Diatomic Gas Research Articles

Energy of One-Dimensional Diatomic Elastic Granular Gas:Theory and Molecular Dynamics Simulation

One-dimensional ideal diatomic gas is simulated through possible types of motions of its molecule. Energy of each type of its motion is calculated by both theoretical and numerical methods. Analytical calculation of kinetic energy of an atom in translational-vibrational motion is not simple, but it can be solved by numerical method using molecular dynamic simulation. This paper justifies that the kinetic energy of a diatomic molecule can be determined by two different approaches which give the same results. In the first approach, the kinetic energy is calculated as a summation of kinetic energy of each atom. In the second approach, the kinetic energy is calculated as a summation of kinetic energy of translational and vibrational motions.

Roadmap on quantum optical systems

This roadmap bundles fast developing topics in experimental optical quantum sciences, addressing current challenges as well as potential advances in future research. We have focused on three main areas: quantum assisted high precision measurements, quantum information/simulation, and quantum gases. Quantum assisted high precision measurements are discussed in the first three sections, which review optical clocks, atom interferometry, and optical magnetometry. These fields are already successfully utilized in various applied areas. We will discuss approaches to extend this impact even further. In the quantum information/simulation section, we start with the traditionally successful employed systems based on neutral atoms and ions. In addition the marvelous demonstrations of systems suitable for quantum information is not progressing, unsolved challenges remain and will be discussed. We will also review, as an alternative approach, the utilization of hybrid quantum systems based on superconducting quantum devices and ultracold atoms. Novel developments in atomtronics promise unique access in exploring solid-state systems with ultracold gases and are investigated in depth. The sections discussing the continuously fast-developing quantum gases include a review on dipolar heteronuclear diatomic gases, Rydberg gases, and ultracold plasma. Overall, we have accomplished a roadmap of selected areas undergoing rapid progress in quantum optics, highlighting current advances and future challenges. These exciting developments and vast advances will shape the field of quantum optics in the future.

Propagation of intense and short circularly polarized pulses in a molecular gas: From multiphoton ionization to nonlinear macroscopic effects

We present a detailed analysis of the propagation dynamics of short and intense circularly polarized pulses in an aligned diatomic gas. Compared to linearly polarized intense pulses, high harmonic generation (HHG) and the coherent generation of attosecond pulses in the intense-circular-polarization case are a new research area. More specifically, we numerically study the propagation of intense and short circularly polarized pulses in the one-electron ${\mathrm{H}}_{2}{}^{+}$ molecular gas, using a micro-macro Maxwell--Schr\odinger model. In this model, the macroscopic polarization is computed from the solution of a large number of time-dependent Schr\odinger equations, the source of dipole moments, and using a trace operator. We focus on the intensity and the phase of harmonics generated in the ${\mathrm{H}}_{2}{}^{+}$ gas as a function of the pulse-propagation distance. We show that short coherent circularly polarized pulses of same helicity can be generated in the molecular gas as a result of cooperative phase-matching effects.

Structural and Functional Evidence Indicates Selective Oxygen Signaling in Caldanaerobacter subterraneus H-NOX.

Acute and specific sensing of diatomic gas molecules is an essential facet of biological signaling. Heme nitric oxide/oxygen binding (H-NOX) proteins are a family of gas sensors found in diverse classes of bacteria and eukaryotes. The most commonly characterized bacterial H-NOX domains are from facultative anaerobes and are activated through a conformational change caused by formation of a 5-coordinate Fe(II)-NO complex. Members of this H-NOX subfamily do not bind O2 and therefore can selectively ligate NO even under aerobic conditions. In contrast, H-NOX domains encoded by obligate anaerobes do form stable 6-coordinate Fe(II)-O2 complexes by utilizing a conserved H-bonding network in the ligand-binding pocket. The biological function of O2-binding H-NOX domains has not been characterized. In this work, the crystal structures of an O2-binding H-NOX domain from the thermophilic obligate anaerobe Caldanaerobacter subterraneus (Cs H-NOX) in the Fe(II)-NO, Fe(II)-CO, and Fe(II)-unliganded states are reported. The Fe(II)-unliganded structure displays a conformational shift distinct from the NO-, CO-, and previously reported O2-coordinated structures. In orthogonal signaling assays using Cs H-NOX and the H-NOX signaling effector histidine kinase from Vibrio cholerae (Vc HnoK), Cs H-NOX regulates Vc HnoK in an O2-dependent manner and requires the H-bonding network to distinguish O2 from other ligands. The crystal structures of Fe(II) unliganded and NO- and CO-bound Cs H-NOX combined with functional assays herein provide the first evidence that H-NOX proteins from obligate anaerobes can serve as O2 sensors.

