Editing Helium (section)

==History==

===Scientific discoveries===
The first evidence of helium was observed on August 18, 1868, as a bright yellow line with a [[wavelength]] of 587.49 nanometers in the [[Emission spectrum|spectrum]] of the [[chromosphere]] of the [[Sun]]. The line was detected by French astronomer [[Pierre Janssen|Jules Janssen]] during [[Solar eclipse of August 18, 1868|a total solar eclipse]] in [[Guntur]], India.<ref name="frnch">{{Cite journal|title = French astronomers in India during the 17th&nbsp;– 19th centuries |journal = Journal of the British Astronomical Association|volume =101|issue = 2|pages = 95–100|bibcode = 1991JBAA..101...95K|author = Kochhar, R. K.|date=1991}}</ref><ref name="nbb" /> This line was initially assumed to be [[sodium]]. On October 20 of the same year, English astronomer [[Norman Lockyer]] observed a yellow line in the solar spectrum, which he named the D<sub>3</sub> because it was near the known D<sub>1</sub> and D<sub>2</sub> [[Fraunhofer line]]s of sodium.<ref name="Lockyer 1868">{{cite journal |last1=Lockyer |first1=J. N. |title=Notice of an observation of the spectrum of a solar prominence |journal= Proceedings of the Royal Society of London |volume=17 |date=October 1868 |pages=91–92 |url= https://babel.hathitrust.org/cgi/pt?id=hvd.32044106279359;view=1up;seq=109 |jstor=112357 |access-date=3 June 2018 |bibcode=1868RSPS...17...91L |doi=10.1098/rspl.1868.0011|s2cid=163097539 }}</ref><ref name="enc">{{Cite book|title= The Encyclopedia of the Chemical Elements |pages =256–268 |first = Clifford A. |last=Hampel |location=New York |isbn = 978-0-442-15598-8 |date = 1968 |publisher =Van Nostrand Reinhold}}</ref> He concluded that it was caused by an element in the Sun unknown on Earth. Lockyer named the element with the Greek word for the Sun, ἥλιος (''[[helios]]'').<ref>{{OEtymD|helium}}</ref><ref>{{Cite journal |last=Thomson |first=William |date=August 3, 1871 |volume=4 |pages=261–278 [268] |doi=10.1038/004261a0 |title=Inaugural Address of Sir William Thomson |journal=Nature |url=https://books.google.com/books?id=IogCAAAAIAAJ&pg=PA268 |quote=Frankland and Lockyer find the yellow prominences to give a very decided bright line not far from D, but hitherto not identified with any terrestrial flame. It seems to indicate a new substance, which they propose to call Helium |bibcode=1871Natur...4..261. |issue=92 |pmc=2070380 |access-date=February 22, 2016 |archive-url=https://web.archive.org/web/20161202011154/https://books.google.com/books?id=IogCAAAAIAAJ&pg=PA268 |archive-date=December 2, 2016 |url-status=live }}</ref> It is sometimes said that English chemist [[Edward Frankland]] was also involved in the naming, but this is unlikely as he doubted the existence of this new element. The ending "-ium" is unusual, as it normally applies only to metallic elements; probably Lockyer, being an astronomer, was unaware of the chemical conventions.<ref name=jensen>{{Cite journal |last=Jensen |first=William B. |date=2004 |volume=81 |issue=7 |page=944 |doi=10.1021/ed081p944 |title=Why Helium ends in "-ium" |journal=Journal of Chemical Education|bibcode=2004JChEd..81..944J }}</ref>
[[File:Helium spectrum.jpg|left|thumb|Spectral lines of helium|alt=Picture of visible spectrum with superimposed sharp yellow and blue and violet lines]]
In 1881, Italian physicist [[Luigi Palmieri]] detected helium on Earth for the first time through its D<sub>3</sub> spectral line, when he analyzed a material that had been [[Sublimation (phase transition)|sublimated]] during a recent eruption of [[Mount Vesuvius]].