follows: P_d ? 1 atm, CO₂; 1 atm ? P_d ? 10 atm, Ar; and P_d ? 10 atm, Ne.     

57Co implanted in reactive and non-reactive frozen gases

⁵⁷Co was implanted in different reactive and non reactive frozen gases like Ne, Ar, N₂, Xe, CH₄ and C₂H₄. Higher ionization states of Fe and cryochemical compounds are detected.     

Structural dynamics in quantum solids

Structural dynamics in semi-quantum and quantum solids (Ne, H₂ and D₂) is reported, and compared to results in classical solids such as Ar. The structural dynamics is driven by excitation of the lowest Rydberg state of the NO impurity. The resulting charge redistribution induces a local radial deformation of the medium (‘bubble’ formation) around the impurity. The steady-state spectroscopic signatures of this process are presented and analysed in the configuration coordinate model and harmonic approximation. Intermolecular potentials describing the impurity-medium interaction are obtained. The dynamics of ‘bubble’ formation and the ensuing medium response are probed in real-time by femtosecond pump-probe spectroscopy. In the very soft H₂ and D₂ environments, ‘bubble’ formation is a one-way process without recurrence of the cage motion and is complete in ∼1–2 ps. In the case of solid Ne, the dynamics are characterized by an initial expansion of the matrix cage around the impurity, followed by a low frequency recurrence. The results in solid Ne are complemented by preliminary molecular dynamics simulations. Overall the trend observed is that the expansion becomes slower in the sequence Ar–Ne–hydrogens, which is counterintuitive. This is discussed in terms of the quantum (delocalised) character of the lighter media, which introduces an additional microscopic friction. These results establish our experimental procedure based on the use of low-n Rydberg states as a novel method for probing structural and electronic solvation dynamics in non-polar media.     

H1+,H2+,H3+和He,Ne,Ar碰撞过程中的巴耳末系Hα,Hβ,Hγ发射

实验利用TN-1710光学多道分析系统(OMA),对H₁⁺,H₂⁺,H₃⁺和He,Ne,Ar碰撞过程中产生的巴耳末系H_α,H_β,H_γ发射进行了测量,入射离子H₁⁺,H₂⁺,H₃⁺的 关键词：     

Effect of buffer gas on the generation of eye-safe 1.54 μm radiation using the stimulated Raman scattering technique in CH4

Experimental results on the generation of 1.54 μm eye-safe radiation in pure CH₄, CH₄:He and CH₄:Ar mixtures pumped by the fundamental of an Nd:YAG laser, using the stimulated Raman scattering (SRS) technique, are described. A decrease in the energy conversion efficiency and degradation in the beam quality of S₁ was observed in pure CH₄ at high pump energies. This problem was overcome in CH₄:He and CH₄:Ar mixtures. Compared with the first Stokes (1.54 μm) energy conversion efficiency in pure CH₄, at a pump energy of 126 mJ, an enhancement of 50% in energy conversion efficiency was observed in the CH₄:Ar mixture (60% argon concentration) and as much as 100% in the CH₄:He mixture (60% helium concentration). The use of these buffer gas mixtures improved the spatial beam quality of the Stokes radiation considerably and also resulted in raising the pump threshold for optical breakdown of the Raman gain medium.     

NeMu* chemiluminescence: Radiolysis effects in gases

Near-infrared chemiluminescent emission from NeMu^*, the analogue of the Rydberg molecule NeH, has been observed in Ne, Ar, and Ne/Ar gas mixtures. Three temporally distinct features were observed: First, a large sharp emission peak at time zero, observed in all gases (Ne, He, N₂, Ar), is assigned to scintillation light during muon thermalization, probably caused by spur electrons. Second, a lowintensity broad region observed in all gases is attributed to e⁺ from muon decay. Finally, NeMu in 1–6 atm Ne with 0.1–2 torr Ar appeared as a high intensitydelayed emission, whose width and intensity depended linearly on the Ar concentration. Its wavelength spectrum from 680–960 nm was measured. Although questions remain as to how NeMu^* is formed, the precursor is likely Ne ⁺. Possible electron donors include metastable Ar^* (³ P ₂ or³ P ₀) and long-lived free (spur) electrons.Contribution from CEMAID, Center of Excellence in Molecular and Interfacial Dynamics; the financial support afforded by participation in Canada's National Centers of Excellence program is greatly appreciated.     

Cq+(q=1-4)与He,Ne,Ar碰撞的电子损失截面测量与研究

在中能区测量了C^q+(q=1-4)与He,Ne,Ar气体原子碰撞的电子损失截面,计算分析了入射离子损失两个电子与一个电子的总截面比 R₂₁. 单反应道分析无法完全解释所有实验结果,必须同时考虑入射离子的电子损失、电子俘获和靶原子电离各种出射道间的耦合作用. 对于不同靶原子的碰撞,入射离子损失一个电子和两个电子的速度阈值可以由屏蔽和反屏蔽理论解释. 然而,该理论不能完全解释截面比 R₂₁ 关键词： 离子-原子碰撞 截面 电子损失     

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.     

Near threshold effects in positron-atom (molecule) scattering

The energy dependence of the total cross-sections for ionization by positron impact has been measured for He, Ne, Ar, CO₂ and O₂. The interplay between this and other scattering channels has been investigated. The data for He, Ne and Ar has been interpreted using a combination ofR-matrix and threshold theories in the neighbourhood of the Ps formation threshold. In CO₂, an enhancement of the Ps formation probability is found when the remnant ion is left in an excited state. In O₂, structure has been observed which indicates channel-coupling with excitation to the Schumann-Runge continuum.     

An experimental investigation of the pressure and concentration dependence of muonic Coulomb capture and cascade in gases

Muonic Coulomb capture ratios and x-ray intensity patterns in four binary mixtures of the gases N₂, Ne, Ar, Kr, and Xe have been measured at three atomic ratios. An influence of the concentration has been established. The Lyman series intensity patterns of pure N₂, Ne, Ar, Kr, and Xe were measured at pressures between 0.4 and 51 bar and found to depend on the pressure. Possible explanations are discussed.