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1.
Summary Experiences are reported in connection with the use of bolt cathode as the object-holder in an electron emission microscope. The bolt cathode consists of a cylindrical Tungsten rod, the bolt, close pinched at one end, the top of the other free end being used as the emission surface. The bolt is surrounded by a Tungsten helix, which can be heated by passing direct current. This helix serves as a primary cathode emitting electrons for electron bombardment of the bolt. In the case of use of bolt cathode as specimen holder in an electron emission microscope the specimen is melted on the top of the Tungsten bolt. Melting occurs by the bombardment of specimen substances with accelerated electrons from an electron gun. This method has many advantages and is described in detail. Two properties of the bolt cathode, important for the emission microscope, i. e. the axial displacement of the object and the magnetic field of the heating helix, are discussed in detail. A micrograph shows the quality of the electron emission pictures obtained.  相似文献   

2.
The bipolar Euler–Poisson system in physics consists of the conservation laws for the electron and ion densities and their current densities, coupled with the Poisson equation for the electrostatic potential. The limit of vanishing ratio of the electron mass to the ion mass in the n-dimensional flat torus is proved in the case of well prepared initial data. The limiting system is composed of two separated equations, where the equation for electron is the incompressible Euler equation with damping, which means physically that the evolution for electrons and ions can be treated as separated motions in the small ratio case.  相似文献   

3.
We obtain a cluster expansion for the two-time retarded Green's functions and the thermodynamic potential of a disordered crystal taking the electron–phonon and electron–electron interactions into account. The electron states of the system are described in the framework of a multiband tight-binding model. The calculations are based on the diagram techniques for the temperature Green's functions. The coherent potential approximation is chosen as a zeroth-order one-site approximation in this cluster expansion method. We show that the contributions from the processes of scattering of elementary excitations on clusters decrease as the number of sites in the cluster increases in accordance with certain small parameters. Analytic estimates of the influence of the electron–phonon interaction on the energy spectrum of electrons of an alloy being ordered are obtained in a one-band model. The applicability of these results to describing the influence of strong electron correlations on the electron structure and properties of alloys of transition metals with narrow energy bands is illustrated with the example of the Fe–Ti alloy.  相似文献   

4.
We consider an infinite two‐dimensional waveguide that, far from the coordinate origin, coincides with a strip. The waveguide has two narrows of diameter ?. The narrows play the role of effective potential barriers for the longitudinal electron motion. The part of the waveguide between the narrows becomes a ‘resonator’, and there can arise conditions for electron resonant tunneling. A magnetic field in the resonator can change the basic characteristics of this phenomenon. In the presence of a magnetic field, the tunneling phenomenon is feasible for producing spin‐polarized electron flows consisting of electrons with spins of the same direction. We assume that the whole domain occupied by a magnetic field is in the resonator. An electron wave function satisfies the Pauli equation in the waveguide and vanishes at its boundary. Taking ? as a small parameter, we derive asymptotics for the probability T(E) of an electron with energy E to pass through the resonator, for the ‘resonant energy’ Eres, where T(E) takes its maximal value and for some other resonant tunneling characteristics. The asymptotic formulas contain some unknown constants. We find them by solving several auxiliary boundary value problems (independent of ?) in unbounded domains. Having the asymptotics with calculated constants, we can take it as numerical approximation to the resonant tunneling characteristics. Independently, we compute numerically the scattering matrix and compare the asymptotic and numerical results. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

5.
Summary In this paper we report the use of the scanning electron beam technique for a measurement of the ambipolar diffusion length, the surface recombination velocity and the electric field distribution in Ge-Li-PIN-Diodes. A simple relation between the diffusion length and the photovoltage induced by the electron beam is derived. The diffusion length as a function of temperature shows a strong increase with decreasing temperature. This fact limits our method to temperatures above –80°C. A measurement of the electric field distribution is demonstrated for the case of double injection in PIN-Diodes with an extended intrinsiczone. The conductivity modulation caused by the electron beam, at constant current in forward direction, results in a change in the terminal voltage which is proportional to the square of the electric field strength at the injection point.  相似文献   