<ref name="Palmieri 1881">{{cite journal |last1=Palmieri |first1=Luigi |title=La riga dell'Helium apparsa in una recente sublimazione vesuviana |trans-title=The line of helium appeared in a recently sublimated material [from Mt.] Vesuvius. |journal=Rendiconto dell'Accademia delle Scienze Fisiche e Matematiche (Naples, Italy) |volume=20 |date=1881 |page=223 |url=https://babel.hathitrust.org/cgi/pt?id=hvd.hnl7mr;view=1up;seq=251 |access-date=1 May 2017 |quote= ''Raccolsi alcun tempo fa una sostanza amorfa di consistenza butirracea e di colore giallo sbiadato sublimata sull'orlo di una fumarola prossima alla bocca di eruzione. Saggiata questa sublimazione allo spettroscopio, ho ravvisato le righe del sodio e del potassio ed una lineare ben distinta che corrisponde esattamente alla D<sub>3</sub> che è quella dell'Helium. Do per ora il semplice annunzio del fatto, proponendomi di ritornare sopra questo argomento, dopo di aver sottoposta la sublimazione ad una analisi chimica.'' (I collected some time ago an amorphous substance having a buttery consistency and a faded yellow color which had sublimated on the rim of a fumarole near the mouth of the eruption. Having analyzed this sublimated substance with a spectroscope, I recognized the lines of sodium and potassium and a very distinct linear line which corresponds exactly to D<sub>3</sub>, which is that of helium. For the present, I'm making a mere announcement of the fact, proposing to return to this subject after having subjected the sublimate to a chemical analysis.) |archive-url= https://web.archive.org/web/20180901111504/https://babel.hathitrust.org/cgi/pt?id=hvd.hnl7mr;view=1up;seq=251 |archive-date=1 September 2018 |url-status=live }}</ref>

[[File:William Ramsay working.jpg|thumb|upright|Sir [[William Ramsay]], the discoverer of terrestrial helium]]
[[File:Clevite sample (35321726345).jpg|thumb|upright|The cleveite sample from which Ramsay first purified helium<ref name="Kirk">{{cite web| last1=Kirk|first1=Wendy L.| title= Cleveite [not Clevite] and helium| url=https://blogs.ucl.ac.uk/museums/2013/01/11/cleveite-and-helium-not-clevite/| website=Museums & Collections Blog| publisher=[[University College London]]| access-date=18 August 2017|archive-url= https://web.archive.org/web/20181018054313/http://blogs.ucl.ac.uk/museums/2013/01/11/cleveite-and-helium-not-clevite/| archive-date=18 October 2018|url-status= live}}</ref>]]
On March 26, 1895, Scottish chemist [[William Ramsay|Sir William Ramsay]] isolated helium on Earth by treating the mineral cleveite (a variety of uraninite with at least 10% [[rare-earth elements]]) with mineral [[acid]]s. Ramsay was looking for [[argon]] but, after separating [[nitrogen]] and [[oxygen]] from the gas, liberated by [[sulfuric acid]], he noticed a bright yellow line that matched the D<sub>3</sub> line observed in the spectrum of the Sun.<ref name="enc" /><ref>{{Cite journal|title = On a Gas Showing the Spectrum of Helium, the Reputed Cause of D<sub>3</sub>, One of the Lines in the Coronal Spectrum. Preliminary Note| last = Ramsay | first= William|author-link = William Ramsay| journal = Proceedings of the Royal Society of London|volume = 58|issue = 347–352|pages = 65–67| date = 1895|doi = 10.1098/rspl.1895.0006| bibcode = 1895RSPS...58...65R| s2cid = 129872109| url = https://zenodo.org/record/1432083|doi-access = free}}</ref><ref>{{Cite journal| title = Helium, a Gaseous Constituent of Certain Minerals. Part I|last = Ramsay | first= William|journal = Proceedings of the Royal Society of London|volume = 58| issue = 347–352|pages = 81–89|date = 1895 |doi = 10.1098/rspl.1895.0010| bibcode = 1895RSPS...58...80R|doi-access = free}}</ref><ref>{{Cite journal |title = Helium, a Gaseous Constituent of Certain Minerals. Part II – Density|last = Ramsay | first= William| journal = Proceedings of the Royal Society of London|volume = 59|issue = 1|pages = 325–330|date = 1895 |doi = 10.1098/rspl.1895.0097|bibcode = 1895RSPS...59..325R|s2cid = 96589261}}</ref> These samples were identified as helium by Lockyer and British physicist [[William Crookes]].<ref>{{Cite journal|title = On the new gas obtained from uraninite. Preliminary note, part II|author = Lockyer, J. Norman|author-link = Norman Lockyer| journal = Proceedings of the Royal Society of London|volume = 58|issue = 347–352| pages = 67–70|date = 1895|doi = 10.1098/rspl.1895.0008|doi-access = free}}</ref><ref>See:
* {{cite journal| last= Crookes| first= William | year= 1895 | url= https://books.google.com/books?id=YCLOAAAAMAAJ&pg=PA151 | title= The spectrum of the gas from clèveite | journal= The Chemical News and Journal of Physical Science| volume= 71 | number= 1844 | page= 151}}
*  {{cite journal| last= Crookes| first= William | year= 1895 | url= https://books.google.com/books?id=lSLOAAAAMAAJ&pg=PA87 | title= The spectrum of helium | journal= The Chemical News and Journal of Physical Science | volume= 72 | number= 1865 | pages=87–89}}</ref> It was independently isolated from cleveite in the same year by chemists [[Per Teodor Cleve]] and [[Abraham Langlet]] in [[Uppsala]], Sweden, who collected enough of the gas to accurately determine its [[atomic weight]].<ref>See:
*  {{cite journal |last1=Clève |first1=P.T. |title=Sur la présence de l'hélium dans le clévéite |journal=Comptes rendus hebdomadaires des séances de l'Académie des sciences |date=1895 |volume=120 |page=834 |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015035451122&view=1up&seq=844&skin=2021 |trans-title=On the presence of helium in cleveite |language=French}}
*  English translation:  {{cite journal |last1=Clève |first1=P.T. |title=On the presence of helium in clèveite |journal=The Chemical News and Journal of Physical Science |date=1895 |volume=71 |issue=1849 |page=212 |url=https://babel.hathitrust.org/cgi/pt?id=hvd.32044048675458&view=1up&seq=272&skin=2021}}
*  {{cite journal |last1=Thorpe |first1=T. E. |title=Terrestrial helium? |journal=Nature |date=1895 |volume=51 |issue=1329 |page=586 |url=https://babel.hathitrust.org/cgi/pt?id=uc1.31210011061270&view=1up&seq=632&skin=2021}}
*  {{cite journal |last1=Clève |title=Sur la densité de l'hélium |journal=Comptes rendus hebdomadaires des séances de l'Académie des sciences |date=1895 |volume=120 |page=1212 |url=https://babel.hathitrust.org/cgi/pt?id=mdp.39015035451122&view=1up&seq=1226&skin=2021 |trans-title=On the density of helium |language=French}}</ref><ref>{{Cite journal|title = Das Atomgewicht des Heliums|trans-title = The atomic weight of helium|author = Langlet, N. A.|journal = Zeitschrift für Anorganische Chemie|volume = 10|issue = 1| pages = 289–292|date = 1895|url=https://books.google.com/books?id=sHcWAAAAIAAJ&pg=PA289|doi =10.1002/zaac.18950100130|language= de}}</ref><ref name="nbb" /><ref>{{cite book |last1=Weaver |first1=E.R. |title=Circular of the Bureau of Standards No. 81: Bibliography of Scientific Literature Relating to Helium |date=1919 |page=6 |publisher=U.S. Government Printing Office |location=Washington, D.C., USA |url=https://nvlpubs.nist.gov/nistpubs/Legacy/circ/nbscircular81.pdf}}</ref> Helium was also isolated by American geochemist [[William Francis Hillebrand]] prior to Ramsay's discovery, when he noticed unusual spectral lines while testing a sample of the mineral uraninite. Hillebrand, however, attributed the lines to [[nitrogen]].<ref>Hillebrand (1890) [https://babel.hathitrust.org/cgi/pt?id=uc1.b2968310&view=1up&seq=511 "On the occurrence of nitrogen in uraninite and on the composition of uraninite in general,"] ''Bulletin of the U.S. Geological Survey'', no. 78, pp. 43–79.</ref> His letter of congratulations to Ramsay offers an interesting case of discovery, and near-discovery, in science.<ref>{{Cite book|last=Munday|first=Pat|author-link=Pat Munday|date=1999|title=Biographical entry for W.F. Hillebrand (1853–1925), geochemist and U.S. Bureau of Standards administrator in American National Biography|editor=John A. Garraty|editor2=Mark C. Carnes|volume=10–11|publisher=Oxford University Press|pages= 808–9; 227–8|title-link=American National Biography}}</ref>

