Kr System Research Articles

Molecular dynamics study of flow of Ar-Kr mixture across a smooth walled nano channel with and without obstacles

Nanofluidics has emerged as an interesting field involving science and engineering, in which a fluid is made to flow across the structures having diameter in the nanometers range such as nanochannels. Nanochannels are channels having any one or all dimensions in the range of nanometers. As a flow in the reduced-size dimensional system, the nanochannel flow manifests a series of special properties and has gained a large attention. The understanding of different properties and dynamic behavior of fluid flows across a nanochannel has great impact on the study of fluid dynamics and various applications in the field of physics, chemistry, medicine and electronics. In the current study, we have studied fluid flow in smooth walled nanochannel, with and without obstacles introduced in the path of fluid flow. For both the cases we studied the velocity profiles of the system and analyzed the effect of varying channel width, varying force field, and varying densities on the velocity profile of the system. It is inferred that there is variation in the mean velocity of system in all cases. The mean velocity of the system increases with increase in the channel width, and applied force and decrease in density of mixture. We have taken pure Ar, pure Kr and Ar-Kr binary mixture as a fluid for the study. The velocity profile of the Ar-Kr mixture lies between that of pure Ar and pure Kr. For Ar system, the value of mean velocity is highest and for Kr system the value is lowest. There is a decrease in the mean velocity of the system with introduction of obstacles in the path of flow of the nanochannel. The value of viscosity of the system remains constant even with the introduction of obstacles in the path of the flow of system.[Copyright information to be updated in production process]

BH4 Ng+ (Ar-Rn): Viable Compounds with a B-Ng Covalent Bond.

In this work, we explore, using high-level calculations, the ability of BH4 + to interact with noble gases. The He system is energetically unstable, while the Ne system could only be observed at cryogenic temperatures. In the case of the Ar, Kr and Xe systems, all are energetically stable, even at room temperature. The different chemical bond descriptors reveal a covalent character between B and the noble gas from Ar to Rn. However, this interaction gradually weakens the multicentric bond between the boron atom and the H2 fragment. Thus, although BH4 Rn+ exhibits a strong covalent bond, it tends to dissociate at room temperature into BH2 Rn+ +H2 .

Inelastic collision dynamics of oriented NO molecules with Kr atoms

Building on our previous work on NO + Ar, this paper presents a complete set of orientation measurements and quantum mechanical calculations for the NO + Kr collision system, including both spin-orbit conserving and changing collisions, and both side-on (x-axis) and end-on (z-axis) orientations. While many of the trends observed in the oriented differential and integral scattering distributions, as well as in the spin-orbit branching fractions, are similar to the ones seen previously for NO + Ar, a direct comparison with the Ar data reveals subtle differences in the scattering dynamics, which we rationalise with the more extended attractive regions on the NO + Kr potential energy surfaces. High-impact parameter collisions that lead to low scattering angles in the spin-orbit conserving manifold are particularly sensitive to the topology in the attractive parts of the potential, whereas more impulsive, low-impact parameter trajectories, which sample the repulsive parts of the potential, produce very similar features in the oriented differential cross sections for the Ar and Kr systems, especially for spin-orbit changing collisions.

Growth of rare gases on coronene

We study the growth of rare gases (Rg) Ne, Ar and Kr on coronene (Cor) molecules, Cor-(Rg)\(_N\). The study is taken up to sizes N=60, and we show the global energy minima for those clusters. Improved Lennard-Jones and atom-bond potentials are used to represent the Rg-Rg and Rg-Cor interactions, respectively. The Basin-Hopping (BH) global optimization technique is employed to locate the putative global energy minimum structures. Results are presented for Cor-(Ne), Cor-(Ar) and Cor-(Kr) systems. Both classical Cor-(Ar)\(_N\) and Cor-(Kr)\(_N\) clusters present the same “magic numbers” for N=3, 6, 10, 14, 19 and 38. This last number marks the first layer of solvation. For Cor-(Ne)\(_N\) clusters, we consider quantum effects adding the zero-point energy (ZPE) into the classical potential energy minima (BH-ZPE). This semiclassical approximation is compared with quantum diffusion Monte Carlo (DMC) calculations up to N=20, obtaining a good agreement and showing that this approximation works reasonably well. In this BH-ZPE approach, high stability configurations for Cor-(Ne)\(_N\) clusters are obtained at N=6, 14, 42, 51 and 57. However, we have not found any evidence of a first solvation layer using either the semiclassical BH-ZPE or the classical BH one.

