Spectral anomalies of the light-induced drift of rubidium atoms caused by the velocity dependence of transport collision frequencies

The spectral features of the light-induced drift (LID) velocity for rubidium atoms (⁸⁵Rb and ⁸⁷Rb) in an argon buffer medium and in binary buffer mixtures of noble gases (Ne + Ar, Ne + Kr, Ne + Xe, He + Ar, He + Kr, and He + Xe) have been investigated theoretically. A strong temperature dependence of the spectral shape of the LID signal for Rb atoms in an Ar atmosphere is predicted in the temperature range 450 K < T < 800 K. It is shown that the anomalous LID of Rb atoms in binary buffer mixtures of noble gases can be observed at almost any temperature (including the room one) depending on the fractions of neon or helium in these mixtures. The results obtained enable a highly accurate testing of the interatomic interaction potentials used to calculate the drift velocity for anomalous LID in LID experiments.     

Viscosity of Lennard-Jones fluid: Integral equation method

One of the most useful models to study the real systems is the Lennard-Jones (LJ) potential which has an attractive and repulsive part. In this work we use this potential model and examine the viscosity of one-component LJ fluids and LJ binary fluid mixtures. For this purpose, we apply the integral equation method and solve numerically the Ornstein-Zernike (OZ) integral equation by using the mean spherical approximation (MSA). Thus, we obtain the pair correlation functions to calculate the viscosity of these fluids. Finally, we compare our results with computer simulation results and the available experimental data and illustrate the ability of the LJ model to predict the results.     

Isotopic thermal diffusion factors of the noble gases

A new set of isotopic thermal diffusion factors for Ar, Kr and Xe is reported. The data have been obtained from thermal diffusion column measurements in a column previously calibrated with Ne gas, and complete the α_T data for the binary mixtures of noble gases given previously. The results lead to the conclusion that the thermal diffusion properties of the noble gases and their mixtures are well described by the law of corresponding states first proposed by Kestin, Ro and Wakeham. It is also concluded that the calibration technique used makes the thermal diffusion column a valuable instrument for the determination of the thermal diffusion factors of isotopic and non-isotopic dilute gas mixtures.     

Electrical Conductivity of Noble Gases at High Pressures

We present experimental and theoretical results for the electrical conductivity of noble gases (He, Ne, Ar, Kr, Xe) up to high pressures where a transition from nonmetallic to metallic‐like conductivities occurs. In addition, we show the behavior of the thermal conductivity and thermopower for xenon as an example. The experiments were performed using explosively driven shock waves. Different geometries allow to probe various parameter regions up to several megabars. Besides single‐shock experiments along the principal Hugoniot curve, also multiple‐shock experiments were performed which follow almost an isentrope. The theoretical calculations were performed within a partially ionized plasma model. The composition is determined by solving a system of mass action laws. The transport coefficients are calculated within linear response theory taking into account the relevant scattering mechanisms of electrons at different ion species, atoms, and other electrons. The general trends of the experimental results can be explained within this theoretical approach. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

Test of the Duh-Haymet-Henderson theory for mixtures: cavity correlation functions and excess volumes

The accuracy of the Duh-Haymet-Henderson (DHH) integral equation theory for predicting the cavity correlation functions of mixtures has been tested by comparison with molecular simulations. We have compared the cavity correlation functions, internal energies, and pressures computed for Lennard-Jones model mixtures of Ar/Kr, Ar/Ne, and Ar/Xe with these same quantities computed from the DHH theory and also, for reference, the Percus-Yevick (PY) integral equation theory. We found that DHH gave much better accuracy than PY at high densities. At low densities DHH and PY give essentially identical predictions. We have computed excess volumes for Ar/Kr mixtures at two pressures (10 and 20?MPa) at 132.32?K, for which experimentally derived data are available. The DHH theory predicts the correct trends and is quantitatively more accurate than the PY theory for predicting the excess volumes. We have tested the local optimality of the DHH theory for pure fluids by adding two adjustable parameters to the DHH bridge function expression to see if it is possible to improve the DHH predictions of the cavity correlation function empirically, holding the form of the bridge function constant. We found that no single set of adjustable parameter values could improve the accuracy of DHH over multiple different isotherms. Furthermore, perturbing DHH leads to a decrease in accuracy of the predictions of both the pressure and energy, although small improvements in the cavity correlation functions were achieved. Thus, the DHH theory is locally optimal, given the form of the bridge function.     

Population processes in high-pressure inert-gas-mixture lasers

Working-level-population processes are analyzed on the basis of detailed investigations of the amplitude-time structure of the laser and spontaneous emission following a pulsed electric discharge in the mixtures He + R (R = Ar, Kr, Xe), Ar + Xe. Account is taken in the analysis of excitation by electrons (direct and stepwise) and of population as a result of relaxation processes (collisions of second kind with electrons; radiative cascades, recombination processes; collisions with the atoms of the working and buffer gases; excitation transfer from helium molecules). It is concluded that under optimum efficiency conditions inversion is produced in the lasers considered as a result of direct electron collision with the working atoms (Ar, Kr, Xe), which are in the ground state.Translated from Lazernye Sistemy, pp. 15–34, 1982.     