In 1907, [[Ernest Rutherford]] and [[Thomas Royds]] demonstrated that [[alpha particle]]s are helium [[atomic nucleus|nuclei]] by allowing the particles to penetrate the thin glass wall of an [[evacuated tube]], then creating a discharge in the tube, to study the spectrum of the new gas inside.<ref>{{Cite journal| doi = 10.1080/14786440808636511| title = XXIV.Spectrum of the radium emanation| journal = Philosophical Magazine| series = series 6| volume = 16| issue = 92| pages = 313–317| year = 1908| last1 = Rutherford| first1 = E.| last2 = Royds| first2 = T.| url = https://babel.hathitrust.org/cgi/pt?id=umn.31951000614205r;view=1up;seq=349}}</ref> In 1908, helium was first liquefied by Dutch physicist [[Heike Kamerlingh Onnes]] by cooling the gas to less than {{convert|5|K|C F}}.<ref>Onnes, H. Kamerlingh (1908) [https://web.archive.org/web/20180809111624/https://babel.hathitrust.org/cgi/pt?id=uva.x002433831;view=1up;seq=309 "The liquefaction of helium,"] ''Communications from the Physical Laboratory at the University of Leiden'', '''9''' (108) : 1–23.</ref><ref>{{Cite journal|title = Little cup of Helium, big Science |author = van Delft, Dirk |journal = Physics Today |url = http://www-lorentz.leidenuniv.nl/history/cold/VanDelftHKO_PT.pdf |pages = 36–42 |date = 2008 |access-date = 2008-07-20|archive-url = https://web.archive.org/web/20080625064354/http://www-lorentz.leidenuniv.nl/history/cold/VanDelftHKO_PT.pdf |archive-date = June 25, 2008|url-status=dead|bibcode = 2008PhT....61c..36V|volume = 61|doi = 10.1063/1.2897948|issue = 3}}</ref> He tried to solidify it by further reducing the temperature but failed, because helium does not solidify at atmospheric pressure. Onnes' student [[Willem Hendrik Keesom]] was eventually able to solidify 1&nbsp;cm<sup>3</sup> of helium in 1926 by applying additional external pressure.<ref>See:
* Preliminary notice: Keesom, W. H. (17 July 1926) Letters to the Editor: "Solidification of helium," ''Nature'', '''118''' : 81.
* Preliminary notice: Keesom, W. H. (1926) [https://archive.org/stream/ComptesRendusAcademieDesSciences0183/ComptesRendusAcadmieDesSciences-Tome183-Juillet-dcembre1926#page/n25/mode/2up "L'hélium solidifié,"] {{Webarchive|url=https://web.archive.org/web/20161022075647/https://archive.org/stream/ComptesRendusAcademieDesSciences0183/ComptesRendusAcadmieDesSciences-Tome183-Juillet-dcembre1926#page/n25/mode/2up |date=2016-10-22 }} ''Comptes rendus'' ... , '''183''' : 26.
* Keesom, W. H. (1926) "Solid Helium," ''Communications from the Physical Laboratory at the University of Leiden'', '''17''' (184) .</ref><ref>{{Cite news| title = Coldest Cold| publisher = Time Inc.| date = 1929-06-10| url = http://www.time.com/time/magazine/article/0,9171,751945,00.html| access-date = 2008-07-27| archive-url = https://web.archive.org/web/20081206015739/http://www.time.com/time/magazine/article/0,9171,751945,00.html| archive-date = 2008-12-06| url-status = dead}}</ref>

In 1913, [[Niels Bohr]] published his "trilogy"<ref name = Hoyer>{{cite book|first = Ulrich|last = Hoyer|chapter = Constitution of Atoms and Molecules|pages = 103–316 (esp. pp. 116–122)|title = Niels Bohr – Collected Works: Volume 2 – Work on Atomic Physics (1912–1917)|chapter-url = https://books.google.com/books?id=zGczmJjSO6kC&pg=PA117|editor-first = Ulrich|editor-last = Hoyer|publisher = [[North Holland Publishing Company]]|location = Amsterdam|year = 1981|isbn = 978-0720418002}}</ref><ref>{{cite book|last = Kennedy|first = P. J.|year = 1985|chapter = A Short Biography|editor1-last = French|editor1-first = A. P.|editor2-last = Kennedy|editor2-first = P. J.|title = Niels Bohr: A Centenary Volume|pages = 3–15|publisher = [[Harvard University Press]]|isbn = 978-0-674-62415-3|chapter-url-access = registration|chapter-url = https://archive.org/details/nielsbohrcentena00bohr}}</ref> on atomic structure that included a reconsideration of the [[Pickering–Fowler series]] as central evidence in support of his [[Bohr model|model of the atom]].<ref>{{cite journal|last = Bohr|first = N.|author-link = Niels Bohr|year = 1913|title = On the constitution of atoms and molecules, part I|journal = [[Philosophical Magazine]]|volume = 26|issue = 151|pages = 1–25|doi = 10.1080/14786441308634955|url = http://web.ihep.su/dbserv/compas/src/bohr13/eng.pdf|access-date = 2017-12-27|archive-url = https://web.archive.org/web/20190404184145/http://web.ihep.su/dbserv/compas/src/bohr13/eng.pdf|archive-date = 2019-04-04|url-status = live|bibcode = 1913PMag...26....1B}}<br />{{cite journal|last = Bohr|first = N.