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, {{SubatomicParticle|beta-}}9.10938356e=-315.48579909070e=-41822.88848454.2ul=u}}).{{val(31)|ul=MeV/c2}}-1elementary charge, which has a positive value for the proton.{{val>-1.6021766208e=-19-4.80320451e=-10Statcoulomb>esu}}−1.00165291(26)Bohr magneton>μB}}1|2}}Chirality (physics): −{{sfrac>1Chirality (physics)>RH: 0}}Chirality (physics): -1, Chirality (physics)>RH: −2}} {{val>6.6u=yr}}JOURNAL
, Agostini, M., etal, Borexino Collaboration
, 2015
, Test of Electric Charge Conservation with Borexino
, Physical Review Letters
, 115, 23, 231802
, 10.1103/PhysRevLett.115.231802
, 2015PhRvL.115w1802A
, 1509.01223
, 26684111
, )}}The electron is a subatomic particle, symbol {{SubatomicParticle|Electron}} or {{SubatomicParticle|beta-}}, whose electric charge is negative one elementary charge.WEB, Coff, Jerry, What Is An Electron,weblink 10 September 2010, 2010-09-10, Electrons belong to the first generation of the lepton particle family, and are generally thought to be elementary particles because they have no known components or substructure. The electron has a mass that is approximately 1/1836 that of the proton. Quantum mechanical properties of the electron include an intrinsic angular momentum (spin) of a half-integer value, expressed in units of the reduced Planck constant, ħ. Being fermions, no two electrons can occupy the same quantum state, in accordance with the Pauli exclusion principle. Like all elementary particles, electrons exhibit properties of both particles and waves: they can collide with other particles and can be diffracted like light. The wave properties of electrons are easier to observe with experiments than those of other particles like neutrons and protons because electrons have a lower mass and hence a longer de Broglie wavelength for a given energy.Electrons play an essential role in numerous physical phenomena, such as electricity, magnetism, chemistry and thermal conductivity, and they also participate in gravitational, electromagnetic and weak interactions. Since an electron has charge, it has a surrounding electric field, and if that electron is moving relative to an observer, said observer will observe it to generate a magnetic field. Electromagnetic fields produced from other sources will affect the motion of an electron according to the Lorentz force law. Electrons radiate or absorb energy in the form of photons when they are accelerated. Laboratory instruments are capable of trapping individual electrons as well as electron plasma by the use of electromagnetic fields. Special telescopes can detect electron plasma in outer space. Electrons are involved in many applications such as electronics, welding, cathode ray tubes, electron microscopes, radiation therapy, lasers, gaseous ionization detectors and particle accelerators.Interactions involving electrons with other subatomic particles are of interest in fields such as chemistry and nuclear physics. The Coulomb force interaction between the positive protons within atomic nuclei and the negative electrons without, allows the composition of the two known as atoms. Ionization or differences in the proportions of negative electrons versus positive nuclei changes the binding energy of an atomic system. The exchange or sharing of the electrons between two or more atoms is the main cause of chemical bonding. In 1838, British natural philosopher Richard Laming first hypothesized the concept of an indivisible quantity of electric charge to explain the chemical properties of atoms. Irish physicist George Johnstone Stoney named this charge 'electron' in 1891, and J. J. Thomson and his team of British physicists identified it as a particle in 1897. Electrons can also participate in nuclear reactions, such as nucleosynthesis in stars, where they are known as beta particles. Electrons can be created through beta decay of radioactive isotopes and in high-energy collisions, for instance when cosmic rays enter the atmosphere. The antiparticle of the electron is called the positron; it is identical to the electron except that it carries electrical and other charges of the opposite sign. When an electron collides with a positron, both particles can be annihilated, producing gamma ray photons.


{{See also|History of electromagnetic theory|label 1=History of electromagnetism}}

Discovery of effect of electric force

The ancient Greeks noticed that amber attracted small objects when rubbed with fur. Along with lightning, this phenomenon is one of humanity's earliest recorded experiences with electricity. In his 1600 treatise , the English scientist William Gilbert coined the New Latin term , to refer to those substances with property similar to that of amber which attract small objects after being rubbed.{{Citation
| last =Benjamin
| first =Park
| title =A history of electricity (The intellectual rise in electricity) from antiquity to the days of Benjamin Franklin
| place =New York
| publisher =J. Wiley
| year =1898
| page =315, 484–5
| url =
| isbn =978-1313106054
}} Both electric and electricity are derived from the Latin ' (also the root of the alloy of the same name), which came from the Greek word for amber, (').

