Argon Xenon Research Articles

Collision-induced absorption in Ar-Xe: a comparative study of empirical and ab initio interaction potentials and electric dipole moments

Empirical Barker-Fisher-Watts and modified Tang-Toennies potential energy curves are obtained through fit to experimental vibrational transition energies for argon–argon, xenon–xenon, and argon–xenon pairs. The potentials are tested against experimental thermophysical and transport properties, and agreement is observed. Also, an interaction-induced electric dipole moment curve for the argon–xenon pair is determined through a fit to experimental spectral moments for collision-induced absorption. The argon–xenon potentials and dipole are tested in a complete quantum dynamical calculation of the collision-induced absorption profiles, which can be compared with a laboratory measurement. This provides further analysis of the accuracy of the empirical argon–xenon data, as calculations of absorption profiles are highly sensitive to the input of molecular data.

Ion dynamics in capacitively coupled argon–xenon discharges

An argon–xenon (Ar/Xe) plasma is used as a model system for complex plasmas. Based on this system, symmetric low-pressure capacitively coupled radiofrequency discharges are examined utilizing particle-in-cell/Monte Carlo collisions simulations. In addition to the simulation, an analytical energy balance model fed with the simulation data is applied to analyze the findings further. This work focuses on investigating the ion dynamics in a plasma with two ion species and a gas mixture as background. By varying the gas composition and driving voltage of the single-frequency discharge, fundamental mechanics of the discharge, such as the evolution of the plasma density and the energy dispersion, are discussed. Thereby, close attention is paid to these measures’ influence on the ion energy distribution functions at the electrode surfaces. The results show that both the gas composition and the driving voltage can significantly impact the ion dynamics. The mixing ratio of argon to xenon allows for shifting the distribution function for one ion species from collisionless to collision dominated. The mixing ratio serves as a control parameter for the ion flux and the impingement energy of ions at the surfaces. Additionally, a synergy effect between the ionization of argon and the ionization of xenon is found and discussed.

A new method to measure the concentration of argon–xenon gas mixture

A new method to measure the concentration of argon–xenon gas mixture

Highly efficient photon detection systems for noble liquid detectors based on perovskite quantum dots

Wavelength shifting photon detection systems (PDS) are the critical functioning components in noble liquid detectors used for high energy physics (HEP) experiments and dark matter search. The vacuum ultraviolet (VUV) scintillation light emitted by these Liquid argon (LAr) and liquid Xenon (LXe) detectors are shifted to higher wavelengths resulting in its efficient detection using the state-of-the-art photodetectors such as silicon photomultipliers (SiPM). The currently used organic wavelength shifting materials [such as 1,1,4,4 Tetraphenyl Butadiene (TPB)] have several disadvantages and are unreliable for longterm use. In this study, we demonstrate the application of the inorganic perovskite cesium lead bromide (CsPbBr3) quantum dots (QDs) as highly efficient wavelength shifters. The absolute photoluminescence quantum yield of the PDS fabricated using these QDs exceeds 70%. CsPbBr3-based PDS demonstrated an enhancement in the SiPM signal enhancement by up to 3 times when compared to a 3 µm-thick TPB-based PDS. The emission spectrum from the QDs was optimized to match the highest quantum efficiency region of the SiPMs. In addition, we have demonstrated the deposition of the QD-based wavelength shifting material on a large area PDS substrate using low capital cost and widely scalable solution-based techniques providing a pathway appropriate for meter-scale PDS fabrication and widespread use for other wavelength shifting applications.

Argon–Xenon Laser-Sustained Plasma Using 1-kW Diode Laser

Argon–xenon laser-sustained plasma (LSP) was generated using a 1-kW class diode laser. At a total pressure of 1 MPa, the threshold laser power of the xenon–argon LSP was higher than that of the pure xenon LSP, whereas the former was lower than the latter at a total pressure of 0.1 MPa because of homonuclear associative ionization effect. The minimum xenon pressure ratio at which LSP could be generated was 7.67% at a total filled pressure of 3 MPa. The maximum value of fractional absorption was 37.7% at a total filled pressure of 0.5 MPa.

Mathematical simulation of kinetic processes in moving irradiated by neutrons gas medium containing uranium nanoparticles

The theoretical model and program complex for mathematical simulation of processes of transformation the nuclear energy into optical radiation energy was developed. The model includes the equations of gas dynamics, as well as the equations describing the kinetic processes in the non-equilibrium plasma excited by uranium fission fragments.The kinetic processes in the moving irradiated by neutrons argon-xenon gas medium containing uranium nanoparticles was investigated.The space-time evolution of this medium in nonuniform changing over time neutron field was studied. The space-time evolution of the gas parameters (temperature, density, velocity, pressure), as well as the distribution of the concentration of uranium nanoparticles under different initial velocities of the gas and the size of the nanoparticles was calculated.The amplifying properties of a laser-active space-nonuniform nuclear-excited moving argon–xenon medium, containing uranium nanoparticles and irradiated by neutrons, was studied.

