@article {1568,
title = {Tracer diffusion in hard sphere fluids from molecular to hydrodynamic regimes},
journal = {Journal of Chemical Physics},
volume = {125},
number = {20},
year = {2006},
note = {ISI Document Delivery No.: 110UZTimes Cited: 6Cited Reference Count: 43Sokolovskii, R. O. Thachuk, M. Patey, G. N.},
month = {Nov},
pages = {10},
type = {Article},
abstract = {Molecular dynamics is employed to investigate tracer diffusion in hard sphere fluids. Reduced densities (rho(*)=rho sigma(3), sigma is the diameter of bath fluid particles) ranging from 0.02 to 0.52 and tracers ranging in diameter from 0.125 sigma to 16 sigma are considered. Finite-size effects are found to pose a significant problem and can lead to seriously underestimated tracer diffusion constants even in systems that are very large by simulation standards. It is shown that this can be overcome by applying a simple extrapolation formula that is linear in the reciprocal cell length L-1, allowing us to obtain infinite-volume estimates of the diffusion constant for all tracer sizes. For higher densities, the range of tracer diameters considered spans diffusion behavior from molecular to hydrodynamic regimes. In the hydrodynamic limit our extrapolated results are clearly consistent with the theoretically expected slip boundary conditions, whereas the underestimated values obtained without extrapolation could easily be interpreted as approaching the stick limit. It is shown that simply adding the Enskog and hydrodynamic contributions gives a reasonable qualitative description of the diffusion behavior but tends to overestimate the diffusion constant. We propose another expression that fits the simulation results for all densities and tracer diameters. (c) 2006 American Institute of Physics.},
keywords = {BOUNDARY-CONDITIONS, BROWNIAN PARTICLE, COEFFICIENT, DYNAMICS SIMULATION, friction, KINETIC-THEORY, RIGID PARTICLES, SINGLE-PARTICLE MOTION, SIZE DEPENDENCE, TRANSPORT-COEFFICIENTS, VELOCITY-AUTOCORRELATION FUNCTION},
isbn = {0021-9606},
url = {://000242408100031},
author = {Sokolovskii, R. O. and Thachuk, M. and Patey, G. N.}
}
@article {5007,
title = {Analysis of physical observables and approximate distribution functions for drifting linear ions},
journal = {Physical Review A},
volume = {64},
number = {6},
year = {2001},
note = {ISI Document Delivery No.: 500CKTimes Cited: 3Cited Reference Count: 22},
month = {Dec},
pages = {13},
type = {Article},
abstract = {The accuracy of two recently proposed approximate distribution functions for drifting linear ions [R. Baranowski and M. Thachuk, Phys. Rev. A 63, 032503 (2001) is tested at a number of levels of microscopic detail. Through formal mathematical manipulations. low-order expressions are derived for a number of physical observables, including the angular momentum dependence of the drift velocity, and parallel and perpendicular translational temperatures. as well as the dependence of the quadrupolar alignment parameter on the parallel and perpendicular velocity components. Finally, comparisons are made between the approximate forms and basis set expansions of the distribution function utilized in formal solutions of the Boltzmann equation, with the goal of suggesting general features of these basis sets that might help improve convergence.},
keywords = {ATOMIC GASES, COLLISIONAL ALIGNMENT, DYNAMICS, MOLECULES, ROTATIONAL ALIGNMENT, SCATTERING, SUPERSONIC EXPANSIONS, SYSTEMS, TRANSPORT-COEFFICIENTS, VELOCITY DISTRIBUTIONS},
isbn = {1050-2947},
url = {://000172608200050},
author = {Baranowski, R. and Thachuk, M.}
}
@article {5008,
title = {Simple analytic form for the velocity-angular-momentum distribution function of drifting linear ions},
journal = {Physical Review A},
volume = {63},
number = {3},
year = {2001},
note = {ISI Document Delivery No.: 408HPTimes Cited: 6Cited Reference Count: 21},
month = {Mar},
pages = {12},
type = {Article},
abstract = {A simple analytic form is presented for the full velocity-angular-momentum distribution function for gasphase linear ions drifting in an atomic bath gas under a constant external electric field. Predictions of temperatures, drift velocities, and alignment parameters from this form are compared in detail against molecular-dynamics calculations for NO+ drifting in helium. The form is accurate, compact, and based upon a physically motivated expansion. In essence, simple Maxwellian-like functions are generalized by allowing appropriate temperatures to become functions of velocity and rotational ang;lar momentum. Over a wide range of reduced field strengths, including the equilibrium state, this form is able to account accurately for many properties at a microscopic level with only a few adjustable parameters.},
keywords = {ATOMIC GASES, COLLISIONAL ALIGNMENT, DYNAMICS, MOLECULES, ROTATIONAL ALIGNMENT, SCATTERING, SUPERSONIC EXPANSIONS, SWARM, TRANSPORT-COEFFICIENTS},
isbn = {1050-2947},
url = {://000167321000041},
author = {Baranowski, R. and Thachuk, M.}
}
@article {4468,
title = {Molecular-dynamics study of rotational alignment of NO+ drifting in helium-velocity and angular momentum distribution functions},
journal = {Journal of Chemical Physics},
volume = {111},
number = {22},
year = {1999},
note = {ISI Document Delivery No.: 258RKTimes Cited: 8Cited Reference Count: 27},
month = {Dec},
pages = {10061-10068},
type = {Article},