Discovery of two kinds of charges

In the early 1700s, French chemist Charles François du Fay found that if a charged gold-leaf is repulsed by glass rubbed with silk, then the same charged gold-leaf is attracted by amber rubbed with wool. From this and other results of similar types of experiments, du Fay concluded that electricity consists of two electrical fluids, vitreous fluid from glass rubbed with silk and resinous fluid from amber rubbed with wool. These two fluids can neutralize each other when combined.BOOK
, Keithley, J.F.
, 1999
, The Story of Electrical and Magnetic Measurements: From 500 B.C. to the 1940s
, IEEE, IEEE Press
, 19–20
, 978-0-7803-1193-0
, American scientist Ebenezer Kinnersley later also independently reached the same conclusion.BOOK, Florian, Cajori, A History of Physics in Its Elementary Branches: Including the Evolution of Physical Laboratories,weblink 1917, Macmillan, {{rp|118}} A decade later Benjamin Franklin proposed that electricity was not from different types of electrical fluid, but a single electrical fluid showing an excess (+) or deficit (-). He gave them the modern charge nomenclature of positive and negative respectively.WEB
, Benjamin Franklin (1706–1790)
, ScienceWorld, Eric Weisstein's World of Biography
, Wolfram Research
, 2010-12-16
, Franklin thought of the charge carrier as being positive, but he did not correctly identify which situation was a surplus of the charge carrier, and which situation was a deficit.BOOK
, Myers, R.L.
, 2006
, The Basics of Physics
, Greenwood Publishing Group
, 242
, 978-0-313-32857-2
, Between 1838 and 1851, British natural philosopher Richard Laming developed the idea that an atom is composed of a core of matter surrounded by subatomic particles that had unit electric charges.JOURNAL
, Farrar, W.V.
, 1969
, Richard Laming and the Coal-Gas Industry, with His Views on the Structure of Matter
, Annals of Science
, 25, 243–254
, 10.1080/00033796900200141
, 3
, Beginning in 1846, German physicist William Weber theorized that electricity was composed of positively and negatively charged fluids, and their interaction was governed by the inverse square law. After studying the phenomenon of electrolysis in 1874, Irish physicist George Johnstone Stoney suggested that there existed a "single definite quantity of electricity", the charge of a monovalent ion. He was able to estimate the value of this elementary charge e by means of Faraday's laws of electrolysis.JOURNAL
, Barrow, J.D.
, 1983
, Natural Units Before Planck
, Astronomy & Geophysics, Quarterly Journal of the Royal Astronomical Society
, 24, 24–26
, 1983QJRAS..24...24B
, However, Stoney believed these charges were permanently attached to atoms and could not be removed. In 1881, German physicist Hermann von Helmholtz argued that both positive and negative charges were divided into elementary parts, each of which "behaves like atoms of electricity".BOOK
, Arabatzis, T.
, 2006
, Representing Electrons: A Biographical Approach to Theoretical Entities
, 70–74, 96
, University of Chicago Press
, 978-0-226-02421-9
, Stoney initially coined the term electrolion in 1881. Ten years later, he switched to electron to describe these elementary charges, writing in 1894: "... an estimate was made of the actual amount of this most remarkable fundamental unit of electricity, for which I have since ventured to suggest the name electron". A 1906 proposal to change to electrion failed because Hendrik Lorentz preferred to keep electron.BOOK
, Sōgo, Okamura
, History of Electron Tubes
, 29 May 2015
, 1994
, IOS Press
, 978-90-5199-145-1
, 11
, In 1881, Stoney named this electromagnetic 'electrolion'. It came to be called 'electron' from 1891. [...] In 1906, the suggestion to call cathode ray particles 'electrions' was brought up but through the opinion of Lorentz of Holland 'electrons' came to be widely used.,
, Stoney, G.J.
, 1894
, Of the "Electron," or Atom of Electricity
, Philosophical Magazine
, 38, 5, 418–420
, 10.1080/14786449408620653
, The word electron is a combination of the words electric and ion."electron, n.2". OED Online. March 2013. Oxford University Press. Accessed 12 April 2013 weblink The suffix (wikt:-on|-on) which is now used to designate other subatomic particles, such as a proton or neutron, is in turn derived from electron.BOOK
, Soukhanov, A.H.
, 1986
, Word Mysteries & Histories
, 73
, Houghton Mifflin
, 978-0-395-40265-8
, Guralnik, D.B.
, 1970
, Webster's New World Dictionary
, Prentice Hall
, 450

