Argon Krypton Research Articles

The importance of laser wavelength for driving inertial confinement fusion targets. II. Target design

We describe details of radiation-hydrodynamics simulations of directly driven targets for inertial confinement fusion using laser drivers with different laser wavelengths. Of particular interest here are comparisons of frequency-tripled glass (laser wavelength 351 nm) lasers with the argon fluoride (193 nm) and krypton fluoride (248 nm) excimer lasers and the effects that these laser wavelengths have on the target designs. We explore the effect these drivers have on the compromise involved between lowering laser plasma instabilities (LPIs) or hydrodynamic instabilities while providing high gains and seek to quantify this trade-off. Short-wavelength drivers have significant advantages, primarily in using less power and energy to drive targets. Additionally, they expand the allowed operating regime that is constrained by LPI avoidance and the production of higher pressures needed for more hydrodynamically stable targets. Potential disadvantages to shorter drive wavelengths, such as increased imprint, are examined and found to be unimportant.

Effects of different window configurations on energy consumption in building: Optimization and economic analysis

Energy saving is one of the challenges of today. In recent years, growing concerns about the environmental impacts of energy consumption and global warming has doubled the importance of this issue. The contribution of building sector to the energy consumption is significant at a country-wide scale, so that various measures have been taken to help save the energy, including the codification of regulations in accordance with local climate conditions. In this research, using DesignBuilder software, a building in Semnan (Iran) with hot arid climate was modeled with various window configurations. To generalize the results, the two cities of Tabriz and Bandar Abbas with different climates were added to the study. One of the important strategies for optimizing energy consumption in a modeled building is to improve the heat transfer coefficient of the window glass based on local climate conditions. In this work, investigations were performed on a variety of single-pane and double-pane windows with argon gas, krypton, and air as the insulator. By changing the gap between the panes and glass thickness, the cooling/heating load of the modeled building were analyzed to find optimum window configuration for the dominant climate condition at Semnan. Finally, an economic assessment was performed by estimating the required capital cost and payback period for different window configurations.

Molecular simulation of volume of mixing, Helmholtz free energy of mixing and entropy of mixing in bulk fluid mixtures

ABSTRACTWe describe a kinetic Monte Carlo molecular simulation procedure to calculate the Helmholtz free energy, the entropy and the chemical potentials of all components in a bulk fluid mixture. This allows us to derive the excess properties (volume, free energy and entropy) resulting from the mixing of homogeneous fluids of pure components at constant temperature and pressure. We have chosen neon–xenon mixtures to illustrate our method because of the large difference in collision diameter and well-depth of the interaction energy. When xenon is predominant in the mixture, the volume of mixing is larger. The excess entropy of mixing correlates with the volume of mixing, since a positive excess volume enables more configurations (more possible molecular distributions). The excess thermodynamic quantities as functions of the total density were found to be insensitive to temperature. To investigate the effects of the molecular parameters, we also studied argon–nitrogen and argon–krypton mixtures. The effect of the difference in molecular parameters is in the order: argon–nitrogen < argon–krypton < neon–xenon. A large difference in the well-depth of the interaction energies results in an increase in the excess thermodynamic variables, which is in agreement with the literature McDonald IR. NpT-ensemble Monte Carlo calculations for binary liquid mixtures. Mol Phys. 1972;23(1):41–58; Singer JVL, Singer K. Monte Carlo calculation of thermodynamic properties of binary mixtures of Lennard-Jones (12-6) liquids. Mol Phys. 1972;24(2):357–390.

Isolated spherical impurity in noble gas crystals

To explain the experimentally observed structural anomalies in diluted solid solutions of argon in krypton, we calculated the positions of atoms in a nine-layer spherical cluster of krypton with an argon atom in the center. The interaction was approximated with the Lenard–Jones potential. The substitution volume ω of an argon atom in the krypton crystal was calculated. It was shown that compared to the generally accepted estimates obtained within the nearest-neighbor approximation, the value of ω is approximately twice as small. This effect is explained by an additional repulsion of the first coordination sphere of krypton atoms arising as the krypton atoms approach each other upon their inward motion.