|author-link = Niels Bohr|year = 1913|title = On the constitution of atoms and molecules, part II: Systems Containing Only a Single Nucleus|journal = [[Philosophical Magazine]]|volume = 26|issue = 153|pages = 476–502|url = http://web.ihep.su/dbserv/compas/src/bohr13b/eng.pdf|doi = 10.1080/14786441308634993|access-date = 2017-12-27|archive-url = https://web.archive.org/web/20171215041355/http://web.ihep.su/dbserv/compas/src/bohr13b/eng.pdf|archive-date = 2017-12-15|url-status = live|bibcode = 1913PMag...26..476B}}<br />{{cite journal|last = Bohr|first = N.|author-link = Niels Bohr|year = 1913|title = On the constitution of atoms and molecules, part III: Systems containing several nuclei|journal = [[Philosophical Magazine]]|volume = 26|issue = 155|pages = 857–875|doi = 10.1080/14786441308635031|url = https://zenodo.org/record/1430922|bibcode = 1913PMag...26..857B}}</ref><ref name = Robotti>{{cite journal|title = The Spectrum of ζ Puppis and the Historical Evolution of Empirical Data|first = Nadia|last = Robotti|author-link=Nadia Robotti|journal = [[Historical Studies in the Physical Sciences]]|volume = 14|issue = 1|year = 1983|pages = 123–145|doi = 10.2307/27757527|jstor = 27757527}}</ref> This series is named for [[Edward Charles Pickering]], who in 1896 published observations of previously unknown lines in the spectrum of the star [[Zeta Puppis|ζ Puppis]]<ref>{{cite journal|last = Pickering|first = E. C.|author-link = Edward Charles Pickering|journal = [[Harvard College Observatory Circular]]|volume = 12|title = Stars having peculiar spectra. New variable stars in Crux and Cygnus|pages = 1–2|year = 1896|bibcode = 1896HarCi..12....1P}} Also published as: {{cite journal|title = Stars having peculiar spectra. New variable stars in Crux and Cygnus|last1 = Pickering|first1 = E. C.|author-link = Edward Charles Pickering|last2 = Fleming|first2 = W. P.|author-link2 = Williamina Fleming|journal = [[Astrophysical Journal]]|volume = 4|pages = 369–370|year = 1896|doi = 10.1086/140291|bibcode = 1896ApJ.....4..369P|doi-access = free}}</ref> (these are now known to occur with [[Wolf-Rayet star|Wolf–Rayet]] and other hot stars).<ref>{{cite journal|title = The relation between the Wolf–Rayet stars and the planetary nebulae|first = W. H.|last = Wright|journal = [[Astrophysical Journal]]|volume = 40|pages = 466–472|year = 1914|doi = 10.1086/142138|bibcode = 1914ApJ....40..466W|doi-access = free}}</ref> Pickering attributed the observation (lines at 4551, 5411, and 10123&nbsp;[[Ångström|Å]]) to a new form of hydrogen with half-integer transition levels.<ref>{{cite journal|title = Stars having peculiar spectra. New variable Stars in Crux and Cygnus|first = E. C.|last = Pickering|author-link = Edward Charles Pickering|year = 1897|journal = [[Astronomische Nachrichten]]|volume = 142|issue = 6|pages = 87–90|doi = 10.1002/asna.18971420605|bibcode = 1896AN....142...87P|url = https://zenodo.org/record/1424755|access-date = 2019-08-24|archive-url = https://web.archive.org/web/20190824143848/https://zenodo.org/record/1424755/files/article.pdf|archive-date = 2019-08-24|url-status = live}}</ref><ref>{{cite journal|title = The spectrum of zeta Puppis|last = Pickering|first = E. C.|author-link = Edward Charles Pickering|year = 1897|journal = [[Astrophysical Journal]]|volume = 5|pages = 92–94|doi = 10.1086/140312|bibcode = 1897ApJ.....5...92P|doi-access = free}}</ref> In 1912, [[Alfred Fowler]]<ref>{{cite book|title = The Methodology of Scientific Research Programmes|first = Imre|last = Lakatos|author-link = Imre Lakatos|publisher = [[Cambridge University Press]]|year = 1980|isbn = 9780521280310|editor1-first = John|editor1-last = Worrall|editor2-first = Gregory|editor2-last = Currie|chapter-url = https://books.google.com/books?id=RRniFBI8Gi4C&pg=PA62|chapter = Bohr: A Research Programme Progressing on Inconsistent Foundations|pages = 55–68}}</ref> managed to produce similar lines from a hydrogen-helium mixture, and supported Pickering's conclusion as to their origin.