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Journal articles on the topic 'Collisional effects'

Author: Grafiati

Published: 4 June 2021

Last updated: 10 February 2022

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1

Na, Sang-Chul, and Young-Dae Jung. "Screened Collision-Induced Quantum Interference in Collisional Plasmas." Zeitschrift für Naturforschung A 64, no. 3-4 (April 1, 2009): 233–36. http://dx.doi.org/10.1515/zna-2009-3-410.

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Abstract The effects of neutral particle collisions on the quantum interference in electron-electron collisions are investigated in collisional plasmas. The effective potential model taking into account the electronneutral particle collision effects is employed in order to obtain the electron-electron collision cross section including the total spin states of the collision system. It is found that the collision effects significantly enhance the cross section. In addition, the collision-induced quantum interference effects are found to be significant in the singlet spin state. It is shown that the quantum interference effects decrease with increasing the thermal energy of the plasma. It is also shown that the quantum interference effects increase with an increase of the collision energy

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2

Ngo, N. H., H. Tran, R. R. Gamache, and J. M. Hartmann. "Pressure effects on water vapour lines: beyond the Voigt profile." Philosophical Transactions of the Royal Society A: Mathematical, Physical and Engineering Sciences 370, no. 1968 (June 13, 2012): 2495–508. http://dx.doi.org/10.1098/rsta.2011.0272.

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A short overview of recent results on the effects of pressure (collisions) regarding the shape of isolated infrared lines of water vapour is presented. The first part of this study considers the basic collisional quantities, which are the pressure-broadening and -shifting coefficients, central parameters of the Lorentzian (and Voigt) profile and thus of any sophisticated line-shape model. Through comparisons of measured values with semi-classical calculations, the influences of the molecular states (both rotational and vibrational) involved and of the temperature are analysed. This shows the relatively unusual behaviour of H 2 O broadening, with evidence of a significant vibrational dependence and the fact that the broadening coefficient (in cm −1 atm −1 ) of some lines increases with temperature. In the second part of this study, line shapes beyond the Voigt model are considered, thus now taking ‘velocity effects’ into account. These include both the influence of collisionally induced velocity changes that lead to the so-called Dicke narrowing and the influence of the dependence of collisional parameters on the speed of the radiating molecule. Experimental evidence of deviations from the Voigt shape is presented and analysed. The interest of classical molecular dynamics simulations, to model velocity changes, together with semi-classical calculations of the speed-dependent collisional parameters for line-shape predictions from ‘first principles’, are discussed.

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Gl/az, W., and G. C. Tabisz. "Collisional propagation effects in collision-induced rotational spectra." Physical Review A 54, no. 5 (November 1, 1996): 3903–11. http://dx.doi.org/10.1103/physreva.54.3903.

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4

Sakagami, H., K. Okada, Y. Kaseda, T. Taguchi, and T. Johzaki. "Collisional effects on fast electron generation and transport in fast ignition." Laser and Particle Beams 30, no. 2 (March 9, 2012): 243–48. http://dx.doi.org/10.1017/s0263034611000887.

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AbstractAs the binary collision process requires much more computation time, a statistical electron-electron collision model based on modified Langevin equation is developed to reduce it. This collision model and a simple electron-ion scattering model are installed into one-dimensional PIC code, and collisional effects on fast electron generation and transport in fast ignition are investigated. In the collisional case, initially thermal electrons are heated up to a few hundred keV due to direct energy transfer by electron-electron collision, and they are also heated up to MeV by Joule heating induced by electron-ion scattering. Thus the number of low energy component of fast electrons increase than that in the collisionless case.

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5

ROSENBERG, M., and V. W. CHOW. "Collisional effects on the electrostatic dust cyclotron instability." Journal of Plasma Physics 61, no. 1 (January 1999): 51–63. http://dx.doi.org/10.1017/s0022377898007247.

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A kinetic analysis of the electrostatic dust cyclotron instability in a weakly ionized collisional dusty plasma is presented. In a plasma with negatively charged dust and a current along the magnetic field B, it is found that the instability can be excited by ions drifting along B. The effect of dust–neutral collisions is stabilizing, while the effect of ion–neutral collisions can be destabilizing. Possible applications to laboratory environments are discussed.

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FIORE, M., F. FIÚZA, M. MARTI, R. A. FONSECA, and L. O. SILVA. "Relativistic effects on the collisionless–collisional transition of the filamentation instability in fast ignition." Journal of Plasma Physics 76, no. 6 (August 20, 2010): 813–32. http://dx.doi.org/10.1017/s0022377810000413.

