You searched for: “electron
electron (s), electrons (pl)
1. A stable elementary particle that is a primary constituent of ordinary matter, contained in the atoms of all elements.

Electrons flowing in a conductor constitute an electric current.

2. A negative beta particle emitted from a radioactive substance.
3. A negatively charged elementary particle that has a specific charge, mass, and spin.

The number of electrons associated with the nucleus of an atom is equal to the atomic number of the substance.

4. A sub-atomic particle with a negative beta particle emitted from a radioactive substance.

A flow of electrical current consi that are in a given material, the greater its electrical conductance (or equivalently, the lower its resistance).

Electrons are the primary charge carriers in electric currents.

All atoms have electrons arranged around a nucleus and an electron may be positive (positron), but as the term is generally used, it refers to the negative form (negatron).

This entry is located in the following units: electro-, electr-, electri- (page 46) -tron, -tronic, -tronics + (page 2)
Word Entries containing the term: “electron
bipolar needle electron (s) (noun), bipolar needle electrons (pl)
An electrode consisting of two insulated wires inside a single cylinder with neither one acting as the reference electrode.

Variations in voltage can be noted between the areas that the wires touch.

This entry is located in the following units: bi-, bin-, bino-, bis- (page 8) electro-, electr-, electri- (page 2)
cryoelectron microscopy, cryo-electron microscopy (s) (noun); cryoelectron microscopies, cryo-electron microscopies (pl)
An electron microscopic technique that involves freezing the biological sample in order to view the sample with the least possible distortion and the fewest possible artifacts. Abbreviated as cryo-EM.

In cryoelectron microscopy, the freezing of the sample is done in ethane slush to produce vitreous, or non-crystalline, ice. The frozen sample grid is then kept at liquid nitrogen temperature in the electron microscope and digital micrographs are collected with a camera.

The advantages of cryo-EM over traditional EM techniques include the preservation of the sample in a near-native hydrated state without the distortions from stains or fixatives needed for traditional EM. With image processing and averaging of multiple images, cyroelectron microscopy provides high resolution information (below 10 angstroms).

An angstrom is a metric unit of length equal to one ten billionth of a meter (or 0.0001 micron); used to specify wavelengths of electromagnetic radiation.

electron accelerator
1. A device which accelerates electrons to high energies.
2. A machine that increases the energy levels of electrons in order to produce a beam of highly charged particles.
This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 2)
electron acceptor
1. An impurity element that is introduced into a pure semiconductor material to produce holes as charge carriers.
2. An atom or part of a molecule joined by a covalent bond to an electron donor.
3. A molecule or compound that gets electrons during an oxidation-reduction reaction.
This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 2)
electron acoustic microscopy (s) (noun), electron acoustic microscopies (pl)
A technique for producing images showing the thermal (heat) and elastic variations in the properties of an object: The process of electron acoustic microscopy consists of an electron beam that generates ultrasonic waves in a specimen which are detected by a piezoelectric transducer whose output controls the brightness of a spot sweeping a cathode-ray tube in synchronism with the electron beam.
electron affinity
1. The energy needed to remove an electron from a negative ion in order to form a neutral atom or molecule.
2. The work needed in removing an electron from a negative ion which will restore the neutrality of an atom or molecule.
3. The work needed to remove an electron from a negative ion and move it to infinity.
This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 2)
electron avalanche, avalanche effect, cascade, cumulative ionization
1. A chain reaction that starts when one free electron collides with one or more orbiting electrons and frees them.

The free electrons then free others in the same manner, etc.

2. The cumulative process in which an electron (or other charged particle) accelerated by a strong electric field collides with and ionizes gas molecules, thereby releasing new electrons which in turn have more collisions, so that the discharge is self-maintained.
This entry is located in the following unit: electro-, electr-, electri- (page 47)
electron beam
1. A stream of electrons emitted from a given source and traveling under the influence of an electric or magnetic field in the same direction and at approximately the same speed.
2. A stream of electrons, or electricity, that is directed towards a receiving object.
3. A narrow stream of electrons moving in the same direction, all having about the same velocity.

The electron beam of the super-microscope has become a basic tool in the research of diseases.

This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 2)
electron beam channeling, electron-beam channeling
1. The process by which high-energy, high-current electron beams are transported from an accelerator through a medium of high-pressure gas directly to an intended target.
2. A device used in atomic physics to produce highly charged ions by bombarding atoms with a powerful electron beam.
3. The technique of transporting high-energy, high-current electron beams from an accelerator to a target through a region of high-pressure gas by creating a path through the gas where the gas density may be temporarily reduced.

The gas may be ionized; or a current may flow whose magnetic field focuses the electron beam on the target.

This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 2)
electron beam computed tomography (s) (noun), EBCT; electron beam computed tomographies (pl)
Ultrafast computed tomography done with a scanner in which the patient is surrounded by a large circular anode that emits X-rays as the electron beam is guided around it.
electron beam generator, electron-beam generator
1. A device; such as, a klystron, in which the velocity of an electron beam is kept at a constant level in order to produce exceedingly high radio frequencies.
2. Velocity-modulated generator, such as a klystron tube (type of vacuum tube used as an amplifier), used to generate extremely high radio frequencies.

A klystron is an evacuated electron-beam tube in which an initial velocity modulation imparted to electrons in the beam results subsequently in density modulation of the beam. A klystron is used either as an amplifier in the microwave region or as an oscillator.

This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 2)
electron binding energy
1. The minimum amount of energy required to extract an electron from an atom or molecule.
2. The energy required to release an electron from its atomic or molecular orbital.
This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 3)
electron bombardment induced conductivity, electron-bombardment-induced conductivity
1. In a multimode display-storage tube, a process in which an electron gun is used to erase the image on a cathode-ray tube interface.
2. A method of writing and storing large numbers of information elements electrostatically on the storage tape of a television information storage tube.

A dielectric-coated optical grating on the tape is bombarded with 10-keV electrons to induce momentary conductivity.

This causes electrons to flow fro the dielectric to the metal base of the tape.

Elemental areas on the surface of the tape lose charge in proportion to light from corresponding elemental areas of the image being stored.

This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 3)
electron capture detector, electron-capture detector
1. A device used in gas chromatography, in which carrier gas molecules flowing through the ionization chamber are radiated and low-energy electrons are formed.

Certain compounds entering the chamber have an affinity for these electrons, and this decrease in electrons is recorded for component identification.

2. An extremely sensitive gas chromatography detector that is a modification of the argon ionization detector, with conditions adjusted to favor the formation of negative ions.
3. An item of laboratory equipment used coupled to a gas chromatograph for the detection and quantification of very minute amounts halogenated organic compounds.
This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 3)
electron capture, electron attachment
1. A process in which an inner shell electron is captured by the nucleus of its own atom.

The mass number is unchanged, but the atomic number is decreased by one and this process is accompanied by the emission of a neutrino.

2. A radioactive decay process in which an atomic nucleus with an excess of protons draws an electron into itself, creating a neutron out of a proton and thus decreasing the atomic number by one.

Often the resulting nucleus is unstable and achieves stability by giving off a gamma ray.

This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 3)
electron carrier
1. A protein; such as, flavoprotein or cytochrome, which can gain and lose electrons in either direction and can transport electrons from one compound to another compound or to oxygen.
2. A molecule that accepts electrons from electron donors and donates them to electron acceptors, creating an energy-producing electron transport chain; such as, that which occurs in respiration and photosynthesis.
3. A molecule associated with membrane-bound proteins that accepts and transfers electrons.
4. Any of various molecules that are capable of accepting one or two electrons from one molecule and donating them to another in the process of electron transport.

As the electrons are transferred from one electron carrier to another carrier, their energy level decreases, and energy is released.