Spectroscopy of atomic orbital sizes using bi-elliptical high-order harmonic generation

We report that high-order harmonic generation (HHG) of atoms driven by $\ensuremath{\omega}\text{\ensuremath{-}}2\ensuremath{\omega}$ bi-elliptical pumps exhibits a substantial sensitivity to variation of the spatial extent of the participating valence orbitals and effective potential. We identify the physical mechanisms responsible for this enhanced sensitivity through theoretical investigations in atomic He, Ne, Ar, and Kr systems using several quantum models. We demonstrate this size sensitivity experimentally by measuring significant disparities in the bi-elliptical HHG spectra of atomic Ar and Kr, which have relatively similar ionization potentials, but substantially different $p$-shell sizes and effective potentials. This result may be useful for ultrafast spectroscopy which is sensitive to effective potentials and orbitals.

Structure and properties of Ar–Kr solid solutions

The transmission electron diffraction technique has been used to explore in detail solid argon-krypton solutions in a temperature range of 5–44 K. Specimens were prepared in situ by depositing the gaseous mixture on a base at temperatures 5 and 20 K. The structure of the Ar–Kr alloys was found to correspond to the face-centered cubic lattice in the entire range of reciprocal concentrations. In the concentration range of 50–70 mol % Ar, separation of the solution into two phases has been observed. The regions where solid argon-krypton solutions exist have been determined. Kinetics of relaxation processes stimulated by annealing the specimens has been studied. Conclusions regarding character of the Ar–Kr system state diagram have been made using the analysis of experimental data.

Quantum and semi-classical collision cross-sections and transport data for a Kr+/Kr system

Krypton ion transport properties in krypton carrier gas have been calculated using various methods and two state-of-the-art sets of diatomic interaction potentials and compared to available experimental data. First, momentum transfer effective cross-sections have been calculated for Kr+/Kr collisions for the ion in either of two fine-structure states ( and ). A full quantum approach, semi-classical approximation, and a hybrid method (classical treatment of nuclei and quantum description of electrons) have been used. Then, an optimized Monte Carlo code has been employed to calculate the basic transport parameters (mobility and diffusion coefficients) of the Kr+ ion in the carrier krypton gas. A thorough comparison of the calculated data with available experiments allowed the assessment of the reliability of the interaction models and methodologies to be used in further calculations. In addition, theoretical predictions are provided for these coefficients where they are not available from measurements.

An experimental study of OH(A2Σ+) + H2: Electronic quenching, rotational energy transfer, and collisional depolarization.

Zeeman quantum beat spectroscopy has been used to determine the thermal (300 K) rate constants for electronic quenching, rotational energy transfer, and collisional depolarization of OH(A2Σ+) by H2. Cross sections for both the collisional disorientation and collisional disalignment of the angular momentum in the OH(A2Σ+) radical are reported. The experimental results for OH(A2Σ+) + H2 are compared to previous work on the OH(A2Σ+) + He and Ar systems. Further comparisons are also made to the OH(A2Σ+) + Kr system, which has been shown to display significant non-adiabatic dynamics. The OH(A2Σ+) + H2 experimental data reveal that collisions that survive the electronic quenching process are highly depolarizing, reflecting the deep potential energy wells that exist on the excited electronic state surface.

構造 H ハイドレートを作動媒体とする熱機関の熱効率

This paper reports the four phase equilibrium conditions and then analyzes thermal efficiency of heat engine using clathrate hydrate as the working medium. The working media was krypton and water plus each of the following substances: Neohexane and Methylcyclohexane. The heat engine was operated in the temperature range between 282 K and 293 K. Thermal efficiency was found to be 2.20% for the Kr hydrate, 2.35% for the Kr + Neohexane hydrate and 2.36 % for the Kr + Methylcyclohexane hydrate systems. The thermal efficiency was increased by 0.16 % when compared to a simple Kr system.

Representations for robot knowledge in the KnowRob framework

In order to robustly perform tasks based on abstract instructions, robots need sophisticated knowledge processing methods. These methods have to supply the difference between the (often shallow and symbolic) information in the instructions and the (detailed, grounded and often real-valued) information needed for execution. For filling these information gaps, a robot first has to identify them in the instructions, reason about suitable information sources, and combine pieces of information from different sources and of different structure into a coherent knowledge base. To this end we propose the KnowRob knowledge processing system for robots. In this article, we discuss why the requirements of a robot knowledge processing system differ from what is commonly investigated in AI research, and propose to re-consider a KR system as a semantically annotated view on information and algorithms that are often already available as part of the robot's control system. We then introduce representational structures and a common vocabulary for representing knowledge about robot actions, events, objects, environments, and the robot's hardware as well as inference procedures that operate on this common representation. The KnowRob system has been released as open-source software and is being used on several robots performing complex object manipulation tasks. We evaluate it through prototypical queries that demonstrate the expressive power and its impact on the robot's performance.

Chirality of weakly bound complexes: the potential energy surfaces for the hydrogen-peroxide-noble-gas interactions.

