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Electron Conduction - Electrical conduction associated with the movement of electrons as opposed to that of holes or ions.
Electron Conduction of Heat - One of the two modes of heat conduction in a metal. The total heat conduction may be considered to be produced by two carriers acting in parallel electrons and phonons, the latter giving rise to lattice conduction.
Electron Current - In a given direction: the number of electrons per second crossing unit area at right angles to the direction.
Electron Density - (1) In general: the number of electrons per unit mass. (2) In astrophysics: the number of eletrons per unit volume.
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Electron Detachment - The detachment of an electron from a negative ion to form a neutral atom or molecule.
Electron Diffraction - Interference which occurs when electrons are scattered by different elements (including magnetic elements) of a solid, liquid or gaseous medium. It arises from the wave nature of electrons.
Electron Diffraction, Low Energy (LEED) - Electron diffraction at energies of 0.3-1 key, used for the study of surface structure, e.g. the effects of gas adsorption in catalysis.
Electron Energy Band- One of the bands or zones of electron energy levels in a crystal by which the total range of energy states is broken up into alternate allowed and forbidden ranges.
Electron Energy Level - (1) One of the stationary electron energy states in an isolated atom. (2) One of the energy levels in an electron energy band, which band may sometimes be conveniently pictured as arising from the broadening of the energy levels referred to in (I) when the individual atoms are brought into close proximity.
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Electron Phase Focusing - The process by which a continuous electron stream, moving with a uniform velocity, is passed through a high frequency field which modulates this velocity so that a variation in electron concentration occurs along the length of the beam, with the formation of maxima and minima.
Electron, Primary - In an absorption or scattering process: an incident electron or one which passes through the energy or direction.
Electron Probe - A very narrow electron beam, used, for example, for scanning or in electron diffraction.
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Electron Wave Tube - An electron tube in which mutually interacting beams of electrons, travelling with different velocities, cause a signal modulation to change progressively along their length.
Electrophotophoresis - The (usually). helical movement of small particles in a gas along the direction of an electric field during their irradiation by light. It is one type of photophoresis.
Electroscope - An instrument by which small electrostatic charges and hence small electric currents are measured by the observation of the movement of light mobile member relative to a fixed electrode. The movement is usually observed with the aid of a microscope.
Electrostatic Generator - An instrument or machine for producing a . large quantity of electric charge by electrostatic means, e.g. by the use of friction or the discharge of electricity from points.
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Electrostatic Induction - The production of electric charge on the surface of a conductor under the influence of an electrostatic field.
Electrostatic Instruments - Instruments for the measurement of potential difference or electric charge which rely on the forces between electric charges to produce some mechanical deflection in the measuring system.
Electrostatic Lens - A lens for focusing an electron beam, which depends typically on three co-linear apertures in diaphragms at different potentials.
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Electron-Probe Microanalysis - A technique for the indentif1cation and estimation of the component elements in a selected micro volume at the surface of a solid specimen, by the analysis of the characteristic X-rays emitted from that volume when bombarded by an electron microbeam.
Electron Radiography - True radiography by photoelectrons. The photoelectrons are generated by a beam of hard X-rays which passes first through a thin sheet (usually of lead) which emits photoelectrons, then through the specimen (which must be very thin) and finally (without appreciable effect) through a fine grained film, close cantact being essential between sheet and specimen, and specimen and fil . The resulting radiograph reveals differences in electron absorption. See also Radiography. (2) Autoradiography by electrons emitted from the specimen itself.
Electron Radius - The value of the radius obtained by equating the electrostatic self energy of the electron to its rest mass energy on the assumptlon that the electron is spherical and has the charge distributed uniformly over' the surface.
Electron Rest Mass - The mass of an electron at rest, or that part of the mass of an electron in motion which is associated purely with the electrostatic field of its stationary charge, i. e. that part which is independent of the relativistic mass acquired in motion. It is about 9.11 x 10-13 kg.
Electron, Secondary - In an absorption or scattering process: an electron other than a Primary electron emerging from the absorbing or scattering medium.
Electron Temperature - A "statistical," temperature obtained from the Boltzmann equation, E = ½KT (E = average kinetic energy per degree of freedom K = Boltzmann's constant, T = absolute temperature), where E refers to the electron energy.
Electron Trap - An electron energy level which becomes available by reason of an imperfection in a crystalin which electrons may be trapped.
Electron Tube: Electron Valve - A device in which conduction takes place. by the passage of electrons or ions between electrodes in a vacuum or a gas.
Electron Volt. A unit of energy equal to the change of kinetic energy suffered by an electron when it is accelerated or decelerated through a potential difference of one volt. (Note: leV = 1.602 x 10-19 J or 1.602 Z 10-12 erg.)
