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Fix Matter see-also invoke

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Fix Matter see-also invoke

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{{Short description|Change of an electron between energy levels in an atom}}

{{Quantum matter backlink|Atoms}}

A '''transition''' is a change of an [[Physics:Quantum atoms/electron|electron]] between different [[Physics:Quantum atoms/energy level|energy levels]] in an [[Physics:Quantum atoms/atom|atom]]. Such transitions occur when energy is absorbed or emitted, typically in the form of a photon.

[[File:Atomic_transition_yellow_landscape-1.png|thumb|right|500px|Electron transitions between quantized atomic energy levels, including absorption and emission of photons, spectroscopy methods, and quantum mechanical selection rules.<ref>Schombert, James. "Quantum physics". University of Oregon Department of Physics.</ref>
<ref>{{Cite book |last=McQuarrie |first=Donald A. |last2=Simon |first2=John D. |title=Physical chemistry: a molecular approach |publisher=Univ. Science Books}}</ref>
<ref>{{cite journal|last1=Itano|first1=W. M.|last2=Bergquist|first2=J. C.|last3=Wineland|first3=D. J.|title=Early observations of macroscopic quantum jumps in single atoms|journal=International Journal of Mass Spectrometry|volume=377|page=403}}</ref>
<ref>{{Cite book|title=Atomic Physics|author=Foot, C. J.|publisher=Oxford University Press}}</ref>
<ref>{{Cite news|last=Gleick|first=James|title=PHYSICISTS FINALLY GET TO SEE QUANTUM JUMP WITH OWN EYES|work=The New York Times}}</ref>
]]
== Description ==
In [[Physics:Quantum mechanics|quantum mechanics]], electrons in atoms occupy discrete quantized energy levels. An '''atomic electron transition''' (also called a ''quantum jump'' or ''quantum leap'') occurs when an electron changes from one energy level to another within an atom or artificial atom.<ref>Schombert, James. [http://abyss.uoregon.edu/~js/cosmo/lectures/lec08.html "Quantum physics"] University of Oregon Department of Physics</ref><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|article-number = 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>

These energy levels are unique to each atom and produce characteristic spectral fingerprints. Techniques such as energy-dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy rely on these characteristic transitions to identify atomic composition.<ref name=":1">{{Cite book |last=McQuarrie |first=Donald A. |title=Physical chemistry: a molecular approach |last2=Simon |first2=John D. |date=200 |publisher=Univ. Science Books |isbn=978-0-935702-99-6 |location=Sausalito, Calif}}</ref>

When an electron moves to a higher energy level, it absorbs energy. When it falls to a lower level, it emits energy. These processes are governed by quantum-mechanical selection rules and conservation of energy.

Transitions between energy levels produce discrete spectral features and are fundamental to atomic spectroscopy.

== Photon absorption and emission ==
[[File:Bohr-atom-electron-to-jump.svg|thumb|right|228px|An electron transition from {{math|''n'' = 3}} to {{math|''n'' = 2}} accompanied by photon emission.]]

Electrons can relax into lower-energy states by emitting electromagnetic radiation in the form of photons. Conversely, they can absorb photons and become excited into higher-energy states.

The energy of the photon must exactly match the energy difference between the two states. Larger energy gaps correspond to shorter photon wavelengths.<ref name=":0">{{cite journal|last1=Itano|first1=W. M.|last2=Bergquist|first2=J. C.|last3=Wineland|first3=D. J.|date=2015|title=Early observations of macroscopic quantum jumps in single atoms|url=http://tf.boulder.nist.gov/general/pdf/2723.pdf|journal=International Journal of Mass Spectrometry|volume=377|page=403|bibcode=2015IJMSp.377..403I|doi=10.1016/j.ijms.2014.07.005}}</ref>

The relation between photon energy and frequency is:

:contentReference[oaicite:0]{index=0}

where {{math|''h''}} is the Planck constant, {{math|''ν''}} is frequency, {{math|''c''}} is the speed of light, and {{math|''λ''}} is wavelength.

== Quantum theory ==
An atom interacting with electromagnetic radiation experiences an oscillating electric field:

:contentReference[oaicite:1]{index=1}

where {{math|''ω''}} is the angular frequency and {{math|''ĕ''<sub>rad</sub>}} is the polarization vector.<ref>{{Cite book|title=Atomic Physics|author=Foot, CJ|year=2004|
publisher=Oxford University Press|isbn=978-0-19-850696-6}}</ref>

The interaction Hamiltonian for an atomic dipole in an electric field is:

:contentReference[oaicite:2]{index=2}

Using time-dependent perturbation theory and Fermi’s golden rule, the stimulated transition probability depends on the dipole matrix element:

:contentReference[oaicite:3]{index=3}

The angular part of this expression leads directly to the quantum-mechanical selection rules for atomic transitions.

== Electromagnetic radiation interactions ==
To excite an electron into a higher energy level, incident radiation must have energy equal to the energy gap between the levels. Because atomic energy differences are often on the scale of ultraviolet and X-ray photons, these wavelengths are widely used in spectroscopy.<ref name=":1" />

The [[Franck–Condon principle]] states that electronic transitions occur much faster than nuclear motion. As a result, transitions occur essentially instantaneously compared to atomic vibrations and are only likely if the initial and final wavefunctions overlap significantly.<ref>{{Cite journal |last1=de la Peña |first1=L. |last2=Cetto |first2=A. M. |last3=Valdés-Hernández |first3=A. |date=2020-12-04 |title=How fast is a quantum jump? |url=https://www.sciencedirect.com/science/article/pii/S0375960120307477 |journal=Physics Letters A |volume=384 |issue=34 |arxiv=2009.02426 |bibcode=2020PhLA..38426880D |doi=10.1016/j.physleta.2020.126880 |issn=0375-9601 |article-number=126880}}</ref>

Radiative relaxation produces photons with wavelengths characteristic of the atom and transition involved.