This entry is located in the following units: electro-, electr-, electri- (page 47) -tron, -tronic, -tronics + (page 3)
electron charge, elementary charge
1. The charge of a single electron or the fundamental unit of an electrical charge.
2. The electric charge carried by a single proton, or equivalently, the absolute value of an electric charge carried by a single electron.
This entry is located in the following unit: electro-, electr-, electri- (page 47)
electron cloud
1. An average region around the nucleus of an atom, in which the electrons are predicted to be at certain states of excitation.
2. The group or system of electrons revolving around the nucleus of an atom; a cloud-like group of electrons.
3. In a vacuum tube, the area between the electrodes that contains a great number of relatively stationary electrons.
This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 3)
electron compound, Hume-Rothery compound, intermetallic compound
1. In a phase diagram one of several homogeneous phases that has a specific crystal structure and a specific valence electron-to-atom ratio.
2. An alloy of two metals in which a progressive change in composition is accompanied by a progression of phases, differing in crystal structure.
This entry is located in the following units: electro-, electr-, electri- (page 48) inter-, intero- (page 1) -tron, -tronic, -tronics + (page 3)
electron configuration
1. A configuration that shows the way in which the electrons in an atom occupy, in order of increasing energy, the available orbitals and spin states.
2. The orbital arrangement of an atom's electrons.

Negatively charged electrons are attracted to a positively charged nucleus to form an atom or an ion.

3. The arrangement of electrons in an atom, molecule, or other physical structure; such as, a crystal.
4. The specific distribution of electrons in atomic orbitals of atoms or or ions.
electron coupler, Cuccia coupler
1. An instrument that increases the power of a microwave tube by submitting its electron beam to changing periods of speeding up and slowing down.
2. A microwave amplifier tube where electron bunching is produced by an electron beam projected parallel to a magnetic field and is also influenced by a transverse electric field produced by a signal generator.
This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 3)
electron coupling, electronic coupling
1. A procedure in which two circuits in an electron tube transfer energy generated by the electron stream passing between the electrodes of one of the circuits.
2. A method of coupling electrical energy from one circuit to another through the electron stream in a vacuum tube.
3. A process of coupling or linking two circuits inside an electron tube, used primarily with multigrid tubes.

The electron stream passing between electrodes in one circuit transfers energy to electrodes in the other circuit.

This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 3)
electron cyclotron resonance source, ECR source, electron cyclotron resonance ion source, ECRIS
1. A source of multiple charged heavy ions which uses microwave power to increase electron energy to extremely high levels in two magnetic-mirror confinement chambers connected in a series.
2. An electrode supplying current of charged heavy ions that uses microwave power to heat electrons to energies of tens of kilovolts in two magnetic mirror confinement chambers in a series.

Ions formed in the first chamber drift into the second chamber, where they become charged.

This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 3)
electron cyclotron wave, whistler wave
1. A circularly polarized wave found in a plasma that runs parallel to the magnetic field produced by electric currents outside the plasma.
2. A wave in a plasma that moves parallel to the magnetic field produced by currents outside the plasma at frequencies less than that of the electron cyclotron resonance, and which is circularly polarized, rotating in the same sense as electrons in the plasma; responsible for whistlers.

A whistler is defined as an effect that occurs when a plasma disturbance, caused by a lightning discharge, travels out along lines of magnetic force of the earth's field and is reflected back to its origin from a magnetic point on the earth's surface.

This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 3)
electron density
1. The number of electrons per a unit volume or in a unit volume.
2. The quantum mechanical probability density for an electron.
This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 3)
electron device
1. An instrument whose operation involves the motion of electrical charge carriers in a gas, semiconductor, or vacuum.
2. A device or tool in which conduction is principally by electrons moving through a vacuum, gas, or semiconductor; such as, in a crystal diode, electron tube, transistor, or selenium rectifier.
This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 3)
electron diffraction (s) (noun), electron diffractions (pl)
The change in the directions and intensities of a group of waves of electrons when they pass through crystalline matter: Electron diffraction is useful in the study of the structures of materials.

Electron diffraction refers to the bending of electromagnetic waves as they pass around corners or through holes smaller than the wavelengths of the waves themselves.

The occurrence or the technique of producing electron diffractions through the incidence of electrons on matter.

The bending of an electron stream which occurs when the electron diffraction travels through a medium; such as, very thin metal foil.

This entry is located in the following units: electro-, electr-, electri- (page 48) frag-, frang-, fract-, fring- (page 1)
electron diffractograph (s) (noun), electron diffractographs (pl)
1. A device which produces an electron-diffraction pattern by focusing an electron beam onto a crystal specimen, allowing the user to examine the crystal structure of the sample.
2. An instrument related to the electron microscope, in which a beam of electrons strikes the sample, showing crystal pattern and other physical attributes on the resulting diffraction pattern: An electron diffractograph is used for chemical analysis, atomic structure determination, etc.
electron distribution
1. An action that describes the electron density in phase space (a spectral representation of physical space).
2. A function that produces the number of electrons per unit volume of phase space.
This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 4)
electron donor
1. An electron donor in an oxidation-reduction (redox) reaction or a molecule or compound that gives up electrons in an oxidation-reduction reaction in which electrons are removed from one molecule or atom and given to another molecule or atom.
2. A chemical element that donates electrons to another compound.

It is a reducing agent which, because of its donating electrons, is itself oxidized in the process.

electron drift
The movement of electrons in a definite direction through a conductor, as opposed to the haphazard transfer of energy from one electron to another electron by collision.
This entry is located in the following unit: electro-, electr-, electri- (page 48)
electron emission
1. The release of electrons from a specific material into the surrounding area or space.

It may be caused by an electric field, light, heat, or impact chemical disintegration.

2. A liberation of electrons from a substance into a vacuum.

Since all substances consist of atoms and since all atoms contain electrons, any substance may emit electrons; usually, however, the term refers to the emission of electrons from the surface of a solid.

3. The freeing of electrons into space from the surface of a body under the influence of heat, light, impact, chemical disintegration, or a potential difference.
This entry is located in the following units: electro-, electr-, electri- (page 48) -tron, -tronic, -tronics + (page 4)
electron emitter
1. A material from which electrons are released or an electrode from which electrons are emitted.
2. In a cathode tube, the electrode which serves as a source for electrons.
This entry is located in the following units: electro-, electr-, electri- (page 49) -tron, -tronic, -tronics + (page 4)
electron energy level
1. The quantum-mechanical representation of the energy level of an electron in an atom, which determines the orbit of the electron around the nucleus.
2. A quantum-mechanical concept for energy levels of electrons around the nucleus.

Electron energies are functions of each particular atomic species.

This entry is located in the following units: electro-, electr-, electri- (page 49) -tron, -tronic, -tronics + (page 4)
electron filter lens
An electrostatic apparatus which uses an electric potential barrier to allow the transmission of electrons at or above a set level of energy while stopping the passage of those electrons below that set level of energy.
This entry is located in the following unit: electro-, electr-, electri- (page 49)
electron flow
1. The movement of electrons through a metal or other conductive material from a negative to a positive point, or from a negative to a positive electrode through a liquid, a gas, or a vacuum.
2. A current produced by the motion of free electrons toward a positive terminal.

The direction of electron flow is opposite to that of the current.

This entry is located in the following units: electro-, electr-, electri- (page 49) -tron, -tronic, -tronics + (page 4)
electron fluence, fluence
1. The total energy per unit area carried by a pulse of electromagnetic radiation.
2. A measure of time-integrated particle flux, expressed in particles per square centimeter.

It is used for electrons in electron irradiation and for neutrons in connection with the effects of nuclear radiation on electronic components.

electron gas
Any system of free electrons.

Each electron goes to form the communal "electron gas" which is responsible for the high electrical and thermal conductivity of the metallic state.