Accelerating Bleaching of Soybean Oil by Ultrasonic Horn and Bath Under Sparge of Helium, Air, Argon and Nitrogen Gas

The aim of this study was to investigate the color (red and yellow) and pigments (carotenoid and chlorophyll) of soybean oil by the ultrasonic horn and bath under different conditions (gas, temperature, time and frequency). According design expert equation gas was a more important factor for the reduction of oil pigments and colors compared with other factors. For this purpose, the reduction percentage of red and yellow color of oil at the ultrasonic horn and bath was as follows: argon > air > helium > nitrogen. However, temperature and frequency could change the effect of gases during ultrasonic bleaching process. Increasing temperature and decreasing frequency reduced the color of bleached oil under diatomic gases compared with monoatomic gases condition. Practical Applications The use of monoatomic or diatomic gases combined with temperature, time and frequency under bath or horn ultrasonic conditions is recommended for accelerating the bleaching process in order to the reduce the consumption of temperature and waste of time.

Thermodynamic Properties of Gold

The thermodynamic properties of gold have been evaluated to 3200 K. Selected values include an enthalpy of sublimation of 368.4 ± 1.1 kJ·mol−1 for the monatomic gas at 298.15 K, a dissociation enthalpy D0 of 221.5 ± 0.8 kJ·mol−1 for the diatomic gas species at absolute zero and a derived equilibrium boiling point of 3131 K at one atmosphere pressure.

Kinetic Models and Gas-Kinetic Schemes for Hybrid Simulation of Partially Rarefied Flows

Approaches to predict flowfields that display rarefaction effects incur a cost in computational time and memory that is considerably higher than methods commonly employed for continuum flows. For this reason, to simulate flowfields where continuum and rarefied regimes coexist, hybrid techniques have been introduced. In the present work, analytically defined gas-kinetic schemes based on the Shakhov and Rykov models, for monatomic and diatomic gas flows, respectively, are proposed and evaluated, with the aim of being used in the context of hybrid simulations. This should reduce the region where more expensive methods are needed by extending the validity of the continuum formulation. Moreover, because, for rarefied gas flows at high velocities, it is necessary to take into account the nonequilibrium among the internal degrees of freedom, the extension of the approach to employ diatomic gas models with rotational relaxation is a mandatory first step toward realistic simulations. Compared to the previous works the presented scheme is defined directly on the basis of kinetic models that involve a Prandtl number correction. Moreover, the methods are defined fully analytically instead of making use of Taylor expansion for the evaluation of the required derivatives. The scheme has been tested for various test cases and Mach numbers proving to produce reliable predictions in agreement with other approaches for near-continuum flows. Finally, the performance of the scheme, in terms of memory and computational time, compared to discrete velocity methods makes it a compelling alternative in place of more complex methods for hybrid simulations of weakly rarefied flows.

Numerical study of shock/vortex interaction in diatomic gas flows

The particle-based direct simulation of Monte Carlo(DSMC) was present and validated for the investigation of non-equilibrium effects in diatomic gas flows. All the validations show that the results of the present DSMC is in agreement with the experimental data. Then, the numerical studies of micro scale shock/composite-vortex interactions in diatomic gas flows were conducted. The substantial attenuation of enstrophy in diatomic gas flow is observed. Differ from the sharp decreasing in diatomic gas, the time evolution of enstrophy in monatomic gas flow decrease linearly in the whole process. This study also shows that the vortex deformation through a shock, in particular, is observed to be strongly dependent on the shock and vortex strengths. Also, it is also found that strong interaction can also cause vorticity production in microscale shock/vortex interaction for diatomic gas flow. The attenuation, analogous to DSMC results, overwhelms the vorticity generation only in a limited set of regimes with low shock Mach number, small vortex size, or weak vortex. Besides, in diatomic gas flow, viscous vorticity generation is also most dominant in the three dynamical processes of vorticity transportation, followed by dilatational and baroclinicvorticity generation. The present study conform that shock/vortex present different features in strong and weak interactions for monatomic and diatomic gas flows. Furthermore, it provides a new way for the investigation of non-equilibrium effects.