== Spectroscopy techniques ==
Several experimental methods use electron transitions:

* '''Ultraviolet–visible spectroscopy''' uses visible or ultraviolet light to probe absorption and transmission spectra.<ref>{{Cite web |title=UV-Visible Spectroscopy |url=https://www2.chemistry.msu.edu/faculty/reusch/virttxtjml/spectrpy/uv-vis/uvspec.htm |access-date=2025-12-09 |website=www2.chemistry.msu.edu}}</ref>

* '''Energy-dispersive X-ray spectroscopy''' excites inner-shell electrons using high-energy electrons and measures emitted X-rays characteristic of the atom.<ref>{{Citation |title=Identification and analytical methods |date=2022-01-01 |work=Heterogeneous Micro and Nanoscale Composites for the Catalysis of Organic Reactions |pages=33–51 |url=https://www.sciencedirect.com:5037/science/chapter/edited-volume/abs/pii/B9780128245279000010 |access-date=2025-12-09 |publisher=Elsevier |language=en-US}}</ref>

* '''X-ray photoelectron spectroscopy''' uses incident X-rays to eject electrons from surfaces and determine elemental composition from their binding energies.<ref>{{Cite web |title=X-ray Photoelectron Spectroscopy |url=https://serc.carleton.edu/msu_nanotech/methods/xps.html |access-date=2025-12-09 |website=Methods |language=en}}</ref>

== History ==
Danish physicist [[Biography:Niels Bohr|Niels Bohr]] first proposed quantum jumps in 1913.<ref>{{Cite news|last=Gleick|first=James|date=1986-10-21|title=PHYSICISTS FINALLY GET TO SEE QUANTUM JUMP WITH OWN EYES|language=en-US|work=The New York Times|url=https://www.nytimes.com/1986/10/21/science/physicists-finally-get-to-see-quantum-jump-with-own-eyes.html|access-date=2021-12-06|issn=0362-4331}}</ref> Shortly afterward, the [[Franck–Hertz experiment]] by [[Biography:James Franck|James Franck]] and [[Biography:Gustav Ludwig Hertz|Gustav Hertz]] experimentally confirmed that atoms possess quantized energy states.<ref>{{Cite web|title=Franck-Hertz experiment {{!}} physics {{!}} Britannica|url=https://www.britannica.com/science/Franck-Hertz-experiment|access-date=2021-12-06|website=www.britannica.com|language=en}}</ref>

In 1975, [[Biography:Hans Dehmelt|Hans Dehmelt]] predicted that individual quantum jumps could be observed directly. In 1986, quantum jumps were experimentally observed using trapped ions of barium and mercury.<ref name=":0" />

== Recent discoveries ==
In 2019, experiments with superconducting artificial atoms demonstrated that some quantum jumps evolve continuously and can even be reversed during the transition.<ref>{{cite journal|last1=Minev|first1=Z. K.|last2=Mundhada|first2=S. O.|last3=Shankar|first3=S.|last4=Reinhold|first4=P.|last5=Gutiérrez-Jáuregui|first5=R.|last6=Schoelkopf|first6=R. J..|last7=Mirrahimi|first7=M.|last8=Carmichael|first8=H. J.|last9=Devoret|first9=M. H.|date=3 June 2019|title=To catch and reverse a quantum jump mid-flight|journal=Nature|volume=570|issue=7760|pages=200–204|arxiv=1803.00545|bibcode=2019Natur.570..200M|doi=10.1038/s41586-019-1287-z|pmid=31160725|s2cid=3739562 }}</ref>

Other quantum jumps remain fundamentally unpredictable due to the probabilistic nature of quantum measurement.<ref>{{Cite journal|last1=Snizhko|first1=Kyrylo|last2=Kumar|first2=Parveen|last3=Romito|first3=Alessandro|date=2020-09-29|title=Quantum Zeno effect appears in stages|url=https://link.aps.org/doi/10.1103/PhysRevResearch.2.033512|journal=Physical Review Research|volume=2|issue=3|article-number=033512|arxiv=2003.10476|doi=10.1103/PhysRevResearch.2.033512|bibcode=2020PhRvR...2c3512S |s2cid=214623209 }}</ref>

== Properties ==

* involves [[Physics:Quantum atoms/energy level|energy levels]]
* associated with emission or absorption of photons
* produces [[Physics:Quantum atoms/spectral line|spectral lines]]
* governed by quantum selection rules
* fundamental to spectroscopy and laser physics

=See also=
{{#invoke:PhysicsQC|tocHeadingAndList|Physics:Quantum basics/See also/Matter}}

=References=
{{reflist|3}}

{{Author|Harold Foppele}}
{{Sourceattribution|Physics:Quantum atoms/transition|1}}

Physics:Quantum atoms/transition - Revision history

imported>WikiHarold: Fix Matter see-also invoke

imported>WikiHarold: Fix Matter see-also invoke