Modeling of direct conversion of the uranium fission product kinetic energy to laser radiation energy in an argon–xenon dusty plasma with uranium nanoparticles

The process of direct conversion of the uranium fission product kinetic energy to laser radiation (LR) energy in a moving argon–xenon laser-active gas medium containing uranium nanoparticles has been investigated.A model and a method have been developed to solve numerically equations for the model of direct uranium fission product kinetic energy conversion to laser radiation energy in such medium. Spatiotemporal evolutions of the uranium nanoparticle concentration distribution have been calculated for different gas flow velocities and uranium nanoparticle sizes.Kinetic processes in a moving argon–xenon laser-active gas medium containing uranium nanoparticles have been studied.It is the first time that amplifying properties of a laser-active spatially heterogeneous nuclear-excited moving argon–xenon medium, containing uranium nanoparticles and irradiated by neutrons, have been studied. As shown by the investigation results, the LR intensity amplification may be sevenfold and more in steady-state conditions. Such a high value makes it possible to state that this medium can be used not only in a nuclear-pumped laser but also in the mode of a single-pass nuclear-pumped laser amplifier.

Laser absorption spectroscopy for xenon monitoring in the cover gas of sodium cooled fast reactors

Xenon is a fission product of uranium that must be monitored on line and in real time in the cover gas of a sodium cooled fast neutron reactor (SFR) for safety reasons. In this paper, tunable diode laser absorption spectroscopy is applied to quantify low concentrations of natural xenon in argon. Optical detection is carried out at 12 145 cm−1 (823 nm) from the 6s[3/2]02 Xe electronic metastable state, populated in a low pressure DC glow discharge. Optimal discharge parameters (110 Pa, 1.3 W) were experimentally determined to maximize the laser absorption signal. Measurement stability, argon pressure spectral broadening, isotope quantification, and linearity of the optical measurement with respect to the xenon concentration in the gas sample were carefully investigated. Under optimized experimental conditions, the detection limit of xenon over argon molar ratio is estimated as 60 ± 10 parts per billion at 1 Hz, corresponding to a xenon number density of 1.6 × 109 atoms.cm−3 along the laser beam.

Attenuation of vacuum ultraviolet light in liquid argon

The transmission of liquid argon has been measured, wavelength resolved, for a wavelength interval from 118 to 250 nm. The wavelength dependent attenuation length is presented for pure argon. It is shown that no universal wavelength independent attenuation length can be assigned to liquid argon for its own fluorescence light due to the interplay between the wavelength dependent emission and absorption. A decreasing transmission is observed below 130 nm in both chemically cleaned and distilled liquid argon and assigned to absorption by the analogue of the first argon excimer continuum. For not perfectly cleaned argon a strong influence of impurities on the transmission is observed. Two strong absorption bands at 126.5 and 141.0 nm with approximately 2 and 4 nm width, respectively, are assigned to traces of xenon in argon. A broad absorption region below 180 nm is found for unpurified argon and tentatively attributed to the presence of water in the argon sample.

Mixture Working Gases in Thermoacoustic Engines for Different Applications

For working gases in thermoacoustic engines, the most important characteristics are low Prandtl number and high ratio of specific heats. These properties change a lot with pressure for some gases, which makes selecting a working gas under high pressure different from that under normal pressure. This article presents optimization calculations for gas mixtures under different pressures. Results show that binary mixtures of helium and xenon can reach the lowest Prandtl number and highest ratio of specific heats when the pressure is lower than 4.5MPa. When the pressure is higher than 4.5MPa, however, the lowest Prandtl number is obtained with a mixture of helium and krypton. It is found that ternary mixtures may be better working gases than binary mixtures in thermoacoustic engines, especially under high pressure. For example, a helium–argon–xenon ternary mixture can be used to obtain a relatively low Prandtl number and high ratio of specific heats. In addition, this article shows that mixtures containing carbon dioxide and other gases can also result in useful working gases. This suggests that it is possible to replace the expensive xenon gas with cheap carbon dioxide for some applications. Finally, the effect of temperature on the Prandtl number, the ratio of specific heats, and the thermal penetration depth is also studied, and a more reasonable construction of the thermoacoutic couple is presented. The results of this study should be useful for helping select working gases in thermoacoustic engines for different applications and design goals.