This entry is located in the following unit: electro-, electr-, electri- (page 49)
electron gun
1. A device, within an electron tube or cathode-ray tube, that produces an electron beam and which directs its movement.
2. A device that directs a steady stream of electrons in a desired direction; for example, in a cathode-ray tube.

Electron guns are also used in oil refining and various other industries.

3. An electrode structure that produces and may control, focus, and deflect a beam of electrons; such as, in a television picture tube, where the beam produces a visual pattern on the tube's screen.

The source of the electron beam is the cathode, a flat metal support covered with oxides of barium and strontium.

When they are heated by a coil behind the support, these oxides produce electrons, that are drawn toward a positively charged sleeve (first anode) which is contoured to allow the electron beam to flow within the inside diameter.

The beam is then electrostatically constricted and collimated by a metal disk with a hole (the

—Compiled from "electron gun", Encyclopædia Britannica; 2010;
Encyclopædia Britannica Online; June 7, 2010.
This entry is located in the following units: electro-, electr-, electri- (page 49) -tron, -tronic, -tronics + (page 4)
electron hole
1. A vacant position in a crystal left by the absence of an electron; especially, a position in a semiconductor that acts as a carrier of positive electric charges.
2. In a semiconductor, the electron vacancy in the valence (combining power of atoms) band that occurs when an electron jumps the gap from the filled valence band to the empty conduction band.

It serves as a positive charge carrier, allowing electrons deeper in the band to move into the vacated area.

A valence is the combining power of atoms or groups measured by the number of electrons the atom or group will receive, give up, or share in forming a compound.

This entry is located in the following units: electro-, electr-, electri- (page 49) -tron, -tronic, -tronics + (page 4)
electron image
1. A pattern of electric charges on an insulating plate, with the magnitude of the charge at each point being proportional to the brightness of the corresponding point in an optical image.
2. A representation of an object formed by a beam of electrons focused by an electron optical system.
3. An image formed in a stream of electrons.

The electron density in a cross section of the stream is at each point proportional to the brightness of the corresponding point in an optical image.

This entry is located in the following unit: electro-, electr-, electri- (page 49)
electron image tube, image tube, image converter
1. A tool which projects an optical image generated by electromagnetic radiation from a photosensitive surface onto a fluorescent screen.
2. An electron tube which reproduces on its fluorescent screen an image of the optical image or other irradiation pattern arriving at or striking its photosensitive surface.
3. A cathode-ray tube that has a photoemissive mosaic upon which an optical image is projected, and an electron gun to scan the mosaic and to convert the optical image into a corresponding electrical current.
This entry is located in the following unit: electro-, electr-, electri- (page 49)
electron injection
1. The release of electrons from one solid material into another solid material.
2. The emission of electrons from one solid into another solid.
3. The process of injecting a beam of electrons with an electron gun into the vacuum chamber of a mass spectrometer, betatron, or other large electron accelerator.
4. The procedure used in forcing a beam of electrons into any large electron accelerator; such as, a beatatron by using an electron gun.
electron injector
An electron gun which injects a beam of electrons into the vacuum chamber of a mass spectrometer, betatron (type of particle accelerator for producing high-energy beams of electrons), or other large electron accelerator.
electron lens
1. Electronic equipment that uses a magnetic or electric field in order to focus a beam of electrons.
2. An electric or magnetic field, or a combination of such, that acts upon an electron beam in a manner similar to that in which an optical lens acts upon a light beam.
3. A tool which uses an electromagnetic field to refract an electron beam in a manner similar to the refraction of light by an optical lens.
4. A system of deflecting electrodes or coils designed to produce an electric field which influences a beam of electrons in the same manner that a lens affects a light beam.
5. An electric field used to focus a stream of electrons on a target.
This entry is located in the following unit: electro-, electr-, electri- (page 49)
electron lepton number (s) (noun), electron lepton numbers (pl)
The number of very small particles and associated neutrinos minus the number of positrons and associated antineutrinos: As an engineer, Mildred made a careful study of the electron lepton numbers during her analysis of colliding atoms in the air, noting that they were generating more electrons as well as x-rays and gamma rays.
This entry is located in the following units: electro-, electr-, electri- (page 49) numer-, number- (page 2)
electron linear accelerator
A linear accelerator or a device that propels charged particles in straight paths by using alternating high-frequency voltages used to accelerate electrons in a straight line, usually by means of radio-frequency fields which are produced in a loaded waveguide and travel with the electrons.
This entry is located in the following unit: electro-, electr-, electri- (page 49)
electron metallography
The study of the microscopic structure of metals using an electron microscope.
electron metallurgy
A branch of metallurgy which uses electron microscopic techniques in the examination of the nature of metals.
This entry is located in the following unit: electro-, electr-, electri- (page 50)
electron micrograph
1. A reproduction of an image formed by the action on an electron beam on a photographic emulsion.
2. A photograph or other reproduction of an image formed by the action of an electron beam by an electron microscope.
electron micrography
The photographic recording of images produced by the electrons from an electron microscope.

The electron beam carries the images through an array of lenses and an enlarged electron image is used to stimulate a fluorescent screen that is photographed by a camera system.

electron microprobe, electron probe
1. An instrument which focuses an accelerated beam of electrons to an extremely small point on the surface of a crystal specimen so it can be studied by the effects of the electron beam.
2. An X-ray machine in which electrons transmitted from a hot-filament source are accelerated electrostatically, then focused to an extremely small point on the surface of a specimen by an electromagnetic lens.

A nondestructive analysis of the specimen can then be made by measuring the back-scattered electrons, the specimen current, the resulting X-radiation, or any other resulting process.

3. A technique of analysis using the electron microscope based on spectral analysis of the scattered X-ray emission from the specimen induced by the electron beam.

By using this technique, it is possible to obtain quantitative data on, for example, the calcium concentration in different parts of a cell; however, it is necessary to use ultra thin frozen sections.

This entry is located in the following unit: electro-, electr-, electri- (page 50)
electron microradiography
The photographic recording and later enlarging of very thin specimens, using an electron beam to form the image.
electron microscope
1. A device which uses electrons, generally focused by electron lenses, to magnify tiny objects onto a fluorescent screen or photographic plate.

It provides much greater plowers of magnification than an optical microscope; that is, up to 1,000,000 times actual size without loss of sharpness and degree of contrast in the image.

2. An electronic instrument that scans cell and tissue sections with a beam of electrons instead of visible light.

The specimen is stained with electron-opaque dyes and with its high magnification power, it creates an image that can be photographed or viewed on a florescent screen.

3. A device for directing streams of electrons by means of electric and magnetic fields in a manner similar to the direction of visible light rays by means of glass lenses in an ordinary microscope.

Since electrons carry waves of much smaller wavelengths than light waves, correspondingly greater magnifications can be obtained.

The electron microscope will resolve details from 1,000 to 10,000 times finer than the optical microscope and images can be studied on a fluorescent screen or recorded photographically.

This entry is located in the following units: electro-, electr-, electri- (page 50) -tron, -tronic, -tronics + (page 4)
electron microscopist
Someone who is skilled in the use of the electron microscope which used beams of electrons instead of beams of light.
This entry is located in the following unit: electro-, electr-, electri- (page 50)
electron mirror, dynode
1. An electron instrument used to totally reflect an electron beam.
2. An electrode that has the primary function of secondary emission of electrons.

It is used in multiplier phototubes and some types of television camera tubes.

This entry is located in the following unit: electro-, electr-, electri- (page 50)
electron mobility (s) (noun), electron mobilities (pl)
1. The average electron-drift velocity in a semiconductor divided by the externally applied electric field.
2. A drift mobility of electrons in a semiconductor which consists of the electron velocity divided by the applied electric field.
This entry is located in the following units: electro-, electr-, electri- (page 50) mobil-, mobi- (page 1)
electron multiplier
1. A tube in which current is amplified by the production of secondary electrons that result from the collisions of electrons with special targets inside the tube.
2. An electron-tube structure that produces current amplification.

