共查询到20条相似文献,搜索用时 31 毫秒
1.
G. M. Fraiman V. A. Mironov A. A. Balakin 《Journal of Experimental and Theoretical Physics》1999,88(2):254-262
We examine elastic and inelastic scattering of electrons by ions in intense laser light. A method of numerical investigation
of the scattering characteristics based on regularizing the Coulomb singularity is proposed. We show that over a broad range
of parameter values the transport scattering cross section is weakly dependent on the intensity of the high-frequency field.
We detect a significant modification of the dependence of the effective inelastic scattering cross section. We also show that
the energy exchange with the field is determined by a fairly small group of electrons, called the representative electrons.
Finally, we propose a qualitative model that explains our results by the fact that the leading contribution is provided by
inelastic collisions of electrons with relatively small impact parameters traversing the region important for the interaction
at large angles.
Zh. éksp. Teor. Fiz. 115, 463–478 (February 1999) 相似文献
2.
A numerical simulation is made of the processes occurring in a plasma lens under conditions when the focusing of a relativistic
electron beam is strongly affected by the ionization of the residual gas in the lens region by the beam itself. The paraxial,
azimuthally symmetric, 1.5-dimensional, electrostatic kinetic model, taking account of plasma production, expansion of the
plasma electrons away from the beam region, and contraction of the ions toward the axis of the beam, was used for the calculation.
The dynamics of the formation of a focal spot is studied, and the size and position of the spot are determined as functions
of time for different values of the gas pressure, initial plasma density, and energy of the beam electrons.
Zh. Tekh. Fiz. 67, 90–94 (October 1997) 相似文献
3.
A. A. Andreev I. A. Litvinenko K. Yu. Platonov 《Journal of Experimental and Theoretical Physics》1999,89(4):632-639
The possibility that fast electrons can escape in a direction close to the trajectory of a reflected ultrashort laser pulse
at extremely high laser radiation fluxes is examined analytically and numerically. Analytic estimates are made of the feasibility
of forming electron bursts in the plasma and of their subsequent motion. The self-consistent, collisionless motion of a plasma
acted on by specified incident and reflected ultrashort laser pulses is modeled in two dimensions by the particle-in-cell
method. It is shown that a substantial number of electrons located in the subcritical region are gathered into bunches by
the resultant forces and escape to the vacuum in a direction different from the normal to the target surface within a narrow
range of solid angles. This demonstrates the feasibility of laser acceleration of an electron burst during reflection of an
ultrashort laser pulse from a solid target.
Zh. éksp. Teor. Fiz. 116, 1184–1197 (October 1999) 相似文献
4.
T. Koga H. Matsuyama J. Molina Molina J.S. Dehesa 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》1999,7(1):17-23
Electron-pair intracule (relative motion) and extracule (center-of-mass motion) densities are studied in both position and
momentum spaces for the
1
P and
3
P terms of the group 2 atoms Be (atomic number Z
=4), Mg (Z
=12), Ca (Z
=20), Sr (Z
=38), Ba (Z
=56), and Ra (Z
=88). In position space, the
1
P
-
3
P difference in the intracule densities shows that the probability of a small interelectronic distance is larger in the triplet
for all the six atoms, as reported for the lightest Be atom in the literature. The position-space extracule density clarifies
that the triplet electrons are more likely to be at opposite positions with respect to the nucleus than the singlet electrons
for all the atoms. In momentum space, the singlet generally has a larger probability of a small relative momentum between
two electrons as a na?ve manifestation of the Fermi hole in the triplet. The extracule density in momentum space shows that
the
1
P term has a distribution larger in a large center-of-mass momentum region than the
3
P term.
Received: 26 August 1998 / Received in final form: 1 February 1999 相似文献
5.
We propose a model describing the destruction of metals under ultrashort intense laser pulses when heated electrons affect
the lattice through the direct electron-phonon interaction. The metal consists of hot electrons and a cool lattice. The lattice
deformation is estimated immediately after the laser pulse up to the electron temperature relaxation time. The hot electrons
are described with help of the Boltzmann and heat conduction equations. We use an equation of motion for the lattice displacements
with the electron force included. Estimates of the lattice deformation show that the ablation regime can be achieved.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 3, 195–199 (10 August 1997)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
6.