New way to build a high-performance gas-dynamic interface to produce and transport ions into a mass analyzer

A new way to form the supersonic gas flow for producing and transportation the ions under study without their significant loss into a mass analyzer is described. The main objective of the paper is to show a relevancy of the approach. For both the argon–xenon gas mixture and atmospheric air fed as supersonic flow and in an effusion mode, the distributions of density for the recorded ions across their moving direction as well as other experimental dependencies were measured. The results of these measurements may be explained by formation of a supersonic gas flow with a divergence which is significantly smaller than the predicted one by “evident” model. The data analysis shows that only very small fraction of the ions formed inside the supersonic gas flow is recorded by the existing system. To eliminate these difficulties, it is suggested to turn the ions from the gas flow in the direction orthogonal to the initial one using two-grid electrostatic mirror before inserting the ions into the time-of-flight mass spectrometer with orthogonal injection of ions. The computer simulation has shown efficiency of such an approach.

Emission in argon and krypton at 147 nm excited by runaway-electron-induced diffusion discharge

Plasma emission of a pulsed diffuse discharge produced at increased pressures due to the preionisation of the gap by runaway electrons is studied in argon, krypton, and xenon. Nanosecond voltage pulses with the amplitude ∼220 kV were applied to the discharge gap. It is shown that the presence of xenon (∼0.01%) in argon and krypton leads to the emergence of high-power narrowband radiation at awavelength of 147 nm. It is assumed that this radiation belongs to the bands of heteronuclear molecules Xe*Ar and Xe*Kr.

Prediction of transport properties of pure noble gases and some of their binary mixtures by ab initio calculations

The ab initio potentials of kinetic theory are used to calculate viscosity and thermal conductivity of pure helium-4, neon, argon, krypton, and xenon over the temperature range from 100 K to 5000 K at zero-density. The viscosity and thermal conductivity of binary mixtures of noble gases like helium–neon, helium–argon, neon–argon, argon–krypton, and argon–xenon are also obtained by ab initio calculations for temperature between 100 K and 5000 K at zero-density. The results of viscosity and thermal conductivity, both for pure noble gases and their binary mixtures are in good agreement with that of the literature. It is concluded that the ab initio calculations lead to a quantitative prediction of viscosity and thermal conductivity of pure noble gases and their binary mixtures.

Tunable VUV light generation for resonance ionization mass spectrometry of Krypton

Tunable coherent VUV radiation from 115.8 to 116.9nm has been produced by non-linear four-wave sum frequency mixing in a xenon–argon mixture. 116.5nm light generated by this means has been used as the first step in a three color, doubly resonant ionization scheme for Kr. In the process of validating the system the xenon refractive index per atom (STP) at 116.5nm has been determined to be (n(Xe)−1)/NXe=−6.8(±0.8)×10−23cm3.

Molecular dynamic simulations of some thermodynamic properties of mixtures of argon with neon, krypton, and xenon using two-body and three-body interaction potentials

Molecular dynamics (MD) has been performed to compute the pressure and internal energy of binary mixtures of argon–neon, argon–krypton, and argon–xenon at different temperatures and compositions using two-body Hartree–Fock dispersion-like (HFD-like), total (two-body + three-body) HFD-like, and Lennard–Jones (LJ) potentials. The results are in a good overall agreement with the experimental data. To elucidate the role of three-body interactions on the thermodynamic properties of the studied mixtures, we have incorporated Wang and Sadus method into MD simulations performed using density-dependent two-body HFD-like potentials. Much better results for pressure have been obtained at high densities using the effective LJ potential. For the second virial coefficient, the HFD-like potential is a better choice. Since a little attention has been paid to the qualitative analysis of RDF in the liquid mixtures so far, we have also analyzed the variation of radial distribution function (RDF) of the mixtures with density and composition.

Matrix isolation infrared spectroscopic and theoretical study of noble gas coordinated dipalladium–dioxygen complexes

The reaction products of palladium atoms with molecular oxygen in solid argon have been investigated using matrix isolation infrared absorption spectroscopy and quantum chemical calculations. In addition to the previously reported mononuclear palladium–dioxygen complexes: Pd(η 2–O 2) and Pd(η 2–O 2) 2, dinuclear palladium–dioxygen complexes: Pd 2(η 2–O 2) and Pd 2(η 2–O 2) 2 were formed under visible light irradiation and were identified on the basis of isotopic substitution and theoretical calculations. In addition, experiments doped with xenon in argon coupled with theoretical calculations suggest that the Pd(η 2–O 2), Pd 2(η 2–O 2) and Pd 2(η 2–O 2) 2 complexes are coordinated by two argon or xenon atoms in solid argon matrix, and therefore, should be regarded as the Pd(η 2–O 2)(Ng) 2, Pd 2(η 2–O 2)(Ng) 2 and Pd 2(η 2–O 2) 2(Ng) 2 (Ng Ar or Xe) complexes isolated in solid argon.