An electron beam containing the desired signal is reflected from the surfaces of each of a series of dynodes (electrodes whose primary function is the secondary emission of electrons), and at each reflection an impinging electron releases two or more secondary electrons, so that the beam builds up in strength.

3. An instrument used for amplifying a very small current using the effects of secondary emission.

Electrons from the original current strike an anode, producing secondary electrons that are directed to the next anode in a multistage process until the desired level of current is obtained.

This entry is located in the following unit: electro-, electr-, electri- (page 50)
electron multiplier phototube, electron-multiplier phototube, multiplier phototube, photoelectric electron-multiplier tube, photomultiplier, photomultiplier tube
A phototube with one or more dynodes (electrodes the primary function of which is secondary emission of electrons) between its photocathode (photosensitive surface that emits electrons when exposed to light or other suitable radiation) and the output electrode.

The electron stream from the photocathode is reflected off each dynode in sequence, with a secondary emission adding electrons to the stream at each reflection.

This entry is located in the following unit: electro-, electr-, electri- (page 50)
electron neutrino, electronic neutrino, e-neutrino
1. A neutrino (a neutral particle with no electric charge and little mass) which obeys a conservation law together with the electron, so that the total number of electrons and electron-neutrinos minus the total number of their antiparticles remains the same.
2. A type of neutrino that obeys a conservation law together with the electron, with the total number of electrons and electron-neutrinos minus the total number of their antiparticles remaining constant.
This entry is located in the following unit: electro-, electr-, electri- (page 50)
electron nuclear double resonance, ENDOR
1. A spectroscopic technique in which a sample is irradiated with a range of nuclear resonance frequencies while electron spin resonance absorption is observed at a single frequency.
2. A type of electron paramagnetic resonance spectroscopy permitting greatly enhanced resolution, in which a material is simultaneously irradiated at one of its frequencies and by a second oscillatory field during which its frequency is swept over the range of nuclear frequencies.
This entry is located in the following unit: electro-, electr-, electri- (page 50)
electron number (s) (noun), electron numbers (pl)
The quantity of negative charges in atoms or ions: Jack and all the other chemistry students had to memorize the electron numbers from the chart that the teacher presented to them.
This entry is located in the following units: electro-, electr-, electri- (page 50) numer-, number- (page 2)
electron opaque tracer, electron-opaque tracer (s) (noun), electron opaque tracers, electron-opaque tracers (pl)
A metallic salt often found in association with binding proteins; such as, antibodies: An electron-opaque tracer is used to detect the presence of specific molecules or structures in an electron microscopic examination of a sample.
This entry is located in the following units: electro-, electr-, electri- (page 51) opaqu- (page 1)
electron optical system
A combination of parts capable of producing and controlling a beam of electrons to produce an image of an object.
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron optics, electron-optics
1. The area of science devoted to the directing and guiding of electron beams using electric fields in the same manner as lenses are used on light beams.
2. The study of the motion of free electrons under the influence of electric and magnetic fields; as in laser technology, light amplificaion, and photoelectricity.
3. The science that deals with the direction, deflection, or focusing of beams of electrons by electric and magnetic fields; such as, in electron lenses.
4. The science of the control of electron motion by electron lenses in systems or under conditions analogous to those involving or affecting visible light.
5. A branch of electronics concerned with the behavior of the electron beam under the influence of electrostatic and electromagnetic forces.
6. The science of the emission and propagation of electrons and of the factors controlling and modifying their flow; especially, when applied to electron microscopy.
7. The science and technology concerned with the use of applied electrical fields to generate and to control optical radiation.

The term electron-optics is often used erroneously as a synonym for optoelectronic.

This entry is located in the following units: electro-, electr-, electri- (page 51) -ics, -tics [-ac after i] (page 13)
electron orbit
The path of an electron or the path described by an electron as it circulates around around the nucleus of an atom.
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron pair
1. Two valence electrons which create a non-polar connection between two adjacent atoms.
2. A pair of valence electrons that form a non-polar bond between two neighboring atoms.
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron pair bond, covalent bond, covalent bonding
1. A bond in which each atom of a bound pair contributes one electron to form a pair of electrons.
2. A chemical bond between two atoms of the same or different elements, in which each atom contributes one electron to be shared in a pair.
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron paramagnetic resonance, EPR, electron spin resonance, ESR, paramagnetic resonance
1. A resonant absorption of electromagnetic radiation by a paramagnetic substance, having unpaired electrons, when the energy levels are split by the application of a strong magnetic field.
2. Magnetic resonance arising from the magnetic moment of unpaired electrons in a paramagnetic substance or in a paramagnetic center in a diamagnetic substance (a group of substances which in a magnetic field become magnetic in an opposite direction to that of iron or relating to a substance that is repelled by a magnet).
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron paramagnetism
1. Paramagnetism arising from the contributions of the net magnetic moments of the unpaired electron of the individual atoms to molecules in a paramagnetic substance, because of the tendency to align magnetic moments with an external magnetic field.
2. Paramagnetism in a substance in which atoms or molecules possess a net electronic magnetic moment.

It arises because of the tendency of a magnetic field to orient the electronic magnetic moments parallel to itself.

A magnetic moment refers to a vector associated with a magnet, current loop, particle, etc., whose cross product with the magnetic induction (or alternatively, the magnetic field strength) of a magnetic field is equal to the torque exerted on the system by the field.

This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron poor, electron-poor
In physical chemistry, being somewhat deficient in electrons, and therefore, able to accept an available pair of electrons.
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron positron pair, electron-positron pair
The electron and the positron (elementary particle having mass equal to that of the electron) simultaneously created by the process of pair production.
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron positron storage ring, electron-positron storage ring
1. A vacuum chamber which is encased with bending and focusing magnets, in which counter-rotating beams of electrons and positrons are stored for several hours and then forced to collide with each other.
2. An annular vacuum chamber, enclosed by bending and focusing magnets, in which counter-rotating beams of electrons and positrons are stored for several hours and can be made to collide with each other.
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron probe microanalysis
1. A technique for the analysis of a very small amount of material by bombarding it with a narrow beam of electrons and examining the resulting x-ray emission spectrum.
2. An analytical technique used to determine the nature of extremely small samples by forming the x-ray spectrum of the samples through excitation by a finely focused electron beam.
3. Identification and measurement of elements and their location based on the fact that 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 is performed with an electron microscope fitted with an x-ray spectrometer, in a scanning or transmission mode.

This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron radius
The classical value of the radius of an electron which is obtained by equating the rest-mass energy of the electron to its electrostatic self-energy.
This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron ray indicator, electron-ray indicator, cathode-ray tuning indicator, magic eye, tuning eye
1. A small cathode-ray tube with a fluorescent screen on which the pattern varies with the voltage applied to the grid which is used to indicate the accuracy of tuning in a radio receiver.
2. A small cathode-ray tube having a fluorescent pattern whose size varies with the voltage applied to the grid.

It is used in radio receivers to indicate the accuracy of tuning and as a modulation indicator in some tape recorders.

This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron ray tube, electron-ray tube; cathode ray tube, cathode-ray tube
1. A small cathode-ray tube having a fluorescent screen on which the pattern varies with the voltage applied to the grid that is used chiefly in radio receivers to indicate accuracy of tuning.
2. A special-purpose electron tube in which electrons are accelerated by high-voltage anodes, formed into a beam by focusing electrodes, and projected toward a phosphorescent screen that forms one face of the tube.

To form a display, or image, on the screen, the electron beam is deflected in the vertical and horizontal directions either by the electrostatic effect of electrodes within the tube or by magnetic fields produced by coils located around the neck of the tube.