Dimers or trimers? A characterization of the halogen bonded complexes of CF3X (X = I or Br) with dimethyl ether and acetone in cryosolutions

Acetone molecules dissolved in liquid krypton are inclined to self-associate into dimers. This behavior affects its use as a prototype Lewis base in studies of weak intermolecular interactions. In this study infrared spectra of mixed solutions of dimethyl ether and CF3X and of acetone and CF3X (with X=I or Br) dissolved in liquid argon and liquid krypton are recorded at constant temperature. The dataset for dimethyl ether is used to validate a numerical method based on least-squares fitting of a model including contributions of both monomers and a heterodimer with 1:1 stoichiometry. The resulting monomer and dimer spectra show excellent agreement with previous studies found in literature. The analysis of the dataset for acetone requires an extension of the model with contributions for the acetone homodimer and for (acetone)2·CF3X and acetone·(CF3X)2 trimers. The results show that many signals for acetone·CF3I and (acetone)2·CF3I are observed, while only a few bands due to acetone·(CF3I)2 occur. The use of numerical approaches adjusted to the specificities of a mixture of two compounds allows to reliably resolve overlapping spectra of monomers and heterocomplexes and characterizing heterocomplex features that could not be deduced using earlier methods. To support the assignments made, ab initio calculations predicting geometries, relative stabilities and harmonic vibrational frequencies for the species envisaged are performed.

Binary Diffusion Coefficient Data of Various Gas Systems Determined Using a Loschmidt Cell and Holographic Interferometry

The paper reports on binary diffusion coefficient data for the gaseous systems argon–neon, krypton–helium, ammonia–helium, nitrous oxide–nitrogen, and propane–helium measured using a Loschmidt cell combined with holographic interferometry between (293.15 and 353.15) K as well as between (1 and 10) bar. The investigations on the noble gas systems aimed to validate the measurement apparatus by comparing the binary diffusion coefficients measured as a function of temperature and pressure with theoretical data. In previous studies, it was already shown that the raw concentration-dependent data measured with the applied setup are affected by systematic effects if pure gases are used prior to the diffusion process. Hence, the concentration-dependent measurement data were processed to obtain averaged binary diffusion coefficients at a mean mole fraction of 0.5. The data for the molecular gas systems complete literature data on little investigated systems of technical interest and point out the capabilities of the applied measurement apparatus. Further experimental data are reported for the systems argon–helium, krypton–argon, krypton–neon, xenon–helium, xenon–krypton, nitrous oxide–carbon dioxide, and propane–carbon dioxide at 293.15 K, 2 bar, and a mean mole fraction of 0.5.

Emission characteristics of pulse-periodic barrier-discharge plasma in a mixture of krypton with argon and liquid freon vapor

Radiation of a nanosecond barrier discharge in a mixture of krypton, argon, and carbon-tetrachloride vapor is studied in the spectral range of 150–300 nm. The plasma radiation spectra and the dependences of the intensities of the 258 nm Cl2(D′ → A′), 222 nm KrCl(B → X), and 175 nm ArCl(B → X) bands on the partial pressure of liquid freon vapor, argon, and krypton, as well as on the discharge excitation conditions, are studied. The optimal compositions of gas mixtures for creating a broadband UV-VUV emitter based on the band system of argon chloride, krypton chloride, and chlorine molecule are determined.

Development of kinetic Monte Carlo and Bin-Monte Carlo schemes for simulation of mixtures – vapor–liquid equilibria & adsorption

We describe algorithms for the recently developed Bin-Monte Carlo (Bin-MC) method (Fan et al., 2012) and kinetic Monte Carlo (kMC) (Ustinov and Do, 2012) to simulate binary liquid mixtures, and compare them with simulations of vapour–liquid equilibria from the canonical and Gibbs MC methods. We have found that in kMC, the rule to choose a molecule to move rests purely on the mobility, irrespective of molecular weight. In the Bin-MC, the choice of a molecule to move from one bin to another bin depends on the selection of a component with equal probability. Our simulations show that the Bin-MC and kMC schemes are very effective for the purpose of describing thermodynamic properties and density profiles across the vapour–liquid interface, and show that the Lorentz–Berthelot (LB) mixing rule works well for subcritical systems, and to improve the description of systems having one component under supercritical condition the cross collision diameter and the cross well depth have to be modified from the LB mixing rules, which is in agreement with previous studies (for example, (Wu and Sadus, 2000)). The benefits of the kMC scheme for the direct determination of chemical potential were also demonstrated with a study of adsorption of an argon–krypton mixture on graphite.

Longitudinal and volume viscosities of fluids confined in nanochannel

Longitudinal and volume viscosities of Lennard-Jones fluid, argon–krypton binary mixture and isotopic fluid mixture confined to nanochannels of different widths are calculated by employing theoretical technique based on Green–Kubo formula. A significant enhancement is observed in longitudinal and volume viscosities when width of the nanochannel is less than 10 nm. Effect of mass ratio of two species on longitudinal and volume viscosities is also studied for equimolar isotopic fluid mixture. It is found that enhancement in viscosity is more for larger mass ratios. It is also noted that enhancement in longitudinal and shear viscosities is more than volume viscosity.

