One-body electron dynamics in a free electron laser

The free electron laser is analyzed by solving the one-body classical Lorentz force equation in the presence of periodic magnetic field and a plane electromagnetic wave. Phase space paths for electrons are related to those of a simple pendulum and describe laser gain, saturation, and coherent electron beam modulation.     

Averaging the electron velocity in three-dimensional models of microwave electron devices in electron gap synthesis

Possible ways of averaging the electron velocity in three-dimensional high-perveance electron gaps are compared. The method proposed for averaging the electron velocity is the most suitable for electron gap synthesis. An estimate is made of the error that occurs in the velocity averaging by this method as a result of the finite value of the beam-focusing magnetic field.St. Petersburg Electrical Engineering Institute of Communications. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika, No. 10, pp. 1303–1310, October, 1994.     

Chaotic electron trajectories in a circular free electron laser

The motion of a relativistic electron is analyzed in the field configuration consisting of a circular wiggler magnetic field, an axial magnetic field, and the equilibrium self-electric and self-magnetic fields produced by the non-neutral electron ring. By generating Poincare surface-of-section maps, it is shown that when the equilibrium self-fields is strong enough, the electron motions become chaotic. Although the realistic circular wiggler magnetic field destroys the integrability of the electron motion as the equilibrium self-fields do, the role the latter plays to make the motions become chaotic is stronger than the former. In addition, the axial magnetic field can restrain the occurrence of the chaoticity.     

Sum rules and electron correlations in two-dimensional electron liquid

The low order frequency moment sum rules of the density response function for quantum 2-dimensional electron liquid are given. These are used to obtain an integral equation for the static structure factor. This integral equation is solved self-consistently for different electron densities. Results obtained for the pair-correlation function are positive for all inter-electron separations even at physical densities.     

Effective electron–electron and electron–phonon interactions in the Hubbard–Holstein model

We investigate the interplay between the electron–electron and the electron–phonon interaction in the Hubbard–Holstein model. We implement the flow-equation method to investigate within this model the effect of correlation on the electron–phonon effective coupling and, conversely, the effect of phonons in the effective electron–electron interaction. Using this technique we obtain analytical momentum-dependent expressions for the effective couplings and we study their behavior for different physical regimes. In agreement with other works on this subject, we find that the electron–electron attraction mediated by phonons in the presence of Hubbard repulsion is peaked at low transferred momenta. The role of the characteristic energies involved is also analyzed.     

高分辨电子显微学的新进展 --走向亚埃电子显微时代

简要介绍了高分辨电子显微学的最新进展．特别指出，随着空间分辨率突破1A和亚埃分辨率的电子显微镜的快速普及，电子显微学及相关研究领域将进入一个快速发展的阶段．装备有球差校正器和能量单色器的新一代电子显微镜将很快进入实验室，给出高质量的原子结构图像（分辨率优于1A）和高能量分辨率的电子能量损失谱（优于0．1eV）．这一进展将对晶体结构学、材料科学、物理学、纳米科学及生命科学产生重大影响，也为解决很多重要结构问题提供新机遇．     

The secondary-electron background problem in electron excited auger electron spectroscopy

Dynamic background subtraction is used to demonstrate that the recently suggested spline-polynomial scheme for characterizing the secondary electron background neglects an important aspect of the Auger feature. As a consequence of this neglect, area measurements using the spline approximation are difficult to relate to the true Auger current.     

Collisionless stopping of electron current in an inhomogeneous electron magnetohydrodynamics plasma

A brief review of a recent work on a novel collisionless scheme for stopping electron current pulse in plasma is presented. This scheme relies on the inhomogeneity of the plasma medium. This mechanism can be used for heating an overdense regime of plasma where lasers cannot penetrate. The method can ensure efficient localized heating at a desired location. The suitability of the scheme to the frontline fast ignition laser fusion experiment has been illustrated.     

The diffraction-dependence of electron damage in a high voltage electron microscope

Abstract

In a high voltage electron microscope the intense electron beam used for imaging can cause visible aggregates of point defects to form in metals in just a few minutes. The diffraction-dependence of the defect cluster production was studied experimentally in Cu and Fe using a 1000 kV electron microscope. Also, a simple method for calculating the diffraction-dependence of the atomic displacement rate was devised from multiple-beam wave-mechanical diffraction theory. The calculations indicate that the rate of point defect production should vary at most by a factor of ～1.7 with Bragg deviation in systematic diffraction cases, and that this variation should decrease rapidly with increasing depth in the crystal. The experimental observations are consistent with these predictions. In addition, the theory allows the diffraction-dependence of the displacement rate to be explained in terms of Bloch wave properties. Some new observations of the defect structures in electron-irradiated Cu and Fe are also described.     