3. A type of recording-level indicator using a luminous display in a special tube.

The display is usually like an "eye" with a keyhole in the middle, and the maximum recording level corresponds to the closing-up of a slot at the bottom of the keyhole which is superseded by meters in current-model recorders.

This entry is located in the following unit: electro-, electr-, electri- (page 51)
electron rich, electron-rich
Having available electrons which can be contributed to an electron-poor atom or a group of atoms.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron ring accelerator, ERA
A proposed particle accelerator in which protons to be accelerated are trapped by the space charge of a ring of relativisitic electrons which is then accelerated.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron scanning
1. The moving of an electron beam back and forth and/or up and down by deflecting the beam electromagnetically or electrostatically.
2. A deflection of a beam of electrons, at regular intervals, across a crt screen (display that is electronically created on the surface of the large end of a cathode-ray tube), according to a definite pattern.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron scanning microscope, scanning electron microscope, SEM
An instrument similar to an electron microscope in that a beam of electrons is used to scan the surface of a specimen.

The beam is moved in a point-to-point manner over the surface of the specimen and these electrons are deflected collected, accelerated, and directed against a scintillator.

The large number of photons that are created are converted into an electric signal which, in turn, modulates the beam scanning the surface of the specimen.

This entry is located in the following units: electro-, electr-, electri- (page 52) -tron, -tronic, -tronics + (page 4)
electron shell
1. The collection of all the electron states in an atom which have a given principal quantum number and a given orbital angular momentum quantum number.
2. The arrangement of electrons at various distances from the nucleus of an atom, according to the energy that they have.

Those with the least energy are in the shell closest to the nucleus, traditionally called the K shell, which can hold no more than two electrons.

The Q shell, farthest from the nucleus, can hold 98 electrons, but it is never completely filled.

This entry is located in the following units: electro-, electr-, electri- (page 52) -tron, -tronic, -tronics + (page 4)
electron spectrometer
A spectrometer which analyzes a substance with electron emissions that are induced by X-rays.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron spectroscopy
1. A study of the energy of photo-electrons or Auger electrons (a two-electron process) emitted when a substance is bombarded with electrons, ions, or electromagnetic radiation.
2. The study of the energy spectra of photo-electrons or Auger electrons that are emitted from a substance upon bombardment by electromagnetic radiation, electrons, or ions.

It is used to investigate atomic, molecular, or solid-state structure, and in chemical analysis.

This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron spectrum
1. A diagram, a graph, or other display indicating the intensity of electrons emitted by an irradiated substance with respect to the kinetic energy of the electrons.
2. A visual display, photograph, or graphical plot of the intensity of electrons emitted from a substance bombarded by X-rays or other radiation as a function of the kinetic energy of the electrons.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron spin
1. The twirling motion of an electron, independent of any orbital motion.
2. The intrinsic half-integer angular momentum of an electron.
3. That property of an electron that gives rise to its angular momentum around an axis within the electron.

Spin is one of the permanent and basic properties of the electron.

This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron spin density
The vector sum of the spin angular momenta of electrons at each point in a substance per unit volume.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron spin resonance spectrometer
A spectrometer or an instrument that produces a spectrum; especially, one in which wavelength, energy, intensity, etc., can be measured based on electron paramagnetic resonance.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron stain
A substance; such as, phosphotungstic acid or osmic acid that scatters large numbers of electrons and so can be used to stain objects to be examined by an electron microscope.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron stream potential, electron-stream potential
1. The time average of the potential difference between a given point in an electron stream and the surface at which electrons are produced.
2. At any point in an electron stream, the time average of the potential difference between that point and the electron-emitting surface.
This entry is located in the following unit: electro-, electr-, electri- (page 52)
electron stream transmission efficiency, electron-stream transmission efficiency
An electrode through which the electron stream (beam) passes.

This includes the ratio of the average stream current through the electrode to the stream current approaching the electrode.

This entry is located in the following units: electro-, electr-, electri- (page 52) trans-, tran-, tra- (page 2)
electron synchrotron
1. A machine which accelerates electrons in a circular path by keeping the frequency of the accelerating stream at a constant level while increasing the strength of the magnetic field guiding the stream.
2. A circular electron accelerator in which the frequency of the accelerating system is constant, the strength of the magnetic guide field increases, and the electrons move in orbits of nearly constant radius.
3. A synchrotron (an apparatus used in nuclear physics to produce beams of energetic charged particles and to direct them against various targets) designed to accelerate electrons.

The electron beam is allowed to strike an internal target, producing high-energy gamma rays which are used outside the machine.

This entry is located in the following units: electro-, electr-, electri- (page 52) syn-, sy-, sym-, syl-, sys- (page 4)
electron telescope
1. A mechanism used to see through haze and fog when an infrared image is formed optically on the photoemissive mosaic of an electron-image tube and then made visible by the tube.
2. An instrument in which the infrared light of a distant object is focused onto a photocathode tube, enlarged by a series of electron lenses, and reproduced onto a fluorescent screen to form an image of the object.
3. A telescope in which an infrared image of a distant object is focused on the photosensitive cathode of an image converter tube.

The resulting electron image is enlarged by electron lenses and made visible by a fluorescent screen.

This entry is located in the following unit: electro-, electr-, electri- (page 53)
electron temperature
The temperature at which the ideal gas molecules would have an average kinetic energy equal to that of electrons in a plasma which is being investigated.
This entry is located in the following unit: electro-, electr-, electri- (page 53)
electron trajectory
The path of one electron in an electron tube.
electron transfer (s) (noun), electron transfers (pl)
The passage of a stable subatomic particle that goes from one atom or molecule to another one either by collision or by other procedures: The electron transfer from one part of a system to another component.
This entry is located in the following units: electro-, electr-, electri- (page 53) trans-, tran-, tra- (page 2)
electron transit time (s) (noun), electron transit times (pl)
The time required for electrons to travel between two electrodes in a vacuum tube.

Such time is extremely important in tubes designed for ultrahigh frequencies.

This entry is located in the following units: electro-, electr-, electri- (page 53) trans-, tran-, tra- (page 2)
electron transition (s) (noun), electron transitions (pl)
The change of an electron from one situation to another one, accompanied by the emission or an absorption of electromagnetic radiation.
This entry is located in the following units: electro-, electr-, electri- (page 53) -tion (page 11) trans-, tran-, tra- (page 2)
electron transport (s) (noun), electron transports (pl)
A process of biological oxidation in which electrons are transferred from a reduced substrate through a series of compounds to oxygen, the energy of the process being conserved by the formation of high-energy bonds in the form of adenosine triphosphate (an organic compound composed of adenine or base, the sugar ribose, and three phosphate groups) which serves as the major energy source within a cell to drive a number of biological processes; such as, photosynthesis, muscle contraction, and the synthesis of proteins.
This entry is located in the following units: electro-, electr-, electri- (page 53) trans-, tran-, tra- (page 2)
electron transport chain (s) (noun), electron transport chains (pl)
1. A series of electron carriers which occurs within certain membranes; such as, the mitochondrial membrane, and produces energy for a cell.
2. The final common pathway of biological oxidation, the series of electron carriers in the inner mitochondrial membrane which pass electrons from reduced co-enzymes to molecular oxygen via sequential redox (oxidation-reduction) reactions coupled to proton transport, generating energy for biological processes.
This entry is located in the following units: electro-, electr-, electri- (page 53) trans-, tran-, tra- (page 3)
electron transport phosphorylation
The conversion of inorganic phosphate into pyrophosphate from a reaction powered by energy in a transmembrane gradient of ions generated by an electron transport chain.

It occurs in respiratory metabolism and in some types of fermentation.

This entry is located in the following units: electro-, electr-, electri- (page 53) trans-, tran-, tra- (page 3)
electron transport system
1. A series of reduction-oxidation reactions, beginning with increased strength and ending in oxygen, which constitutes the final stage of aerobic respiration.

