稀有气体纯质热物理性质的预测

根据量子力学和分子运动学理论,采用稀有气体的ab initio势能,分别计算了氦-4、氖、氩、氪和氙纯质在低密度时的热物理性质,包括第二维里系数,热扩散系数和热扩散因子,计算的温度范围为50—5000 K.预测结果具有较高的精度,与采用经验势能的计算结果相比,本文结果更接近实验数据和REFPROP 8.0的标准值,为相关的科学研究和工程应用提供了所需的基础数据. 关键词： ab initio势能')" href="#">ab initio势能 稀有气体 热物理性质     

H-H and C-H coupling constants in neutral and protonated azines

New measurements are reported of the density dependent depolarization ratio for argon, krypton, xenon, methane and sulphur hexafluoride, and the results are analysed to provide values for the second and third depolarization virial coefficients. The relationships between the second depolarization virial coefficient, the zeroth moment of the two-body Rayleigh spectrum and the second Kerr virial coefficient are considered, and it is shown that they now provide consistent results for the collision-induced pair polarizability anisotropy. Former inconsistencies are attributed to insufficient allowance for the effects of three-body interactions. Calculations of the second and third depolarization virial coefficients based on the DID model and using the Maitland-Smith potential are in excellent agreement with the experimental results for argon, krypton and xenon.     

Glory undulations in the total cross section for scattering of heavy rare gas atoms

In a supersonic molecular beam apparatus the velocity dependence of the total cross section for scattering of argon and krypton beams by argon, krypton and xenon has been measured for relative velocities ranging from 0.55 to 4.30 km · s^-1. For all these systems a number of glory extrema were well resolved. The measured cross sections are compared with cross sections calculated on the basis of recently proposed pair potentials. For the systems Ar-Ar, Kr-Kr and Ar-Kr the glory structure is fairly well described by the potentials, however, the energy dependence of the cross sections is not. The available potentials for the systems Ar-Xe and Kr-Xe describe the glory structure less accurately. Rather severe changes of the potentials will be required to obtain agreement with the total cross section data. A qualitative analysis of the required changes is presented.     

Elementary vibrations in rare-gas crystals: Frequencies of phonons in compressed argon, krypton, and xenon crystals

The lattice dynamics of rare-gas crystals is investigated in the framework of the ab initio approach with the inclusion of the nonadiabatic effects over a wide range of pressures. The frequencies of phonons in argon, krypton, and xenon crystals are calculated at pressures p ≠ 0. Analysis of the contributions from different interactions to the lattice dynamics of the crystals demonstrates that the difference between the phonon frequencies calculated within several models is most pronounced at the boundary of the Brillouin zone. Under strong compressions, the phonon spectrum along the Δ direction is distorted and the longitudinal mode is softened as a result of the electron-phonon interaction, with the relative contribution decreasing in the series Ar, Kr, and Xe. The calculated phonon frequencies are in good agreement with the experimental data available in the literature for argon crystals at a pressure p = 3.1 GPa.     

Accurate second Kerr virial coefficient of rare gases from the state-of-the-art ab initio potentials and (hyper)polarizabilities

The second Kerr virial coefficient of rare gases is studied in this work using the best ab initio potentials and (hyper)polarizabilities in the literature. The second Kerr virial coefficient of helium-4, helium-3, neon, argon, and krypton and its polarizability component of xenon are computed by the semi-classical method together with the Padé approximant over a wide temperature range. In addition, the uncertainty of second Kerr virial coefficient is estimated from the uncertainties of the ab initio interaction-induced properties. The experimental and theoretical data in the literature is compared with our calculated values to examine the quality of this work. It is shown that our computed values in the supplementary materials are as accurate as the literature data at medium and high temperatures and are more reliable at low temperatures.     

Lattice dynamics in heavy rare-gas crystals under pressure

The lattice dynamics of compressed rare-gas crystals is theoretically investigated within the ab initio approach in the framework of the Tolpygo model, which explicitly includes the deformation of electron shells in the dipole approximation. The phonon frequencies of compressed rare-gas crystals are calculated with allowance made for the electron-phonon interaction at the mean-value points with the use of the dynamic matrix constructed with the ab initio short-range repulsive potential. The energy of zero-point vibrations and the heat capacity of compressed krypton and xenon face-centered cubic crystals are calculated in the harmonic approximation. The calculated temperature dependences of the specific heat capacity and the Debye temperature are in good agreement with the data available in the literature on the experiment at zero pressure and the results of the calculations within the density-functional theory for all pressures. The quantum effects, in particular, the energies E _zp of zero-point vibrations for krypton and xenon crystals, are investigated at different pressures.     