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AbstractRelativistic collisional effects on the filamentation instability are analytically and numerically investigated by comparing collisionless and collisional scenarios for a fast ignition (FI) configuration. The theoretical kinetic model, including warm species and space charge effects, predicts the preferential formation of larger filaments and the inhibition/enhancement of the instability when collisions are accounted for. These collisional effects are qualitatively and quantitatively confirmed by 1D and 2D particle-in-cell (PIC) simulations, also providing a physical picture for the inhibition/enhancement regime due to collisions, based on the electron beam slowdown. By plugging typical FI parameters in the dispersion relation, the theoretical model predicts significant growth rates of the instability deep inside the FI target, thus showing the potential role of the filamentation instability as a mechanism for energy deposition into the pellet core.

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7

JUNG, YOUNG-DAE, and WOO-PYO HONG. "Effects of temperature and electron collision frequency on the elastic electron–ion collisions in a collisional plasma." Journal of Plasma Physics 79, no. 5 (January 30, 2013): 553–58. http://dx.doi.org/10.1017/s0022377813000056.

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AbstractThe effects of dynamic temperature and electron–electron collisions on the elastic electron–ion collision are investigated in a collisional plasma. The second-order eikonal analysis and the velocity-dependent screening length are employed to derive the eikonal phase shift and eikonal cross section as functions of collision energy, electron collision frequency, Debye length, impact parameter, and thermal energy. It is interesting to find out that the electron–electron collision effect would be vanished; however, the dynamic temperature effect is included in the first-order approximation. We have found that the dynamic temperature effect strongly enhances the eikonal phase shift as well as the eikonal cross section for electron–ion collision since the dynamic screening increases the effective shielding distance. In addition, the detailed characteristic behavior of the dynamic screening function is also discussed.

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8

Øien, Alf H. "Kinetic and transport theory for a non-neutral plasma taking account of strong gyration and non-uniformities on the collisional scale." Journal of Plasma Physics 38, no. 3 (December 1987): 351–71. http://dx.doi.org/10.1017/s0022377800012654.

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From the BBGKY equations for a pure electron plasma a derivation is made of a collision integral that includes the combined effects of particle gyration in a strong magnetic field and non-uniformities of both the distribution function and the self-consistent electric field on the collisional scale. A series expansion of the collision integral through the distribution function and the electric field on the collisional scale is carried out to third order in derivatives of the distribution function and to second order in derivatives of the electric field. For the strong-magnetic-field case when collision-term contributions to only first order in 1/B are included, a particle flux transverse to the magnetic field proportional to l/B2 is derived. The importance of long-range collective collisions in this process is shown. The result is in contrast with the classical l/B4 proportionality, and is in accordance with earlier studies.

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9

Niknam, A. R., S. Barzegar, B. Bokaei, F. Haji Mirzaei, and A. Aliakbari. "Collisional effects on the modulational instability of intense laser pulses in magnetoactive plasmas." Laser and Particle Beams 33, no. 4 (October 14, 2015): 705–11. http://dx.doi.org/10.1017/s0263034615000889.

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AbstractThe modulational instability associated with propagation of an intense laser pulse through a transversely magnetized plasma is investigated in the presence of collisional effects. The source-dependent expansion method for analyzing the wave equation is employed. The dispersion relation is obtained and modulational instability and its growth rate are studied. It is shown that in the absence of collisional effects the modulational instability is restricted to the small wavenumber region and the constant magnetic field reduces the growth rate of the instability. In contrast, in the collisional plasma, there is no upper limit of wavenumber for the existence of modulational instability. In addition, in this case, the growth rate of instability increases as the collision frequency goes up.

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10

KHALILPOUR, H., and G. FOROUTAN. "Simulation study of collisional effects on the propagation of a hot electron beam and generation of Langmuir turbulence for application in type III radio bursts." Journal of Plasma Physics 79, no. 3 (October 9, 2012): 239–48. http://dx.doi.org/10.1017/s0022377812000876.

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AbstractThe propagation of a localized beam (cloud) of hot electrons and generation of Langmuir waves are investigated using numerical simulation of the quasi-linear equations in the presence of collisional effects for electrons and beam-driven Langmuir waves. It is found that inclusion of the collisional damping of Langmuir waves has remarkable effects on the evolution of the electron distribution function and the spectral density of Langmuir waves, while the effect of collision term for electrons is almost negligible. It is also found that in the presence of collisional damping of Langmuir waves, the relaxation of the beam distribution function in velocity space is retarded and the Langmuir waves are strongly suppressed. The average propagation velocity of the beam is not constant and is larger when collisional damping of Langmuir waves is considered. The collisional damping for electrons does not affect the upper boundary of the plateau but the collisional damping of Langmuir waves pushes it towards small velocities. It is also found that the local velocity of the beam and its width decrease when the collisional damping of Langmuir waves is included.

