Editing Electron (section)

=== Interaction ===
An electron generates an electric field that exerts an attractive force on a particle with a positive charge, such as the proton, and a repulsive force on a particle with a negative charge. The strength of this force in nonrelativistic approximation is determined by [[Coulomb's law|Coulomb's inverse square law]].<ref name=Griffiths1998>
{{cite book
 |last=Griffiths |first=David J.
 |title=Introduction to Electrodynamics |edition=3rd
 |publisher=Prentice Hall |year=1998
 |isbn=978-0-13-805326-0
 |url=https://archive.org/details/introductiontoel00grif_0
}}</ref>{{rp|pages=58–61}} When an electron is in motion, it generates a [[magnetic field]].<ref name="munowitz" />{{rp|page=140}} The [[Ampère's circuital law|Ampère–Maxwell law]] relates the magnetic field to the mass motion of electrons (the [[electric current|current]]) with respect to an observer. This property of induction supplies the magnetic field that drives an [[electric motor]].<ref>
{{cite book
 |last=Crowell
 |first=B.
 |title=Electricity and Magnetism
 |url=https://books.google.com/books?id=s9QWZNfnz1oC&pg=PT129
 |pages=129–152
 |publisher=Light and Matter
 |year=2000
 |isbn=978-0-9704670-4-1
 |access-date=2020-08-25
 |archive-date=2022-02-04
 |archive-url=https://web.archive.org/web/20220204083733/https://books.google.com/books?id=s9QWZNfnz1oC&pg=PT129
 |url-status=live
}}</ref> The electromagnetic field of an arbitrary moving charged particle is expressed by the [[Liénard–Wiechert potential]]s, which are valid even when the particle's speed is close to that of light ([[special relativity|relativistic]]).<ref name=Griffiths1998 />{{rp|pages=429–434}}

[[File:Lorentz force.svg|right|thumb|alt=A graph with arcs showing the motion of charged particles|A particle with charge ''q'' (at left) is moving with velocity ''v'' through a magnetic field ''B'' that is oriented toward the viewer. For an electron, ''q'' is negative, so it follows a curved trajectory toward the top.]]
When an electron is moving through a magnetic field, it is subject to the [[Lorentz force]] that acts perpendicularly to the plane defined by the magnetic field and the electron velocity. This [[centripetal force]] causes the electron to follow a [[Helix|helical]] trajectory through the field at a radius called the [[gyroradius]]. The acceleration from this curving motion induces the electron to radiate energy in the form of synchrotron radiation.<ref>
{{cite journal
 |last1 = Mahadevan |first1 = R.
 |last2 = Narayan |first2 = R.
 |last3 = Yi |first3 = I.
 |year = 1996
 |title = Harmony in Electrons: Cyclotron and Synchrotron Emission by Thermal Electrons in a Magnetic Field
 |journal = [[The Astrophysical Journal]]
 |volume = 465 | pages = 327–337
 |arxiv = astro-ph/9601073
 |doi = 10.1086/177422 |bibcode=1996ApJ...465..327M
 |s2cid = 16324613
}}</ref>{{efn|Radiation from non-relativistic electrons is sometimes termed [[cyclotron radiation]].}}<ref name=munowitz />{{rp|page=160}} The energy emission in turn causes a recoil of the electron, known as the [[Abraham–Lorentz force#Abraham–Lorentz–Dirac Force|Abraham–Lorentz–Dirac Force]], which creates a friction that slows the electron. This force is caused by a [[back-reaction]] of the electron's own field upon itself.<ref>
{{cite journal
 |last = Rohrlich |first = F.
 |year = 1999
 |title = The Self-Force and Radiation Reaction
 |journal = [[American Journal of Physics]]
 |volume = 68 |issue = 12 |pages = 1109–1112
 |doi = 10.1119/1.1286430
 |bibcode = 2000AmJPh..68.1109R
}}</ref>