Discovery of free electrons outside matter

File:Cyclotron motion wider view.jpg|right|thumb|alt=A round glass vacuum tube with a glowing circular beam inside|A beam of electrons deflected in a circle by a magnetic fieldBOOK
, Born, M.
, Blin-Stoyle, R.J.
, Radcliffe, J.M.
, 1989
, Atomic Physics
, 26
, Courier Dover
, 978-0-486-65984-8 Courier DoverThe discovery of electron by Joseph Thomson was closely tied with the experimental and theoretical research of cathode rays for decades by many physicists. While studying electrical conductivity in (wikt:rarefied|rarefied) gases in 1859, The German physicist Julius Plucker observed that the phosphorescent light, which was caused by radiation emitted from the cathode, appeared at the tube wall near the cathode, and the region of the phosphorescent light could be moved by application of a magnetic field. In 1869, Plucker’s student Johann Wilhelm Hittorf found that a solid body placed in between the cathode and the phosphorescence would cast a shadow upon the phosphorescent region of the tube. Hittorf inferred that there are straight rays emitted from the cathode and that the phosphorescence was caused by the rays striking the tube walls. In 1876, the German physicist Eugen Goldstein showed that the rays were emitted perpendicular to the cathode surface, which distinguished between the rays that were emitted from the cathode and the incandescent light. Goldstein dubbed the rays cathode rays.{{citation|last=Whittaker|first= E. T.|title=A history of the theories of aether and electricity. Vol 1| publisher=Nelson, London |year=1951|url =}}{{rp|393}} During the 1870s, the English chemist and physicist Sir William Crookes developed the first cathode ray tube to have a high vacuum inside.JOURNAL
, DeKosky, R.K.
, 1983
, William Crookes and the quest for absolute vacuum in the 1870s
, Annals of Science
, 40, 1, 1–18
, 10.1080/00033798300200101
, He then showed in 1874 that the cathode rays can turn a small paddle wheel when placed in their path. Therefore, he concluded that the rays carried momentum. Furthermore, by applying a magnetic field, he was able to deflect the rays, thereby demonstrating that the beam behaved as though it were negatively charged.BOOK
, Leicester, H.M.
, 1971
, The Historical Background of Chemistry
, 221–222
, Courier Dover
, 978-0-486-61053-5
, In 1879, he proposed that these properties could be explained by regarding cathode rays as composed of negatively charged gaseous molecules in fourth state of matter in which the mean free path of the particles is so long that collisions may be ignored.{{rp|394-395}} The German-born British physicist Arthur Schuster expanded upon Crookes' experiments by placing metal plates parallel to the cathode rays and applying an electric potential between the plates. The field deflected the rays toward the positively charged plate, providing further evidence that the rays carried negative charge. By measuring the amount of deflection for a given level of current, in 1890 Schuster was able to estimate the charge-to-mass ratio of the ray components. However, this produced a value that was more than a thousand times greater than what was expected, so little credence was given to his calculations at the time.In 1892 Hendrik Lorentz suggested that the mass of these particles (electrons) could be a consequence of their electric charge.Frank Wilczek: "Happy Birthday, Electron" Scientific American, June 2012.File:J.J Thomson.jpg|thumb|upright|J. J. ThomsonJ. J. ThomsonWhile studying naturally fluorescing minerals in 1896, the French physicist Henri Becquerel discovered that they emitted radiation without any exposure to an external energy source. These radioactive materials became the subject of much interest by scientists, including the New Zealand physicist Ernest Rutherford who discovered they emitted particles. He designated these particles alpha and beta, on the basis of their ability to penetrate matter.JOURNAL
, Trenn, T.J.
, 1976
, Rutherford on the Alpha-Beta-Gamma Classification of Radioactive Rays
, Isis (journal), Isis
, 67, 1, 61–75
, 231134
, 10.1086/351545
, In 1900, Becquerel showed that the beta rays emitted by radium could be deflected by an electric field, and that their mass-to-charge ratio was the same as for cathode rays.JOURNAL
, Becquerel, H.
, 1900
, Déviation du Rayonnement du Radium dans un Champ Électrique
, Comptes rendus de l'Académie des sciences
, 130, 809–815
Buchwald and Warwick (2001:90–91).)JOURNAL
, Myers, W.G.
, 1976
, Becquerel's Discovery of Radioactivity in 1896
, Journal of Nuclear Medicine
, 17, 7, 579–582
, 775027