Correlation of electron self-energy with geometric structure in low-energy electron diffraction

In low-energy electron diffraction (LEED) studies of surface geometries where the energy dependence of the intensities is analyzed, the in-plane lattice parameter of the surface is usually set to a value determined by x-ray diffraction for the bulk crystal. In cases where it is not known, for instance in films that are incommensurate with the substrate, it is desirable to fit the in-plane lattice parameters in the same analysis as the perpendicular interlayer spacings. We show that this is not possible in a conventional LEED I(E) analysis because the inner potential, which is typically treated as an adjustable parameter, is correlated with the geometrical structure. Therefore, without having prior knowledge of the inner potential, it is not possible to determine the complete surface structure simply from LEED I(E) spectra, and the in-plane lattice parameter must be determined independently before the I(E) analysis is performed. This can be accomplished by establishing a more precise experimental geometry. Further, it is shown that the convention of omitting the energy dependency of the real part of the inner potential means geometrical LEED results cannot be trusted beyond a precision of approximately 0.01 ?.     

f electron versus conduction electron superconductivity in the periodic Anderson model

We investigate the superconducting order parameter of strongly correlated electrons originating fromf states in the Anderson lattice model. Self-consistent calculations demonstrate rapid decrease of this quantity with the deviation of chemical potential from the centre of the band forT=0. The results indicate that although heavyf electrons are present at the Fermi surface, the superconductivity seems to be more likely supported by conduction electrons. Thus, we confirm the existence of cross-over effects derived by us previously within non self-consistent theory and suggest that the conduction electron contribution to the superconductivity of heavy fermion systems can be important and even dominating one.Supported by PAN, CPBP, 01.12., 2.7     

Intramolecular electron scattering and electron transfer following autoionization in dissociating molecules

Resonant Auger decay of core-excited molecules during ultrafast dissociation leads to a Doppler shift of the emitted electrons depending on the direction of the electron emission relative to the dissociation axis. We have investigated this process by angle-resolved electron-fragment ion coincidence spectroscopy. Electron energy spectra for selected emission angles for the electron relative to the molecular axis reveal the occurrence of intermolecular electron scattering and electron transfer following the primary emission. These processes amount to approximately 25% of the resonant atomic Auger intensity emitted in the studied transition.     

Giant electron tails and passing electron pinch effects in tokamak-core turbulence

The anomalous particle transport in a tokamak core is believed to be linked to the advection of magnetically trapped electrons alone, owing to the passing electrons maintaining a thermal equilibrium along the field lines. Surprisingly, in nonlinear numerical studies, the radial flux of passing electrons rivals that of the trapped ones. The strong interaction of passing electrons and electric fluctuations is mediated by long tails of the modes along the magnetic field, which are generated by the passing electrons in the first place.     

电子脉冲在飞秒电子衍射系统中的传输特性

优化设计了一套超快电子衍射系统.用轨迹追踪法讨论了光电子在阴极上有150 fs的时间弥散量，及其静态、动态特性(电子束斑、时间弥散、方位角、倾角)在超快电子衍射系统中的传输情况.用Monte Carlo方法对光电子的初始状态进行抽样、用有限差分法计算二维、三维空间电场分布，用有限元法计算磁场分布.     

Coherent electron density distribution oscillations in electron capture by fast protons in helium

Assuming the validity of a recent model of Lyman-α beat behaviour from fast H atoms under conditions of reversal of an applied electric field, we find strong electric dipole density distribution oscillations in electron capture to n=2 levels of hydrogen by fast protons (≈ 2 au) in helium. Possibilities for testing relative orbital phase calculations in charge-transfer theory, and for making comparisons between beam-surface and single ion-atom collision models of projectile passage through solids exist.     

Image contrast in the backscattered electron mode in scanning electron microscopy and microtomography

The problem of image contrast production in the backscattered electron (BSE) mode in a scanning electron microscope (SEM) in bulk and film structures is discussed. The considerable influence of the parameters of a semiconductor detector on the image contrast is shown. Calculations for contrast in dependence on the composition of target sections, the energy of primary electrons, and the signal detection technique are presented.     

Comparison of spin and electron diffusion coefficients in a two-dimensional electron gas

The results from femtosecond four-wave-mixing experiments carried out in two-dimensional gas at the GaAs/AlGaAs heterojunction boundary under room temperature conditionsare presented. The obtained values of the spin and electron diffusion coefficients are 163.2 and 200 cm²/s respectively. The spin and electron relaxation times are found to be 50.7 ps and 3 ns respectively.     

投影电子束光刻中电子穿透掩膜的Monte Carlo模拟

利用基于Mott散射截面和介电函数模型的Monte Carlo方法模拟了电子穿透掩膜的能量损失分布，其计算结果与实验结果符合很好. 由此进一步计算了角度限制投影电子束光刻(SCALPEL)掩膜的穿透率和衬度，结果表明：散射体的厚度对衬度的影响较大，衬度随散射体厚度的增加而增强，而支撑体对衬度的影响较小；增大限制孔的孔径角时，透射率相应增大，但衬度会降低；衬度随入射电子的能量增加而减小. 关键词： Monte Carlo模拟 电子束光刻 掩膜     

Coherent interaction of ion and electron beams in systems with electron cooling

A hydrodynamic approximation is used to study the behavior of dipole modes of the transverse oscillations of an ion beam in a storage ring with an electron cooling section. It is shown that in addition to the finite interaction time of the beams, instability may be caused by a specific interaction effect between the ion and electron beams in the magnetic field which leads to redistribution of energy between the various modes of the ion beam oscillations. In this case, the condition that the determinant of the transfer matrix for the cooling section does not exceed unity no longer guarantees the stability of the transverse coherent oscillations of the ion beam and all the eigenvalues of the complete matrix of the ion motion including the storage ring must be analyzed. Calculations of the stability of ion beam dipole oscillations are presented for the parameters of CELSIUS.