K. B. Korotchenko 《Journal of Surface Investigation: X-ray, Synchrotron and Neutron Techniques》2010,4(4):599-602
A new type of combinational channeling radiation induced by subbarrier (interband) transitions for the transverse motion of
relativistic electrons (positrons) is studied. It is known as diffracted channeling radiation (DCR). The formula describing
the DCR angular distribution in the case of axial channeling is obtained by taking into account the band structure of energy
levels for the transverse motion of electrons (positrons). It is shown that, in the two-wave approximation of the wave function
A(r) of virtual photons, the DCR matrix elements in the dipole approximation for axial and plane channeling coincide formally
(with the dimension of the problem taken into account). However, the formulas for DCR angular distributions in the cases of
axial and plane channeling differ considerably. 相似文献
7.
We propose a kinetic model of transient nonequilibrium phenomena in metals exposed to ultrashort laser pulses when heated
electrons affect the lattice through direct electron-phonon interaction. This model describes the destruction of a metal under
intense laser pumping. We derive the system of equations for the metal, which consists of hot electrons and a cold lattice.
Hot electrons are described with the help of the Boltzmann equation and equation of thermoconductivity. We use the equations
of motion for lattice displacements with the electron force included. The lattice deformation is estimated immediately after
the laser pulse up to the time of electron temperature relaxation. An estimate shows that the ablation regime can be achieved.
Zh. éksp. Teor. Fiz. 115, 149–157 (January 1999)
Published in English in the original Russian journal. Reproduced here with stylistic changes by the Translation Editor. 相似文献
8.
Abstract Thermo- and photostimulated processes are studied in reduced hydrogen containing α-Al2O3 excited by UV light. It is found that UV excitation in F absorption band at 90 K results in a ionization of the F-centers and capture of released electrons at defects thus producing an anisotropy absorption band at 4.2 eV and the dominant thermoluminescence (TL) peak at 260 K. The 260 K TSL peak is accompanied by complete bleaching of the 4.2 eV absorption band and vice versa—by light stimulation in the region of the 4.2 eV band the 260 K TSL peak disappear and released electrons recombine with F+-centers. Both the effect of the preliminary high-temperature thermal treatment of samples on formation of 4.2 eV-centers and the observed dichroism characteristics allows to conclude that corresponding complex defect contains hydrogen and can involve vacancy pair. 相似文献
9.
Kiyohiko Someda 《Molecular physics》2018,116(10):1377-1396
Correlated motion of electrons in the He atom irradiated with linearly polarised light is discussed. Mixing of the 2pz orbital into the 1s orbital is interpreted as motion of an electron along the z-axis. The transitions to the configurations (1s)(2pz) and (2pz)(2pz) from (1s)(1s) are described by using 1s–2pz hybridised orbitals with variable coefficients of hybridisation, in other words, by using the Thouless parameters. The quasi-eigenstates of the atom in stationary light are obtained on the basis of the Floquet formalism, and the behaviour of the Thouless parameters is analysed. Trajectories of time evolution of the Thouless parameters are found to be useful to grasp the motion of electrons. Shapes of the trajectories are classified into four modes: (1) two electrons try to stay away from each other due to Coulomb repulsion, (2) one of the electrons is solely driven to run, (3) two electrons are driven to travel together and (4) two electrons run anti-parallel with each other. The conditions of intensity and frequency of light causing these four modes are clarified and summarised in a kind of phase diagram. 相似文献
10.
H.-C. Wu J. Meyer-ter-Vehn 《The European Physical Journal D - Atomic, Molecular, Optical and Plasma Physics》2009,55(2):443-449
The coherent reflectivity of a dense, relativistic,
ultra-thin electron layer is derived analytically for an obliquely
incident probe beam. Results are obtained by two-fold Lorentz
transformation. For the analytical treatment, a plane uniform
electron layer is considered. All electrons move with uniform
velocity under an angle to the normal direction of the plane; such
electron motion corresponds to laser acceleration by direct action
of the laser fields, as it is described in a companion paper [Eur. Phys. J. D 55, 433 (2009)]. Electron density is chosen high enough to ensure that many
electrons reside in a volume λR
3, where λR is the
wavelength of the reflected light in the rest frame of the layer.