, In 1897, the British physicist J. J. Thomson, with his colleagues John S. Townsend and H. A. Wilson, performed experiments indicating that cathode rays really were unique particles, rather than waves, atoms or molecules as was believed earlier. Thomson made good estimates of both the charge e and the mass m, finding that cathode ray particles, which he called "corpuscles," had perhaps one thousandth of the mass of the least massive ion known: hydrogen. He showed that their charge-to-mass ratio, e/m, was independent of cathode material. He further showed that the negatively charged particles produced by radioactive materials, by heated materials and by illuminated materials were universal.WEB
, Thomson
, J.J.
, 1906
, Nobel Lecture: Carriers of Negative Electricity
, Nobel Foundation, The Nobel Foundation
, 2008-08-25
,weblink" title="">weblink
, 2008-10-10
, yes
, The name electron was adoted for these particles by the scientific community, mainly due to the advocation by G. F. Fitzgerald, J. Larmor, and H. A. Lorenz.Roughly one million years after the big bang, the first generation of stars began to form. Within a star, stellar nucleosynthesis results in the production of positrons from the fusion of atomic nuclei. These antimatter particles immediately annihilate with electrons, releasing gamma rays. The net result is a steady reduction in the number of electrons, and a matching increase in the number of neutrons. However, the process of stellar evolution can result in the synthesis of radioactive isotopes. Selected isotopes can subsequently undergo negative beta decay, emitting an electron and antineutrino from the nucleus.JOURNAL
, Burbidge, E.M.
, 1957
, Synthesis of Elements in Stars
, Reviews of Modern Physics
, 29, 4, 548–647
, 10.1103/RevModPhys.29.547, 1957RvMP...29..547B
url =weblink
, An example is the cobalt-60 (60Co) isotope, which decays to form nickel-60 ({{SimpleNuclide2|Nickel|60}}).
, Rodberg, L.S.
, Weisskopf, V.
, 1957
, Fall of Parity: Recent Discoveries Related to Symmetry of Laws of Nature
, Science (journal), Science
, 125, 3249, 627–633
, 10.1126/science.125.3249.627
, 17810563, 1957Sci...125..627R,
(File:AirShower.svg|left|thumb|alt=A branching tree representing the particle production|An extended air shower generated by an energetic cosmic ray striking the Earth's atmosphere)At the end of its lifetime, a star with more than about 20 solar masses can undergo gravitational collapse to form a black hole.JOURNAL
, Fryer, C.L.
, 1999
, Mass Limits For Black Hole Formation
, The Astrophysical Journal
, 522, 1, 413–418
, 1999ApJ...522..413F
, 10.1086/307647
classical physics, these massive stellar objects exert a Gravitation>gravitational attraction that is strong enough to prevent anything, even electromagnetic radiation, from escaping past the Schwarzschild radius. However, quantum mechanical effects are believed to potentially allow the emission of Hawking radiation at this distance. Electrons (and positrons) are thought to be created at the event horizon of these stellar remnants.When a pair of virtual particles (such as an electron and positron) is created in the vicinity of the event horizon, random spatial positioning might result in one of them to appear on the exterior; this process is called quantum tunnelling. The gravitational potential of the black hole can then supply the energy that transforms this virtual particle into a real particle, allowing it to radiate away into space.JOURNAL
, Parikh
, M.K.
, Wilczek
, F.
, 2000
, Hawking Radiation As Tunneling
, Physical Review Letters
, 85
, 24
, 5042–5045
, 10.1103/PhysRevLett.85.5042
, 11102182
, 2000PhRvL..85.5042P
, hep-th/9907001, 1874/17028
, In exchange, the other member of the pair is given negative energy, which results in a net loss of mass-energy by the black hole. The rate of Hawking radiation increases with decreasing mass, eventually causing the black hole to evaporate away until, finally, it explodes.
, Hawking, S.W.
, 1974
, Black hole explosions?
, Nature (journal), Nature
, 248, 30–31
, 10.1038/248030a0, 1974Natur.248...30H
, 5443,
Cosmic rays are particles traveling through space with high energies. Energy events as high as {{val|3.0|e=20|u=eV}} have been recorded.JOURNAL
, Halzen, F.
, Francis Halzen
, Hooper, D.
, 2002
, High-energy neutrino astronomy: the cosmic ray connection
, Reports on Progress in Physics
, 66, 1025–1078
, 2002RPPh...65.1025H
, 10.1088/0034-4885/65/7/201, astro-ph/0204527
, 7, When these particles collide with nucleons in the Earth's atmosphere, a shower of particles is generated, including pions.
, Ziegler, J.F.
, Terrestrial cosmic ray intensities
, IBM Journal of Research and Development
, 42, 1, 117–139
, 10.1147/rd.421.0117, 1998, 1998IBMJ...42..117Z
, More than half of the cosmic radiation observed from the Earth's surface consists of muons. The particle called a muon is a lepton produced in the upper atmosphere by the decay of a pion.

