Quantum effects in the electronic polarization energy in molecular systems

Binding energy of the electronic polaron in molecular condensates is examined in a simple model permitting quantum dynamical as well as classical microelectrostatic energy calculations. Quantum effects in the electron (hole) polarization energy due to dipole-dipole correlations (and their distortion by an excess charge) among neutral molecules and molecular ion are studied. It is found that these quantum effects lead to a decrease of the magnitude of the electron (hole) polarization energy in realistic situations.     

A Similar Change in the Kinetic-Energy Components of Longitudinal Continuous Motion of Magnetized Electrons within the Landau Levels and Determination of the Characteristics of a Degenerate System

Account is taken of a similar change in the kinetic-energy components of a longitudinal electron motion along the magnetic field within each Landau energy level. The maximum electron energy is found as well as the kinetic energy of a transverse electron motion in the magnetic field. The electron concentrations are determined depending on the magnetic-field strength, whose intrinsic magnetic moments are directed along and opposite the field. The magnetic-field strengths for which a certain number of Landau quantum levels is realized in an electron degenerate system of a specified concentration are also found.__________Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 3, pp. 18–22, March, 2005.     

An application of the electron mirror in the time-of-flight spectrometer

We suggest applying of the spherical electron mirror in the time-of-flight electron spectrometer with a position sensitive detector in order to increase the effective acceptance solid angle of the spectrometer. The spherical electron mirror is placed near the specimen and it focuses electrons on a position sensitive detector as a converging electron flux. The electron mirror increases the acceptance angle of the spectrometer by a factor of 20. The electron mirror of the spectrometer consists of an inner spherical electrode of the radius R and an outer spherical electrode of the radius 1.1R. The central segment of the inner electrode inside the linear angle of 80° is made of a grid. The detector plate radius is about 0.23R. The acceptance solid angle of the spectrometer with this electron mirror is about 1.1sr, the range of the polar angle of emission is 20°–90° relative to the surface normal, and the range of the azimuth angle of emission at its maximum is ±36° relative to the basic plane of the spectrometer. The design of the spectrometer allows to recover the electron trajectory for each detected electron and to calculate the energy and the emission angle of the electron. The energy resolution of the spectrometer is about 0.2 eV/ns for the electron energy of 10 eV. The energy range is from E_min0.1eU_r up to eU_r, where U_r is the retarding potential of the electron mirror. The perturbing influence of the grid of the electron mirror limits mainly the angular resolution of the spectrometer and affects relatively slightly the energy resolution. The electron spectrometer with two detectors and two electron mirrors symmetric about the spectrometer axis allows to measure electron pairs in coincidence in a wide range of emission angles and energies with k-resolutions.     

The spread of the initial energy of electrons in a gyrotron due to the negative-mass instability developing in a magnetron-injector gun

The formation of an electron beam in a magnetron-injector gun of a gyrotron is investigated in the case when it is affected by the negative-mass instability due to the Coulomb repulsion and nonisochronous cyclotron rotation of particles. A technique is proposed for calculating the spread of the initial energy of electrons caused by the instability, which develops as the electron beam moves in the presence of a nonuniform magnetostatic field of the magnetron-injector gun. It is demonstrated that this instability can be one of the main factors providing the energy spread in electron guns of gyrotrons.     

弱电离大气等离子体电子碰撞能量损失的理论研究

在前期计算电子能量分布函数的基础上, 求出弱电离大气等离子体中各碰撞反应过程的电子能量损失. 由于在弹性碰撞中电子-重粒子能量交换很少, 同时氮气、氧气分子又有很多能量阈值较低的转动、振动能级存在, 因此在大气等离子体中弹性碰撞电子能量损失所占份额很小(直流电场下小于6%). 研究发现, 弱电离大气等离子体中在不同能量区间占主导的能量损失过程不同. 随着有效电子温度(或约化场强)增加, 占主导的电子能量损失过程依次为转动激发、振动激发、电子态激发、碰撞电离、加速电离产生的二次电子. 在约化场强E/N=1350 Td (或有效电子温度为14 eV)附近, 平均电离一个电子所需的能量最小, 约为57 eV. 因此可以根据不同的需求调节电场强度, 从而达到较高的能量利用率. 关键词： 弱电离大气等离子体 碰撞反应过程 电子能量损失     

氧化物薄膜研制中的电子能谱技术

随着科学技术的不断发展，人们正在寻求更新的实用材料．金属氧化物，包括金属氧化物薄膜的各种实用材料，在工业界、信息产业界和能源开发等方面的应用前景，早已引起国内外学者的极大关注．例如，由于氧化物具有各种特殊的介电和光学性质，研究和开发基于氧化物薄膜的气敏材料非常热门．如何制备出有实用价值的各种薄膜材料，是科学家们一直关心和深入研究的课题．电子能谱技术在各种材料的基础研究和实际应用中起着重要的作用．本文以有序金属氧化物薄膜研制为例，简要评述了电子能谱技术（包括X射线光电子能谱（XPS），紫外光电子能谱（UPS），俄歇电子能谱（AES）和高分辨电子能量损失谱（HREELS）），以及低能电子衍射（LEED）等技术在氧化物薄膜材料制备和表征中的应用．     