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11

Kiselman, Dan. "NLTE Effects on Oxygen Lines." Highlights of Astronomy 12 (2002): 429–31. http://dx.doi.org/10.1017/s153929960001399x.

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AbstractThe NLTE effects affecting oxygen-abundance determinations of solar-type stars are discussed. LTE is safe for the forbidden lines. The permitted triplet at 777 nm is expected to show NLTE effects so that assuming LTE overestimates the abundance, but the magnitude of the effects is dependent on the poorly known cross sections of collisional excitation by collisions with neutral hydrogen atoms. Little is known about the NLTE effects on molecular line formation.

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12

Schelin, A. B., I. L. Caldas, R. L. Viana, and S. Benkadda. "Collisional effects in the tokamap." Physics Letters A 376, no. 1 (November 2011): 24–30. http://dx.doi.org/10.1016/j.physleta.2011.10.025.

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13

Agarwal, Ashish, and R. Ghosh. "Collisional effects in gas lasers." Physical Review A 47, no. 2 (February 1, 1993): 1407–14. http://dx.doi.org/10.1103/physreva.47.1407.

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14

Porcù, Federico, Leo Pio D’Adderio, Franco Prodi, and Clelia Caracciolo. "Effects of Altitude on Maximum Raindrop Size and Fall Velocity as Limited by Collisional Breakup." Journal of the Atmospheric Sciences 70, no. 4 (April 1, 2013): 1129–34. http://dx.doi.org/10.1175/jas-d-12-0100.1.

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Abstract Coalescence and breakup of drops are recognized as the main mechanisms determining raindrop size distributions on the ground. Full knowledge of these processes is hindered by the challenging difficulties both in the laboratory and tunnel experiments and during observations in the open air. In real rain breakup is mainly due to collision between drops of different sizes (collisional breakup) and occurs when the collisional kinetic energy (CKE) is not absorbed by the colliding drops. In this work, the authors observe and measure the dependence on altitude of the occurrence of collisional breakup in real rainfall events, and then estimate the corresponding limit terminal velocities of drops and their size when breakup significantly takes place. Data from Pludix, an X-band microwave disdrometer, were collected at three locations at different elevations: collisional breakup position in the power spectrum of Pludix increases toward higher frequencies with increasing altitude. Terminal velocities and sizes of the drops at breakup were determined consequently, with drop sizes resulting in 4.55 ± 0.35, 4.02 ± 0.32, and 3.16 ± 0.3 mm for altitudes of 15, 950, and 3300 m MSL, respectively. The authors computed the CKE of the colliding drops at the breakup, finding an upper limiting value of about 1.22 × 10−5 J for all three altitudes. This shows that most dominant collisional breakup signature occurs at similar CKE values for all three locations, corresponding to different drop diameters at different altitudes because of the effect of air density on the drop terminal velocity.

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15

Popescu Braileanu, B., V. S. Lukin, E. Khomenko, and Á. de Vicente. "Two-fluid simulations of Rayleigh-Taylor instability in a magnetized solar prominence thread." Astronomy & Astrophysics 650 (June 2021): A181. http://dx.doi.org/10.1051/0004-6361/202140425.

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Solar prominences are formed by partially ionized plasma with inter-particle collision frequencies generally warranting magnetohydrodynamic treatment. In this work we explore the dynamical impacts and observable signatures of two-fluid effects in the parameter regimes when ion-neutral collisions do not fully couple the neutral and charged fluids. We perform 2.5D two-fluid (charges-neutrals) simulations of the Rayleigh-Taylor instability (RTI) at a smoothly changing interface between a solar prominence thread and the corona. The purpose of this study is to deepen our understanding of the RTI and the effects of the partial ionization on the development of RTI using nonlinear two-fluid numerical simulations. Our two-fluid model takes into account neutral viscosity, thermal conductivity, and collisional interaction between neutrals and charges: ionization–recombination, energy and momentum transfer, and frictional heating. In this paper, the sensitivity of the RTI dynamics to collisional effects for different magnetic field configurations supporting the prominence thread is explored. This is done by artificially varying, or eliminating, effects of both elastic and inelastic collisions by modifying the model equations. We find that ionization and recombination reactions between ionized and neutral fluids do not substantially impact the development of the primary RTI. However, such reactions can impact the development of secondary structures during the mixing of the cold prominence and hotter surrounding coronal material. We find that collisionality within and between ionized and neutral particle populations plays an important role in both linear and nonlinear development of RTI; ion-neutral collision frequency is the primary determining factor in development or damping of small-scale structures. We also observe that the degree and signatures of flow decoupling between ion and neutral fluids can depend on the inter-particle collisionality and on the magnetic field configuration of the prominence thread.

