| electron lens | <physics> A device for focusing an electron beam. (05 Aug 1998) |
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| electron magneton | bohr magneton |
| electron micrograph | <microscopy> A photographic reproduction of an image formed by the action of an electron beam. Electron microscope See: microscope, electron. (05 Aug 1998) |
| electron microprobe | A technique of elemental analysis in the electron microscope based on spectral analysis of the scattered X-ray emission from the specimen induced by the electron beam. Using this technique it is possible to obtain quantitative data on, for example: the calcium concentration in different parts of a cell, but it is necessary to use ultra thin frozen sections. (18 Nov 1997) |
| electron microscope | <instrument> A microscope (device used to magnify small objects) which beams electrons at and through the object of interest instead of light beams. Instead of a glass lens to bend the light, a powerful magnet is used to bend the electron beam. The microscope can only be operated in a vacuum. This type of microscope provides the greatest resolution of extremely small details available and has been used to see individual atoms in an object or substance. (09 Oct 1997) |
| electron microscopy | <procedure> Any form of microscopy in which the interactions of electrons with the specimens are used to provide information about the final structure of that specimen. In transmission electron microscopy the diffraction and adsorption of electrons as the electron beam passes normally through the specimen is imaged to provide information on the specimen. In scanning electron microscopy an electron beam falls at a nonnormal angle on the specimen and the image is derived from the scattered and reflected electrons. Secondary X-rays generated by the interaction of electrons with various elements in the specimen may be used for electron microprobe analysis. (18 Nov 1997) |
| electron optical axis | <physics> The path of an electron through an electron optical system along which it suffers no deflection due to lens fields. This axis does not necessarily coincide with the mechanical axis of the system. (05 Aug 1998) |
| electron optical system | <apparatus> A combination of parts capable of producing and controlling a beam of electrons to produce an image of an object. (05 Aug 1998) |
| electron optics | <study> The science that deals with propagation electrons, as light optics deals with that of light and its phenomena. Eye lens (see lens, eye). (05 Aug 1998) |
| electron paramagnetic resonance | <physics> A spectrometric method, based on measurement of electron spins and magnetic moments, for detecting and estimating free radicals in reactions and in biological systems. Synonym: electron paramagnetic resonance. (05 Mar 2000) |
| electron probe | <physics> A narrow beam of electrons used to scan or illuminate an object or screen. (05 Aug 1998) |
| electron probe microanalyser | <apparatus> The qualitative and quantitative use of X-rays excited by a microprobe of electrons. Available with scanning electron microscope and transmission electron microscope. Acronym: EMA (05 Aug 1998) |
| electron probe microanalysis | Identification and measurement of concentration of elements based on the fact that primary-emission X-rays emitted by an element excited by an electron beam have a wavelength characteristic of that element and an intensity related to its concentration. It may be performed by an electron probe microanalyzer, an electron microscope microanalyzer, or by an electron microscope, or scanning electron microscope, fitted with an X-ray spectrometer. (12 Dec 1998) |
| electron radiography | <radiology> Radiographic imaging in which X-radiation incident on the receptor is converted to a latent charge image and subsequently recovered by a special printing process; advantages include wider latitude of exposure and greater sensitivity than conventional film-screen combinations. See: xeroradiography, phosphor plate. (05 Mar 2000) |
| electron resonance absorption | <physics> A spectrometric method, based on measurement of electron spins and magnetic moments, for detecting and estimating free radicals in reactions and in biological systems. Synonym: electron paramagnetic resonance. (05 Mar 2000) |
| scanning electron microscope | <instrument> An electron microscope in which the image is formed by a beam synchronised with an electron probe scanning the object. The intensity of the image forming beam is proportional to the scattering or secondary emission of the specimen where the probe strikes it (05 Aug 1998) |
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| scanning electron microscopy | <procedure> Technique of electron microscopy in which the specimen is coated with heavy metal and then scanned by an electron beam. The image is built up on a monitor screen (in the same way as the raster builds a conventional television image). The resolution is not so great as with transmission electron microscopy, but preparation is easier (often by fixation followed by critical point drying), the depth of focus is relatively enormous, the surface of a specimen can be seen (though not the interior unless the specimen is cracked open) and the image is aesthetically pleasing. (18 Nov 1997) |
| scanning transmission electron microscopy | <procedure> Method of electron microscopy in which image formation depends upon analysis of the pattern of energies of electrons that pass through the specimen. Has comparable resolving power to conventional transmission EM. (18 Nov 1997) |
| secondary electron | <microscopy> Produced by an incident electron passing near an atom in the specimen, near enough to impart some of its energy to a lower energy electron (usually in the K-shell). This causes a slight energy loss and path change in the incident electron and the ionisation of the electron in the specimen atom. This ionised electron then leaves the atom with a very small kinetic energy (5eV) and is then termed a secondary electron. Each incident electron can produce several secondary electrons. (05 Aug 1998) |
| secondary electron imaging | <microscopy> Production of secondary electrons is very topography related. Due to their low energy, 5eV, only secondaries that are very near the surface (less than 10nm) can exit the sample and be examined. Any changes in topography in the sample that are larger than this sampling depth will change the yield of secondaries due to collection efficiencies. Collection of these electrons is aided by using a collector in conjunction with the secondary electron detector. The collector is a grid or mesh with a +100V potential applied to it which is placed in front of the detector, attracting the negatively charged secondary electrons to it which then pass through the grid-holes and into the detector to be counted. When a Secondary Electrons collide with the solid-state saemiconductor detector an electron-hole pairs are created which are then counted. This quantity is translated into a pixel intensity and displayed on the CRT, forming the image. (05 Aug 1998) |
| Selected Area Electron Diffraction | <technique> In this diffraction mode an aperture is used to define the area from which a diffraction pattern is to be recorded from a thin sample. This aperture is typically located in an image plane below the sample. Selected Area Electron Diffraction patterns are simple spot patterns and are of use in phase determination (lattice spacing measurement) and defect analysis (sample orientation). Acronym: SAED (05 Aug 1998) |
| immune electron microscopy | Electron microscopy of biological specimens to which specific antibody has been bound. (05 Mar 2000) |
| internal conversion electron | An electron, similar to an Auger electron, released from one of the electron orbits of the atom upon activation by a gamma-ray from that atom's nucleus; the electron has kinetic energy equal to the net energy transition of the disintegration. (05 Mar 2000) |
| emission electron | <physics>? A beta particle resulting from radioactive decay. (05 Mar 2000) |
| transition electron | An electron that moves from one energy level to another to fill a vacancy in a shell, with the emission of characteristic radiation. (05 Mar 2000) |
| transmission electron microscopy | <technique> Those forms of electron microscopy in which electrons are transmitted through the object to be imaged, suffering energy loss by diffraction and to a small extent by absorption. Acronym: TEM (18 Nov 1997) |
| Environmental Scanning Electron Microscopy | <technique> Scanning electron microscopy is performed by scanning a focused probe across the surface of the sample to be studied. In the environmental scanning electron microscopy the composition and pressure of the atmosphere around the specimen may be controlled. In favourable cases non-conductive specimens may be examined without coating, and hydrated specimens may be examined with the water still in place. Acronym: ESEM (05 Aug 1998) |
| free electron | <radiobiology> An electron not bound to an atom, molecule, or other particle via electromagnetic forces. (09 Oct 1997) |