电子束在相对论返波管振荡器收集极上的能量沉积

在圆周对称的磁场作用下,环形电子束以一定角度轰击在圆柱面的相对论返波管振荡器(RBWO)收集极上并将能量沉积其中,采用蒙特卡罗程序FLUKA,建立了电子的能量沉积分布计算模型,研究了电子能量沉积分布规律;建立了背散射电子的运动模型,模拟了磁场作用下背散射电子的运动轨迹;研究了圆周对称径向磁场的近似方法。研究结果表明:随着磁场强度的增大,最大能量沉积密度增大,背散射电子在更靠近电子束入射区域的位置再次入射并沉积能量,且可能形成一个新的能量沉积峰值。在磁场强度较大时,采用单向的径向磁场即可较好地计算圆周对称径向磁场下背散射电子的能量沉积分布。     

Quantum-mechanical substantiation of a similar change in the kinetic energy component of an electron along the magnetic field within each Landau level

A detailed solution to the Schr?dinger equation for an electron in the presence of a quantizing magnetic field is considered using the method of separation of variables. The discrete energy levels occurring in this case are regarded as the potential barriers of finite height, with an electron moving normal to them along the magnetic-field direction. A similar change in the difference between the energy values within the neighboring Landau levels allows us to show, basing on the general properties of one-dimensional electron motion in the magnetic field, that within each quantum energy level, the kinetic-energy component of a longitudinal electron motion continuously is varied between 0 and 2μ_BH, whereas the probability density of particle location is practically damped into the potential-barrier depth as it moves along the magnetic-field direction. __________ Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 3–7, October, 2006.     

氮气开关流柱形成过程的理论研究

使用蒙特卡罗-粒子模拟方法对氮气开关中的流柱形成过程进行模拟, 并结合计算结果对其进行理论分析. 发现在流柱击穿发生前(即空间电荷场远小于本底电场), 等离子体的电离频率、电子平均能量及其迁移速度等都近似为常数, 因此可以解析求解电子数密度方程对等离子体的演化行为进行分析. 在击穿发生后, 随机碰撞过程会破坏初始等离子体区域分布的对称性, 并出现分叉的等离子体区域结构. 在放电过程中, 随着等离子体密度增加, 其内部基本保持电中性且电场不断减小, 靠近阴阳极两端电荷分离产生的净电荷密度不断增加, 场强也不断增加, 且靠近阳极端的电荷密度(绝对值)和场强都大于阴极端. 通过改变极板间电压发现, 平均电子能量随极板间场强增加而增加, 电子迁移速度随着场强近似线性增加, 电离频率随场强的变化快慢介于E⁴与E⁵之间.     

Electron trajectory evaluation in laser-plasma interaction for effective output beam

Using the ellipsoidal cavity model, the quasi-monoenergetic electron output beam in laser-plasma interaction is described. By the cavity regime the quality of electron beam is improved in comparison with those generated from other methods such as periodic plasma wave field, spheroidal cavity regime and plasma channel guided acceleration. Trajectory of electron motion is described as hyperbolic, parabolic or elliptic paths. We find that the self-generated electron bunch has a smaller energy width and more effective gain in energy spectrum. Initial condition for the ellipsoidal cavity is determined by laser-plasma parameters. The electron trajectory is influenced by its position, energy and cavity electrostatic potential.     

Electron excitation of a surface by atoms from hydrogen plasma in the presence of ultraviolet radiation

The dependence describing the probability of the electron excitation of a crystal by the energy of a chemical reaction on the energy of electron transitions is derived. It is found that the probability of electron chemoexcitation grows exponentially when the energy of electron transitions falls in the solid state. The efficiency of the nonadiabatic chemo-electronic conversion of energy in structures of hydrogen energetics based on Schottky diodes is calculated.     

Multiphoton stimulated bremsstrahlung for broad (in the momentum representation) electron wave packets in an ultrashort laser pulse field

We consider features of absorption and emission of external laser field quanta by a broad (in the momentum representation) electron wave packet during its scattering from a potential center. Various scattering modes for the electron wave packet in a high-intensity laser field are analyzed using perturbation theory of potential energy. It is found that the absorption of laser field energy by an electron is substantially more effective as compared to the case of a plane wave. The important role of a number of interference effects associated with the large width of the initial electron momentum distribution is demonstrated.     

Threshold behaviour in the process of electron stimulated desorption

Measurements of ionic desorption efficiency in the region of threshold for electron stimulated desorption are reported with the common molecular gases oxygen, carbon monoxide and hydrogen adsorbed at the (100) and (110) faces of tungsten single crystal. The technique of study is based on a time-of-flight method which, in conjunction with techniques of single-particle counting, allows the determination of desorption efficiency to be extended to 10^?10 ion/electron. The limitation in threshold definition due to the inherent energy spread of electrons generated thermionically is discussed, and it is shown that threshold values are most correctly identified with the gradient of the semi-logarithmic plot of desorption efficiency versus electron energy. Values of threshold energy derived from the study reveal no dependence on the crystallographic orientation of the substrate. In all cases the results are reconciled with the predictions of the Redhead, Menzel and Gomer theory with both the bombarding as well as the ionizing election terminating at the vacuum (zero) level. The relevance of the results to the theory of electron stimulated desorption proposed by Zingerman and Ishchuk is also discussed.     