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16

Struck-Marcell, Curtis. "Caustic Waves in Galaxy Disks Produced in Collisions with Low Mass Companions." International Astronomical Union Colloquium 124 (1990): 743–47. http://dx.doi.org/10.1017/s0252921100005911.

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At this meeting much attention has been focussed on interactions and mergers between roughly equal mass galaxies. On the contrary, I will begin by mentioning a few justifications for studying collisions with relatively low mass companions, specifically, less than about one third of the mass of the target galaxy. The first is simply that such collisions are likely to be common, given that the galaxy luminosity function is broad. The second reason is that such collisions have evidently been less well studied than collisions between nearly equal partners. However, there are a few important exceptions to this generalization, including the sinking satellite problem (e.g. Quinn and Goodman 1986), and the collisional model for the formation of shell galaxies in which a companion of negligible mass is completely disrupted(e.g. Dupraz and Combes 1986, Hernquist and Quinn 1988). The third, and potentially most important reason, is that the effects of a collision with a low-mass companion are less extreme (at least from the big galaxy’s point of view!). Thus, these effects are closer to the theorist’s ideal of a “small perturbation”. This is important for both conceptually understanding the effects of the collision, and for justifying the use of approximate numerical techniques (e.g. restricted three-body) to study them.

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17

Richman, M. W., and A. A. Oyediran. "Grain Size Reduction in Granular Flows of Spheres: The Effects of Critical Impact Energy." Journal of Applied Mechanics 59, no. 2S (June 1, 1992): S17—S22. http://dx.doi.org/10.1115/1.2899485.

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We extend methods employed to derive recent kinetic theories for rapid noncomminuting granular flows, to homogeneous flows in which a fraction of the repeated collisions produce tiny fractures on the particles’ peripheries and gradually reduce their effective diameters. The theory consists of balance equations for mass, momentum, and energy, as well as constitutive relations for the pressure tensor and collisional rates of mass and energy lost. We improve upon the work of Richman and Chou (1989) by incorporating into the constitutive theory the critical impact energy below which no mass loss occurs in a binary collision. The theory is applied to granular shear flows and, for fixed shear rates, predicts the time variations of the solid fraction, granular temperature, and induced stresses, as well as their extreme sensitivities to small changes in the critical impact energy.

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Silva, S. S. A., J. C. Santos, J. Büchner, and M. V. Alves. "Nonlocal heat flux effects on temperature evolution of the solar atmosphere." Astronomy & Astrophysics 615 (July 2018): A32. http://dx.doi.org/10.1051/0004-6361/201730580.

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Context. Heat flux is one of the main energy transport mechanisms in the weakly collisional plasma of the solar corona. There, rare binary collisions let hot electrons travel over long distances and influence other regions along magnetic field lines. Thus, the fully collisional heat flux models might not describe transport well enough since they consider only the local contribution of electrons. The heat flux in weakly collisional plasmas at high temperatures with large mean free paths has to consider the nonlocality of the energy transport in the frame of nonlocal models in order to treat energy balance in the solar atmosphere properly. Aims. We investigate the impact of nonlocal heat flux on the thermal evolution and dynamics of the solar atmosphere by implementing a nonlocal heat flux model in a 3D magnetohydrodynamic simulation of the solar corona. Methods. We simulate the evolution of solar coronal plasma and magnetic fields considering both a local collision dominated and a nonlocal heat flux model. The initial magnetic field is obtained by a potential extrapolation of the observed line-of-sight magnetic field of AR11226. The system is perturbed by moving the plasma at the photosphere. We compared the simulated evolution of the solar atmosphere in its dependence on the heat flux model. Results. The main differences for the average temperature profiles were found in the upper chromosphere/transition region. In the nonlocal heat transport model case, thermal energy is transported more efficiently to the upper chromosphere and lower transition region and leads to an earlier heating of the lower atmosphere. As a consequence, the structure of the solar atmosphere is affected with the nonlocal simulations producing on average a smoother temperature profile and the transition region placed about 500 km higher. Using a nonlocal heat flux also leads to two times higher temperatures in some of the regions in the lower corona. Conclusions. The results of our 3D MHD simulations considering nonlocal heat transport supports the previous results of simpler 1D two-fluid simulations. They demonstrated that it is important to consider a nonlocal formulation for the heat flux when there is a strong energy deposit, like the one observed during flares, in the solar corona.