Calculation of the pressure shift of the positronium hyperfine interval

We calculate the fractional positronium hyperfine pressure shift Δ(T) using a quantum mechanical thermal averaging and obtain for Δ(293 K)(±30%) in He, Ne, Ar, Kr, Xe, N₂ and SF₆ respectively; (-0.15, -0.34, -0.96, -1.41, -1.85, -1.12, -1.1) × 10^-7/torr (0°C).     

Electrical and optical characteristics of inert-gas plasmas in spatially nonuniform electrode systems

The characteristics of unipolar and bipolar corona discharges in mixtures He/Ar/Kr, He/Ar/Xe, and He/Kr/Xe at atmosphere pressures in electrode systems of the point-plane and point-grid type distributed along the length. It is shown that bipolar corona discharges can be used in the preionization systems of high-pressure inert-gas-atom lasers. The spectral characteristics of the plasma are investigated, and the dependence of the relative intensity of the radiation in the lines Ar(4s-4p), Kr(5s-5p), and Xe(6s-6p) on the composition and pressure of the working mixtures and on the value of the corona discharge current are determined. Zh. Tekh. Fiz. 67, 15–18 (November 1997)     

产生惰性气体高价离子的新方法

此文介绍了一种产生惰性气体高价离子的新方法。在飞行时间质谱仪（ＴＯＦ－ＭＳ）上，把聚焦后的３０８ｎｍ激光掠射到不锈钢栅网上，产生超短脉冲的电子束，利用这种电子束来轰击惰性气体（Ｈｅ，Ｎｅ，Ａｒ，Ｋｒ，Ｘｅ），产生高价离子，并给出了这些离子的飞行时间质谱。这些高价离子可能是电子逐次电离气体原子产生的。这种方法可作为飞行时间质谱的一种理想的“软电离”的“点”离子源     

Editorial

A high resolution electron spectroscopy technique is used to study the autoionization of noble gases excited by fast neutral noble gas atoms with 80–600 eV kinetic energy. The energy and notation of the excited states is determined by considering the proper quantum defects in the Rydberg series. The doubly excited states prevail over the singly excited ones. Like and unlike colliding pairs are studied and various excitation processes are suggested for the HeKr, ArKr and ArXe systems.     

Vacuum ultraviolet spectra of heteronuclear dimers of inert gases in a direct-current discharge

The emission bands appearing near the resonance lines of Kr and Xe in the spectra of the gas-discharge plasma of binary Xe-X and Kr-Y mixtures (X is He, Ne, Ar, or Kr; Y is He, Ne, or Ar) are experimentally studied. It is concluded that the emission bands investigated are related to electronic transitions in hetero-nuclear dimers. The mechanisms of formation of the spectra under study are analyzed.     

Simulation of above-threshold ionization experiments using the strong-field approximation

Recently performed above-threshold ionization (ATI) experiments with noble gases allow the determination of the complete energy and angular distribution of the emitted photoelectrons. In order to simulate such experiments, we have generalized our numerical code for the calculation of ATI spectra in order to achieve a realistic simulation of ATI of the noble gases He, Ne, Ar, Kr, and Xe. Our method is based on an improved version of the strong-field approximation and includes focal averaging. A semiclassical analysis of the dependence of the cutoff law on the photoelectron emission angle is presented. The effects of channel closings on the high-energy spectra are analyzed.     

The effect of fluorocarbon gases on sonoluminescence: a failure of the electrical hypothesis

Ultrasonic irradiation of solutions containing volatile organometallic complexes results in intense emission from excited-state metal atoms. We have determined the effect of dissolved gases (Xe, Kr, Ar, Ne, He, CF₄, C₂F₆, CO, N₂) on the intensity of the sonoluminescence resulting from ultrasonic irradiation of silicone oil solutions of Cr(CO)₆. This provides a well-defined, spectrally resolved probe of sonoluminescence with emission resulting from a single species, the chromium atom excited states. As predicted by the hot-spot, thermal mechanisms of sonoluminescence, the intensity of excited-state Cr emission decreases with increasing thermal conductivity of the noble gases. The intensity of sonoluminescence increases with increasing γ (i.e. C_p/C_v), which is also in accord with a thermal mechanism. Sonoluminescence is substantially diminished by the addition of even small amounts (≈ 1%) of CF₄ or C₂F₆, even though they are capable of supporting electrical discharge. This is in agreement with a thermal mechanism, but is in direct conflict with electrical theories of sonoluminescence.     

