高Z等离子体中的双电子复合与电子碰撞激发

采用准相对论性Hartree-Fock-Relativistic方法与不可分辨跃迁组模型相结合,对Au和Ta元素的类Ni离子的双电子复合速率,以及Au元素类Cu离子的电子碰撞激发速率进行了计算。计算结果表明,对于Au类Ni离子的3d10-3d94l5f-3d104l双电子复合过程以及类Cu离子的3d104l-3d94l5f电子碰撞激发过程,当电子温度高于1.0 keV时,电子离子碰撞激发速率随电子温度增加而增加,双电子复合速率随电子温度增加而减小,并且电子碰撞激发对谱线辐射的贡献要比双电子复合大得多。     

高Z等离子体中的双电子复合与电子碰撞激发

 采用准相对论性Hartree-Fock-Relativistic方法与不可分辨跃迁组模型相结合,对Au和Ta元素的类Ni离子的双电子复合速率,以及Au元素类Cu离子的电子碰撞激发速率进行了计算。计算结果表明,对于Au类Ni离子的3d¹⁰-3d⁹4l5f-3d¹⁰4l双电子复合过程以及类Cu离子的3d¹⁰4l-3d⁹4l5f电子碰撞激发过程,当电子温度高于1.0 keV时,电子离子碰撞激发速率随电子温度增加而增加,双电子复合速率随电子温度增加而减小,并且电子碰撞激发对谱线辐射的贡献要比双电子复合大得多。     

Effective-viscosity approach for nonlocal electron kinetics in inductively coupled plasmas

In inductively coupled plasmas, nonlocal electron kinetics lead to the anomalous skin effect. We show that this can be approximately described through a fluid equation for electron momentum including a viscosity term with an effective-viscosity coefficient. The solution of this momentum equation coupled with the Maxwell equations is in good agreement with results from a particle-in-cell simulation over a wide range of conditions, reproducing the nonmonotonic structure of the anomalous skin with sometimes local negative power absorption.     

On test charge potentials in collisional plasmas

The effect of electron-electron collisions on the potential of a slowly moving test charge in a plasma is considered. A new dipole-like term is found.     

Kinetic ion-acoustic solitary waves in collisional plasmas

In this study, a bipolar high-voltage pulse with 20 ns rising time is employed to generate diffuse dielectric barrier discharge plasma using wire-plate electrode configuration in nitrogen at atmospheric pressure. The gas temperature of the plasma is determined by comparing the experimental and the best fitted optical emission spectra of the second positive bands of N₂(C³Π_u → B³ Π_g, 0-2) and the first negative bands of N₂ ⁺ (B² Σ_u ⁺ → X² Σ_g ⁺, 0-0). The effects of the concentration of argon and oxygen on the emission intensities of N₂ (C³Π_u → B³Π_g, 0-0, 337.1 nm), OH?(A ²Σ → X²Π, 0-0) and N₂ ⁺ (B² Σ_u ⁺ → X² Σ_g ⁺, 0-0, 391.4 nm) are investigated. It is shown that the plasma gas temperature keeps almost constant with the pulse repetition rate and pulse peak voltage increasing. The emission intensities of N₂ (C³Π_u → B³Π_g, 0-0, 337.1 nm), OH(A²Σ → X²Π, 0-0) and N₂ ⁺ (B² Σ_u ⁺ → X² Σ_g ⁺, 0-0, 391.4 nm) rise with increasing the concentration of argon, but decrease with increasing the concentration of oxygen, and the influences of oxygen concentration on the emission intensities of N₂(C³Π_u → B³Π_g, 0-0, 337.1 nm) and OH (A²Σ → X²Π, 0-0) are more greater than that on the emission intensity of N₂ ⁺ (B² Σ_u ⁺ → X² Σ_g ⁺, 0-0, 391.4 nm).     