Under these conditions, the probe light is back-scattered coherently
and is directed close to the layer normal rather than the direction
of electron velocity. An important consequence is that the Doppler
shift is governed by γx=(1-(Vx/c)2)-1/2 derived from
the electron velocity component Vx in normal direction rather
than the full γ-factor of the layer electrons. 相似文献
11.
Quantum crystallization of electrons in a quantum dot (QD) subjected to an external magnetic field is considered. Two-electron
QDs with two-dimensional (2D) parabolic confining potential in an external transverse magnetic field are calculated. The Hamiltonian is numerically diagonalized
in the basis of one-particle functions to find the energy spectra and wave functions for the relative motion of electrons
with inclusion of electron-electron interaction for a broad range of the confining-potential steepness (α) and external magnetic fields (B). The region of the external parameters (α, B) within which a gradual transition to quantum crystalline order occurs is numerically determined. In contrast to a 2D unbounded system, a magnetic field acts nonmonotonically on “crystallization” in a quantum dot with several electrons because
of a competition between two effects taking place with increasing B, namely, decreasing spread of the electron wave functions and increasing effective steepness of the confining potential,
which reduces the average separation between electrons.
Fiz. Tverd. Tela (St. Petersburg) 40, 1753–1759 (September 1998) 相似文献
12.
The thickness dependence of the electronic conductivity of thin (5–150 nm) single-crystal (100) films of refractory metals
is investigated at different temperatures ranging from 4.2 K to room temperature. Regions of square-root, quasilinear, and
quadratic dependences are observed. The quasilinear thickness dependence is explained by the influence of quantum effects
on the transverse motion of electrons in the case when electron scattering by the film surfaces dominates. For macroscopic
film thicknesses 30–50 nm, much greater than the Fermi wavelength of an electron, quantum corrections to the electronic conductivity
reach values of the order of 50%. This is a consequence of the quantum size effect for grazing electrons, which leads to an
anomaly in electron scattering by the film surfaces. The region of the quadratic thickness dependence corresponds to the quantum
limit, and the square-root region corresponds to the classical limit. The effect is explained in a quasiclassical two-parameter
model (the effective angle α* for small-angle electrons and the parameter γ, equal to the ratio of this angle to the diffraction angle) that takes into account the diffraction angular limits for grazing
electrons. The effect occurs for parameters α*≪1 and γ∼1 and differs from the “ordinary” quantum size effect.
Pis’ma Zh. éksp. Teor. Fiz. 66, No. 11, 693–698 (10 December 1997) 相似文献
13.
We study the orbital magnetism of 2D lattices with chaotic motion of electrons within a primitive cell. Using the temperature
diagrammatic technique, we evaluate the averaged value and rms fluctuation of the magnetic response in the diffusive regime
within the model of noninteracting electrons. The fluctuations of the magnetic susceptibility turn out to be large and at
low temperature can be of the order of χL(k
Fl)3/2, where k
F is the Fermi wave vector, l is the mean free path, and χL is the Landau susceptibility. In a certain region of magnetic fields the paramagnetic contribution to the averaged response
is field-independent and larger than the absolute value of the Landau response.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 12, 979–983 (25 June 1996)
Published in English in the original Russian journal. Edited by Steve Torstveit. 相似文献
14.
For Josephson junctions in sandwich geometry and in thin-film geometry we formulate the equations of nonlocal electrodynamics
which take account of the influence of normal electrons in superconductors. On the basis of these equations we examine the
spectrum and decay of generalized Swihart waves. We find that the decay of these waves by normal electrons becomes especially
prominent in the short-wavelength region. Comparison of various dissipation mechanisms has revealed the conditions for efficient
emission of electromagnetic waves from Josephson structures with finite dimensions.