6.
7.
The electron pulsation event is defined in the paper. Firstly, a slow Halo CME on March 16, 2001 that led to low-energetic solar proton event, electron pulsation event and major geomagnetic storm was analyzed. And then, dozens of events are collected. The interrelations among the solar flare, CME, solar proton event, electron pulsation event and geomagnetic storm are studied. The results show that: (ⅰ) Solar proton events can be regarded as the indication that CMEs get to the earth and the electron pulsation events can be regarded as the indication of solar proton flux. (ⅱ) Not only can fast CMEs strongly influence the earth, but also slow CMEs can influence the earth, and its influences are more frequent and cannot be neglected. (ⅲ) Most of high-energetic solar proton events with E≥10 MeV can lead to geomagnetic storms, but most of the medium and weak geomagnetic storms result from low-energetic solar proton events that are caused by CMEs. (ⅳ) Both the electron pulsation events and geomagnetic storms are the link effects of high- and low-energetic solar proton events, but the occurrence of electron pulsation event are generally prior to the geomagnetic storm. So in the circumstance where the near real-time observing data of the low-energetic solar proton event cannot be obtained, we can regard electron pulsation event as the indication of the low-energetic solar proton flux reaching the earth, which can be used as one of the important 参考文献 of short-term prediction and alert of the geomagnetic storm.  相似文献   

8.
A three-level scheme for modeling nanosized semiconductor heterostructures with account for spontaneous and piezoelectric polarization effects is presented. The scheme combines quantummechanical calculations at the atomic level for obtaining the charge density on heterointerfaces, calculation of the distribution of carriers in the heterostructure based on the solution to the Schrödinger and Poisson equations, and the calculation of electron mobility in the two-dimensional electron gas with account for various scattering mechanisms. To speed up the computations of electron density in the heterostructure, the approach based on the approximation of the nonlinear dependence of the electron density on the potential in combination with the linearization of the Poisson equation is used. The efficiency of this approach in problems of the class in question is demonstrated.  相似文献   

9.
It is shown thatin a linear periodic chain at whose sites electron wave functions of opposite parities alternate the existence of zitterbewegung of a nonrelativistic electron can be established without passage to the limiting case of a continuum. An analogy is established with the relations obtained earlier by the authors for the motion of a nonrelativistic electron in a two-site system. The zitterbewegung of the nonrelativistic electron in the considered system is given an interpretation analogous to the interpretation obtained by the first two authors for the zitterbewegung of a relativistic electron in Dirac's theory. A connection between the energy and effective mass of the nonrelativistic electron in the considered system is established.Institute of Metal Physics, Urals Branch of the Russian Academy of Sciences. Translated from Teoreticheskaya i Matematicheskaya Fizika, Vol. 94, No. 2, pp. 343–352, February, 1993.  相似文献   

10.
The electron pulsation event is defined in the paper. Firstly, a slow Halo CME on March 16, 2001 that led to low-energetic solar proton event, electron pulsation event and major geomagnetic storm was analyzed. And then, dozens of events are collected. The interrelations among the solar flare, CME, solar proton event, electron pulsation event and geomagnetic storm are studied. The results show that: (i) Solar proton events can be regarded as the indication that CMEs get to the earth and the electron pulsation events can be regarded as the indication of solar proton flux. (ii) Not only can fast CMEs strongly influence the earth, but also slow CMEs can influence the earth, and its influences are more frequent and cannot be neglected. (iii) Most of high-energetic solar proton events withE≥10 MeV can lead to geomagnetic storms, but most of the medium and weak geomagnetic storms result from low-energetic solar proton events that are caused by CMEs. (iv) Both the electron pulsation events and geomagnetic storms are the link effects of high- and low-energetic solar proton events, but the occurrence of electron pulsation event are generally prior to the geomagnetic storm. So in the circumstance where the near real-time observing data of the low-energetic solar proton event cannot be obtained, we can regard electron pulsation event as the indication of the low-energetic solar proton flux reaching the earth, which can be used as one of the important references of short-term prediction and alert of the geomagnetic storm.  相似文献   

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