锂原子与部分惰性气体原子间相互作用势的计算

基于碱金属原子与惰性气体原子间相互作用的交换势主要来自碱金属原子的最外层S电子与惰性气体原子的最外层S电子之间 ,将面积分方法 (thesurfaceintegralmethod)推广 ,计算了Li原子与Ne、Ar、Kr和Xe原子间相互作用的vanderWaals势能曲线。其势阱的位置和深度与实验结果和其它理论计算结果符合得相当好     

Coexistence of non-registered monolayer and bilayer solid films: Statistical mechanics

A statistical mechanical theory is developed for low temperature solid monolayer and bilayer films of inert gases which are not in registry with the adsorbing substrate. The free energy is evaluated in terms of harmonic lattice vibrations of the solids, which is a quasiharmonic approximation. The lattice constant discontinuity in the transition under compression from the monolayer to the bilayer is found to be small, in accord with experiments on the adsorption of xenon and of krypton on silver and of argon on basal plane graphite. The calculations use realistic models for adatom interactions and substrate holding potentials in these three systems. At the bilayer formation, the lattice constant is still distinctly larger than that of the corresponding bulk solid under its vapor pressure. Thermodynamic functions of the phases at monolayer and bilayer coexistence are evaluated: the spreading pressure and the bilayer latent heat of adsorption are nearly constant along the coexistence curve for temperatures of 1 to 35 K. The calculated difference between the latent heats of adsorption of the monolayer and the bilayer is in good agreement with experimental data for the xenon/silver system, but it is smaller than the experimental difference for the krypton/silver and argon/graphite systems.     

One-Particle Distribution Functions and Thermodynamics of Crystals with Many-Body Forces. General Consideration and Investigation of the Properties of the Inert Gas Solids

A crystal is described by a probability density which is not symmetric regarding the interchange of phase-space coordinates between two molecules. The set of approximate equations for one-particle distribution functions with many-body forces is derived from the LIOUVILLE equation. The expression for the HELMHOLTZ free energy and the equation of state are obtained. The developed method is applied to the determination of the thermodynamic properties of crystalline argon, krypton, and xenon. The nearest-neighbor distances, internal energies, isothermal and adiabatic compressibilities, linear thermal expansion coefficients, specific heats C_v and C_p are calculated using the pair potentials of BARKER -POMPE , of BARKER -BOBETIC , and of LENNARD -JONES , together with the AXILROD -TELLER three-body potential. The obtained results are compared with the experimental data and discussed.     

Derivation of three-body collision-induced light-scattering spectrum moments for argon,krypton, xenon

The expressions for the zeroth and second moments of the three-body component of the collision-induced light-scattering spectrum are derived within the pair-potential and pair-polarizability approximations.

Computer calculation of the three-dimensional integrals which appear in the moment expressions is performed for Lennard-Jones and Barker potentials of argon, krypton and xenon within the dipole-induced-dipole approximation for the pair-polarizability.

The comparison of the results which are obtained with the two different potentials shows the very important role which is played by the choice of the potential in the determination of the values of the moments. An example of the applicability of the moment analysis of the three-body spectrum is also given for argon and the results compared with those of two-body.     

Positron annihilation in solid krypton and xenon

A computation of the life time of positrons as well as the angular distribution of the resulting gamma pair for polycrystalline krypton and xenon has been made. The calculations are based on the technique employed by Salvadori and Carbotte for the case of solid argon. The field seen by the positrons is constructed from the charge densities derived from Herman-Skillman wave functions. The positron wave functions are obtained using the Wigner-Seitz approximation. For electrons Herman-Skillman wave functions have been used. The computed distributions, when the effects of correlation are ignored, are wider than the experimental ones. The calculated values for the mean lives of positrons for krypton and xenon are 2.2×10⁻⁹ sec and 2.7×10⁻⁹ sec, respectively, and that for xenon is, as usual, longer than the measured value of 0.43×10⁻⁹ sec. Effects of electronpositron correlations on the angular distribution and the life time have been calculated for the case of krypton. When these corrections are taken into account, the life time of positrons in krypton is reduced by a factor of about eight and the angular distribution shows a slight narrowing. Paper A24 presented at 3rd Internat'l Conf. Positron Annihilation, Otaniemi, Finland (August 1973).     