Weak dissipation of electrostatic solitary structures in warm collisional pair-ion plasmas with non-Maxwellian electron population

The localized electrostatic structures with dissipation due to ion-neutral collisions in a symmetric warm pair-ion plasma in the presence of non-Maxwellian population of electrons are studied. The analytical model for ion dynamics is based on fluid equations and the evolution equation is derived by using the reductive perturbation scheme in the form of a damped Korteweg-de Vries equation. The parameter regime relevant to space-based observations and laboratory plasmas is considered and time evolution of the propagating ion-acoustic soliton is discussed. The energetic-particles-driven properties of soliton for various spectral indices, dissipation, ion temperature, and density are illustrated with comparison to the thermal mode for Boltzmann distribution of electrons.     

Damped dust-ion-acoustic solitons in collisional magnetized nonthermal plasmas

A multispecies magnetized collisional nonthermal plasma system, containing inertial ion species, noninertial electron species following nonthermal -distribution, and immobile dust particles, is considered to examine the characteristics of the dissipative dust-ion-acoustic soliton modes, theoretically and parametrically. The electrostatic solitary modes are found to be associated with the low-frequency dissipative dust-ion-acoustic solitary waves (DIASWs). The ion-neutral collision is taken into account, and the influence of ion-neutral collisional effects on the dynamics of dissipative DIASWs is investigated. It is reported that most of the plasma medium in space and laboratory are far from thermal equilibrium, and the particles in such plasma system are well fitted via the -nonthermal distribution than via the thermal Maxwellian distribution. The reductive perturbation approach is adopted to derive the damped KdV (dKdV) equation, and the solitary wave solution of the dKdV equation is derived via the tangent hyperbolic method to analyse the basic features (amplitude, width, speed, time evolution, etc.) of dissipative DIASWs. The propagation nature and also the basic features of dissipative DIASWs are seen to influence significantly due to the variation of the plasma configuration parameters and also due to the variation of the supethermality index in the considered plasma system. The implication of the results of this study could be useful for better understanding the electrostatic localized disturbances, in the ion length and time scale, in space and experimental dusty plasmas, where the presence of excess energetic electrons and ion-neutral collisional damping are accountable.     

Asymptotic evolution of weakly collisional Vlasov-Poisson plasmas

We study the role of (weak) numerical diffusion on the long time evolution of the Vlasov-Poisson plasma. We consider the classical problem of phase space vortex formation by particle trapping. We show that the asymptotic macroscopic state is not independent of diffusion even if the dissipative length scale is much shorter than any characteristic physical length scale of the system.     

Penetration of waves into semi-infinite collisional plasmas

Penetration of longitudinal and transverse fields into a semi-infinite collisional plasma with fractionally accommodating boundary, having specular and diffuse reflecions is studied. The penetration of longitudinal field was studied by Landau and recently by Mason which was extended for transverse waves by Gupta and Varma. The theory is extended for collisions between electrons and ions according to B.G.K. Model, and its resemblence with metals for electrons and holes, gives its practical significance. The reflection coefficients and surface impedence are observed. The results are compared with non-collisional cases and it is observed that depth of penetration for collisional plasma decreases.     

Nonlocal power deposition in inductively coupled plasmas.

Radiofrequency (rf) plasmas exhibit field penetration well beyond the classical skin depth. Two physical explanations are proposed. First, by tracing orbits of electrons through many rf cycles in a cylindrical system, it is shown that numerous ionizing electrons can reach the interior. Second, current-carrying electrons can form a long-lived torus that drifts toward the axis, causing frequently observed interference phenomena. The pressure dependence of this effect does not agree with collisionless theories of anomalous skin effect, but is consistent with the proposed mechanism.     

流注放电低温等离子体中电子输运系数计算的蒙特卡罗模型

流体或者粒子-流体混合数值仿真是研究流注放电基本物理机制的常用手段,而精确的电子输运系数是保证其仿真正确性的必要前提.鉴于现有电子输运系数求解工具存在一定缺陷,本文开发了采用蒙特卡罗方法求解低温等离子体中电子输运系数的仿真工具,测试表明其准确性和精确度均较高.研究了氮氧气体混合比及大气压下三体碰撞吸附对电子输运系数的影响.氮气中流注放电仿真表明,流体仿真中采用本模型改进后的电子输运系数可显著改善流注通道内部的等离子体参数分布.     