射频辉光放电CH4等离子体中电子的能量分布

通过求解Lorentz简化的玻尔兹曼方程,得到射频放电CH₄等离子体中电子的能量分布函数.求解过程中使用一个简化的射频电场模型代替泊松方程求解放电电场.共计包含6类环境气体及27种电子碰撞反应.通过EEDF对等离子体中的电子反应率系数、电子平均能量、电子的传输率系数等进行求解分析.结果表明,在等离子体鞘层区域电子能量具有Maxwell分布形式,在正柱区域具有Druyvesteyn分布形式.最高电子能量和最大反应率系数出现在鞘层区域.电子的迁移率系数和扩散率系数随射频周期的演化时空分布不均匀.     

The effect of multiple electron-electron scattering on the energy distribution of electrons in a correlated pair

A unit event of electron-electron scattering in LiF layers is studied by correlation spectroscopy of scattered electrons. The energy distribution of electrons in a correlated pair when a 15-to 55-eV free electron is scattered by a valence electron of LiF is studied. It is shown that single electron-electron scattering prevails and the distribution is uniform when the energy of the primary electron is below 25 eV. As the energy of the primary electron increases, the formation of correlated pairs of electrons with equal energies becomes the most probable. With the energy of the primary electron above 40 eV, the pairs with substantially different electron energies dominate. Such evolution of the energy distribution of the electrons in the pair stems from the fact that first one and then the other electron of the pair successively takes part in electron-electron scattering. A phenomenological model for the single scattering and double scattering of primary electrons in LiF films is considered. Results obtained indicate that the strengths of single scattering and double scattering channels become comparable at electron energies above 25 eV.     

Determination of the mean energy of backscattered electrons in dependence on the exit angle

A semiconductor detector was used to measure the mean energy of backscattered electrons as a function of the exit angle. New regularities of electron backscattering were found. A nonmonotonic dependence of the mean energy of backscattered electrons on the exit angle and the primary electron energy for materials with different atomic numbers was revealed.     

Electron temperature in a decaying krypton plasma in the presence of a low electric field

The influence of low electric fields on the average electron energy in an afterglow krypton plasma is studied by means of probe diagnostics and theoretical analysis. It is shown that, when the average electron energy is lower than the energy corresponding to the minimum scattering transport cross section, the degree of plasma ionization substantially affects the shape of the electron energy distribution function (EEDF). The nonequlibrium character of the EEDF results in the density dependence of the coefficient of ambipolar diffusion, which leads to a change in the radial profile of the charged particle density, an increase in the drop in the ambipolar potential across the plasma, and an increase in the rate of diffusive plasma decay. These effects substantially enhance the diffusive cooling of electrons, which is probably a decisive factor influencing the electron energy balance in high-Z noble gases.     

One-electron capture from the inner shells in atom-multicharged ion collisions

The electron capture from the inner atomic shells by multiply charged ions at intermediate and high collision energies is considered. The cross section scaling laws, as well as the reduced energy parameter, are discussed. Universal curves for the reduced cross section versus the reduced collision energy are presented for electron capture from the K, L and M shells of Ar atoms colliding with multiply charged ions. A comparison of theoretical results with the existing experimental data is given.     

Electron energy gain in the fundamental mode of an elliptical waveguide in the presence of static helical magnet by microwave radiation

The dynamics and energy gain of an electron in the field of a transverse electric wave propagating inside an elliptical waveguide is analytically investigated by considering the existence of a helical magnet in which the field is perpendicular to the axis of the waveguide and rotating as a function of position along the magnet. Besides, by solving the relativistic momentum and energy equations, the deflection angle and the acceleration gradient of the electron in the waveguide are obtained. It is shown that the electron is deflected due to the field components of the transverse electric mode of this microwave, and at the same time, it is accelerated by these fields. Furthermore, the expressions of the acceleration gradient and deflection angle for an electron in the transverse electric mode inside the plasma elliptical waveguide without a static helical magnet are presented, which was injected initially along the propagation direction of the microwave. The results are graphically presented.     

晶粒尺寸对1 MeV电子在金属Ni中能量沉积的影响

采用脉冲电沉积方法制备出高致密、高质量的纳米晶Ni, 并对其密度、组织成分和微观结构进行了表征. 利用高能粒子加速器产生的1 MeV高能电子为辐照源, 研究高能电子在纳米晶Ni和常规粗晶Ni中的能量损失. 通过辐照过程中放置的吸收剂量片来准确表征其电子的能量沉积. 结果表明, 晶粒尺寸对高能电子在材料中的能量沉积有明显的影响, 1 MeV电子在穿过一定厚度的金属Ni后, 在晶粒尺寸细小的纳米晶Ni中测得总的吸收剂量较大, 证明了高能电子在纳米材料中的总能量沉积较小, 从而表现出纳米材料抗辐照的优异性能. 关键词： 高能电子 纳米金属 辐射损伤