Obtention des bandes de cameron par photo excitation de co en matrices d'argon de krypton et de xenon

CO trapped in solid matrices of argon, krypton and xenon has been excited by 10 eV photons. Cameron bands v′=0, v″=0,1,2,3,4 are observed during the irradiation. If red shifts are observed in argon and krypton matrices, the transition in xenon shows no differences with gas phase data.     

Size estimates of nobel gas clusters by Rayleigh scattering experiments

Noble gases (argon, krypton, and xenon) are puffed into vacuum through a nozzle to produce clusters for studying laser-cluster interactions. Good estimates of the average size of the argon, krypton and xenon clusters are made by carrying out a series of Rayleigh scattering experiments. In the experiments, we have found that the scattered signal intensity varied greatly with the opening area of the pulsed valve. A new method is put forward to choose the appropriate scattered signal and measure the size of Kr cluster.     

Emission characteristics and electron kinetic coefficients of the plasma of a transverse volume discharge initiated in a mixture of heavy inert gases with chlorine molecules

The results of studying the radiation due to argon, krypton, and xenon monochloride bands, as well as to the bands of chlorine molecules, from the plasma of a transverse Ar-Kr-Xe-Cl₂ volume discharge are reported. The working mixture of a pulse radiation source is optimized with regard to its pressure and elemental composition and parameters of an excitation system. By numerically solving the Boltzmann kinetic equation for the electron energy distribution function, the transport characteristics of plasma electrons and discharge power specific losses are found for different values of the reduced electric field strength. The plasma parameters are simulated for the quaternary mixture, which is most appropriate for a multiwave UV-VUV source. Qualitative analysis is conducted for the most important electron processes in the multicomponent plasma that govern the joint formation of argon, krypton, and xenon monochlorides in the transverse discharge.     

稀有气体在电离区压缩特性研究

采用Saha方程加Debye-Hückel修正简单近似模型,给出了稀有气体He, Ne, Ar, Kr, Xe在电离区的物态方程以及离化度.计算结果与已有实验和理论计算进行比较,验证了模型的可靠性.通过对稀有气体等温和冲击压缩特性理论分析,讨论了其压缩和电离的规律性.论证了在稀有气体He, Ne, Ar, Kr, Xe中,气体Xe具有较好的抗压缩性.     

Equilibrium properties of crystalline argon,krypton and xenon

By assuming an interaction energy for krypton and xenon of the same shape as that established for argon in an earlier paper and without introducing any adjustable parameters, values of the equilibrium properties of the crystals have been calculated which agree with the measured values to within the experimental accuracy or to within one per cent.     

Transitions and level lifetimes in Ne II, III, Ar II, III, Kr II, III and Xe II

Beam-foil spectra of neon, argon, krypton, and xenon have been recorded photographically with a fast spectrograph. The particle energies ranged from 150 to 750 keV. Transitions in Ne II, III; Ar II, III; Kr II, III; and Xe II have been identified. In addition, new multiples were identified in Ne II and Xe II and a number of unidentified lines were observed in neon, argon, and krypton. Characteristic intensity decays of over 170 lines were measured, giving the mean lives of ≈ 80 levels, with an estimated error of 30 per cent. Tabulation of energy levels with similar electron configurations in neon, argon, krypton, and xenon shows a definite progression to larger mean lives as the nuclear change increases.     

Atomic compound states in rare gases: Bound-state energies

Bound state energy of the compound states of the rare gases has been computed in the Hartree-Fock approximation. Results obtained for neon and xenon well agree with the experimental data and their usual interpretation. Different behaviour is shown by argon and krypton.     

Output power saturation in high current regions of different noble-gas ion lasers

Detailed experiments with cw noble gas ion lasers in high current regions are reported. Optimum lasing conditions and saturation behaviour of individual laser transitions in singly and doubly ionized argon, krypton, and xenon have been investigated. Various saturation mechanisms are discussed, such as resonance-radiation trapping, collisional deexcitation, multiple ionization, radial and axial gas pumping, and optical degradation of the cavity mirrors. The experimental results indicate that resonanceradiation trapping is the most probable cause of power limitation in noble-gas ion lasers.     

Neutron yields from structural metals during bombardment by heavy ions with 2.5 MeV/nucleon energy

Neutron yields during irradiation of structural metals and polymer film by argon, krypton, and xenon ions with 2.4 and 2.5 MeV/nucleon energies are measured on the CYTRACK and DC-110 cyclotrons. The angular distributions of neutrons from the target are measured. The LISE⁺⁺ is used for extrapolating the data obtained to other ions, their energy, and to other targets. The program was tested on experimental data found in the literature. As a result of comparison, it is established that the calculation results coincide with the experimental data within a coefficient of two.