It is also involved in the light reaction of photosynthesis.

2. The components of the final sequence of reactions in biological oxidations.

They are composed of a series of oxidizing agents arranged in an order of increasing strength and terminating in oxygen.

This entry is located in the following units: electro-, electr-, electri- (page 53) trans-, tran-, tra- (page 3)
electron trap
The defect or chemical impurity in a semiconductor or insulator that acquires mobile electrons.
This entry is located in the following unit: electro-, electr-, electri- (page 53)
electron trapping optical memory (s) (noun), ETOM
A method of erasable optical data storage in which information is stored by visible light, then read by illumination with an infrared source that returns trapped electrons to their ground state.

Erasability is achieved by using a higher infrared level than that which is used in reading.

This entry is located in the following units: electro-, electr-, electri- (page 53) memor-, memen- (page 1)
electron tube amplifier, electron-tube amplifier (s) (noun); electron tube amplifiers, electron-tube amplifiers (pl)
A circuit which uses electron tubes to provide the additional power needed to increase a signal: "An electron-tube amplifier provides the required increase in signal strength."
This entry is located in the following units: ampli-, ampl- (page 1) electro-, electr-, electri- (page 53)
electron tube generator, electron-tube generator
1. A tool which transforms direct current into a radio frequency by passing it through an electron tube in an oscillator circuit.
2. A generator in which direct-current (DC) energy is converted to radio-frequency (RF) energy by an electron tube in an oscillator circuit.
This entry is located in the following unit: electro-, electr-, electri- (page 53)
electron tube heater, electron-tube heater
An electric heating element for supplying heat to an indirectly heated cathode in an electron tube.
This entry is located in the following unit: electro-, electr-, electri- (page 53)
electron tube static characteristic, electron-tube static characteristic
1. The relationship among the various parameters in an electron tube when voltage and current are constant.
2. The relation between two of variables of an electron tube; such as, electrode voltage and electrode current of an electrode with all other voltages maintained constant.
This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron tube, electron valve
1. An instrument in which electrons move through a vacuum or gaseous medium within a gas-tight chamber; used to generate, to amplify, and to correct electric oscillations and AC currents.
2. An electronic apparatus that consists, typically, of a sealed glass bulb containing two or more electrodes.

It is used to generate, to amplify, and to rectify electric oscillations and alternating currents.

3. An electron device in which electricity is conducted by electrons moving through a vacuum or gaseous medium within an hermetically sealed envelope.

A tube can perform rectification, amplification, modulation, demodulation, oscillation, limiting, and a variety of other activities.

Examples include cathode-ray tubes, gas tubes, phototubes, and vacuum tubes.

This entry is located in the following units: electro-, electr-, electri- (page 54) -tron, -tronic, -tronics + (page 4)
electron tubes
Instruments that are used to control the flow of electrons.

Such tools may be either gas filled, or partially or fully evacuated; such as,vacuums.

Common tubes include vacuum tubes, cathode-ray tubes, phototubes, mercury vapor tubes, thyratrons, and microwave tubes.

Thyratrons are gas-filled hot-cathode tubes which are used as electronic switches or relays in which signals applied to the control grids initiates anode currents but does not limit them and cannot interrupt, the flow of electrons.

This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron tunneling, quantum tunneling
1. The passage of electrons through a potential barrier which they would not be able to cross according to classical mechanics; such as, a thin insulating barrier between two superconductors.
2. The phenomena of a particle's ability to penetrate energy barriers within electronic structures.
This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron unit (s) (noun), electron units (pl)
A unit of charge, negative or positive, which is equal to the charge on an electron.
This entry is located in the following units: electro-, electr-, electri- (page 54) uni-, un- (page 1)
electron vacuum gage
A tool used to measure a vacuum with the ionization effect that an electron flow (from an incandescent filament to a charged grid) has on gas molecules.
This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron velocity
The rate or speed of motion of an electron.
This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron volt, electronvolt, eV
1. A unit of energy equal to the energy acquired by an electron falling through a potential difference of one volt.
2. A unit of energy defined as the kinetic energy acquired by an electron that is accelerated through a potential difference of one volt; equivalent to 1.6022 x 10-19 joules.
3. A unit of energy used in atomic and nuclear physics, equal to the energy gained by an electron.
4. A unit of electrical energy used in nuclear physics.

It is equal to the energy gained by an electron when it moves from one point to a point higher in potential by one volt and it is a unit of energy or work, not of voltage.

This entry is located in the following units: electro-, electr-, electri- (page 54) -tron, -tronic, -tronics + (page 4) volt + (page 1)
electron wave
The de Broglie wave, or probability amplitude wave (amount by which a voltage or current changes from zero or an average value), associated with an electron.
This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron wave function, electron-wave function
A function of the spin orientation and position of one or more electrons, specifying the dynamical state of the electrons.

The square of the function's modulus gives the probability per unit volume of finding electrons at a given position.

This entry is located in the following units: electro-, electr-, electri- (page 54) funct-, fungi- (page 1)
electron wavelength
The wavelength necessary to account for the deviation of electron rays in crystals by wave diffraction theory.
This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron-beam bonding
A process using a stream of electrons to heat and to bond two conductors within a vacuum.
This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron-beam drilling, electron beam drilling
1. The process of boring tiny holes into a material; such as, a ferrite or semiconductor, with a tightly focused electron beam.
2. Drilling of tiny holes in a ferrite, semiconductor, or other material by using a sharply focused electron beam to melt and evaporate or sublimate the material in a vacuum.
This entry is located in the following units: electro-, electr-, electri- (page 54) -tron, -tronic, -tronics + (page 4)
electron-beam evaporation, e-beam evaporation
1. An evaporation technique in which the evaporant is heated with electron bombardment.
2. An electronic transducer, either fixed or adjustable, that reduces the amplitude of a wave without causing significant distortion.

Electron beam evaporation is a commonly used process for coating lenses and filters with anti-reflection, scratch-resistant or other specialized coatings.

The process is also commonly used for coating insulating and resistor films on electronic components.

This entry is located in the following unit: electro-, electr-, electri- (page 54)
electron-beam fusion, electron beam fusion
1. A process in which strong electron beams implode tiny pellets of deuterium and tritium, causing them to attain the temperature and density needed to initiate a fusion reaction.
2. The use of intense beams of electrons to implode small pellets of deuterium and tritium so that they reach the temperature and density required for initiating a fusion reaction.
electron-beam gun
A device generally used in a cathode-ray or camera tube to emit a stream of electrons moving at uniform velocity in a straight line.

It consists of an emitting cathode and an anode, with an aperture for passage of some of the electrons.

This entry is located in the following unit: electro-, electr-, electri- (page 55)
electron-beam instrument, cathode-ray instrument
A tool in which a beam of electrons is deflected by an electric or magnetic field (or both).

Usually the beam is made to strike a fluorescent screen so the deflection can be observed.

This entry is located in the following unit: electro-, electr-, electri- (page 55)
electron-beam ion source, electron beam ion source, EBIS
1. A source of multiple charged heavy ions used by a highly energized electron beam to ionize injected gas.
2. A source of multiple charged heavy ions which uses an intense electron beam with energies of five to ten kiloelectronvolts to successively ionize injected gas.
This entry is located in the following units: electro-, electr-, electri- (page 55) -tron, -tronic, -tronics + (page 5)
electron-beam laser, electron beam laser
A semiconductor laser in which the electron beam that provides pumping action in a thin plate of cadmium sulfide or other material is swept electrically in two dimensions by a deflection yoke, much as in a cathode-ray tube.

The resulting laser output beam moves correspondingly, to provide high-speed scanning for data retrieval and imaging applications.

The beam can be electronically blanked, unblanked, or modulated with analog video signals for the projection of picture or other graphic data.

