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{{Distinguish|text=[[onium ion]]s such as ammonium}}
{{Distinguish|text=[[onium ion]]s such as ammonium}}
{{Antimatter}}
{{Antimatter}}
[[File:Structure of Protonium.svg|thumb|An illustration of the protonium atom.]]
[[File:Structure of Protonium.svg|thumb|An illustration of the [[protonium]] atom.]]
An '''onium''' (plural: '''onia''') is a [[bound state]] of a [[particle]] and its [[antiparticle]].<ref>{{cite book |last=Walker |first=D.C. |title=Muon and Muonium Chemistry |date=1983 |publisher=[[Cambridge University Press]] |isbn=978-0-521-24241-7 |page=5 |url=https://books.google.com/books?id=PM88AAAAIAAJ&pg=PA5-IA8 |access-date=23 June 2020 |language=en}}</ref> These states are usually named by adding the suffix ''-onium'' to the name of one of the constituent particles (replacing an ''-on'' suffix when present), with one exception for "[[muonium]]"; a muon–antimuon bound pair is called "[[true muonium]]" to avoid confusion with old nomenclature.{{efn|"[[Muonium]]" is the name assigned by [[IUPAC]] to an [[electron]]–[[antimuon]] bound state before the current convention became popular. So, despite its name, [[muonium]] is not a bound muon–antimuon onium. A muon–antimuon bound state is called "[[true muonium]]" to reduce confusion.}}
An '''onium''' (plural: '''onia''') is a [[bound state]] of a [[particle]] and its [[antiparticle]].<ref>{{cite book |last=Walker |first=D.C. |title=Muon and Muonium Chemistry |date=1983 |publisher=[[Cambridge University Press]] |isbn=978-0-521-24241-7 |page=5 |url=https://books.google.com/books?id=PM88AAAAIAAJ&pg=PA5-IA8 |access-date=23 June 2020 |language=en}}</ref> These states are usually named by adding the suffix ''-onium'' to the name of one of the constituent particles (replacing an ''-on'' suffix when present), with one exception for "[[muonium]]"; a muon–antimuon bound pair is called "[[true muonium]]" to avoid confusion with old nomenclature.{{efn|"[[Muonium]]" is the name assigned by [[IUPAC]] to an [[electron]]–[[antimuon]] bound state before the current convention became popular. So, despite its name, [[muonium]] is not a bound muon–antimuon onium. A muon–antimuon bound state is called "[[true muonium]]" to reduce confusion.}}


==Examples==
==Examples==
[[Positronium]] is an onium which consists of an [[electron]] and a [[positron]] bound together as a long-lived [[metastable]] state. Positronium has been studied since the 1950s to understand bound states in [[quantum field theory]]. A recent development called non-relativistic [[quantum electrodynamics]] (NRQED) used this system as a proving ground.<ref>{{cite journal |last1=Labelle |first1=P. |last2=Zebarjad |first2=S.M. |last3=Burgess |first3=C.P. |year=1997 |title=Nonrelativistic QED and next-to-leading hyperfine splitting in positronium |journal=Physical Review D |volume=56 |issue=12 |pages=8053–8061 |bibcode=1997PhRvD..56.8053L |arxiv=hep-ph/9706449 |doi=10.1103/PhysRevD.56.8053 |s2cid=6258393 }}</ref>
[[Positronium]] is an onium which consists of an [[electron]] and a [[positron]] bound together as a long-lived [[metastable]] state. Positronium has been studied since the 1950s to understand bound states in [[quantum field theory]]. A recent development called [[non-relativistic quantum electrodynamics]] (NRQED) used this system as a proving ground.<ref>{{cite journal |last1=Labelle |first1=P. |last2=Zebarjad |first2=S.M. |last3=Burgess |first3=C.P. |year=1997 |title=Nonrelativistic QED and next-to-leading hyperfine splitting in positronium |journal=Physical Review D |volume=56 |issue=12 |pages=8053–8061 |bibcode=1997PhRvD..56.8053L |arxiv=hep-ph/9706449 |doi=10.1103/PhysRevD.56.8053 |s2cid=6258393 }}</ref>