DFT investigation on molecular structure of zirconia nanoparticle and its adsorption structures with elementary gases

The geometry optimizations of zirconia nanoparticle (ZrO2–NP), represented by the high symmetric (ZrO2)12 cluster and its adsorption configurations with diatomic (H2, N2, O2, CO and NO), triatomic (CO2, N2O, NO2, H2O, SO2 and H2S) and polyatomic (C2H2, C2H4, CH4 and NH3) gases were carried out using density functional theory method. Adsorption energies of all relevant gases on the ZrO2–NP obtained by the B3LYP and M06–2X methods are reported. Two types of adsorption sites on the ZrO2–NP, the planar and the v–shaped sites of Zr centers which adsorption strength of the former is higher than the later, were found. The zirconia nanoparticle applied for detecting oxygen molecule via its conductivity measurement could be recommended.

Control of an air siphon nozzle using hydrogen and gases other than air

Air siphon nozzles are a simple device commonly used to transport liquid fuel to a combustor. Recent research in dual fuel combustion demonstrates benefits to using gas and liquid phase fuels in the same system. This paper demonstrates the use of hydrogen and other gases other than air to control liquid fuel flow through the siphon nozzle. It is shown mathematically that the two major variables controlling liquid flow rate are the specific heat ratio and upstream pressure of the gas. Since diatomic gases have similar specific heat ratios (k = 1.4 at 300 K), a mixture of hydrogen and air can control liquid flow using only pressure, regardless of mixture composition. At relevant gas pressures, it is analytically shown that the error from changing k is small for 1.1 < k < 1.67. The analytical work was verified experimentally by measuring the suction pressure on the fuel line. Tests using air, hydrogen, argon and helium showed good agreement between gases. However, the deviation begins to increase with the use of propane. This flexibility with gas selection enables liquid flow control with gas mixtures such as hydrogen rich reformate.

On the calibration of polarimetric Thomson scattering by Raman polarimetry

Polarimetric Thomson scattering (TS) is an alternative method for the analysis of Thomson scattering spectra in which the plasma temperature Te is determined from the depolarization of the TS radiation. This is a relativistic effect and therefore the technique is suitable only for very hot plasmas (Te > 10 keV) such as those of ITER. The practical implementation of polarimetric TS requires a method to calibrate the polarimetric response of the collection optics carrying the TS light to the detection system, and in particular to measure the additional depolarization of the TS radiation introduced by the plasma-exposed first mirror. Rotational Raman scattering of laser light from diatomic gases such as H2, D2, N2 and O2 can provide a radiation source of predictable intensity and polarization state from a well-defined volume inside the vacuum vessel and is therefore suitable for these calibrations. In this paper we discuss Raman polarimetry as a technique for the calibration of a hypothetical polarimetric TS system operating in the same conditions of the ITER core TS system and suggest two calibration methods for the measurement of the additional depolarization introduced by the plasma-exposed first mirror, and in general for calibrating the polarimetric response of the detection system.

A CRITERION FOR THE VALIDITY OF PARKER’S MODEL IN THERMAL ESCAPE PROBLEMS FOR PLANETARY ATMOSPHERES

Mass escape rate of mon- and diatomic gases from a planetary atmosphere is studied based on Parker's model for a broad range of surface conditions. The escape rate is found to follow two asymptotic regimes, namely, high- and low-density regimes, with a short intermediate regime between them. Equations for the escape rate in every asymptotic regime are found theoretically. A comparison of the obtained escape rates with results of recent kinetic simulations shows that Parker's model satisfactorily predicts escape rates only in the high-density regime. Based on this finding, a criterion of applicability of Parker's model for the calculation of the mass escape rate is established.

Thermodynamic Properties of Silver

The thermodynamic properties of silver have been evaluated to 2700 K. Selected values include an enthalpy of sublimation of 284.8 ± 0.9 kJ/mol for the monatomic gas at 298.15 K, a dissociation enthalpy D 0 of 157.7 ± 2.2 kJ/mol for the diatomic gas species at absolute zero, and a derived equilibrium boiling point of 2433 K at one atmosphere pressure.