{{SubatomicParticle|Pion-|link=yes}} → {{SubatomicParticle|Muon|link=yes}} + {{SubatomicParticle|Muon antineutrino|link=yes}}
A muon, in turn, can decay to form an electron or positron.NEWS
, Sutton, C.
, August 4, 1990
, Muons, pions and other strange particles
, New Scientist
, 2008-08-28
{{SubatomicParticle|Muon}} → {{SubatomicParticle|Electron}} + {{SubatomicParticle|Electron antineutrino|link=yes}} + {{SubatomicParticle|Muon neutrino|link=yes}}


File:Aurore australe - Aurora australis.jpg|right|thumb|alt=A swirling green glow in the night sky above snow-covered ground|Aurorae are mostly caused by energetic electrons precipitating into the atmosphere.NEWS atmosphereRemote observation of electrons requires detection of their radiated energy. For example, in high-energy environments such as the corona of a star, free electrons form a plasma that radiates energy due to Bremsstrahlung radiation. Electron gas can undergo plasma oscillation, which is waves caused by synchronized variations in electron density, and these produce energy emissions that can be detected by using radio telescopes.JOURNAL
, Gurnett, D.A.
, Anderson, R.
, 1976
, Electron Plasma Oscillations Associated with Type III Radio Bursts
, Science (journal), Science
, 194, 4270, 1159–1162
, 10.1126/science.194.4270.1159
, 17790910, 1976Sci...194.1159G,
The frequency of a photon is proportional to its energy. As a bound electron transitions between different energy levels of an atom, it absorbs or emits photons at characteristic frequencies. For instance, when atoms are irradiated by a source with a broad spectrum, distinct absorption lines appear in the spectrum of transmitted radiation. Each element or molecule displays a characteristic set of spectral lines, such as the hydrogen spectral series. Spectroscopic measurements of the strength and width of these lines allow the composition and physical properties of a substance to be determined.WEB
, Martin, W.C.
, Wiese, W.L.
, 2007
, Atomic Spectroscopy: A Compendium of Basic Ideas, Notation, Data, and Formulas
, National Institute of Standards and Technology
, 2007-01-08
, Fowles, G.R.
, 1989
, Introduction to Modern Optics
, 227–233
, Courier Dover
, 978-0-486-65957-2
, In laboratory conditions, the interactions of individual electrons can be observed by means of particle detectors, which allow measurement of specific properties such as energy, spin and charge. The development of the Paul trap and Penning trap allows charged particles to be contained within a small region for long durations. This enables precise measurements of the particle properties. For example, in one instance a Penning trap was used to contain a single electron for a period of 10 months.WEB
, Staff
, 2008
, The Nobel Prize in Physics 1989
, Nobel Foundation, The Nobel Foundation
, 2008-09-24
, The magnetic moment of the electron was measured to a precision of eleven digits, which, in 1980, was a greater accuracy than for any other physical constant.JOURNAL
, Ekstrom, P.
, 1980
, The isolated Electron
, Scientific American
, 243, 2, 91–101
, 2008-09-24
, 10.1038/scientificamerican0880-104
, Wineland
, David, 1980SciAm.243b.104E,
The first video images of an electron's energy distribution were captured by a team at Lund University in Sweden, February 2008. The scientists used extremely short flashes of light, called attosecond pulses, which allowed an electron's motion to be observed for the first time.WEB
, Mauritsson, J.
, Electron filmed for the first time ever
, Lund University
, 2008-09-17
,weblink" title="">weblink
, March 25, 2009
, Mauritsson, J.
, 2008
, Coherent Electron Scattering Captured by an Attosecond Quantum Stroboscope
, Physical Review Letters
, 100, 073003
, 10.1103/PhysRevLett.100.073003, 2008PhRvL.100g3003M
, 18352546
, 7
display-authors=etal, The distribution of the electrons in solid materials can be visualized by angle-resolved photoemission spectroscopy (ARPES). This technique employs the photoelectric effect to measure the reciprocal space—a mathematical representation of periodic structures that is used to infer the original structure. ARPES can be used to determine the direction, speed and scattering of electrons within the material.JOURNAL
, Damascelli, A.
, 2004
, Probing the Electronic Structure of Complex Systems by ARPES
, Physica Scripta
, T109, 61–74
, 10.1238/Physica.Topical.109a00061
bibcode = 2004PhST..109...61D,