We consider the analytical representation of the potential energy surfaces of relevance for the intermolecular dynamics of weakly bound complexes of chiral molecules. In this paper we study the H2O2-Ng (Ng=He, Ne, Ar, Kr, and Xe) systems providing the radial and the angular dependence of the potential energy surface on the relative position of the Ng atom. We accomplish this by introducing an analytical representation which is able to fit the ab initio energies of these complexes in a wide range of geometries. Our analysis sheds light on the role that the enantiomeric forms and the symmetry of the H2O2 molecule play on the resulting barriers and equilibrium geometries. The proposed theoretical framework is useful to study the dynamics of the H2O2 molecule, or other systems involving O-O and S-S bonds, interacting by non-covalent forces with atoms or molecules and to understand how the relative orientation of the O-H bonds changes along collisional events that may lead to a hydrogen bond formation or even to selectivity in chemical reactions.

Kinetic fractionation of gases by deep air convection in polar firn

Abstract. A previously unrecognized type of gas fractionation occurs in firn air columns subjected to intense convection. It is a form of kinetic fractionation that depends on the fact that different gases have different molecular diffusivities. Convective mixing continually disturbs diffusive equilibrium, and gases diffuse back toward diffusive equilibrium under the influence of gravity and thermal gradients. In near-surface firn where convection and diffusion compete as gas transport mechanisms, slow-diffusing gases such as krypton (Kr) and xenon (Xe) are more heavily impacted by convection than fast diffusing gases such as nitrogen (N2) and argon (Ar), and the signals are preserved in deep firn and ice. We show a simple theory that predicts this kinetic effect, and the theory is confirmed by observations using a newly-developed Kr and Xe stable isotope system in air samples from the Megadunes field site on the East Antarctic plateau. Numerical simulations confirm the effect's magnitude at this site. A main purpose of this work is to support the development of a proxy indicator of past convection in firn, for use in ice-core gas records. To this aim, we also show with the simulations that the magnitude of the kinetic effect is fairly insensitive to the exact profile of convective strength, if the overall thickness of the convective zone is kept constant. These results suggest that it may be feasible to test for the existence of an extremely deep (~30–40 m) convective zone, which has been hypothesized for glacial maxima, by future ice-core measurements.

Hydrogen bonding to xenon: A comparison with neon, argon and krypton complexes

H-bonding-like interactions between AH acids and Ne, Ar, Kr and Xe are examined by analysis of predicted A–H⋯Rg geometry, energy, A–H stretching vibration (CCSD(T) level) as well as assumed proton affinitiy, pKa, polarizability and chemical hardness of the complex components. The Kr and Xe systems are described as mostly the acid–base contacts and reveal properties of typical H-bonded complexes. These contacts are also influenced by structural factors. Properties of the Ne contacts are qualitatively different. The A–H⋯Xe complexes can be divided into stronger and weaker ones using the 129Xe chemical shift as the criterion.

Electron Density Topological Analysis the Intermolecular Weak Interaction between GeH<sub>4</sub> and X(X=He, Ne, Ar and Kr)

The intermolecular weak interaction between GeH4 and X(X=He, Ne, Ar, Kr) has been studied at MP2/aug-cc-pvtz level. Electron density topological properties of the studied systems have been calculated to investigate the critical points of H…X weak bonds. The molecules electrostatic potential (MESP) image is one of the tools for conformational analysis, and the related data suggests the view of the non-electrostatic weak interaction in nature of the GeH4…X(X=Ar, Kr) systems. To help possible experimental identification of the intermolecular weak interactions described in this work, the frequencies analysis and NMR properties were also calculated at MP2/aug-cc-pvtz level.

A new potential energy surface for OH(A 2Σ+)–Kr: The van der Waals complex and inelastic scattering

New ab initio studies of the OH(A(2)Σ(+))-Kr system reveal significantly deeper potential energy wells than previously believed, particularly for the linear configuration in which Kr is bound to the oxygen atom side of OH(A(2)Σ(+)). In spite of this difference with previous work, bound state calculations based on a new RCCSD(T) potential energy surface yield an energy level structure in reasonable accord with previous studies. However, the new calculations suggest the need for a reassignment of the vibrational levels of the electronically excited complex. Quantum mechanical and quasi-classical trajectory scattering calculations are also performed on the new potential energy surface. New experimental measurements of rotational inelastic scattering cross sections are reported, obtained using Zeeman quantum beat spectroscopy. The values of the rotational energy transfer cross sections measured experimentally are in good agreement with those derived from the dynamical calculations on the new adiabatic potential energy surface.