Experimental and theoretical analysis of effects of atomic, diatomic and polyatomic inert gases in air and EGR on mixture properties, combustion, thermal efficiency and NOx emissions of a pilot-ignited NG engine

Argon (Ar), nitrogen (N2) and carbon dioxide (CO2), present in exhaust gas recirculation (EGR) and air, are common atomic, diatomic and polyatomic inert gases, separately. As dilution gases, they are always added into the intake charge to reduce nitrogen oxides (NOx) emissions, directly or along with EGR and air. This paper presents the effects of Ar, N2 and CO2 on mixture properties, combustion, thermal efficiency and NOx emissions of pilot-ignited natural gas engines. Thermodynamic properties of the air-dilution gas mixture with increasing dilution gases, including density, gas constant, specific heat ratio, specific heat capacity, heat capacity and thermal diffusivity, were analyzed theoretically using thermodynamic relations and ideal gas equations based on experimental results. The thermal and diluent effects of dilution gases on NOx emissions were investigated based on Arrhenius Law and Zeldovich Mechanism, experimentally and theoretically. The experiments were arranged based on an electronically controlled heavy-duty, 6-cylinder, turbocharged, pilot-ignited natural gas engine. The resulted show that adding different inert gases into the intake charge had different influences on the thermodynamic properties of the air-dilution gas mixture. No great change in combustion phase was found with increasing dilution ratio (DR) of Ar, while the flame development duration increased significantly and CA50 moved far away from combustion top dead center (TDC) obviously with increasing DR for both of N2 and CO2. Adding Ar was superior in maintaining high thermal efficiencies than CO2 and N2, but adding CO2 was superior in maintaining low NOx emissions than N2 and Ar. In addition, the mechanisms of reducing NOx emissions were different for different dilution gases.

Thermodynamic Properties of Copper

The thermodynamic properties of copper have been evaluated to 2900 K. Selected values include an enthalpy of sublimation of 337.2 ± 1.7 kJ/mol for the monatomic gas at 298.15 K, a dissociation enthalpy D 0 of 192.0 ± 2.0 kJ/mol for the diatomic gas species at absolute zero and a derived equilibrium boiling point of 2843 K at one atmosphere pressure.

Nonequilibrium Flows Revisited with a Generalized Chapman–Enskog Procedure

Chapman–Enskog methods used for the analysis of hypersonic flows in vibrational and chemical nonequilibrium are presented. Taking into account the nonuniqueness of these methods, a more general procedure is developed and is shown to be able to cover all practical situations, including vibration–chemistry interaction. Application to a dissociating diatomic gas flow is proposed and discussed, adopting a step-by-step description, to point out the hypotheses and eventual approximations made at each step. Exact and approximate solutions are tested and compared by computing corresponding flows generated by a strong shock wave.

Origin and Impact of Nitric Oxide in Pseudomonas aeruginosa Biofilms

The formation of the organized bacterial community called biofilm is a crucial event in bacterial physiology. Given that biofilms are often refractory to antibiotics and disinfectants to which planktonic bacteria are susceptible, their formation is also an industrially and medically relevant issue. Pseudomonas aeruginosa, a well-known human pathogen causing acute and chronic infections, is considered a model organism to study biofilms. A large number of environmental cues control biofilm dynamics in bacterial cells. In particular, the dispersal of individual cells from the biofilm requires metabolic and morphological reprogramming in which the second messenger bis-(3′-5′)-cyclic dimeric GMP (c-di-GMP) plays a central role. The diatomic gas nitric oxide (NO), a well-known signaling molecule in both prokaryotes and eukaryotes, is able to induce the dispersal of P. aeruginosa and other bacterial biofilms by lowering c-di-GMP levels. In this review, we summarize the current knowledge on the molecular mechanisms connecting NO sensing to the activation of c-di-GMP-specific phosphodiesterases in P. aeruginosa, ultimately leading to c-di-GMP decrease and biofilm dispersal.