[[File:Bremsstrahlung.svg|thumb|left|upright|alt=A curve shows the motion of the electron, a red dot shows the nucleus, and a wiggly line the emitted photon|Here, [[Bremsstrahlung]] is produced by an electron ''e'' deflected by the electric field of an atomic nucleus. The energy change ''E''<sub>2</sub>&nbsp;−&nbsp;''E''<sub>1</sub> determines the frequency ''f'' of the emitted photon.]]
Photons mediate electromagnetic interactions between particles in [[quantum electrodynamics]]. An isolated electron at a constant velocity cannot emit or absorb a real photon; doing so would violate [[conservation of energy]] and [[momentum]]. Instead, virtual photons can transfer momentum between two charged particles. This exchange of virtual photons, for example, generates the Coulomb force.<ref>
{{cite book
 |last=Georgi
 |first=H.
 |chapter=Grand Unified Theories
 |page=427
 |editor=Davies, Paul
 |title=The New Physics
 |chapter-url=https://books.google.com/books?id=akb2FpZSGnMC&pg=PA427
 |publisher=Cambridge University Press
 |year=1989
 |isbn=978-0-521-43831-5
 |access-date=2020-08-25
 |archive-date=2014-09-21
 |archive-url=https://web.archive.org/web/20140921171123/http://books.google.com/books?id=akb2FpZSGnMC&pg=PA427
 |url-status=live
}}</ref> Energy emission can occur when a moving electron is deflected by a charged particle, such as a proton. The deceleration of the electron results in the emission of [[Bremsstrahlung]] radiation.<ref>
{{cite journal
 |last1=Blumenthal |first1= G.J.
 |last2=Gould |first2=R.
 |year=1970
 |title=Bremsstrahlung, Synchrotron Radiation, and Compton Scattering of High-Energy Electrons Traversing Dilute Gases
 |journal=[[Reviews of Modern Physics]]
 |volume=42 |issue=2 |pages=237–270
 |doi=10.1103/RevModPhys.42.237 |bibcode=1970RvMP...42..237B
}}</ref>

An inelastic collision between a photon (light) and a solitary (free) electron is called [[Compton scattering]]. This collision results in a transfer of momentum and energy between the particles, which modifies the wavelength of the photon by an amount called the [[Compton scattering|Compton shift]].{{efn|The change in wavelength, Δ''λ'', depends on the angle of the recoil, ''θ'', as follows,
: <math>\textstyle \Delta \lambda = \frac{h}{m_{\mathrm{e}}c} (1 - \cos \theta),</math>
where ''c'' is the speed of light in vacuum and ''m''<sub>e</sub> is the electron mass. See Zombeck (2007).<ref name=Zombeck2007 />{{rp|page=393, 396}} }} The maximum magnitude of this wavelength shift is ''h''/''m''<sub>e</sub>''c'', which is known as the [[Compton wavelength]].<ref>
{{cite web
 |title=The Nobel Prize in Physics 1927
 |publisher=[[Nobel Foundation|The Nobel Foundation]]
 |year=2008
 |url=https://nobelprize.org/nobel_prizes/physics/laureates/1927/
 |access-date=2008-09-28
 |df=dmy-all
 |archive-date=2008-10-24
 |archive-url=https://web.archive.org/web/20081024124054/http://nobelprize.org/nobel_prizes/physics/laureates/1927/
 |url-status=live
}}</ref> For an electron, it has a value of {{val|2.43|e=-12|u=m}}.<ref name="CODATA" /> When the wavelength of the light is long (for instance, the wavelength of the [[Light|visible light]] is 0.4–0.7&nbsp;μm) the wavelength shift becomes negligible. Such interaction between the light and free electrons is called [[Thomson scattering]] or linear Thomson scattering.<ref name="Chen1998">
{{cite journal
 |last1=Chen |first1=S.-Y.
 |last2=Maksimchuk |first2=A.
 |last3=Umstadter |first3=D.
 |year=1998
 |title=Experimental observation of relativistic nonlinear Thomson scattering
 |journal=[[Nature (journal)|Nature]]
 |volume=396 |issue=6712 |pages=653–655
 |doi=10.1038/25303 |arxiv=physics/9810036
 |bibcode=1998Natur.396..653C|s2cid=16080209
}}</ref>

The relative strength of the electromagnetic interaction between two charged particles, such as an electron and a proton, is given by the [[fine-structure constant]]. This value is a dimensionless quantity formed by the ratio of two energies: the electrostatic energy of attraction (or repulsion) at a separation of one Compton wavelength, and the rest energy of the charge. It is given by {{physconst|alpha|symbol=yes|round=9|after=,}} which is approximately equal to {{sfrac|1|137}}.