Plasma applications

Particle beams

File:Nasa Shuttle Test Using Electron Beam full.jpg|right|thumb|alt=A violet beam from above produces a blue glow about a Space shuttle model|During a NASA wind tunnel test, a model of the Space Shuttle is targeted by a beam of electrons, simulating the effect of ionizing gases during re-entry.WEB
, Staff
, April 4, 1975
, Image # L-1975-02972
, Langley Research CenterLangley Research CenterElectron beams are used in welding.WEB
, Elmer, J.
, March 3, 2008
, Standardizing the Art of Electron-Beam Welding
, Lawrence Livermore National Laboratory
, 2008-10-16
, They allow energy densities up to {{val|e=7|u=W·cm−2}} across a narrow focus diameter of {{nowrap|0.1–1.3 mm}} and usually require no filler material. This welding technique must be performed in a vacuum to prevent the electrons from interacting with the gas before reaching their target, and it can be used to join conductive materials that would otherwise be considered unsuitable for welding.BOOK
, Schultz, H.
, 1993
, Electron Beam Welding
, 2–3
, Woodhead Publishing
, 978-1-85573-050-2
, Benedict, G.F.
, 1987
, Nontraditional Manufacturing Processes
, Manufacturing engineering and materials processing
, 19, 273
, CRC Press
, 978-0-8247-7352-6
, Electron-beam lithography (EBL) is a method of etching semiconductors at resolutions smaller than a micrometer.CONFERENCE
, Ozdemir, F.S.
, June 25–27, 1979
, Electron beam lithography
, Proceedings of the 16th Conference on Design automation
, 383–391
, IEEE Press
, San Diego, CA
, 2008-10-16
, This technique is limited by high costs, slow performance, the need to operate the beam in the vacuum and the tendency of the electrons to scatter in solids. The last problem limits the resolution to about 10 nm. For this reason, EBL is primarily used for the production of small numbers of specialized integrated circuits.BOOK
, Madou, M.J.
, 2002
, 2nd
, Fundamentals of Microfabrication: the Science of Miniaturization
, 53–54
, CRC Press
, 978-0-8493-0826-0
, Electron beam processing is used to irradiate materials in order to change their physical properties or sterilize medical and food products.CONFERENCE
, Jongen, Y.
, Herer, A.
, May 2–5, 1996
, Electron Beam Scanning in Industrial Applications
, APS/AAPT Joint Meeting
, American Physical Society
, 1996APS..MAY.H9902J
, Electron beams fluidise or quasi-melt glasses without significant increase of temperature on intensive irradiation: e.g. intensive electron radiation causes a many orders of magnitude decrease of viscosity and stepwise decrease of its activation energy.JOURNAL, Mobus, G., etal, 2010, Nano-scale quasi-melting of alkali-borosilicate glasses under electron irradiation, Journal of Nuclear Materials, 396, 2–3, 264–271, 10.1016/j.jnucmat.2009.11.020, 2010JNuM..396..264M, Linear particle accelerators generate electron beams for treatment of superficial tumors in radiation therapy. Electron therapy can treat such skin lesions as basal-cell carcinomas because an electron beam only penetrates to a limited depth before being absorbed, typically up to 5 cm for electron energies in the range 5–20 MeV. An electron beam can be used to supplement the treatment of areas that have been irradiated by X-rays.JOURNAL
, Beddar, A.S.
, Mobile linear accelerators for intraoperative radiation therapy
, AORN Journal
, 2001
, 74, 700–705
, 10.1016/S0001-2092(06)61769-9
, 5
, Domanovic
, Mary Ann
, Kubu
, Mary Lou
, Ellis
, Rod J.
, Sibata
, Claudio H.
, Kinsella
, Timothy J.
, Gazda, M.J.
, Coia, L.R.
, June 1, 2007
, Principles of Radiation Therapy
, 2013-10-31
, Particle accelerators use electric fields to propel electrons and their antiparticles to high energies. These particles emit synchrotron radiation as they pass through magnetic fields. The dependency of the intensity of this radiation upon spin polarizes the electron beam—a process known as the Sokolov–Ternov effect.{{refn|The polarization of an electron beam means that the spins of all electrons point into one direction. In other words, the projections of the spins of all electrons onto their momentum vector have the same sign.|group=note}} Polarized electron beams can be useful for various experiments. Synchrotron radiation can also cool the electron beams to reduce the momentum spread of the particles. Electron and positron beams are collided upon the particles' accelerating to the required energies; particle detectors observe the resulting energy emissions, which particle physics studies .BOOK
, Chao, A.W.
, Tigner, M.
, 1999
, Handbook of Accelerator Physics and Engineering
, World Scientific
, 155, 188
, 978-981-02-3500-0