Thermal Decomposition of Tungsten Nitrido Precursors for Low Temperature MOCVD of WNxCy

As the feature size of electronic devices continues to shrink, the integrated circuit device density increases. This not only modifies the RC time delay to severely limit the device performance, but also places increased demand on Cu metallization effectiveness (1). The extremely high diffusivity of Cu in Si and its ‘killer’ effect on devices has led to the requirement of a barrier layer to prevent Cu transport into the underlying Si. Among various candidates, W-based nitrides have shown promise as replacements of current barrier layers due to their good thermal stability, low resistivity, and the possibility of one-step CMP with Cu slurry (2, 3). In addition, a single barrier layer process is simpler than the Ta-based barrier layer, which needs a double layer of TaN and Ta. The performance of W-based nitrides increases when they are alloyed with carbide to make WNxCy due to its higher crystallization temperature and possibility to adjust film resistivity to lower values. The tungsten nitrido complex WN(NMe2)3 was demonstrated to serve as a single-source precursor for metal organic chemical vapor deposition (MOCVD) of WNxCy films at temperatures as low as 125 ˚C (4). The goal of this study is to understand decomposition mechanisms and their kinetics for the WN(NMe2)3 precursor, and furthermore, to optimize conditions for deposition of the WNxCy film. To elucidate the mechanism and kinetics of thermal decomposition of WN(NMe2)3, in-situ Raman spectroscopy was used to quantitatively measure the disappearance of precursor and appearance of products. An up-flow, cold-wall MOCVD reactor was designed to perform Raman scattering experiments along the centerline of the reactor (5). The system design allows the CVD reactor to translate along three-dimensionally, to permit the laser to focus on any spot in the reactor. In-situ Raman experiments were performed using a heater set point temperature of 650 ˚C. Axial centerline temperature profiles in the reactor are measured by analysis of the rotational bands of the diatomic N2 carrier gas. Due to the low volatility of the precursor, it was dissolved in liquid pyridine and delivered to the reactor as an aerosol with N2 carrier gas (6). The 532 nm line of a Nd:YVO4 solid-state laser at 1.5 W was used as the light source to excite the molecules in the sample. Raman spectra were measured at various distances below the heated susceptor surface and thus various temperatures from 159 ˚C to 474 ˚C. Density Functional Theory (DFT) calculations (using the B3LYP functional and LanL2DZ basis sets) were performed to assess possible pathways of thermal decomposition of WN(NMe2)3 and to assign observed Raman peaks to the decomposition products. The results of this study are consistent with proposed mechanistic steps for the thermal decomposition of the precursor, including dimerization of the precursor and loss of the amine. In addition to gas phase data, liquid phase Raman experiments were performed to better define additional species that are Raman active but not detected in the lower density gas phase experiments and to find vibrational frequencies before the molecule is decomposed.

China: Columbian – carbon black

Through the use of the electrum-tarnish method the following equation has been found to interrelate the composition of pyrrhotite, fugacity of sulfur, and temperature: In this equation fs2 is the fugacity of sulfur relative to the ideal diatomic gas at 1 atm, N is the mol fraction of FeS in pyrrhotite (in the system FeS-S2), and T the absolute temperature. The experimental uncertainty in the equation is 0–003 in N. The activity of FeS (aFeS) in pyrrhotite relative to the pure substance at the temperature of consideration follows from the above equation by virtue of the Gibbs-Duhem relation; it is given by:The electrum-tarnish method has permitted us to determine the fs2 vs. T curve for the univariant assemblage pyrrhotite-pyrite-vapor from 743 to 325°C. Our determinations of the composition of pyrrhotite are in excellent agreement with the results of Arnold. The activity of FeS in pyrite-saturated pyrrhotite is very different from unity, a fact that greatly influences the interpretation of some other phase equilibrium studies involving pyrrhotite and their application to sulfide mineral assemblages, but has little effect on the more general calculations of composition of hydrothermal or magmatic fluids.Pressure effects calculated from available volumetric data on the phases are small.

Energetic evaluation of possible interstitial compound formation of BaSi2 with 2p-, 3s-, and 3d-elements using first-principle calculations

The energy changes in the formation of interstitially doped BaSi2, caused by doping with Na, Mg, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, B, C, N, O, F, and Ne, are calculated using the Perdew–Wang generalized gradient approximations of the density functional theory. It is predicted that the majority of the elements, apart from Na, Mg, Zn, and Ne, are capable of forming interstitially doped compounds with BaSi2, if these elements are provided as an isolated atom. However, the energetic stabilities of the standard states of these elements (metals, diatomic gases, etc.) exceed the energy gain accompanying the formation of the interstitial compounds and, therefore, the conventional diffusion method using metals or gaseous source materials cannot produce the interstitial compounds. From the energetic perspective, B, C, N, O, and F appear to be favorably inserted into the BaSi2 lattice, but the observed behavior of B-implanted BaSi2 suggests that substitution of B for Si may occur.