Some thermodynamic properties of fluids SF6, SF6–Ar, and SF6–Kr using new HFD-like potentials including three-body interactions: The inversion method and molecular dynamics simulation

A new pair-potential energy function of sulfur hexafluoride has been determined via the inversion of reduced viscosity collision integrals at zero pressure and fitted to obtain a Hartree–Fock dispersion (HFD)-like potential form. The pair-potential reproduces the second virial coefficient and transport properties of sulfur hexafluoride in a good accordance with experimental data over wide ranges of temperatures. Molecular dynamics (MD) simulation has been also performed to obtain pressure, self-diffusion coefficient, and radial distribution function of fluid sulfur hexafluoride at different temperatures and densities using the calculated HFD-like pair-potential. We have also obtained pressures of SF6–Ar and SF6–Kr fluid mixtures at constant temperature at different densities using new two-body HFD-like models. To take higher-body forces into account, three-body potentials of Wang and Sadus (2006) [22,23] and Hauschild and Prausnitz (1993) [24] have been used with the two-body HFD-like potentials of SF6, SF6–Ar, and SF6–Kr systems to improve the prediction of the calculated properties without requiring an expensive three-body calculation. The MD simulation of sulfur hexafluoride has been also used to determine a new equation of state.

Calculations of laser induced quadrupole–quadrupole collisional energy transfer in Xe–Kr

A laser induced quadrupole–quadrupole collisional energy transfer system of Xe–Kr is proposed, and the three-level laser induced collisional energy transfer (LICET) model is presented. Calculating results show that the peak of the LICET profile moves to the red and the FWHM becomes narrower, obviously with the laser field intensity increasing, while the resulting spectra is shifted in frequency toward the blue and the full width at half peak of the profile becomes larger as the relative velocity increases. The spectrum of the quadrupole–quadrupole LICET in the Xe–Kr system has a wider tunable range in an order of magnitude than the dipole–dipole LICET spectra. A cross section of 3.36×10−15 cm2 is obtained, which indicates that the quadrupole–quadrupole LICET process also can be an effective way to transfer energy selectively from a storage state to a target state.

Laser-induced quadrupole—quadrupole collisional energy transfer in Xe—Kr

By considering the relative velocity distribution function and multipole expansion interaction Hamiltonian, a three-state model for calculating the cross section of laser-induced quadrupole—quadrupole collisional energy transfer is presented. Calculated results in Xe—Kr system show that in the present system, the laser-induced collision process occurs for ∼4 ps, which is much shorter than the dipole—dipole laser-induced collisional energy transfer (LICET) process. The spectrum of laser-induced quadrupole—quadrupole collisional energy transfer in Xe—Kr system has wider tunable range in an order of magnitude than the dipole—dipole LICET spectra. The peak cross section decreases and moves to the quasi-static wing with increasing temperature and the full width at half peak of the profile becomes larger as the system temperature increases.

On the role of charge transfer in the stabilization of weakly bound complexes involving water and hydrogen sulphide molecules

Integral cross section data for collisions of water and hydrogen sulphide molecules with noble gas atoms, measured with the same apparatus under identical conditions and analyzed by exploiting the same potential model, provided a set of internally consistent potential parameters. Their critical comparison is exploited not only to identify those systems where the intermolecular bond is not simply due to the balancing of size repulsion with dispersion and induction attraction, but also to establish the amount of bond stabilization by charge-transfer effects. Such experimental findings are analyzed through extensive and accurate ab initio calculations, addressed at discovering the relevant differences in the basic features of the potential energy surfaces. In particular, we have analyzed in detail the prototype H2S, H2O–Kr systems and found pronounced differences in the dependence of the interaction nature and energy on the relative orientation of the colliding systems. Using the recently proposed charge-displacement analysis we have been able to quantitatively assess charge-transfer effects, which differ significantly in the two systems and exhibit different stereoselectivity. This casts further light on the specificity of water interactions.

Theoretical study of the intermolecular potential energy and second virial coefficient in the mixtures of CH4 and Kr gases: a comparison with experimental data

The intermolecular potential energy surface (IPS) in the mixtures of CH4–Kr gases from ab initio calculations has been explored. The ab initio calculation was performed at the second-order Møller–Plesset perturbation theory (MP2), with the 6-311+G(2df,2pd) basis set, for three relative orientations of two CH4–Kr molecules as a function of CH4–Kr separation distance. In this work, the IPS, U(r), of the CH4–Kr complex has been investigated, where the vertex (V), edge (E) and face (F) of CH4 approaches to Kr have been considered. Then, adjustable parameters of the Lennard-Jones and Buckingham potential energy function are fitted to the ab initio MP2/6-311+G(2df,2pd) interaction energies for three different orientations. Assuming a given set of parameters, we theoretically obtained second virial coefficients for the CH4–Kr system, and compared with the experimental data at different temperatures. Trivial differences can be observed between the experimental and computational results.