Low-energy electron diffraction (LEED) is a method of bombarding a crystalline material with a collimated beam of electrons and then observing the resulting diffraction patterns to determine the structure of the material. The required energy of the electrons is typically in the range 20–200 eV.BOOK
, Oura, K.
, 2003
, Surface Science: An Introduction
, 1–45
, Springer Science+Business Media, Springer
, 978-3-540-00545-2, etal, The reflection high-energy electron diffraction (RHEED) technique uses the reflection of a beam of electrons fired at various low angles to characterize the surface of crystalline materials. The beam energy is typically in the range 8–20 keV and the angle of incidence is 1–4°.
, Ichimiya, A.
, Cohen, P.I.
, 2004
, Reflection High-energy Electron Diffraction
, 1
, Cambridge University Press
, 978-0-521-45373-8
, Heppell, T.A.
, 1967
, A combined low energy and reflection high energy electron diffraction apparatus
, Measurement Science and Technology, Journal of Scientific Instruments
, 44, 686–688
, 10.1088/0950-7671/44/9/311, 1967JScI...44..686H
, 9,
The electron microscope directs a focused beam of electrons at a specimen. Some electrons change their properties, such as movement direction, angle, and relative phase and energy as the beam interacts with the material. Microscopists can record these changes in the electron beam to produce atomically resolved images of the material.WEB
, McMullan, D.
, 1993
, Scanning Electron Microscopy: 1928–1965
, University of Cambridge
, 2009-03-23
, In blue light, conventional optical microscopes have a diffraction-limited resolution of about 200 nm.BOOK
, Slayter, H.S.
, 1992
, Light and electron microscopy
, 1
, Cambridge University Press
, 978-0-521-33948-3
, By comparison, electron microscopes are limited by the de Broglie wavelength of the electron. This wavelength, for example, is equal to 0.0037 nm for electrons accelerated across a 100,000-volt potential.BOOK
, Cember, H.
, 1996
, Introduction to Health Physics
, 42–43
, McGraw-Hill, McGraw-Hill Professional
, 978-0-07-105461-4
, The Transmission Electron Aberration-Corrected Microscope is capable of sub-0.05 nm resolution, which is more than enough to resolve individual atoms.JOURNAL
, Erni, R.
, 2009
, Atomic-Resolution Imaging with a Sub-50-pm Electron Probe
, Physical Review Letters
, 102, 9, 096101
, 10.1103/PhysRevLett.102.096101
, 19392535
, 2009PhRvL.102i6101E
, etal,weblink
, This capability makes the electron microscope a useful laboratory instrument for high resolution imaging. However, electron microscopes are expensive instruments that are costly to maintain.Two main types of electron microscopes exist: transmission and scanning. Transmission electron microscopes function like overhead projectors, with a beam of electrons passing through a slice of material then being projected by lenses on a photographic slide or a charge-coupled device. Scanning electron microscopes rasteri a finely focused electron beam, as in a TV set, across the studied sample to produce the image. Magnifications range from 100× to 1,000,000× or higher for both microscope types. The scanning tunneling microscope uses quantum tunneling of electrons from a sharp metal tip into the studied material and can produce atomically resolved images of its surface.BOOK
, Bozzola, J.J.
, Russell, L.D.
, 1999
, Electron Microscopy: Principles and Techniques for Biologists
, Jones & Bartlett Learning, Jones & Bartlett Publishers
, 12, 197–199
, 978-0-7637-0192-5
, Flegler, S.L.
, Heckman Jr., J.W.
, Klomparens, K.L.
, 1995
, Scanning and Transmission Electron Microscopy: An Introduction
, Oxford University Press
, 43–45, Reprint
, 978-0-19-510751-7
, Bozzola, J.J.
, Russell, L.D.
, 1999
, Electron Microscopy: Principles and Techniques for Biologists
, Jones & Bartlett Learning, Jones & Bartlett Publishers
, 2nd, 9
, 978-0-7637-0192-5