When electrons and positrons collide, they [[Electron–positron annihilation|annihilate]] each other, giving rise to two or more gamma ray photons. If the electron and positron have negligible momentum, a [[Positronium|positronium atom]] can form before annihilation results in two or three gamma ray photons whose energies total 1.022&nbsp;MeV.<ref>
{{cite journal
 | last1 = Beringer | first1 = R.
 | last2 = Montgomery | first2 = C.G.
 | year = 1942
 | title = The Angular Distribution of Positron Annihilation Radiation
 | journal = [[Physical Review]]
 | volume = 61 | issue = 5–6 | pages = 222–224
 | doi = 10.1103/PhysRev.61.222
 | bibcode = 1942PhRv...61..222B }}</ref><ref>{{cite book
 | last = Buffa | first = A.
 | title = College Physics
 | publisher = Prentice Hall | edition = 4th | year = 2000
 | isbn = 978-0-13-082444-8
 | url = https://archive.org/details/collegephysicsvo00jerr/page/888
 | page =888
}}</ref> On the other hand, a high-energy photon can transform into an electron and a positron by a process called [[pair production]], but only in the presence of a nearby charged particle, such as a nucleus.<ref>
{{cite journal
 | last = Eichler | first = J.
 | year = 2005
 | title = Electron–positron pair production in relativistic ion–atom collisions
 | journal = [[Physics Letters A]]
 | volume = 347 | issue = 1–3 | pages = 67–72
 | doi = 10.1016/j.physleta.2005.06.105
 | bibcode = 2005PhLA..347...67E
}}</ref><ref>
{{cite journal
 | last = Hubbell
 | first = J.H.
 | year = 2006
 | title = Electron positron pair production by photons: A historical overview
 | journal = {{ill|Radiation Physics and Chemistry|fr}}
 | volume = 75
 | issue = 6
 | pages = 614–623
 | bibcode = 2006RaPC...75..614H
 | doi = 10.1016/j.radphyschem.2005.10.008
 | url = https://zenodo.org/record/1259327
 | access-date = 2019-06-21
 | archive-date = 2019-06-21
 | archive-url = https://web.archive.org/web/20190621192329/https://zenodo.org/record/1259327
 | url-status = live
}}</ref>

In the theory of [[electroweak interaction]], the [[Chirality (physics)|left-handed]] component of electron's wavefunction forms a [[weak isospin]] doublet with the [[Neutrino|electron neutrino]]. This means that during [[weak interaction]]s, electron neutrinos behave like electrons. Either member of this doublet can undergo a [[charged current]] interaction by emitting or absorbing a {{SubatomicParticle|W boson|link=yes}} and be converted into the other member. Charge is conserved during this reaction because the W&nbsp;boson also carries a charge, canceling out any net change during the transmutation. Charged current interactions are responsible for the phenomenon of [[beta decay]] in a [[Radioactive decay|radioactive]] atom. Both the electron and electron neutrino can undergo a [[neutral current]] interaction via a {{SubatomicParticle|Z boson0|link=yes}} exchange, and this is responsible for neutrino–electron [[elastic scattering]].<ref name="quigg">
{{cite conference
 |last=Quigg |first=C.
 |title=The Electroweak Theory |page=80
 |conference=TASI 2000: Flavor Physics for the Millennium
 |date=4–30 June 2000
 |place=Boulder, Colorado
 |arxiv=hep-ph/0204104 |bibcode = 2002hep.ph....4104Q
}}</ref>
{{clear}}