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19

Belyaev, Andrey K. "Nonadiabatic effects in inelastic collisional processes." Physica Scripta 80, no. 4 (October 2009): 048113. http://dx.doi.org/10.1088/0031-8949/80/04/048113.

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20

Wallace, J. M., J. U. Brackbill, C. W. Cranfill, D. W. Forslund, and R. J. Mason. "Collisional effects on the Weibel instability." Physics of Fluids 30, no. 4 (1987): 1085. http://dx.doi.org/10.1063/1.866305.

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21

Kim, G. ‐H, N. Hershkowitz, D. A. Diebold, and M. ‐H Cho. "Magnetic and collisional effects on presheaths." Physics of Plasmas 2, no. 8 (August 1995): 3222–33. http://dx.doi.org/10.1063/1.871153.

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22

Cravens, T. E., and D. F. Strobel. "Pluto’s solar wind interaction: Collisional effects." Icarus 246 (January 2015): 303–9. http://dx.doi.org/10.1016/j.icarus.2014.04.011.

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23

Boulet, Christian. "Collisional effects on spectral line-shapes." Comptes Rendus Physique 5, no. 2 (March 2004): 201–14. http://dx.doi.org/10.1016/j.crhy.2004.01.014.

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24

Kumar, Pardeep, and Hari Mohan. "Hydromagnetic Stability Analysis of a Partially Ionized Medium." Academic Journal of Applied Mathematical Sciences, no. 65 (May 25, 2020): 53–57. http://dx.doi.org/10.32861/ajams.65.53.57.

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Rayleigh-Taylor instability of a composite medium with variable density and viscosity is considered by taking into account the frictional effect of collisions of ionized with neutral atoms in the presence of a variable horizontal magnetic field. The criteria determining stability and instability are independent of the effects of viscosity and collisional effects. The magnetic field stabilizes the system which is otherwise unstable in the absence of the magnetic field. The viscosity of the medium has stabilizing as well as destabilizing effect on the growth rates. The collisional frequency has stabilizing effect on the growth rates, but has also destabilizing effect in some region.

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Ciappina, M. F., W. R. Cravero, and M. Schulz. "Post-collisional effects on single ionization in 75 keV p + He collisions." Journal of Physics B: Atomic, Molecular and Optical Physics 40, no. 13 (June 15, 2007): 2577–86. http://dx.doi.org/10.1088/0953-4075/40/13/004.

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Clegg, R. E. S., and J. P. Harrington. "Helium Abundances in Gaseous Nebulae." Symposium - International Astronomical Union 131 (1989): 211. http://dx.doi.org/10.1017/s0074180900138227.

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New collision strengths, from a 19-state quantum calculation for He I, are used to derive revised He/H ratios in planetary nebulae (PN). Empirical formulae are given, for the correction of He I recombination line fluxes for collisional effects, and for the calculation of the population of metastable helium (He I 23S) in gaseous nebulae. The revised He abundances for PN, for four samples of published line fluxes, show a mean ratio He/H = 0.100 ±0.007 if nebulae with neutral He and Type I PN are excluded. The mean reduction due to collisional effects is only 10% for Galactic PN. It is shown that the hypothesis, that He/H should be independent of nebular temperature and density, is better satisfied when collisional effects are allowed for. The new He abundances indicate that there is very little He enrichment in Galactic PN of Types II, III, and IV, and that the enhancement of Type I PN in He over H II regions is reduced from earlier values by one third.

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Ki, Dae-Han, and Young-Dae Jung. "Friedel oscillation effects on the elastic collision in degenerate quantum collisional plasmas." Physics of Plasmas 18, no. 4 (April 2011): 044504. http://dx.doi.org/10.1063/1.3581027.

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28

Flammang, Robert, Julien De Winter, Pascal Gerbaux, Vinh Son Nguyen, and Minh Tho Nguyen. "Internal Energy Effects on the Ion/Molecule Reactions of Ionized Methyl Isocyanide." European Journal of Mass Spectrometry 14, no. 5 (April 1, 2008): 299–309. http://dx.doi.org/10.1255/ejms.936.