Other applications

In the free-electron laser (FEL), a relativistic electron beam passes through a pair of undulators that contain arrays of dipole magnets whose fields point in alternating directions. The electrons emit synchrotron radiation that coherently interacts with the same electrons to strongly amplify the radiation field at the resonance frequency. FEL can emit a coherent high-brilliance electromagnetic radiation with a wide range of frequencies, from microwaves to soft X-rays. These devices are used in manufacturing, communication, and in medical applications, such as soft tissue surgery.BOOK
, Freund, H.P.
, Antonsen, T.
, 1996
, Principles of Free-Electron Lasers
, 1–30
, Springer Science+Business Media, Springer
, 978-0-412-72540-1
, Electrons are important in cathode ray tubes, which have been extensively used as display devices in laboratory instruments, computer monitors and television sets.BOOK
, Kitzmiller, J.W.
, 1995
, Television Picture Tubes and Other Cathode-Ray Tubes: Industry and Trade Summary
, 3–5
, Diane Publishing
, 978-0-7881-2100-5
, In a photomultiplier tube, every photon striking the photocathode initiates an avalanche of electrons that produces a detectable current pulse.BOOK
, Sclater, N.
, 1999
, Electronic Technology Handbook
, 227–228
, McGraw-Hill, McGraw-Hill Professional
, 978-0-07-058048-0
, Vacuum tubes use the flow of electrons to manipulate electrical signals, and they played a critical role in the development of electronics technology. However, they have been largely supplanted by solid-state devices such as the transistor.WEB
, Staff
, 2008
, The History of the Integrated Circuit
, Nobel Foundation, The Nobel Foundation
, 2008-10-18

See also

{hide}cmn|colwidth=18em| {edih}




, Anastopoulos, C.
, 2008
, Particle Or Wave: The Evolution of the Concept of Matter in Modern Physics
, 236–237
, Princeton University Press
, 978-0-691-13512-0
, Shipley, J.T.
, 1945
, Dictionary of Word Origins
, 133
, The Philosophical Library
, 978-0-88029-751-6
, Buchwald, J.Z.
, Warwick, A.
, 2001
, Histories of the Electron: The Birth of Microphysics
, 195–203
, MIT Press
, 978-0-262-52424-7, refBaW2001,
, Thomson, J.J.
, 1897
, Cathode Rays
, Philosophical Magazine
, 44, 293–316
, 10.1080/14786449708621070
, 269
, P.J. Mohr, B.N. Taylor, and D.B. Newell, "The 2014 CODATA Recommended Values of the Fundamental Physical Constants". This database was developed by J. Baker, M. Douma, and S. Kotochigova. Available: weblink. National Institute of Standards and Technology, Gaithersburg, MD 20899.}}

External links

{{Wikisource1911Enc|Electron}}{{Commons category|Electrons}}
  • WEB

, The Discovery of the Electron
, American Institute of Physics, Center for History of Physics
  • WEB

, Particle Data Group
, University of California
  • BOOK

, Bock, R.K.
, Vasilescu, A.
, 1998
, The Particle Detector BriefBook
, 14th
, Springer
, 978-3-540-64120-9
, {{QED}}{{Particles}}{{Featured article}}{{Authority control}}

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