Programmable color tuning of a multiline laser by means of a twisted nematic liquid crystal display

An optical system useful to tune in a controlled way the color of a triline argon krypton (Ar-Kr) laser by means of a twisted nematic liquid crystal display (TNLCD) is presented. The optical setup employs a 4f system and two blazed gratings to first separate and then recombine the spectrum of the light beam. The TNLCD is included in the intermediate focal plane operating in the amplitude modulation mode to control the relative transmission of each spectral line. The resulting color is accurately predicted by using a previously developed physical model of the spectral and voltage dependence of the TNLCD birefringence. By simply changing the gray level image addressed to the display, the Ar-Kr laser is color modulated at a video rate, thus becoming an interesting, reconfigurable, coherent light source for applications such as multicolor holography or color inspection.

Calculations of the thermophysical properties of binary mixtures of noble gases at low density from ab initio potentials

Interaction potentials determined ab initio from quantum mechanics were used to calculate the thermophysical properties of six binary mixtures of noble gases: helium–neon, helium–argon, helium–krypton, neon–argon, neon–krypton and argon–krypton. From the ab initio potentials, the second pressure virial coefficient, the binary diffusion coefficient and the thermal diffusion factor were computed for the considered binary mixtures at low density in the temperature range 100–5000 K employing well-established formulas in statistical thermodynamics and the kinetic theory of dilute gases. In all cases, while not as good as that for pure noble gases, close agreement between experimental data and the theoretically calculated values shows that ab initio potentials are reliable for the calculation of accurate thermophysical properties of binary mixtures of noble gases over a wide temperature range.

Excitation Mechanism of Silver Ionic Lines Through Collisions with Metastable Atoms of Plasma Gas in a Glow-Discharge Plasma

ABSTRACT Emission spectra of silver from glow-discharge plasmas using argon, krypton, and a krypton–argon gas mixture were analyzed to elucidate the excitation phenomenon of silver ionic lines occurring in collisions with the plasma gases. The intensities of the ionic lines that were assigned to the 4d95p–4d95s transition were largely different between argon and krypton; for instance, the intensity of the Ag II 243.78-nm line (9.94 eV) emitted from the krypton plasma was five times larger than that from the argon plasma, while the Ag II 228.00-nm line (11.14 eV) yielded much larger intensity in the argon plasma by a factor of 70. This effect can be explained by an excitation process through collisional energy transfer from the metastable atom of argon or krypton to the silver ion in the ground state (Penning excitation). This type of collision requires both matching in the excitation energy between the colliding partners and conservation in the total spin before and after the collision. The 3p54s metastable state of argon (11.72 eV for the singlet and 11.55 eV for the triplet) and the 4p55s metastable state of krypton (10.56 eV for the singlet and 9.92 eV for the triplet) would take part in the collision and principally determine the population of the 4d95p excited levels of the silver ion.

Emission Spectroscopic Study on Gas-Gas Interactions in Glow Discharge Plasmas Using Several Binary Gas Mixtures

Emission spectra of constituent gas species from glow discharge plasmas using argon-helium, krypton-helium, argon-krypton, and krypton-argon gas mixtures were analyzed to elucidate collisional energy transfer between these gas species occurring in the plasma. In the argon-helium mixed gas plasma, the enhancement or quenching of particular Ar II lines was observed when helium was added to an argon-matrix glow discharge plasma, meaning that a redistribution in the population among the excited levels could be induced through argon-helium collisions. On the other hand, the krypton-helium plasma showed little change in the emission intensities of Kr II lines when helium was added to a krypton-matrix glow discharge plasma, meaning that energy exchanges between krypton and helium excited species occur inactively. These phenomena are principally because the excitation energy as well as the spin multiplicity between collision partners follow both the energy resonance conditions and the spin conservation rule in collisions of the second kind in the argon-helium system, but not in the krypton-helium system. In the argon-krypton and krypton-argon mixed gas plasmas, significant intensity changes of particular Ar II or Kr II lines could not be found; therefore, there were no dominant channels for energy exchanges between argon and krypton species in the mixed gas plasmas.

An evolutionary algorithm for global minimum search of binary atomic clusters

Abstract We propose an evolutionary algorithm (EA) for global optimization of binary atomic clusters. The method is applied to binary Lennard–Jones (BLJ) clusters as a testing ground, while a limited set of results for mixed argon–krypton clusters are also reported. We show that the method is effective in discovering all global minima of BLJ clusters for nuclearities up to N = 50 and different values of the atoms size ratio. Moreover, one new global minimum has been discovered for N = 38 and size ratio 1.05.