<ref>{{cite journal|title = Observations of the Principal and other Series of Lines in the Spectrum of Hydrogen|first = A.|last = Fowler|author-link = Alfred Fowler|journal = [[Monthly Notices of the Royal Astronomical Society]]|volume = 73|issue = 2|year = 1912|pages = 62–63|doi = 10.1093/mnras/73.2.62|bibcode = 1912MNRAS..73...62F|doi-access = free}}</ref> Bohr's model does not allow for half-integer transitions (nor does quantum mechanics) and Bohr concluded that Pickering and Fowler were wrong, and instead assigned these spectral lines to ionised helium, He<sup>+</sup>.<ref>{{cite journal|title = The Spectra of Helium and Hydrogen|first = N.|last = Bohr|author-link = Niels Bohr|journal = [[Nature (journal)|Nature]]|volume = 92|issue = 2295|year = 1913|pages = 231–232|doi = 10.1038/092231d0|bibcode = 1913Natur..92..231B|s2cid = 11988018|url = https://zenodo.org/record/1429570}}</ref> Fowler was initially skeptical<ref>{{cite journal|title = The Spectra of Helium and Hydrogen|first = A.|last = Fowler|author-link = Alfred Fowler|journal = [[Nature (journal)|Nature]]|volume = 92|issue = 2291|year = 1913|pages = 95–96|doi = 10.1038/092095b0|bibcode = 1913Natur..92...95F|s2cid = 3972599|url = https://zenodo.org/record/1429568}}</ref> but was ultimately convinced<ref>{{cite journal|title = Reply to: The Spectra of Helium and Hydrogen|first = A.|last = Fowler|author-link = Alfred Fowler|journal = [[Nature (journal)|Nature]]|volume = 92|issue = 2295|year = 1913|pages = 232–233|doi=10.1038/092232a0|bibcode = 1913Natur..92..232F|s2cid = 3981817|url = https://zenodo.org/record/1429568}}</ref> that Bohr was correct,<ref name = Hoyer /> and by 1915 "spectroscopists had transferred [the Pickering–Fowler series] definitively [from hydrogen] to helium."<ref name = Robotti /><ref>{{cite journal|title = The Spectra of Hydrogen and Helium|first = N.|last = Bohr|author-link = Niels Bohr|journal = [[Nature (journal)|Nature]]|volume = 95|issue = 6–7|pages = 6–7|year = 1915|doi = 10.1038/095006a0|bibcode = 1915Natur..95....6B|s2cid = 3947572|url = https://zenodo.org/record/1429597}}</ref> Bohr's theoretical work on the Pickering series had demonstrated the need for "a re-examination of problems that seemed already to have been solved within classical theories" and provided important confirmation for his atomic theory.<ref name = Robotti />

In 1938, Russian physicist [[Pyotr Leonidovich Kapitsa]] discovered that [[helium-4]] has almost no [[viscosity]] at temperatures near [[absolute zero]], a phenomenon now called [[superfluidity]].<ref>{{Cite journal|title = Viscosity of Liquid Helium below the λ-Point |author = Kapitza, P. |author-link = Pyotr Leonidovich Kapitsa |journal =Nature|volume = 141|issue = 3558 |page = 74 |doi = 10.1038/141074a0 |date = 1938|bibcode = 1938Natur.141...74K |s2cid = 3997900 |doi-access = free }}</ref> This phenomenon is related to [[Bose–Einstein condensation]]. In 1972, the same phenomenon was observed in [[helium-3]], but at temperatures much closer to absolute zero, by American physicists [[Douglas D. Osheroff]], [[David M. Lee]], and [[Robert Coleman Richardson|Robert C. Richardson]]. The phenomenon in helium-3 is thought to be related to pairing of helium-3 [[fermion]]s to make [[boson]]s, in analogy to [[Cooper pairs]] of electrons producing [[superconductivity]].<ref>{{Cite journal|title = Evidence for a New Phase of Solid He<sup>3</sup> |author = Osheroff, D. D. |author2 = Richardson, R. C. |author3 = Lee, D. M. |journal = Phys. Rev. Lett. |volume = 28 |issue = 14 |pages = 885–888 |doi = 10.1103/PhysRevLett.28.885 |date = 1972 |bibcode=1972PhRvL..28..885O|s2cid = 89609083 |doi-access = free }}</ref>

In 1961, Vignos and Fairbank reported the existence of a different phase of solid helium-4, designated the gamma-phase. It exists for a narrow range of pressure between 1.45 and 1.78 K.<ref>{{Cite journal |last1=Vignos |first1=James H. |last2=Fairbank |first2=Henry A. |date=1961-03-15 |title=<nowiki>New Solid Phase in ${\mathrm{He}}^{4}$</nowiki> |url=https://link.aps.org/doi/10.1103/PhysRevLett.6.265 |journal=Physical Review Letters |volume=6 |issue=6 |pages=265–267 |doi=10.1103/PhysRevLett.6.265}}</ref>