[[Pionium]], a bound state of two oppositely-charged [[pion]]s, is interesting for exploring the [[strong interaction]]. This should also be true of [[protonium]]. The true analogs of positronium in the theory of strong interactions are the [[quarkonium]] states: they are [[meson]]s made of a heavy quark and antiquark (namely, charmonium and bottomonium). Exploration of these states through non-relativistic [[quantum chromodynamics]] (NRQCD) and [[lattice QCD]] are increasingly important tests of [[quantum chromodynamics]].
[[Pionium]], a bound state of two oppositely-charged [[pion]]s, is interesting for exploring the [[strong interaction]]. This should also be true of [[protonium]]. The true analogs of positronium in the theory of strong interactions are the [[quarkonium]] states: they are [[meson]]s made of a heavy quark and antiquark (namely, charmonium and bottomonium). Exploration of these states through [[non-relativistic quantum chromodynamics]] (NRQCD) and [[lattice QCD]] are increasingly important tests of [[quantum chromodynamics]].


Understanding bound states of [[hadron]]s such as [[pionium]] and [[protonium]] is also important in order to clarify notions related to [[exotic hadron]]s such as [[mesonic molecule]]s and [[pentaquark]] states.
Understanding bound states of [[hadron]]s such as [[pionium]] and [[protonium]] is also important in order to clarify notions related to [[exotic hadron]]s such as [[mesonic molecule]]s and [[pentaquark]] states.

Latest revision as of 20:22, 20 December 2024

Not to be confused with onium ions such as ammonium.
Antimatter
A Feynman diagram showing the annihilation of an electron and a positron (antielectron), creating a photon that later decays into an new electron–positron pair.
Antiparticles

Onia

Concepts and phenomena
Devices
Uses
Scientists
An illustration of the protonium atom.

An onium (plural: onia) is a bound state of a particle and its antiparticle.[1] These states are usually named by adding the suffix -onium to the name of one of the constituent particles (replacing an -on suffix when present), with one exception for "muonium"; a muon–antimuon bound pair is called "true muonium" to avoid confusion with old nomenclature.[a]

Examples

[edit]

Positronium is an onium which consists of an electron and a positron bound together as a long-lived metastable state. Positronium has been studied since the 1950s to understand bound states in quantum field theory. A recent development called non-relativistic quantum electrodynamics (NRQED) used this system as a proving ground.[2]

Pionium, a bound state of two oppositely-charged pions, is interesting for exploring the strong interaction. This should also be true of protonium. The true analogs of positronium in the theory of strong interactions are the quarkonium states: they are mesons made of a heavy quark and antiquark (namely, charmonium and bottomonium). Exploration of these states through non-relativistic quantum chromodynamics (NRQCD) and lattice QCD are increasingly important tests of quantum chromodynamics.

Understanding bound states of hadrons such as pionium and protonium is also important in order to clarify notions related to exotic hadrons such as mesonic molecules and pentaquark states.

See also

[edit]
Look up onium in Wiktionary, the free dictionary.

Footnotes

[edit]
  1. ^ "Muonium" is the name assigned by IUPAC to an electron–antimuon bound state before the current convention became popular. So, despite its name, muonium is not a bound muon–antimuon onium. A muon–antimuon bound state is called "true muonium" to reduce confusion.

References

[edit]
  1. ^ Walker, D.C. (1983). Muon and Muonium Chemistry. Cambridge University Press. p. 5. ISBN 978-0-521-24241-7. Retrieved 23 June 2020.
  2. ^ Labelle, P.; Zebarjad, S.M.; Burgess, C.P. (1997). "Nonrelativistic QED and next-to-leading hyperfine splitting in positronium". Physical Review D. 56 (12): 8053–8061. arXiv:hep-ph/9706449. Bibcode:1997PhRvD..56.8053L. doi:10.1103/PhysRevD.56.8053. S2CID 6258393.
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