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.

Experimental determination of scattering matrices of dust particles at visible wavelengths: The IAA light scattering apparatus

We present a new apparatus for measuring the complete scattering matrix as a function of the scattering angle of dust irregular particles. The design is based on the well-known apparatus located in Amsterdam, The Netherlands. In this improved version we have extended the scattering angle ranging from 3° to 177°. Moreover, the measurements are performed with a tunable argon–krypton laser that emit at a wavelength ( λ ) of 483, 488, 520, 568, or 647 nm. The apparatus has been developed at the Instituto de Astrofísica de Andalucía (IAA), Granada, Spain. To measure the scattering matrix elements we use a number of different optical components such as polarizers, a quarter-wave plate, and an electro-optic modulator. These components are used to manipulate the polarization state of light. By using eight different combinations for the orientation angles of the optical components, all scattering matrix elements are obtained as functions of the scattering angle. The accuracy of the instrument is tested by comparing the measured scattering matrices of water droplets at 488, 520, and 647 nm with Lorenz–Mie calculations for a distribution of homogeneous water droplets.

Vacuum UV Radiation of a Plasma Jet Operated With Rare Gases at Atmospheric Pressure

The vacuum ultraviolet (VUV) emissions from 115 to 200 nm from the effluent of an RF (1.2 MHz) capillary jet fed with pure argon and binary mixtures of argon and xenon or krypton (up to 20%) are analyzed. The feed gas mixture is emanating into air at normal pressure. The Ar <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> excimer second continuum, observed in the region of 120-135 nm, prevails in the pure Ar discharge. It decreases when small amounts (as low as 0.5%) of Xe or Kr are added. In that case, the resonant emission of Xe at 147 nm (or 124 nm for Kr, respectively) becomes dominant. The Xe <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> second continuum at 172 nm appears for higher admixtures of Xe (10%). Furthermore, several N I emission lines, the O I resonance line, and H I line appear due to ambient air. Two absorption bands (120.6 and 124.6 nm) are present in the spectra. Their origin could be unequivocally associated to O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">2</sub> and O <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> . The radiance is determined end-on at varying axial distance in absolute units for various mixtures of Ar/Xe and Ar/Kr and compared to pure Ar. Integration over the entire VUV wavelength region provides the integrated spectral distribution. Maximum values of 2.2 mW middotmm <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-2</sup> middotsr <sup xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">-1</sup> are attained in pure Ar and at a distance of 4 mm from the outlet nozzle of the discharge. By adding diminutive admixtures of Kr or Xe, the intensity and spectral distribution is effectively changed.

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.

Determining the Quantum Efficiency for Activation of an Organometallic Photoinitiator for Cationic Polymerization

We present a new laboratory experiment on the photochemistry of organometallic ?5,?6-mixed-sandwich compounds, which is suitable for both the physical chemistry and inorganic chemistry laboratory. Specifically, students use 1,10�phenanthroline to trap the intermediate formed when [CpFe(isopropylbenzene)]PF6 is photolyzed with 458 nm light from an argon�krypton laser. Using quantitative UV�vis spectroscopy students then determine the quantum yield of arene ring displacement from the mixed-sandwich complex. The photogenerated intermediate, [CpFe(solvent)3]+ is an efficient initiator for the polymerization of epoxides, dicyanate esters, pyrrole, styrene, dioxolenes, and acrylates. The efficiency with which the intermediate is photochemically formed is therefore an important property in determining its commercial utility. Although the experiment can easily be done in one 3�4 hour laboratory period, it readily lends itself to broadening into a multi-week research project. In this mode, students can examine how changing the nature of the solvent and the irradiation wavelength affect the quantum yield of reaction. Such information can be used to reveal the role of the solvent in the reaction and the electronic excited states from which reaction occurs. Furthermore, in the inorganic laboratory, students could be asked to synthesize [CpFe(isopropylbenzene]PF6 before looking at its photochemical behavior, thus gaining experience in working under air-free conditions.

Coherent Rayleigh–Brillouin scattering in binary gas mixtures

In this paper we present the first theoretical study of the coherent Rayleigh–Brillouinscattering in binary mixtures of monatomic ideal gases. The line shape of the coherentspectrum is determined by solving a kinetic model of the Boltzmann equation that replacesthe collision operators by simple relaxation-time terms which are compatible with thetwo-fluid hydrodynamic theory. Theoretical predictions for the coherent light scatteringspectrum in dilute argon–krypton gas mixtures are presented and its dependence onconcentration and pressure is analysed.