===Extraction and use===
{{Globalize|section|date=February 2022|discuss=Talk:Helium#Other history}}
[[File:Kansas Helium Marker.jpg|thumb|Historical marker, denoting a massive helium find near [[Dexter, Kansas]]]]
After an oil drilling operation in 1903 in [[Dexter, Kansas]] produced a gas geyser that would not burn, Kansas state geologist [[Erasmus Haworth]] collected samples of the escaping gas and took them back to the [[University of Kansas]] at Lawrence where, with the help of chemists [[Hamilton Cady]] and David McFarland, he discovered that the gas consisted of, by volume, 72% nitrogen, 15% [[methane]] (a [[combustible]] percentage only with sufficient oxygen), 1% hydrogen, and 12% an unidentifiable gas.<ref name="nbb" /><ref>{{Cite journal|author = McFarland, D. F. |title = Composition of Gas from a Well at Dexter, Kan |volume = 19|pages = 60–62 |date = 1903 |journal = Transactions of the Kansas Academy of Science |doi = 10.2307/3624173|jstor = 3624173}}</ref> With further analysis, Cady and McFarland discovered that 1.84% of the gas sample was helium.<ref>{{cite web | title = Discovery of Helium in Natural Gas at the University of Kansas | website = National Historic Chemical Landmarks | publisher = American Chemical Society | url = http://www.acs.org/content/acs/en/education/whatischemistry/landmarks/heliumnaturalgas.html | access-date = 2014-02-21 | archive-url = https://web.archive.org/web/20140226053732/http://www.acs.org/content/acs/en/education/whatischemistry/landmarks/heliumnaturalgas.html | archive-date = 2014-02-26 | url-status = live }}</ref><ref>{{Cite journal|author = Cady, H. P. |last2=McFarland|first2=D. F.|title = Helium in Natural Gas |journal = Science |volume = 24 |issue = 611|page = 344 |doi = 10.1126/science.24.611.344 |date = 1906 |pmid = 17772798|bibcode = 1906Sci....24..344D |s2cid=27441003 |url=https://zenodo.org/record/1447970}}</ref> This showed that despite its overall rarity on Earth, helium was concentrated in large quantities under the [[American Great Plains]], available for extraction as a byproduct of [[natural gas]].<ref>{{Cite journal|author = Cady, H. P.|author2 = McFarland, D. F.|title = Helium in Kansas Natural Gas |journal = Transactions of the Kansas Academy of Science |volume = 20 |pages = 80–81 |date = 1906|doi = 10.2307/3624645|jstor = 3624645}}</ref>

Following a suggestion by Sir [[Richard Threlfall]], the [[United States Navy]] sponsored three small experimental helium plants during World War I. The goal was to supply [[barrage balloon]]s with the non-flammable, lighter-than-air gas. A total of {{convert|5700|m3|ft3|abbr=on}} of 92% helium was produced in the program even though less than a cubic meter of the gas had previously been obtained.<ref name="enc" /> Some of this gas was used in the world's first helium-filled airship, the U.S. Navy's [[C-class blimp]] C-7, which flew its maiden voyage from [[Hampton Roads, Virginia]], to [[Bolling Field]] in Washington, D.C., on December 1, 1921,<ref>{{Cite book |editor=Emme, Eugene M. comp. |editor-link=Eugene M. Emme |title=Aeronautics and Astronautics: An American Chronology of Science and Technology in the Exploration of Space, 1915–1960 |date=1961 |pages=11–19 |chapter=Aeronautics and Astronautics Chronology, 1920–1924 |chapter-url=http://www.hq.nasa.gov/office/pao/History/Timeline/1920-24.html |publisher=[[NASA]] |location=Washington, D.C. |access-date=2006-10-27 |archive-date=2019-07-14 |archive-url=https://web.archive.org/web/20190714112810/https://www.hq.nasa.gov/office/pao/History/Timeline/1920-24.html |url-status=dead }}</ref> nearly two years before the Navy's first ''rigid'' helium-filled airship, the [[Naval Aircraft Factory]]-built [[USS Shenandoah (ZR-1)|USS ''Shenandoah'']], flew in September 1923.

