Editing Positronium (section)

== History ==

[[File:Positronium Beam.jpg|thumb|upright=1.4|The Positronium Beam at [[University College London]], a lab used to study the properties of positronium.<ref>{{Cite journal|last1=N.|first1=Zafar|last2=G.|first2=Laricchia|last3=M.|first3=Charlton|last4=T.C.|first4=Griffith|date=1991|title=Diagnostics of a positronium beam|url=https://inis.iaea.org/search/search.aspx?orig_q=RN:23020661|journal=Journal of Physics B|language=en|volume=24|issue=21|page=4661|doi=10.1088/0953-4075/24/21/016|bibcode=1991JPhB...24.4661Z|s2cid=250896764 |issn=0953-4075}}</ref>]]

The Croatian physicist [[Stjepan Mohorovičić]] predicted the existence of positronium in a 1934 article published in ''[[Astronomische Nachrichten]]'', in which he called it the "electrum".<ref>
{{cite journal
 |last=Mohorovičić |first=S.
 |date=1934
 |journal=[[Astronomische Nachrichten]]
 |volume=253 |pages=93–108
 |doi=10.1002/asna.19342530402
 |title=Möglichkeit neuer Elemente und ihre Bedeutung für die Astrophysik
 |issue=4
|bibcode = 1934AN....253...93M }}</ref> Other sources incorrectly credit [[Carl David Anderson|Carl Anderson]] as having predicted its existence in 1932 while at [[Caltech]].<ref name="DeutschObit">
{{cite press release
 |publisher=MIT
 |year=2002
 |title=Martin Deutsch, MIT physicist who discovered positronium, dies at 85
 |url=http://web.mit.edu/newsoffice/2002/deutsch.html
}}</ref> It was experimentally discovered by [[Martin Deutsch]] at [[MIT]] in 1951 and became known as positronium.<ref name="DeutschObit"/>  Many subsequent experiments have precisely measured its properties and verified predictions of quantum electrodynamics. 

A discrepancy known as the ortho-positronium lifetime puzzle persisted for some time, but was resolved with further calculations and measurements.<ref>{{Cite news|url = http://physicsworld.com/cws/article/news/2003/may/28/positronium-puzzle-is-solved|title = Positronium puzzle is solved|last = Dumé |first = Belle|date = May 23, 2003|work = [[Physics World]]}}</ref> Measurements were in error because of the lifetime measurement of unthermalised positronium, which was produced at only a small rate. This had yielded lifetimes that were too long. Also calculations using relativistic quantum electrodynamics are difficult, so they had been done to only the first order.  Corrections that involved higher orders were then calculated in a non-relativistic quantum electrodynamics.<ref name="Kat">{{cite journal|last1=Kataoka|first1=Y.|last2=Asai|first2=S.|last3=Kobayashi|first3=t.|title=First Test of O(α<sup>2</sup>) Correction of the Orthopositronium Decay Rate|journal=Physics Letters B|volume=671|issue=2|pages=219–223|url=https://www.icepp.s.u-tokyo.ac.jp/papers/ps/icepp-report/ut-icepp-08-09.pdf|year=2009|bibcode=2009PhLB..671..219K|arxiv=0809.1594|doi=10.1016/j.physletb.2008.12.008}}</ref>

In 2024, the [[AEgIS experiment|AEgIS]] collaboration at [[CERN]] was the first to cool positronium by laser light, leaving it available for experimental use. The substance was brought to {{Convert|-100|C}} using [[laser cooling]].<ref>
{{cite journal
 |last=Glöggler |first=L. T.
 |date=2024
 |journal=[[Physical Review Letters]]
 |volume=132 |pages=083402 
 |doi=10.1103/PhysRevLett.132.083402
 |title=Positronium Laser Cooling via the 13S−23P Transition with a Broadband Laser Pulse
 |issue=8
 |pmid=38457696
 |bibcode = |doi-access=free
 |hdl=11311/1261341
 |hdl-access=free
 }}</ref><ref>{{Cite news |last=Ghosh |first=Pallab |date=2024-02-22 |title=Antimatter: Scientists freeze positronium atoms with lasers |url=https://www.bbc.com/news/science-environment-68349448 |access-date=2024-02-23 |work=[[BBC]] |language=en-GB}}</ref>