Quantum beat measurements on spin-polarized electrons in oxygen ions emerging from magnetized Ni- andGd-layers

Employing the time-differential perturbed -angular correlation technique it is shown that 1s- and2s-electrons of highly stripped¹⁶O(3^–)-ions have their spin polarized on emergence from magnetized thin Ni- andGd-layers into vacuum. The mean degree of polarization of 2s-electrons is found to be twice as large as for 1s-electrons.     

电子和负离子的反射运动对碰撞电负性磁鞘的影响

研究了鞘层中电子和负离子的反射运动对碰撞电负性磁鞘玻姆判据和鞘层结构的影响.通过理论推导得到了考虑鞘层中电子和负离子的反射运动时鞘层玻姆判据表达式,并通过数值模拟得到了电子和负离子采用玻尔兹曼模型和反射运动模型时离子马赫数的下限随参数的变化曲线以及鞘层中带电粒子密度的分布曲线.结果表明,电子和负离子的反射运动模型和玻尔兹曼模型离子马赫数的上限完全相同,下限表达式不同,反射运动模型中下限还与基板电势有关,且随着基板电势值的增加而增大,达到与玻尔兹曼分布中相同值后保持不变,随着鞘边负离子浓度和温度的不同达到最大值的速度不同;离子马赫数的下限在玻尔兹曼和反射运动模型中都随鞘边负离子浓度的增加和温度的降低而减小,只是在反射运动模型中的最大值要小;两种模型中离子马赫数的下限都随鞘边电场的增加而增加,但在玻尔兹曼模型中增加得更快最终值更大;两种模型离子马赫数的下限都随碰撞参数或磁场角度的增加而降低,但在玻尔兹曼模型中降低更快,随着碰撞参数或者磁场角度的增加两种模型中离子马赫数的下限趋于一致;当基板电势值较小时,电子和负离子的反射运动对鞘层结构影响较大,当基板电势值较大时电子和负离子反射运动对鞘层中带电粒子密度分布的影响很小.     

Dust-ion-acoustic solitary waves in magnetized plasmas with positive and negative ions: The role of electrons superthermality

The formation of dust-ion-acoustic solitary waves (DIASWs), and their basic properties in a magnetized dusty plasma system containing inertial, hot positively and negatively charged ion fluids, κ-distributed superthermal electrons, and negatively charged stationary dust species are investigated theoretically. An ambient magnetic field is assumed along z-direction, and the wave propagation is considered obliquely to the direction of that ambient magnetic field. Two types of modes, the fast and the slow modes, are shown to exist in the linear regime. The reductive perturbation method (which is valid for small but finite amplitude DIASWs) as well as pseudo-potential approach (which is valid for arbitrary amplitude DIASWs) are employed to identify the basic properties of the DIASWs. The effects of key plasma composition parameters, namely the superthermality effect of electrons, the temperature of positive and negative ions, the number density of positive and negative ions, on the dynamics of small amplitude as well as on large amplitude DIASWs, are investigated. The influence of the obliquity parameter and the magnetic field on the propagation characteristics of DIASWs are also examined.     

Spin-polarized electrons in collisions of multicharged nitrogen ions with a magnetized Fe(001) surface

We report on the first spin-resolved energy spectra for the emission of electrons during grazing scattering of 150 keV multicharged nitrogen ions from a magnetized Fe(001) surface. A substantial spin polarization for KLL Auger electrons emitted in the final stage of the neutralization sequence during the interaction of multicharged ions with a metal surface is observed. We conclude from our data that the projectile L shell is dominantly populated by electrons from the conduction band of the target. For low energy electrons we find an increase of their spin polarization with an increase of the projectile charge.     

Dynamic response of electrons and dispersion force fields near bimetallic interfaces

The induced potential due to an oscillating charge source near the interface of two metals whose electron densities differ slightly, is calculated in the hydrodynamic approximation. Results are given for both planar and spherical interfaces. The potential is used to evaluate the dispersion force field on an atomic system near the interface. It is shown that the force field is divergence-free at very small separation from the planar interface if the electron density profile is diffuse.     

Drag of ballistic electrons by an ion beam

Drag of electrons of a one-dimensional ballistic nanowire by a nearby one-dimensional beam of ions is considered. We assume that the ion beam is represented by an ensemble of heavy ions of the same velocity V. The ratio of the drag current to the primary current carried by the ion beam is calculated. The drag current turns out to be a nonmonotonic function of velocity V. It has a sharp maximum for V near v _nF/2, where n is the number of the uppermost electron miniband (channel) taking part in conduction and v _nF is the corresponding Fermi velocity. This means that the phenomenon of ion beam drag can be used for investigation of the electron spectra of ballistic nanostructures. We note that whereas observation of the Coulomb drag between two parallel quantum wires may in general be complicated by phenomena such as tunneling and phonon drag, the Coulomb drag of electrons of a one-dimensional ballistic nanowire by an ion beam is free of such spurious effects.     

