Electron capture 82381 224327066 2008-07-08T10:38:34Z SkyLined 6429027 /* Common Examples */ Updated table to use nuclide templates '''Electron capture''' (sometimes called '''inverse beta decay''') is a [[decay mode]] for [[isotope]]s that will occur when there are too many [[proton]]s in the [[atomic nucleus|nucleus]] of an [[atom]] and insufficient energy to emit a [[positron]]; however, it continues to be a viable decay mode for [[radioactive]] isotopes that can decay by [[positron emission]]. If the energy difference between the parent atom and the daughter atom is less than 1.022 [[MeV]], positron emission is forbidden and electron capture is the sole decay mode. For example, [[Rubidium]]-83 will decay to [[Krypton]]-83 solely by electron capture (the energy difference is about 0.9 MeV). In this case, one of the orbital [[electron]]s, usually from the K or L [[electron shell]] ('''K-electron capture''', also '''K-capture''', or '''L-electron capture''', '''L-capture'''), is captured by a proton in the nucleus, forming a [[neutron]] and a [[neutrino]]. Since the proton is changed to a neutron, the number of neutrons increases by 1, the number of protons decreases by 1, and the [[atomic mass]] number remains unchanged. By changing the number of protons, electron capture transforms the [[nuclide]] into a new [[chemical element|element]]. The atom moves into an [[excited state]] with the inner shell missing an electron. When transiting to the ground state, the atom will emit an [[X-rays|X-ray photon]] (a type of [[electromagnetic radiation]]) and/or [[Auger electrons]]. ===Reaction Details=== <!-- Autogenerated using Phykiformulae 0.12 [[User:SkyLined#Phykiformulae]] p+ + e- -> n + ve !Examples: Al-26 + e- -> Mg-26 + ve Ni-59 + e- -> Co-59 + ve K-40 + e- -> Ar-40 + ve -->:{| border="0" |- style="height:2em;" |{{SubatomicParticle|link=yes|Proton}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron}}&nbsp;||&rarr;&nbsp;||{{SubatomicParticle|link=yes|Neutron}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron Neutrino}} |- style="height:2em;" |colspan=99|Examples: |- style="height:2em;" |{{Nuclide|Link|aluminium|26}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron}}&nbsp;||&rarr;&nbsp;||{{Nuclide|Link|magnesium|26}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron Neutrino}} |- style="height:2em;" |{{Nuclide|Link|nickel|59}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron}}&nbsp;||&rarr;&nbsp;||{{Nuclide|Link|cobalt|59}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron Neutrino}} |- style="height:2em;" |{{Nuclide|Link|potassium|40}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron}}&nbsp;||&rarr;&nbsp;||{{Nuclide|Link|argon|40}}&nbsp;||+&nbsp;||{{SubatomicParticle|link=yes|Electron Neutrino}} |} (Please note that it is one of the initial atom's own electrons that is captured, not a new, incoming electron as might be suggested by the way the above reactions are written.) Radioactive isotopes which decay by pure electron capture can, in theory, be inhibited from radioactive decay if they are fully [[ion]]ized ("stripped" is sometimes used to describe such ions). It is hypothesized that such elements, if formed by the [[r-process]] in exploding [[supernova]]e, are ejected fully ionized and so do not undergo radioactive decay as long as they do not encounter electrons in outer space. Anomalies in elemental distributions are thought to be partly a result of this effect on electron capture. [[Chemical bonds]] can also affect the rate of electron capture to a small degree (generally less than 1%) depending on the proximity of electrons to the nucleus.[http://www.nature.com/news/2004/040913/pf/040913-24_pf.html] Around the elements in the middle of the [[periodic table]], isotopes that are lighter than stable isotopes of the same element tend to decay through [[beta decay#electron capture|electron capture]], while isotopes heavier than the stable ones decay by [[beta decay#.CE.B2.E2.88.92_decay|electron emission]]. A good example of this is [[Isotopes of silver|silver]]. ===Common Examples=== Some common radioisotopes that decay by electron capture include: {| class="wikitable" |- ! Radioisotope !! Half-life |- | {{SimpleNuclide|Link|Beryllium|7}} | 53.28 d |- | {{SimpleNuclide|Link|Argon|37}} | 35.0 d |- | {{SimpleNuclide|Link|Calcium|41}} | 1.03E5 a |- | {{SimpleNuclide|Link|Titanium|44}} | 52 a |- | {{SimpleNuclide|Link|Vanadium|49}} | 337 d |- | {{SimpleNuclide|Link|Chromium|51}} | 27.7 d |- | {{SimpleNuclide|Link|Manganese|53}} | 3.7E6 a |- | {{SimpleNuclide|Link|Cobalt|57}} | 271.8 d |- | {{SimpleNuclide|Link|Nickel|56}} | 6.10 d |- | {{SimpleNuclide|Link|Gallium|67}} | 3.260 d |- | {{SimpleNuclide|Link|Germanium|68}} | 270.8 d |- | {{SimpleNuclide|Link|Selenium|72}} | 8.5 d |} For a full list, see the [[table of nuclides]]. {{Nuclear_processes}} [[Category:Nuclear physics]] [[Category:Nuclear chemistry]] [[Category:Radioactivity]] [[ast:Captura electrónica]] [[ca:Captura electrònica]] [[de:Elektroneneinfang]] [[es:Captura electrónica]] [[eu:Elektroi-harrapaketa]] [[fa:گیراندازی الکترون]] [[fr:Capture électronique]] [[ko:전자 포획]] [[it:Cattura elettronica]] [[he:לכידת אלקטרון]] [[nl:Elektronenvangst]] [[ja:電子捕獲]] [[pl:Wychwyt elektronu]] [[pt:Captura eletrônica]] [[ru:Электронный захват]] [[sl:Zajetje elektrona]] [[sr:Електронски захват]] [[fi:Elektronin sieppaus]] [[sv:Elektroninfångning]] [[th:Electron capture]] [[tr:Eksicik yakalanması]]