This entry is located in the following unit: electro-, electr-, electri- (page 55)
electron-beam lithography, electron beam lithography, e-beam lithography
1. Lithography in which radiation-sensitive film is exposed to an electron beam.
2. The practice of scanning a beam of electrons in a patterned fashion across a surface covered with a film called the resist, exposing the resist, and of selectively removing either exposed or non-exposed regions of the resist called, "developing".
3. Lithography in which the radiation-sensitive film or resist is placed in the vacuum chamber of a scanning-beam electron microscope and exposed by an electron beam under digital computer control.

After exposure, the film is removed from the vacuum chamber for conventional development and other production processes.

electron-beam machining
1. A process in which controlled electron beams are used to weld or to shape a piece of material.
2. A machining process which takes place in a vacuum.

Heat is produced by a focused and controlled electron beam at a sufficiently high temperature to volatilize and so to remove metal in a specified manner.

Drilling and cutting are examples of specific applications.

This entry is located in the following unit: electro-, electr-, electri- (page 55)
electron-beam magnetometer, electron beam magnetometer
1. An instrument that measures the magnetic intensity of a magnetic field according to the movement and intensity of an electron beam, which passes through the field.
2. An instrument which measures the intensity and direction of magnetic forces by the immersion of an electron beam into the magnetic field.
This entry is located in the following units: electro-, electr-, electri- (page 55) -tron, -tronic, -tronics + (page 5)
electron-beam melting
A melting process which takes place in a vacuum, the heat being produced by a focused electron beam.

It's used principally for refining metals to a higher degree of purity than is possible with conventional vacuum-melting techniques.

Its chief advantage is the ability to control the temperature of the molten material and the time it remains melted because both affect the degree of volatilization of impurities.

Volatilization is the conversion of a chemical substance from a liquid or solid state to a gaseous or vapor state by the application of heat, by reducing pressure, or by a combination of these processes. It is also known as vaporization.

This entry is located in the following unit: electro-, electr-, electri- (page 55)
electron-beam mode discharge
A form of discharge produce by a perforated-wall hollow cathode operating under conditions of pressure, voltage, and geometry which is usually associated with the abnormal glow discharge.
This entry is located in the following unit: electro-, electr-, electri- (page 55)
electron-beam parametric amplifier, electron beam parametric amplifier (s) (noun); electron-beam parametric amplifiers, electron beam parametric amplifiers (pl)
1. A device that boosts a signal by varying the energy pumped from an electrostatic field into an electron beam traveling down the length of a tube, and then manipulating the beam at either end of the tube.
2. A parametric amplifier in which energy is pumped from an electrostatic field into a beam of electrons traveling down the length of the tube, and electron couplers impress the input signal at one end of the tube and translate spiraling electron motion into electric output at the other end.
This entry is located in the following units: ampli-, ampl- (page 1) electro-, electr-, electri- (page 55) -tron, -tronic, -tronics + (page 5)
electron-beam pumping, electron beam pumping
1. A process in which an electron beam provides the energy necessary to move the majority of electrons in a semiconductor out of a ground condition.
2. The use of an electron beam to produce excitation for population inversion and lasing action in a semiconductor laser.
This entry is located in the following units: electro-, electr-, electri- (page 55) -tron, -tronic, -tronics + (page 5)
electron-beam recorder, electron beam recorder
1. An instrument in which an electron beam places signals or data on film in a vacuum chamber.
2. A recorder in which a moving electron beam is used to record signals or data on to photographic or thermoplastic film in a vacuum chamber.
3. A device that transfers computer data onto microfilm using an electron beam.
This entry is located in the following units: electro-, electr-, electri- (page 55) -tron, -tronic, -tronics + (page 5)
electron-beam recording
The recording of the information contained in a modulated electron beam onto photographic or silicon resin-coated materials.
This entry is located in the following unit: electro-, electr-, electri- (page 55)
electron-beam tube, electron beam tube
1. An instrument; such as, a klystron (type of vacuum tube used as an amplifier), oscilloscope tube, or television picture tube, which functions through the generation of one or more electron beams.
2. An electron tube whose performance depends on the formation and control of one or more electron beams.
This entry is located in the following units: electro-, electr-, electri- (page 55) -tron, -tronic, -tronics + (page 5)
electron-beam welding
1. The process of using a focused beam of electrons to heat materials to the fusion point.
2. A process in which a welder generates a stream of electrons traveling at up to 60 percent of the speed of light as it focuses the beam to a small, precisely controlled spot in a vacuum, and converts the kinetic energy into an extremely high temperature on impact with the piece being worked on.
3. A welding process which takes place in a vacuum.

Heat is produced by a focused electron beam that can produce welds having depth-to-width ratios of up to twenty to one.

Applications include welding of thin metal foils to thicker metal without burning, sealing of metal cans containing uranium fuel elements for reactors, and direct fusion welding of ceramic objects.

This entry is located in the following unit: electro-, electr-, electri- (page 56)
electron-bombarded semiconductor amplifier, EBS (s) (noun); electron-bombarded semiconductor amplifiers (pl)
An amplifier consisting of an electron-gun modulation system, semiconductor target and output coupling network all within a glass or ceramic envelope.

The semiconductor target is a pair of silicon diodes, each consisting of two metallic electrodes with a pn (positive-negative) junction under the top contact.

A pn junction or a diode (one way valve) is a pn junction with p-type (positive-type) on one side and n-type (negative-type) on the other side.

When a positive voltage is applied to the p-type side (forward bias), it shrinks and overcomes the depletion zone, causing the current to flow from the p-type to the n-type side. When a negative voltage is applied to the p-type of the diode (reverse bias), it increases the depletion zone and prevents current from flowing.

The amplifier operation is based on the fact that a modulated electron beam can control the current in a reverse-based semiconductor junction.

This entry is located in the following units: ampli-, ampl- (page 1) electro-, electr-, electri- (page 56)
electron-coupled oscillator, electron coupled oscillator, ECO, Dow oscillator
1. A device that generates alternating current.

It is characterized by a circuitry that feeds a portion of the generated energy back into the system to sustain its operation, and by an electron stream that is coupled between the screen and the plate to reduce the effects of the load.

2. An oscillator employing a multigrid tube in which the cathode and two grids operate as a conventional oscillator and the electron couples the plate-circuit load to the oscillator.

The anode-circuit load is coupled to the oscillator through the electron stream.

This entry is located in the following units: electro-, electr-, electri- (page 56) -tron, -tronic, -tronics + (page 5)
electron-dense, electron dense
1. In electron microscopy, having a density that prevents penetration by electrons.
2. Characterized by being relatively opaque to the passage of the electron beam in an electron microscope.

Such an object will appear as a dark area on the viewing screen and photographic prints.

This entry is located in the following units: electro-, electr-, electri- (page 56) -tron, -tronic, -tronics + (page 5)
electron-density map, electron density map
1. A contoured representation of electron density at various points in a crystal structure expressed in electrons per cubic angstrom with the highest near atomic centers.

The map is calculated using a Fourier synthesis, a summation of waves of known phase, frequency, and amplitude.

2. A three-dimensional representation of the electron density of a molecular structure based on x-ray diffraction data.
This entry is located in the following units: electro-, electr-, electri- (page 56) -tron, -tronic, -tronics + (page 5)
electron-diffraction analysis, electron diffraction analysis (s) (noun); electron-diffraction analyses, electron diffraction analyses (pl)
1. The study of crystal structure by electron-diffraction methods.
2. The diffraction of electrons when they pass through crystalline matter, useful in the study of the structure of materials.
3. An examination of solid surfaces by observing the diffraction of a stream of electrons on the surfaces.