Matrix Isolation Infrared Spectroscopic and Theoretical Study of Noble Gas Coordinated Rhodium−Dioxygen Complexes

Reactions of rhodium atoms with dioxygen molecules in solid argon have been investigated using matrix isolation infrared absorption spectroscopy. The rhodium-dioxygen complexes, Rh(eta2-O2), Rh(eta2-O2)2, and Rh(eta2-O2)2(eta1-OO), are produced spontaneously on annealing. The Rh(eta2-O2) complex rearranges to the inserted RhO2 molecule under visible light irradiation. Experiments doped with xenon in argon show that the rhodium-dioxygen complexes are coordinated by one or two noble gas atoms in solid noble gas matrixes. Hence, the Rh(eta2-O2), Rh(eta2-O2)2, and Rh(eta2-O2)2(eta1-OO) molecules trapped in solid noble gas matrixes should be regarded as the Rh(eta2-O2)(Ng)2, Rh(eta2-O2)2(Ng)2, and Rh(eta2-O2)2(eta1-OO)(Ng) (Ng = Ar or Xe) complexes. The product absorptions are identified on the basis of isotopic substitution and density functional theory calculations.

Laser-induced fluorescence measurements of argon ion velocities near the sheath boundary of an argon–xenon plasma

The Bohm sheath criterion in single- and two-ion species plasma is studied with laser-induced fluorescence using a diode laser. Xenon is added to a low pressure unmagnetized dc hot filament argon discharge confined by surface multidipole magnetic fields. The Ar II transition at 668.614 nm is adopted for optical pumping to detect the fluorescence from the plasma and to measure the argon ion velocity distribution functions with respect to positions relative to a negatively biased boundary plate. The structures of the plasma sheath and presheath are measured by an emissive probe. The ion concentrations of the two-species in the bulk plasma are calculated from ion acoustic wave experiments. Results are compared with previous experiments of Ar–He plasmas in which the argon ions were the heavier ion species. Unlike the previous results, the argon speed is slower than its own Bohm velocity near the sheath–presheath boundary in the Ar–Xe plasma where argon ions are the lighter ion species. We argue that this result is consistent with the behaviour of the helium ion required by the generalized Bohm criterion in the previous experiments with Ar–He plasmas. Further, our results suggest that the measured argon ion speed approaches the ion sound speed of the system.

Coordination of ScO+ and YO+ by Multiple Ar, Kr, and Xe Atoms in Noble Gas Matrixes: A Matrix Isolation Infrared Spectroscopic and Theoretical Study

The combination of matrix isolation infrared spectroscopic and quantum chemical calculation results provide strong evidence that scandium and yttrium monoxide cations, ScO+ and YO+, coordinate multiple noble gas atoms in forming noble gas complexes. The results showed that ScO+ coordinates five Ar, Kr, or Xe atoms, and YO+ coordinates six Ar or Kr and five Xe atoms in solid noble gas matrixes. Hence, the ScO+ and YO+ cations trapped in solid noble gas matrixes should be regarded as the [ScO(Ng)5]+ (Ng = Ar, Kr, or Xe), [YO(Ng)6]+ (Ng = Ar or Kr) or [YO(Xe)5]+ complexes. Experiments with dilute krypton or xenon in argon or krypton in xenon produced new IR bands, which are due to the stepwise formation of the [ScO(Ar)(5-n)(Kr)n]+, [ScO(Kr)(5-n)(Xe)n]+ (n = 1-5), [YO(Ar)(6-n)(Kr)n]+ (n = 1-6), and [YO(Ar)(6-n)(Xe)n]+ (n = 1-4) complexes.

Spatially resolved X-ray spectroscopy of an ECR plasma – indication for evaporative cooling

We have used an X-ray CCD camera in single photon counting mode and a pinhole to obtain spatially and spectrally resolved images of the plasma of an electron cyclotron resonance ion source. Software based on the CERN ROOT package was developed to process and analyse the data. Comparison of plasma images from trapped xenon to that from a xenon–argon mixture provides evidence for evaporative cooling of the ion cloud in ECR ion sources. This results in more localised and highly charged ion clouds when lighter-mass argon gas is added to a heavy-ion xenon plasma. This observation can have implications on the thermodynamics and charge state balance in astrophysical and other laboratory plasmas.