Attraction of positively charged particles in highly collisional plasmas

It is shown that the electrostatic interaction potential between a pair of positively charged particles embedded in a highly collisional plasma has a long-range attractive asymptote. The effect is due to continuous plasma absorption on the particles. The relevance of this result to experimental investigations of complex (dusty) plasmas is discussed.     

Ion acoustic solitons in magnetized collisional non-thermal dusty plasmas

The oblique propagation of ion-acoustic solitary waves (IASWs) is considered, in a magnetized non-thermal collisional dusty plasma, composed of non-Maxwelian κ-distributed electrons, inertial ions, and stationary dust. The reductive perturbation approach is adopted to derive the damped Korteweg de-Vries (dKdV) equation, and the dissipative oblique ion-acoustic wave properties are investigated in terms of different key plasma parameters via the numerical solution of the dKdV equation. The collisional effect, describing the ion-neutral collision in the plasma, is taken into account, and seen to influence the dynamics of IASWs significantly. The basic features of IASWs are observed to modify, and the polarity of the wave is seen to change due to the variation of dust to that of ion number density and also due to the variation of the supethermality index κ in the considered plasma system.     

Characteristics of electron drift in the low-pressure gas discharge

The features of the energy distribution function of electrons during their drift in neon are analyzed for typical conditions of experiments with dust structures in plasma. The energy balance of electrons and drift characteristics in an electric field at strengths 13 < E/N < 42 Td were calculated taking into account inelastic collisions and the effect of electron loss on gas-discharge tube walls.     

Kinetic susceptibility and transport theory of collisional plasmas

A system of nonlocal electron transport equations for electrostatic perturbations in (omega,k) space in a high-Z plasma is derived from the Fokker-Planck equation for arbitrary relations between the time, space, and collisionality scales. The closed scheme for obtaining the longitudinal plasma susceptibility epsilon(omega,k) in the entire (omega,k) plane is proposed. Regions in the (omega,k) plane have been mapped for problems such as the relaxation of the local temperature enhancement with a time-dependent heat conductivity. The electron dielectric permittivity has been calculated over the entire range of parameters, including the transition region between Vlasov and Fokker-Planck equation solutions.     

Nonlocal effects in a two-dimensional electron gas with a periodic lattice of scatterers

The nonlocal resistance of a two-dimensional electron gas in a periodic lattice of antidots is investigated. Anomalous growth of this resistance is observed when 2R _c ≈d (R _c is the Larmor radius). This growth is caused by the appearance of runaway trajectories, skipping along the antidots and running away along the rows of antidots. It is shown on the basis of a comparative analysis of the local and nonlocal magnetoresistance that the character of the electronic billiard trajectories corresponds to the characteristic features of magnetotransport. Pis’ma Zh. éksp. Teor. Fiz. 63, No. 5, 336–341 (10 March 1996)     

Filamentation instabilities associated with ordinary electromagnetic waves in collisional plasmas

It is shown that parametric coupling of an ordinary electromagnetic wave with purely damped convective cell modes as well as other collisional modes leads to purely growing perturbations in the direction perpendicular to the incoming radiation. The excitation of purely growing modes in a magnetized plasma is important because the resulting E × B drift can cause particle transport across the external magnetic field.     

Orientation phenomena for electron-ion collisional excitations in strongly coupled plasmas

In strongly coupled plasmas, the orientation phenomena for direct excitations in electron-hydrogenic ion collisions are investigated using the ion-sphere interaction potential. For small impact parameters, the orientation parameters have minima which correspond to the complete transitions. The target screening effects slightly increase the probability of populating the 2p_-1 state. Received: 16 December 1998 / Received in final form: 23 March 1999