Kr/Xe气体在塑料闪烁体表面的吸附与扩散行为研究

采用基于Compass力场的分子动力学(MD)方法,研究了惰性气体氙(Xe)和氪(Kr)在塑料闪烁体(聚乙烯基对甲苯)的平整和粗糙表面的吸附和扩散行为.由惰性气体吸附曲线的均方根位移(MSD),得到了Xe/Kr气体在聚乙烯基对甲苯表面的扩散系数.研究结果表明,Kr/Xe气体均被稳定地吸附在塑料闪烁体表面,其稳定性随着温度的升高而增加,Xe分子的吸附性强于Kr分子. Kr/Xe气体在聚乙烯基对甲苯表面具有较强的扩散性能,扩散深度随着温度与厚度的增加而增加,最大为22.865?,Kr分子扩散能力强于Xe分子.基底粗糙表面增加了两种惰性气体分子的吸附和扩散.     

Density dependence of the structural properties and translational diffusion of carbonyl sulphide diluted in monoatomic solvents. A molecular dynamics investigation

We report a study of the intermolecular structure and translational diffusion of Carbonyl Sulphide (OCS) dissolved in Ne and Kr, using Molecular Dynamics (MD) simulation. The mixtures have been investigated at different thermodynamic points corresponding to the pressures between 5 and 300 bar and at temperature of 293 K. The computations were carried out with effective site-site Lennard-Jones (LJ) potential model. We found that the proposed model predicts a non-linear T-shaped dimer structure of Ne-OCS and Kr-OCS in accordance with experiment. The study of the local structure of the solute-solvents was based upon the calculated relevant pair distribution functions. The self-diffusion coefficients of both components in the mixtures were calculated and compared. The results show a non-linear dependence in the density range under study. In the case of Kr as solvent and at the whole density range under study, the diffusion coefficient of Kr appears to be larger than that of OCS. This unusual result on the solute-solvent diffusivities (m_OCS < m_Kr, D_OCS < D_Kr) has been further discussed in terms of the microscopic dynamics of the species.     

Leading relativistic correction to the interaction coefficients between atoms and molecules using Borel integral II

Lower and upper bounds to the leading relativistic correction to the interaction coefficients between H, He, Ne, Kr, and Xe atoms, and H₂ and N₂ molecules have been evaluated by using Borel integral for the dynamic dipole polarizability. Our results for these bounds are in agreement with others.     

Viscosity and thermal conductivity from non-conformal potentials. I Theory and application to noble gases

The approximate non-conformal (ANC) theory provides effective spherical potentials for more than 40 pure real gases and predicts many of their binary mixtures in the case of the second volumetric virial coefficients B(T). Each substance is characterized by only three parameters; besides the usual minimum energy ε and its corresponding position r _m, a softness parameter s is proposed to take account of the form of a particular potential. In this work the ANC theory is extended to take account of viscosity η(T) and thermal conductivity λ(T) coefficients in dilute gases. Very simple expressions are derived to calculate the appropriate collision integral Ω as a function of temperature and in terms of the parameters ε, r _m and s, using a reference collision integral Ω₀(T). The theory is successfully applied to the noble gases Ne, Ar, Kr and Xe, with deviations from experiment for η(T) and λ(T) within experimental uncertainties. In the case of Ne, the ANC potential obtained here reproduces simultaneously η(T) and λ(T) as well as B(T) within experimental uncertainty, using a single set of parameters. A prediction for the radon gas is proposed.     

Third virial coefficients of Ar+Kr and Kr+Xe mixtures

Third virial coefficients, calculated from the potentials of Lee, Henderson and Barker are given for Ar+Kr and Kr+Xe mixtures. The contributions of the three-body triple-dipole, dipole-dipole-quadrupole, and fourth-order triple-dipole interactions are included.     

惰性气体黏度的剩余熵标度模型

黏度是能源、动力、化工等系统设计分析中常用的重要物性参数.本文探讨了5种惰性气体(He、Ne、Ar、Kr、Xe)气相和超临界黏度的计算,以实际气体与同温度稀薄气体的黏度之比作为无量纲对比黏度,发现5种惰性气体的无量纲对比黏度与剩余熵之间满足同一单值函数关系,据此建立了惰性气体的气相和超临界黏度模型,其中稀薄气体黏度关联...     

Excitation of iron atoms in a plasma of excimer emitters under transverse-discharge pumping

The optical characteristics of a transverse-discharge plasma initiated in He/Xe(Kr)/HCl(CF₂Cl₂) mixtures were studied. The mixtures contained a small amount of iron vapor due to metal cathode erosion. The iron atoms were shown to be excited by the spontaneous emission of KrCl (λ=22 nm) and XeCl (λ=308 nm) molecules in a nanosecond transverse discharge.