Editing Nuclear fusion (section)

=== Theory ===
[[File:EffetTunnel.gif|thumb|Animation of an electron's wave function as [[quantum tunneling]] allows transit through a barrier with a low probability. In the same fashion, an atomic nucleus can quantum tunnel through the [[Coulomb barrier]] to another nucleus, making a fusion reaction possible.]]
American chemist [[William Draper Harkins]] was the first to propose the concept of nuclear fusion in 1915.<ref name=":0">
{{cite journal
|author=Robert S. Mulliken
|author-link=Robert S. Mulliken
|year=1975
|url=http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/harkins-william-d.pdf
|title=William Draper Harkins 1873–1951
|journal=Biographical Memoirs
|volume=46
|pages=47–80
|publisher=National Academy of Sciences
|access-date=23 August 2023
|archive-date=10 May 2017
|archive-url=https://web.archive.org/web/20170510115525/http://www.nasonline.org/publications/biographical-memoirs/memoir-pdfs/harkins-william-d.pdf
|url-status=live
}}</ref> [[Francis William Aston]]'s 1919 invention of the [[mass spectrometer]] allowed the discovery that four hydrogen atoms are heavier than one helium atom. Thus in 1920, [[Arthur Eddington]] correctly predicted fusion of hydrogen into helium could be the primary source of stellar energy.<ref>{{cite journal |last1=Eddington |first1=A.S. |title=The internal constitution of the stars |journal=Nature |date=2 September 1920 |volume=106 |issue=2653 |pages=14–20 |doi=10.1038/106014a0 |bibcode=1920Natur.106...14E |s2cid=36422819 |url=https://zenodo.org/record/1429642 |doi-access=free |access-date=25 March 2020 |archive-date=17 July 2022 |archive-url=https://web.archive.org/web/20220717115105/https://zenodo.org/record/1429642 |url-status=live }} 
*Reprinted in: {{cite journal |last1=Eddington |first1=A.S. |title=The internal constitution of the stars |journal=The Scientific Monthly |date=October 1920 |volume=11 |issue=4 |pages=297–303 |bibcode=1920SciMo..11..297E |url=https://babel.hathitrust.org/cgi/pt?id=hvd.32044102928264&view=1up&seq=313&skin=2021 |access-date=17 August 2022 |archive-date=17 August 2022 |archive-url=https://web.archive.org/web/20220817051553/https://babel.hathitrust.org/cgi/pt?id=hvd.32044102928264&view=1up&seq=313&skin=2021 |url-status=live }}
*Reprinted in: {{cite journal |last1=Eddington |first1=A.S. |title=The internal constitution of the stars |journal=The Observatory |date=October 1920 |volume=43 |issue=557 |pages=341–358 |bibcode=1920Obs....43..341E |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015011432153&view=1up&seq=347&skin=2021 |access-date=17 August 2022 |archive-date=17 August 2022 |archive-url=https://web.archive.org/web/20220817060446/https://babel.hathitrust.org/cgi/pt?id=mdp.39015011432153&view=1up&seq=347&skin=2021 |url-status=live }}</ref> 

[[Quantum tunneling]] was discovered by [[Friedrich Hund]] in 1927, with relation to electron levels.<ref>{{cite journal |last1=Hund |first1=F. |title=Zur Deutung der Molekelspektren. I. |journal=Zeitschrift für Physik |date=October 1927 |volume=40 |issue=10 |pages=742–764 |doi=10.1007/BF01400234 |bibcode=1927ZPhy...40..742H |s2cid=186239503 |trans-title=On the explanation of molecular spectra I. |language=German}}</ref><ref>Tunnelling was independently observed by Soviet scientists [[Grigory Samuilovich Landsberg]] and [[Leonid Isaakovich Mandelstam]]. See: 
*{{cite journal |last1=Ландсберг |first1=Г.С. |last2=Мандельштам |first2=Л.И. |title=Новое явление в рассеянии света (предварительный отчет) |journal=Журнал Русского физико-химического общества, Раздел физики [Journal of the Russian Physico-Chemical Society, Physics Section] |year=1928 |volume=60 |page=335 |trans-title=A new phenomenon in the scattering of light (preliminary report) |language=Russian}}
*{{cite journal |last1=Landsberg |first1=G. |last2=Mandelstam |first2=L. |title=Eine neue Erscheinung bei der Lichtzerstreuung in Krystallen |journal=Die Naturwissenschaften |year=1928 |volume=16 |issue=28 |pages=557–558 |doi=10.1007/BF01506807 |bibcode=1928NW.....16..557. |s2cid=22492141 |trans-title=A new phenomenon in the case of the scattering of light in crystals |language=German}}
*{{cite journal |last1=Landsberg |first1=G.S. |last2=Mandelstam |first2=L.I. |title=Über die Lichtzerstreuung in Kristallen |journal=Zeitschrift für Physik |year=1928 |volume=50 |issue=11–12 |pages=769–780 |doi=10.1007/BF01339412 |bibcode=1928ZPhy...50..769L |s2cid=119357805 |trans-title=On the scattering of light in crystals |language=German}}</ref> In 1928, [[George Gamow]] was the first to apply tunneling to the nucleus, first to [[alpha decay]], then to fusion as an inverse process. From this, in 1929, [[Robert d'Escourt Atkinson|Robert Atkinson]] and [[Fritz Houtermans]] made the first estimates for stellar fusion rates.<ref>{{Cite journal |last1=Abu-Shawareb |first1=H. |last2=Acree |first2=R. |last3=Adams |first3=P. |last4=Adams |first4=J. |last5=Addis |first5=B. |last6=Aden |first6=R. |last7=Adrian |first7=P. |last8=Afeyan |first8=B. B. |last9=Aggleton |first9=M. |last10=Aghaian |first10=L. |last11=Aguirre |first11=A. |last12=Aikens |first12=D. |last13=Akre |first13=J. |last14=Albert |first14=F. |last15=Albrecht |first15=M. |date=2024-02-05 |title=Achievement of Target Gain Larger than Unity in an Inertial Fusion Experiment |url=https://link.aps.org/doi/10.1103/PhysRevLett.132.065102 |journal=Physical Review Letters |language=en |volume=132 |issue=6 |page=065102 |doi=10.1103/PhysRevLett.132.065102 |pmid=38394591 |bibcode=2024PhRvL.132f5102A |issn=0031-9007}}</ref><ref>{{cite journal |last1=Atkinson |first1=R. d'E. |last2=Houtermans |first2=F. G. |title=Zur Frage der Aufbaumöglichkeit der Elemente in Sternen |journal=Zeitschrift für Physik |year=1929 |volume=54 |issue=9–10 |pages=656–665 |doi=10.1007/BF01341595 |bibcode=1929ZPhy...54..656A |s2cid=123658609 |trans-title=On the question of the possibility of forming elements in stars |language=German}}</ref>  

In 1938, [[Hans Bethe]] worked with [[Charles Critchfield]] to enumerate the [[proton–proton chain]] that dominates Sun-type stars. In 1939, Bethe published the discovery of the [[CNO cycle]] common to higher-mass stars.