A diffraction is the bending or spreading out of waves; such as, of sound or light, as they pass around the edge of an obstacle or through a narrow opening as when light passes sharp edges or goes through narrow slits and the rays are deflected and produce fringes of light and dark bands.

electron-diffraction camera, electron diffraction camera (s) (noun); electron-diffraction camera, electron diffraction camera (pl)
1. A camera used to obtain a photographic record of the position and intensity of diffracted beams which may be produced when a specimen is irradiated by a beam of electrons.
2. A special evacuated camera equipped with the means for holding a specimen and bombarding it with a sharply focused beam of electrons.

A cylindrical film placed around a specimen and which records the electrons that might be scattered or diffracted by it.

This entry is located in the following units: camer- + (page 2) electro-, electr-, electri- (page 56) frag-, frang-, fract-, fring- (page 1)
electron-discharge machining, electron discharge machining, electrical discharge machining, EDM, electric spark machining; electroerosive machining; electrospark machining
1. The process of machining which is performed by electric sparks in a non-conductive liquid intervening substance.
2. A process by which materials that conduct electricity can be removed from a metal by an electric spark.

It is used to form holes with different shapes in materials that have poor machine operations.

This entry is located in the following units: electro-, electr-, electri- (page 56) -tron, -tronic, -tronics + (page 5)
electron-distribution curve, electron distribution curve
1. A curved line on a graph that shows the electron distribution in a solid at different energy levels.
2. A curve or line indicating the electron distribution in the different available energy levels of a solid substance.
This entry is located in the following units: electro-, electr-, electri- (page 56) -tron, -tronic, -tronics + (page 5)
electron-energy loss spectroscopy, electron energy loss spectroscopy, electron impact spectroscopy
1. Photoelectron spectroscopy or the use of electron beams to induce transitions between electronic energy levels.

The study of the distribution of energy that is lost by scattered electrons when a substance is bombarded with monochromatic electrons.

2. A technique for studying atoms, solids, or molecules in which a substance is bombarded with monochromatic electrons, and the energies of scattered electrons are measured to determine the distribution of energy loss.
This entry is located in the following units: electro-, electr-, electri- (page 57) -tron, -tronic, -tronics + (page 5)
electron-gun-density multiplication, electron gun density multiplication
1. The ratio of the average amount of current density at a given opening to the average current density at the cathode surface.
2. A ratio of the average current density at any specified opening through which the electron stream passes to the average current density at the cathode surface.
This entry is located in the following units: electro-, electr-, electri- (page 57) -tron, -tronic, -tronics + (page 6)
electron-hole droplets, electron hole droplets
1. An electronic excitation, observed at low cryogenic temperatures in silicon and germanium, in which an electron-hole Fermi liquid is formed in an unstable condition.
2. A process by which a molecule is excited from a low-lying electronic state to a higher energy electronic state as observed in germanium and silicon at sufficiently low cryogenic temperatures.

It is associated with a liquid-gas phase transition of the charge carriers, and consists of regions of conducting electron-hole Fermi liquid coexisting with regions of insulating exciton gas.

This entry is located in the following units: electro-, electr-, electri- (page 57) -tron, -tronic, -tronics + (page 6)
electron-hole pair, electron hole pair
A conduction electron in a conduction band and an accompanying electron hole in the valence band, that result when an electron jumps the gap in an intrinsic semiconductor.
This entry is located in the following units: electro-, electr-, electri- (page 57) -tron, -tronic, -tronics + (page 6)
electron-hole recombination, electron hole recombination
A process in which a hole is combined again with an electron within a doped semiconductor (a process where impurities are added to a semiconductor), accompanied by a release of energy, normally in the form of radiation.
This entry is located in the following units: electro-, electr-, electri- (page 57) -tron, -tronic, -tronics + (page 6)
electronic magnetic moment, electron magnetic moment, electron dipole moment
1. The total amount of polarization (dipole moment) caused by the movement of electrons within an atom.
2. The magnetic dipole moment which an electron possesses by virtue of its spin.
3. The total magnetic dipole moment associated with the orbital motion of all the electrons of an atom and the electron spins.

This is opposed to a nuclear magnetic moment.

This entry is located in the following units: electro-, electr-, electri- (page 66) -tron, -tronic, -tronics + (page 10)
electron-multiplier section
A section of an electron tube in which an electron current is amplified by one or more successive dynode states.

A dynode is an electrode whose primary function is the secondary emission of electrons which are used in multiplier phototubes and some types of television camera tubes.

This entry is located in the following unit: electro-, electr-, electri- (page 72)
electron-multiplier tube
An electron tube which includes an electron multiplier.
This entry is located in the following unit: electro-, electr-, electri- (page 72)
electron-optical
Having to do with electron optics.

An electron-optical lens focuses the highly accelerated electrons into a tiny spot.

This entry is located in the following unit: electro-, electr-, electri- (page 72)
electron-optical transistor
A transistor capable of responding in nanoseconds to both light and electrical signals.
This entry is located in the following units: electro-, electr-, electri- (page 72) trans-, tran-, tra- (page 3)
electron-tube coupler
A couple (component used to transfer energy from one circuit to another circuit) specifically designed to be inserted between an electron tube and an input or an output tool, as between a magnetron and a transmission line.
This entry is located in the following unit: electro-, electr-, electri- (page 72)
electron-wave tube, electron wave tube
1. An electron tube which has mutually interacting streams of electrons with different velocities that cause a signal modulation to change progressively along the length of the electron streams.
2. An electron tube in which stream of electrons having different velocities interact and cause a progressive change in signal modulation along their length.
This entry is located in the following unit: electro-, electr-, electri- (page 72)
free electron
1. An electron in or beyond the outermost electron shells of an atom which is unbound or very weakly bound.
2. An electron which is not attached to an atom, an ion, or a molecule but it is free to move under the influence of an electric field.
3. An electron that is not bonded to an atom or a molecule and so is free to move under external electric or magnetic fields.
This entry is located in the following unit: electro-, electr-, electri- (page 92)
orbital electron
An electron in an orbit within an atom or molecule, as distinguished from a free electron.
This entry is located in the following unit: electro-, electr-, electri- (page 96)
scanning electron microscopy
The technique using a scanning electron microscope on a specimen.
This entry is located in the following units: electro-, electr-, electri- (page 99) -tron, -tronic, -tronics + (page 14)
secondary electron, recoil electron
An electron knocked out of its normal habitat by an incident photon or particle.
This entry is located in the following unit: electro-, electr-, electri- (page 100)
thermionic electron
An electron emitted by heating a substance.
transmission electron microscopy (s) (noun), transmission electron microscopies (pl)
1. The study of materials by means of the electron microscope.
2. Referring to a microscope in which an electron beam replaces light to form an image.
3. A technique using an electron microscope in which a beam of electrons is focused by an electromagnetic lens and directed onto an extremely thin specimen.

The emerging electrons are focused and directed by a second lens onto a fluorescent screen.

The magnified image which is produced is 1000 times greater than that produced by an optic microscope and well resolved, but it is two-dimensional because of the thinness of the specimen.

valence electron
One or more of the electrons in an atom's outermost, incomplete electron shell.

Such electrons are exchanged or shared in chemical reactions.

This entry is located in the following unit: electro-, electr-, electri- (page 102)
Word Entries at Get Words: “electron
electron
1. A negatively charged, low-mass particle which orbits the nucleus of an atom or exists free in space and in stars.
2. An elementary particle of an atom with a negative electrical charge and a mass of 1/1837 of a proton; electrons surround the positively charged nucleus of an atom and determine the chemical properties of an atom.

The movement of electrons in an electrical conductor constitutes an electric current.

This entry is located in the following unit: Astronomy and related astronomical terms (page 9)
Word Entries at Get Words containing the term: “electron
electron volt; eV
The amount of kinetic energy gained by an electron when accelerated through an electric potential difference of 1 Volt; equivalent to 1.603 x 10^-19; a unit of energy or work.