Angular distribution of electrons elastically scattered from hydrogen atoms

Shyn, T. W.; Cho, S. Y.

doi:10.1103/physreva.40.1315

“…Laboratory measurements of the e-H momentum transfer cross sections have been performed by Williams (1975a,b); Callaway & Williams (1975); Shyn & Cho (1989); Shyn & Grafe (1992) (for a detailed review of the experimental methods and results, see Bederson & Kieffer 1971;Trajmar & Kanik 1995). Theoretical and experimental results are shown in Fig.…”

Section: E -Hmentioning

confidence: 99%

Three-fluid plasmas in star formation

Pinto

¹

,

Galli

²

2008

A&A

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Context. The charged component of the insterstellar medium consists of atomic and molecular ions, electrons, and charged dust grains, coupled to the local Galactic magnetic field. Collisions between neutral particles (mostly atomic or molecular hydrogen) and charged species, and between the charged species themselves, affect the magnetohydrodynamical behaviour of the medium and the dissipation of electric currents. Aims. The friction force due to elastic collisions between particles of different species in the multi-component interstellar plasma is a nonlinear function of the temperature of each species and the Mach number of the relative drift velocity. The aim of this paper is to provide an accurate and, as far as possible, complete set of momentum transfer rate coefficients for magnetohydrodynamical studies of the interstellar medium. Methods. Momentum transfer rates are derived from available experimental data and theoretical calculations of cross sections within the classic approach developed by Boltzmann and Langevin for a wide range of values of the temperature and the drift velocity. Results. Accurate numerical values for momentum transfer rates are obtained and fitted to simple analytical formulae expressing the dependence of the results on the gas temperature and the relative drift velocity. The often used polarization approximation is in satisfactory agreement with our results only for collisions between H 2 and molecular ions (HCO + , H + 3 ). For other kinds of collisions, the polarization approximation fails by large factors, and must be replaced by more accurate expressions.

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“…( 14) of Draine (1983) for the same values of the drift velocity (dotted curve).The dashed line shows the Langevin rate. fer cross sections have been performed by Williams (1975a,b), Callaway & Williams (1975), Shyn & Cho (1989), and Shyn & Grafe (1992) (for a detailed review of the experimental methods and results, see Bederson &Kieffer 1971 andKanik 1995). Theoretical and experimental results are shown in Fig.…”

Section: E -Hmentioning

confidence: 99%

Three-fluid plasmas in star formation II. Momentum transfer rate coefficients

Pinto,

Galli

2008

Preprint

0

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Context. The charged component of the insterstellar medium consists of atomic and molecular ions, electrons, and charged dust grains, coupled to the local Galactic magnetic field. Collisions between neutral particles (mostly atomic or molecular hydrogen) and charged species, and between the charged species themselves, affect the magnetohydrodynamical behaviour of the medium and the dissipation of electric currents. Aims. The friction force due to elastic collisions between particles of different species in the multi-component interstellar plasma is a nonlinear function of the temperature of each species and the Mach number of the relative drift velocity. The aim of this paper is to provide an accurate and, as far as possible, complete set of momentum transfer rate coefficients for magnetohydrodynamical studies of the interstellar medium. Methods. Momentum transfer rates are derived from available experimental data and theoretical calculations of cross sections within the classic approach developed by Boltzmann and Langevin for a wide range of values of the temperature and the drift velocity. Results. Accurate numerical values for momentum transfer rates are obtained and fitted to simple analytical formulae expressing the dependence of the results on the gas temperature and the relative drift velocity. The often used polarization approximation is in satisfactory agreement with our results only for collisions between H 2 and molecular ions (HCO + , H + 3 ). For other kinds of collisions, the polarization approximation fails by large factors, and must be replaced by more accurate expressions.

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“…In the case of electrons, the collisions can be elastic or inelastic depending on the energies of the particles involved. Collision cross sections have been taken from the literature [2,11,[16][17][18][19] (figure 2). They consist of only the most important reaction paths.…”

Section: The Instant Of Collisionmentioning

confidence: 99%

“…In this investigation the hard sphere model is preferred, because in the case of hydrogen equation (4) strongly overestimates the variation in the differential cross section with electron energy. For example, the differential cross sections of hydrogen atoms have been found to be nearly independent of the scattering angle at an electron energy of 5 eV [17], while equation (4) suggests a sixfold higher cross section at χ = 0 • compared to χ = 180 • . Nevertheless, we tried equation ( 5) in our code but found that the sum of the power shares of the different processes is then approximately 25-30% higher than the input power.…”

Section: Elastic Collisionsmentioning

confidence: 99%

Monte Carlo simulation of a microwave plasma in hydrogen

Rau¹

2000

J. Phys. D: Appl. Phys.

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Monte Carlo simulations of a microwave plasma (frequency 2.45 GHz, pressure 2-15 kPa) in hydrogen are reported. The simulation follows the chaotic motion of a number of electrons and ions under the influence of outer (microwave) and inner (other charge carriers) electric fields. The charge carriers collide with the neutral gas particles either in an elastic or inelastic manner. In such a simulation only basic physical laws have to be applied. The simulations produce reaction rates for the different reaction paths of main importance in a straightforward way. The electron energy distribution function (EEDF), which is simply a time average of the actual energies of the electrons, deviates from the Maxwell distribution by a depletion at low and high electron energies. Correction functions are derived which allow EEDFs under widely different plasma conditions to be calculated from the respective Maxwell distributions. Finally the results are applied to calculate mean mass densities in a closed plasma tube which are then compared with measured values.

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Angular distribution of electrons elastically scattered from hydrogen atoms

Cited by 22 publications

References 11 publications

Three-fluid plasmas in star formation

Three-fluid plasmas in star formation

Three-fluid plasmas in star formation II. Momentum transfer rate coefficients

Monte Carlo simulation of a microwave plasma in hydrogen

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