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In [[atomic physics]] and [[chemistry]], an '''atomic electron transition''' (also called an '''electronic (de-)excitation''', '''atomic transition''', or '''quantum jump''') is a change (or jump) of an [[electron]] from one [[energy level]] to another within an [[atom]]<ref>Schombert, James. [http://abyss.uoregon.edu/~js/cosmo/lectures/lec08.html "Quantum physics"] University of Oregon Department of Physics</ref> or [[artificial atom]].<ref>{{Cite journal |arxiv = 1009.2969|bibcode = 2011PhRvL.106k0502V|title = Observation of Quantum Jumps in a Superconducting Artificial Atom|journal = Physical Review Letters|volume = 106|issue = 11|pages = 110502|last1 = Vijay|first1 = R|last2 = Slichter|first2 = D. H|last3 = Siddiqi|first3 = I|year = 2011|doi = 10.1103/PhysRevLett.106.110502|pmid = 21469850| s2cid=35070320 }}</ref> It appears discontinuous as the electron "jumps" from one quantized energy level to another, typically in a few [[nanosecond]]s or less.
Electron transitions cause the [[Spontaneous emission|emission]] or [[Absorption (electromagnetic radiation)|absorption]] of [[electromagnetic radiation]] in the form of quantized units called [[photon]]s. Their statistics are [[Poisson distribution|Poissonian]], and the time between jumps is [[Exponential distribution|exponentially distributed]].<ref>{{Cite web |url=http://www.mpq.mpg.de/Theorygroup/CIRAC/wiki/images/8/86/Samuel.pdf |last=Deléglise |first=S. |title=Observing the quantum jumps of light |access-date=September 17, 2010 |archive-url=https://web.archive.org/web/20101107043403/http://www.mpq.mpg.de/Theorygroup/CIRAC/wiki/images/8/86/Samuel.pdf |archive-date=November 7, 2010 |url-status=dead }}</ref> The damping time constant (which ranges from [[nanosecond]]s to a few seconds) relates to the natural, pressure, and field [[Spectral line#Line broadening and shift|broadening of spectral lines]]. The larger the energy separation of the states between which the electron jumps, the shorter the [[wavelength]] of the photon emitted.<ref name=":0" /> The emitted photon changes the [[kinetic energy]] of the atom, enabling the [[laser cooling]] technology to slow down the motion of atoms.
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