Drag force on heavy quarks from holographic QCD

We study the drag force of a relativistic heavy quark using a holographic QCD model with conformal invariance broken by a background dilaton.The effects of the chemical potential and the confining scale on this quantity are analyzed.The drag force in this model is shown to be larger than that of N=4 supersymmetric Yang-Mills(SYM) plasma.In particular,the inclusion of the chemical potential and confining scale both enhance the drag force,in agreement with earlier findings.Moreover,we discuss how the chemical potential and confining scale influence the diffusion coefficient.     

具有非广延分布电子的碰撞等离子体磁鞘的结构

很多关于等离子体鞘层的研究工作都是基于电子满足经典的麦克斯韦速度分布函数,而等离子体中的粒子具有长程电磁相互作用,使用Tsallis提出的非广延分布来描述电子更为恰当.本文建立一个具有非广延分布电子的碰撞等离子体磁鞘模型,理论推导出受非广延参数q影响的玻姆判据,离子马赫数的下限数值会随着参数q的增大而减小.经过数值模拟,发现与具有麦克斯韦分布(q=1)电子的碰撞等离子体磁鞘对比,具有超广延分布(q<1)和亚广延分布(q>1)电子的碰撞等离子体磁鞘的结构各有不同,包括空间电势分布、离子电子密度分布、空间电荷密度分布.模拟结果显示非广延分布的参数q对碰撞等离子体磁鞘的结构具有不可忽略的影响.希望这些结论对相关的天体物理、等离子体边界问题的研究有参考价值.     

Electron spin polarization of secondary electrons ejected from magnetized europium oxide

It is found that secondary electrons ejected (by incident 1 keV electrons) from an oxidized europium layer, which is at about 20 K in a magnetic field of 1.5 T, show longitudinal spin polarization. The maximum value observed in first experiments is 32 per cent.     

Dielectric properties of a magnetized electron gas in a nanotube

A quantum expression is derived for the longitudinal permittivity of a magnetized electron gas in a quantum cylinder. The asymptotics of the dispersion law are calculated for longitudinal plasma waves in a degenerate electron gas. The approximations of the weak and strong spatial dispersions are considered. It is shown that the longitudinal permittivity is an oscillating function of the magnetic flux through the cross section of the nanotube.     

Drag force of moving quark in STU background

In this paper we consider a quark moving in D=5, supergravity thermal plasma. By using the three charges non-extremal black hole solution (STU solution) we calculate the drag force on the quark and the diffusion constant from the AdS/CFT correspondence.     

Ionization-Excitation of helium-like ions by high-energy electrons

The differential and total cross sections are calculated for the ionization of helium-like ions that is accompanied by the excitation of residual ions to ns states owing to an electron impact. Nonrelativistic perturbation theory in electron–electron interaction with Coulomb functions used for a zero-order approximation underlies these calculations. The expressions obtained in this way have a universal character. They are applicable at moderate values of the target charge number Z and high energies of incident electrons. A comparison with total cross sections calculated for the helium atom within various theoretical approaches is performed.     

Dielectric constant of solvents at nano to bulk regimes: linear response theory and statistical mechanics-based approaches

Statistical mechanics and generalised linear response theory based approaches are employed to derive the analytical expressions for size-dependent dielectric constant and normalised orientation polarisation of solvents. As an illustrative example, water is considered and the dielectric constants for the same are calculated over the entire range of water clusters. Our results reveal that the dielectric constant and normalised orientation polarisation are monotonically increasing with the increase in the number of solvent molecules and converge to the respective bulk values in the thermodynamic limit. More importantly, the dielectric constant of water is found to be independent of the nature, geometry and microscopic charges of the non-spherical ions. This finding offers a new platform for calculating the hydration energy and orientation polarisation based on linear response theory for different kinds of ions in the solvent medium.     

Drag force reduction on an airfoil via glow discharge plasma-based control

Glow discharge plasma on a solid surface will result in a body force which modifies the pressure distribution along the flow boundary layer, and consequently re-attaches the separated flows for reduction of a hydrodynamic drag force. In this paper, we investigate the discharge performance of various plasma-actuated electrodes in terms of their arrangements and structures. The resulting optimal configuration for the electrode separation distance was used to develop a flexible actuated panel to be mounted onto a NACA 0015 airfoil. Both uniphase and eight-phase power inputs were used to examine its drag reduction performance at various attack angles and flow velocities. Numerical calculations were also performed by including an electrostatic body force in the hydrodynamic equation. Good agreement were found between the numerical and experiment results.