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Electron ionization of methyl isocyanide in various chemical ionization conditions is reported and, depending on the energy conditions used, different ion/molecule reactions are observed. It is proposed, on the basis of combined quantum chemical (DFT) calculations and tandem mass spectrometric experiments, that a common intermediate could be a cumulenic ionized dimer dissociating in the ion source following two energy depending competitive channels, a loss of a hydrogen atom and a loss of a methyl group. Proposed structures for new cumulenic ions are supported by collision experiments in the high (collisional activation) or/and low (collision-induced dissociations) translational energy regime.

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Øien, Alf H. "Kinetic equations for a non-uniform plasma in strong fields and resulting particle transport." Journal of Plasma Physics 43, no. 2 (April 1990): 189–215. http://dx.doi.org/10.1017/s0022377800014744.

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From the BBGKY equations for a multi-component plasma a derivation of generalized kinetic equations valid for non-uniform, neutral as well as non-neutral plasmas in strong electric and magnetic fields is made. Explicit effects of particle gyration and non-uniformities on the collisional scale are included in the collision terms. For each particle species the collision terms describing interaction between the same or other particle species consist of two parts. The first part is a generalization of the corresponding classical term, to which it reduces when fields and non-uniformities are negligible on the collisional scales. The second part is non-vanishing when non-uniformities are taken account of on the collisional scale. For the case of a neutral plasma, particle transport transverse to the magnetic field and along the density gradient is found. The result shows an increase of particle transport as compared with the classical formula when the Larmor radii are smaller than the Debye length. The underlying mechanism for this increase is pointed out.

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Baalrud, S. D., J. D. Callen, and C. C. Hegna. "Kinetic theory of instability-enhanced collisional effects." Physics of Plasmas 17, no. 5 (May 2010): 055704. http://dx.doi.org/10.1063/1.3346448.

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MASTRODOMENICO, A., M. A. IZQUIERDO, and J. L. PAZ. "SOLVENT COLLISIONAL EFFECTS IN FOUR-WAVE MIXING." Journal of Nonlinear Optical Physics & Materials 21, no. 02 (June 2012): 1250016. http://dx.doi.org/10.1142/s0218863512500166.

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The stochastic effects of a thermal bath on a two-level molecular system interacting with a classical electromagnetic field are considered. The collective effects are modeled as a random Bohr frequency, whose manifestation is the broadening of the upper level according to a prescribed random function. A methodology based in cumulant expansions to obtain the average in the Fourier components associated with the coherence and populations, calculated by Optical Stochastic Bloch Equations (OSBE), is employed. The Four-wave mixing signal intensity as a function of the detuning of the pump beam, parametrized by the ratio of the relaxation times and other variables, is analyzed.

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Jia-tai, Zhang, Liu Cheng-hai, Liang Hua-xiang, Yu Shu-zhen, Zhang Shu-gui, and Xu Lin-bao. "Collisional Effects in Cloud-in-Cell Scheme." Communications in Theoretical Physics 5, no. 3 (April 1986): 243–52. http://dx.doi.org/10.1088/0253-6102/5/3/243.

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Douglas, D. J., and J. B. French. "Collisional focusing effects in radio frequency quadrupoles." Journal of the American Society for Mass Spectrometry 3, no. 4 (May 1992): 398–408. http://dx.doi.org/10.1016/1044-0305(92)87067-9.

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CADJAN, M. G., and M. F. IVANOV. "Langevin approach to plasma kinetics with Coulomb collisions." Journal of Plasma Physics 61, no. 1 (January 1999): 89–106. http://dx.doi.org/10.1017/s0022377898007363.

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The Langevin approach to the kinetics of a collisional plasma is developed. Some collision models are considered, and the corresponding stochastic differential equations are derived. These equations can be regarded as an alternative to the description of a plasma in terms of a distribution function. The method developed here allows one to simulate plasma processes, taking account of both collective kinetics effects and Coulomb collisions. Results of the numerical simulation of the intervention of laser pulses with an overdense plasma are presented. The dependence of the absorption coefficient on the plasma parameters is calculated. The features of the plasma dynamics under the action of intense laser radiation are observed and discussed. The results of numerical tests of the validity of this method are also presented.

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Sipos, András A., Gábor Domokos, and János Török. "Particle size dynamics in abrading pebble populations." Earth Surface Dynamics 9, no. 2 (March 26, 2021): 235–51. http://dx.doi.org/10.5194/esurf-9-235-2021.