abstract = {Collision-induced rotational alignment of NO+ ions drifting in a helium buffer gas is studied with molecular dynamics using the ab initio potential surface of S. K. Pogrebnya [Int. J. Mass Spectrom. Ion Proc. 149/150, 207 (1995)], obtained via a coupled-cluster singles-doubles approximation. We examine average translational and rotational temperatures, velocity and angular momentum distributions, and the dependence of these quantities on the applied electric field. The distributions show that angular momentum is preferentially aligned perpendicular to the electric field vector. We investigate the mechanism of this alignment through a multipolar moment expansion, and propose and demonstrate the accuracy of a bi-Maxwellian analytic form for describing the angular momentum distribution. (C) 1999 American Institute of Physics. [S0021-9606(99)00546-2].},
keywords = {ATOMIC GASES, HE, IONS, KINETIC-THEORY, MOBILITIES, NA+, TRANSPORT-COEFFICIENTS, TUBE EXPERIMENTS},
isbn = {0021-9606},
url = {://000083852700018},
author = {Baranowski, R. and Thachuk, M.}
}
@article {4328,
title = {The Quadrature Discretization Method (QDM) in comparison with other numerical methods of solution of the Fokker-Planck equation for electron thermalization},
journal = {Journal of Mathematical Chemistry},
volume = {24},
number = {4},
year = {1998},
note = {ISI Document Delivery No.: 165EGTimes Cited: 7Cited Reference Count: 67},
pages = {291-319},
type = {Article},
abstract = {The determination of the relaxation of electrons in atomic gases continues to be an important physical problem. The main interest is the determination of the time scale for the thermalization of electrons in different moderators and the nature of the time-dependent electron energy distribution. The theoretical basis for the study of electron thermalization is the determination of the electron distribution function from a solution of the Lorentz-Fokker- Planck equation. The present paper considers a detailed comparison of different numerical methods of solution of the Lorentz-Fokker- Planck equation for the electron distribution function. The methods include a pseudospectral method referred to as the Quadrature Discretization Method (QDM) which is based on non-standard polynomial basis sets, a finite-difference method, and a Lagrange interpolation method. The Fokker-Planck equation can be transformed to a Schrodinger equation, and methods developed for the solution of either equation apply to the other.},
keywords = {ACCELERATION, BOLTZMANN-EQUATION, DISCRETE-ORDINATE, ENERGY-DISTRIBUTION, FIELD DEPENDENCE, method, MULTITERM CALCULATIONS, QUANTUM-MECHANICS, RARE-GAS MODERATORS, STOCHASTIC, TRANSPORT-COEFFICIENTS, VELOCITY DISTRIBUTION FUNCTION},
isbn = {0259-9791},
url = {://000078506600001},
author = {Leung, K. and Shizgal, B. D. and Chen, H. L.}
}
@article {7288,
title = {ELECTRON DEGRADATION AND THERMALIZATION IN CH4 GAS},
journal = {Journal of Chemical Physics},
volume = {97},
number = {3},
year = {1992},
note = {ISI Document Delivery No.: JE891Times Cited: 17Cited Reference Count: 44},
month = {Aug},
pages = {2061-2074},
type = {Article},
abstract = {The relaxation to equilibrium of an ensemble of electrons dilutely dispersed in a large excess of CH4 is studied with solutions of the Boltzmann equation. Elastic and vibrationally inelastic collision processes are included in the analysis. The relaxation time for the approach to equilibrium defined for the relaxation of the average electron energy is determined for two different cross section sets. The kinetic theory formalism, based on the Boltzmann equation, is compared with the formalism used in radiation chemistry and physics and based on the Spencer-Fano equation.},
keywords = {APPROXIMATION, equation, INITIAL PRODUCTS, NEUTRAL GASES, SPENCER-FANO, SUBEXCITATION ELECTRONS, SWARMS, TIME-DEPENDENT ASPECTS, TRANSPORT-COEFFICIENTS, VELOCITY DISTRIBUTION FUNCTION, YIELDS},
isbn = {0021-9606},
url = {://A1992JE89100051},
author = {Kowari, K. and Demeio, L. and Shizgal, B.}
}
@article {7108,
title = {A UNIFORM WKB ANALYSIS OF THE COUPLING OF ELECTRON-ATTACHMENT AND THERMALIZATION IN GASES},
journal = {Journal of Physics B-Atomic Molecular and Optical Physics},
volume = {24},
number = {13},
year = {1991},
note = {ISI Document Delivery No.: FX594Times Cited: 11Cited Reference Count: 44},
month = {Jul},
pages = {2909-2923},
type = {Article},
abstract = {The presence of small amounts of strongly electronegative gases such as SF6 and CCl4 can greatly perturb from equilibrium the electron energy distribution function in a variety of electron devices. The effect of the addition of these electron attaching gases on the relaxation behaviour of a non-equilibrium electron distribution is studied with a linear Fokker-Planck equation. The time dependence of the electron mobility as well as other transport properties can be expressed as a sum of exponential terms with each term characterized by an eigenvalue of the Fokker-Planck operator. This eigenvalue problem can be transformed to a Schrodinger equation with a potential function parametrized by the electron-atom cross sections, the electric field strength and the gas temperature. In the present paper, the eigenvalues and eigenfunctions are calculated with a WKB semiclassical approximation and compared with exact results. The application of the WKB approximation provides a useful way to calculate these strongly perturbed distributions. The specific applications in this paper are for the relaxation of electrons in the inert gases in the presence of small amounts of SF6 or CCl4.},
keywords = {CROSS-SECTIONS, DISCHARGES, FOKKER-PLANCK EQUATION, MIXTURES, MODERATORS, RARE, relaxation, SF6, SWARM DEVELOPMENT, TRANSPORT-COEFFICIENTS},
isbn = {0953-4075},
url = {://A1991FX59400007},
author = {Shizgal, B.}
}