Electron Wavelength - The de Broglie wavelength associated with an electron. For electron energies of 50 or 100 kV the wavelength has about the same value as atomic radii, and beams of such electrons may therefore be diffracted by crystals.
Electron Gas - A concentration of electrons whose behaviour is primarily or significantly determined, by the interactions between the electrons themselves.
Electron Gun - An assembly of electrodes which produces an electron beam for use in such equipment as a cathode-ray tube or electron microscope.
Electron Hole: Positive Hole - A vacancy in a, previously filled energy band in a solid, caused by the excitation of an electron from that band to one of higher energy.
Electron Lens - A device for focusing an electron beam. It may be magnetic (having coils or permanent magnets) or electrostatic, or take the form of an aperture in a diaphragm.
Electron Lens, Immersion - An electron lens in which the object is deeply immersed in the field so that the refractive index varies rapidly in its neighbourghood.
Electron Mass - The rest mass of an electron, equal to 9.109 x 10-13 kg.
Electron Microscope - An instrument in which a beam of electrons is used to form a magnified image in a manner somewhat analogous to that in a light microscope.
Electron Microscopy - The process of making and interpreting highly magnified images produced by electrons.
Electron Multiplier: Photomultiplier - A sensitive detector of light in which the initial electron current, derived from photoelectric emission, is amplified by a series of stages of multiplicative secondary electron emission.
Electron Nuclear Double Resonance (endor) - A combination of electron paramagnetic- resonance and nuclear magnetic resonance in which nuclear resonance is detected by the resulting electron paramagnetic resonance.
Electron Optics- The study of the controlled motion of electrons in free spece, and, to some extent, in solids
Electron Paramagnetic Resonance (EPR) - Electron Spin Resonance (ESR). The resonant absorption of microwaves by a specimen possessing unpaired electrons (and hence a resultant magnetic moment) when the electrons are separated into two or more energy, levels by the application of a strong unidirectional magnetic field of approprivate value. It is a branch of microwave sectroscopy.
Electrostatics - The study of the properties of the properties of electric charges at rest.
Electrostenolysis - The precipitation of metals in the pores of a membrane by electrolysis.
Electrostriction - Electrostrictive Effect. A second-order effect shown by all crystals, whereby a strain appears when an electric field is applied.
Elementary Particles - Fundamental Particles. Those particles which are held to be simple, such as neutrons, protons, electrons, mesons, hyperons, and photons. They are characterized by their mass, electric charge. spin. magnetic moment, or interaction properties, as appropriate. Some are stable, e.g. neutrinos, electrons, and protons. Others are unstable, e.g. neutrons, mesons and hyperons.
Elementary Particles, Interactions Betwee - . Four types of interaction which occur between elementary particles. Their relative strengths are; strong (about 1), electromagnetic (1/137,) weak (about 10-14), and gravitational (about 10-39).
Elevation Head. The energy possessed per unit mass of fluid due to its elevation above some datum. Also known as potential head.
Ellipsometer: Elliptic Polarimeter - An instrument for the measurement of the elliptical polarization of light. It is usually associated with the determination of the thickness and optical constants of surface films on metals and dielectrics.
Elongation - of a celestial object: the angle between the direction of the object and a chosen reference direction, e.g., the angle between the direction of a planet and that of the Sun.
Emanation: Radioactive Emanation - The inert radioactive gases, consisting of seventeen isotopes of atomic number 86, and having mass numbers ranging from 204 to 223. The best known are radon itself (22286RN), thoron (22086Rn) and actinon (21986RN) which are decay products of radium, thorium, and actinium respectively.
Emissive, Power - Of a body losing energy to its surroundings by radiation:
(1) The total energy emitted per second per unit area of surface, known as the total emissive power or emittance.
(2) The quantity e λin the expression e λ. dλ for the rate at which energy is lost over a small range of wavelengths λ to λ + dλ, known as the emissive power for the wavelength λ and sometimes the monochromatic emissive power.
Emissivity - Of a body losing energy to its surroundings by radiation: the ratio of its emissive power to that of a black body at the same temperature. It is known as thc total emissivity when the total heat is taken into account, and the spectral emissivity, when related to some selected region of the heat spectrum.
Emitron Tube - CPS Tube. A television camera tube in which the optical image is focused on the a photo-emissive mosaic formed on a transparent dielectric and capacitatively associated with a conducting signal plate.
Emittance - The total emissive power.
Encephalograph - The radiographic examination of the brain, the cavities and spaces of which have previously been filled with air See also: .Electroencephalography.
Endoscope - An optical instrument used for the medical inspection ofbody cavities and having an optical system similar to that of aperiscope but on a much smaller scale.
End Radiation - Another term for quantum limit.
Energy - The capacity of a body or a system for doing work. It may, for example, be thermal, electrical, mechanical, chemical or nuclear.
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