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Abstract. Abrasion of sedimentary particles in fluvial and eolian environments is widely associated with collisions encountered by the particle. Although the physics of abrasion is complex, purely geometric models recover the course of mass and shape evolution of individual particles in low- and middle-energy environments (in the absence of fragmentation) remarkably well. In this paper, we introduce the first model for the collision-driven collective mass evolution of sedimentary particles. The model utilizes results of the individual, geometric abrasion theory as a collision kernel; following techniques adopted in the statistical theory of coagulation and fragmentation, the corresponding Fokker–Planck equation is derived. Our model uncovers a startling fundamental feature of collective particle size dynamics: collisional abrasion may, depending on the energy level, either focus size distributions, thus enhancing the effects of size-selective transport, or it may act in the opposite direction by dispersing the distribution.

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Kim, Hwa-Min, and Young-Dae Jung. "Collision effects on the electron–ion bremsstrahlung spectrum in a warm collisional plasma." Physica Scripta 77, no. 4 (April 2008): 045503. http://dx.doi.org/10.1088/0031-8949/77/04/045503.

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37

Micelotta, E. R., J. Cami, E. Peeters, H. Zettergren, H. T. Schmidt, H. Cederquist, A. P. Jones, and A. G. G. M. Tielens. "The Stability of Cosmic Fullerenes and Fullerenic Aggregates." Proceedings of the International Astronomical Union 9, S297 (May 2013): 339–43. http://dx.doi.org/10.1017/s1743921313016086.

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AbstractEstablishing the stability of cosmic fullerenes and fullerenic aggregates is extremely relevant for a variety of reasons. For instance, the emission features of C60 and C70 fall in the same spectral region as the Un-identified InfraRed (UIR) bands, which they could contribute to. To be able to contribute to the UIR emission, however, fullerenes must be able to survive long enough against the destruction mechanisms operating in the interstellar medium. In this study we focus on the effects of collisional processing, i.e., the bombardment by energetic ions and electrons. A recent experimental/theoretical study has shown that ion collisions with C60 clusters result in the dissociation of the cluster with the simultaneous formation of covalent fullerene dimers, which could play a role as DIBs carriers. We present here our first results about the collisional processing of C60 molecules and clusters by H, He and C ions in interstellar shocks. We have adapted the models that have previously been developed to successfully treat the collisional processing of PAHs in space. The nature of the interaction and the similarities between PAHs and fullerenes make this approach appropriate. In addition, our study shows that the formation of covalent dimers following ion collisions with C60 clusters is compatible with the astrophysical conditions under consideration.

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Prakash, Kirti, and Seema Manchanda. "Effects of Finite Larmor Radius and Hall Currents on Thermosolutal Instability of a Partially Ionized Plasma in Porous Medium." Zeitschrift für Naturforschung A 49, no. 3 (March 1, 1994): 469–74. http://dx.doi.org/10.1515/zna-1994-0304.

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Abstract The effects of finite ion Larmor radius (FLR), collisions and Hall currents on thermosolutal instability of a partially ionized plasma in porous medium in the presence of uniform vertical magnetic field are investigated. It is found that the presence of each magnetic field, FLR, Hall currents and collisions, introduces oscillatory modes which were, otherwise, non-existent. In the case of stationary convection, finite Larmor radius, Hall currents, medium permeability and magnetic field may have stabilizing or destabilizing effects, but for a certain wave number range, FLR, magnetic field and Hall currents have a complete stabilizing effect. The stable solute gradient always has stabilizing effect on the system whereas the collisional effects disappear for the case of stationary convection.

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Zweigle, J. "Dynamical simulations of the shaping of PNe including radiation effects." Symposium - International Astronomical Union 180 (1997): 294. http://dx.doi.org/10.1017/s0074180900131110.

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In order to investigate the shaping of aspherical planetary nebulae the gasdynamical conservation laws of mass, momentum and energy including radiation effects are solved numerically in twodimensional, spherical coordinates. The simulations describe the dynamical interaction of a fast, tenuous, spherically symmetric wind from the central star with the slow, dense, axisymmetric AGB-wind remnant and include photoionization, collisional ionization, collisional excitation, radiative recombination and forbidden line emission as radiation effects.

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40

Žigman, V. J., and B. S. Milić. "Kinetic theory of the high-frequency part of the slow electromagnetic mode in weakly ionized gas-discharge argon plasma with inelastic collisions." Journal of Plasma Physics 38, no. 2 (October 1987): 223–33. http://dx.doi.org/10.1017/s0022377800012538.