Fiz. Tverd. Tela (St. Petersburg) 41, 1160–1167 (July 1999) 相似文献
15.
In-situ/operando techniques have been developed for spectromicroscopic studies of heavy elements using hard X-rays with high transmittance in samples and long focal length of optical elements (i.e., long working distance) at photon energies >4 keV. On the other hand, in-situ measurements in the soft X-ray region for spectromicroscopic studies of light elements at deep inner shells and heavy elements at shallow inner shells face significant technical challenges due to several difficulties, including low transmittance and short focal lengths of optical elements. Scanning transmission X-ray microscopy (STXM) in the soft X-ray region is a promising technique for in-situ observation in comparison with other microscopic techniques using electrons and ions, considering its characteristics, such as high resolving power in energy and in space, low radiation damage, and two-dimensional (and three-dimensional) chemical state analysis using near-edge X-ray absorption fine structure. 相似文献
16.
K. Yu. Amosov V. A. Verzilov I. E. Vnukov B. N. Kalinin G. A. Naumenko A. P. Potylitsyn 《JETP Letters》1996,63(3):153-158
The radiation spectra from 900 and 400 MeV electrons in thin Ta, Cu, and Sn foils are measured at an angle of 19° with respect
to the direction of motion of the beam. The radiation yield and its dependence on the electron energy agree satisfactorily
with the theory of polarization bremsstrahlung. This result represents the first direct observation of polarization bremsstrahlung
from ultrarelativistic electrons in homogeneous condensed matter.
Pis’ma Zh. éksp. Teor. Fiz. 63, No. 3, 145–149 (10 February 1996) 相似文献
17.
T. V. Liseykina V. Yu. Bychenkov G. I. Dudnikova F. Pegoraro 《Applied physics. B, Lasers and optics》2005,81(4):537-542
Two-dimensional particle-in-cell (PIC) simulations of laser-triggered ion acceleration in overdense plasma at moderate intensity (≃1.4×1018 W/cm2) and pulse duration (≃0.5 ps) are presented. We focus on the comparison of the efficiency of ion acceleration for normal and oblique incidence of the laser light, for backward and forward directions of ion emission, and for large and small focal spots. We discuss the correlation between the properties of accelerated ions and hot electrons, and identify the tendency of the ion spectra in the forward direction to those typical for the isothermal and adiabatic regimes of plasma expansion. 相似文献
18.
Abstract We review the phenomenon of coherent bremsstrahlung (CB) of electrons in a crystal. This well-studied process in a new light after the realization by Andersen [J. U. Andersen, Nucl. Inst. and Methods 170, 1 (1980)] that CB and the phenomenon of channeling radiation (CR) are two aspects of the same physical process. These two types of radiation may be described in a unified framework by the use of Bloch functions for the electron in the crystal. The kinematics of CB is discussed from this viewpoint and a model calculation for CB in a strained-layer superlattice is presented. 相似文献
19.
S. B. Dabagov 《辐射效应与固体损伤》2013,168(1-3):103-106
Abstract A method of calculation of angular distributions of channeled electrons is proposed in the paper. The depth dependence of the angular distribution is investigated. At large penetration depths, the planar channeled particles are seen to spread widely parallel to the atomic planes, while the transverse motion is more confined. 相似文献
20.
AbstractThe theory of the nonequilibrium charge carrier transport in unipolar multivalley semiconductors is developed. It is shown that the diffusion of photoexcited nonequilibrium heavy and light electrons in multivalley semiconductors is a correlated process, like the ambipolar diffusion in the case of the electron-hole plasma. The light-induced intervalley transitions, resulting in the imbalance between the subsystems of the light and heavy electrons, give rise to the electromotive force (emf) through the mechanism of the Dember photovoltaic effect. The value of the emf occurring in the ‘metal-semiconductor-metal’ structure is calculated in the linear approximation in terms of the light intensity as a small parameter. It is shown that the emf is determined by the conductivity of heavy and light electron subsystems, as well as by the surface conductivity of the metal-semiconductor interface. 相似文献