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The spectral characteristics of the high-frequency part of the slow electromagnetic mode, specific for plasmas placed in an external d.c. electric field, as well as the features of the corresponding instability, are analysed for weakly ionized argon gas-discharge plasmas with E/n ranging from 25 to 150 Td, and with electron temperatures between 60000 and 70000 K. The analysis is based on the linear theory of perturbation, and the dynamics of the electrons is described by appropriately modified kinetic equations for the one-particle distribution function. Attention is focused on the collisional processes between electrons and neutrals, and both elastic and excitational collisions are taken into account. Apart from the ‘indirect’ collision effects (modifications of the form of the electron steady-state distribution function, evaluated here analytically, with the thermal motion of the neutrals included), their ‘direct’ influence (arising from perturbations of the collision integrals) is also significant in the electron temperature range considered. As a consequence of the ‘direct’ influence of inelastic collisions, in particular, the mode studied was found to exist in two distinctly separate wavelength ranges. The instability was found to develop only in the one corresponding to shorter wavelengths (below some 30 cm).

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41

Derouich, M. "Hybrid approach for treating the depolarization of the solar lines of the Ba ii, Ca ii, and Mg ii ions by collisions." Monthly Notices of the Royal Astronomical Society 491, no. 3 (November 27, 2019): 3990–95. http://dx.doi.org/10.1093/mnras/stz3311.

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ABSTRACT Isotropic collisions between atoms of hydrogen and solar ions emitting polarized light contribute to reducing the observed polarization (depolarization). The aim of this work is to apply a hybrid method in order to provide new collisional depolarization rates of the 2P1/2 and 2P3/2 states of the Mg ii, Ca ii, and Ba ii ions. The hybrid method proposed in this work takes into account the spin effects in the calculation of the interaction potential and in the treatment of the collision dynamics. We detect the region of the interaction potential that is of importance in the determination of the depolarization rates. We conclude that the best strategy is to combine semiclassical and quantum potentials in order to build the so-called hybrid potentials. The dynamics of collisions proposed in this work is based on coupled differential equations that take into account the effects of the spins of the Mg ii, Ca ii, and Ba ii ions and the spin of the hydrogen. Hybrid depolarization rates are then inferred by solving the dynamics of collisions and using hybrid potentials. Comparison with previous quantum and semiclassical rates is presented. Our results should be of use for interpreting solar spectropolarimetric observations and our method can be applied to other ions.

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Gamache, Robert R., and Jean-Michel Hartmann. "Collisional parameters of H2O lines: effects of vibration." Journal of Quantitative Spectroscopy and Radiative Transfer 83, no. 2 (January 2004): 119–47. http://dx.doi.org/10.1016/s0022-4073(02)00296-0.

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43

Iglesias, Carlos A., and Richard W. Lee. "Density effects on collisional rates and population kinetics." Journal of Quantitative Spectroscopy and Radiative Transfer 58, no. 4-6 (October 1997): 637–43. http://dx.doi.org/10.1016/s0022-4073(97)00070-8.

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Korenman, G. Ya, N. P. Yudin, and S. N. Yudin. "Collisional effects on HFS transitions of antiprotonic helium." Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms 214 (January 2004): 94–97. http://dx.doi.org/10.1016/s0168-583x(03)01772-5.

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Kingdon, J., and G. J. Ferland. "Collisional effects in He I: an observational analysis." Astrophysical Journal 442 (April 1995): 714. http://dx.doi.org/10.1086/175476.

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Qiu, Hua-Tan, You-Nian Wang, and Teng-Cai Ma. "Collisional effects on the radio-frequency sheath dynamics." Journal of Applied Physics 90, no. 12 (December 15, 2001): 5884–88. http://dx.doi.org/10.1063/1.1419267.

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Kim, Chang-Geun, and Young-Dae Jung. "Quantum effects on collisional ionizations in semiclassical plasmas." Physics of Plasmas 9, no. 4 (April 2002): 1443–48. http://dx.doi.org/10.1063/1.1456528.

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Manuel, M. J. E., M. Flaig, T. Plewa, C. K. Li, F. H. Séguin, J. A. Frenje, D. T. Casey, et al. "Collisional effects on Rayleigh-Taylor-induced magnetic fieldsa)." Physics of Plasmas 22, no. 5 (May 2015): 056305. http://dx.doi.org/10.1063/1.4919392.

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Nguyen, Viet Q., and František Tureček. "Energy Effects in Collisional Neutralization with Organic Molecules." Journal of Mass Spectrometry 31, no. 8 (August 1996): 843–54. http://dx.doi.org/10.1002/(sici)1096-9888(199608)31:8<843::aid-jms360>3.0.co;2-9.

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Petrović, D., J. Vranjes, and S. Poedts. "Effects of ionization on the collisional streaming instability." Physics of Plasmas 12, no. 11 (November 2005): 112103. http://dx.doi.org/10.1063/1.2135279.

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