Although the extraction process using low-temperature [[gas liquefaction]] was not developed in time to be significant during World War I, production continued. Helium was primarily used as a [[lifting gas]] in lighter-than-air craft. During World War II, the demand increased for helium for lifting gas and for shielded arc [[welding]]. The [[helium mass spectrometer]] was also vital in the atomic bomb [[Manhattan Project]].<ref>{{Cite book|chapter=Leak Detection|last=Hilleret|first=N.|publisher=[[CERN]]|title=CERN Accelerator School, vacuum technology: proceedings: Scanticon Conference Centre, Snekersten, Denmark, 28 May&nbsp;– 3 June 1999 |editor=S. Turner |location=Geneva, Switzerland|chapter-url=http://cdsweb.cern.ch/record/455564 |chapter-format=PDF| date=1999 |pages=203–212 |doi=10.5170/CERN-1999-005.203 |quote=At the origin of the helium leak detection method was the Manhattan Project and the unprecedented leak-tightness requirements needed by the uranium enrichment plants. The required sensitivity needed for the leak checking led to the choice of a mass spectrometer designed by Dr. A.O.C. Nier tuned on the helium mass.}}</ref>

The [[government of the United States]] set up the [[National Helium Reserve]] in 1925 at [[Amarillo, Texas]], with the goal of supplying military [[airship]]s in time of war and commercial airships in peacetime.<ref name="enc" /> Because of the [[Helium Act of 1925]], which banned the export of scarce helium on which the US then had a production monopoly, together with the prohibitive cost of the gas, German [[Zeppelin]]s were forced to use hydrogen as lifting gas, which would gain infamy in the [[Hindenburg disaster]]. The helium market after World War II was depressed but the reserve was expanded in the 1950s to ensure a supply of [[liquid helium]] as a coolant to create oxygen/hydrogen [[rocket fuel]] (among other uses) during the [[Space Race]] and [[Cold War]]. Helium use in the United States in 1965 was more than eight times the peak wartime consumption.<ref>{{Cite journal| doi = 10.2307/3627447| author = Williamson, John G.| title = Energy for Kansas| journal = Transactions of the Kansas Academy of Science| volume = 71| issue = 4| pages = 432–438|date =1968| jstor = 3627447}}</ref>

After the Helium Acts Amendments of 1960 (Public Law 86–777), the [[United States Bureau of Mines|U.S. Bureau of Mines]] arranged for five private plants to recover helium from natural gas. For this helium conservation program, the Bureau built a {{convert|425|mi|km|adj=on}} pipeline from [[Bushton, Kansas]], to connect those plants with the government's partially depleted Cliffside gas field near Amarillo, Texas. This helium-nitrogen mixture was injected and stored in the Cliffside gas field until needed, at which time it was further purified.<ref>{{Cite journal|journal = Federal Register|date = 2005-10-06|volume = 70|issue = 193|page = 58464|url = http://edocket.access.gpo.gov/2005/pdf/05-20084.pdf|title = Conservation Helium Sale|access-date = 2008-07-20|archive-url = https://web.archive.org/web/20081031082452/http://edocket.access.gpo.gov/2005/pdf/05-20084.pdf|archive-date = 2008-10-31|url-status = live}}</ref>

By 1995, a billion cubic meters of the gas had been collected and the reserve was US$1.4&nbsp;billion in debt, prompting the [[Congress of the United States]] in 1996 to discontinue the reserve.<ref name="nbb" /><ref name="stwertka">Stwertka, Albert (1998). ''Guide to the Elements: Revised Edition''. New York; Oxford University Press, p. 24. {{ISBN|0-19-512708-0}}</ref> The resulting [[Helium Privatization Act of 1996]]<ref>{{USPL|104|273|Helium Privatization Act of 1996}}</ref> (Public Law 104–273) directed the [[United States Department of the Interior]] to empty the reserve, with sales starting by 2005.<ref>{{Cite book |url = http://www.nap.edu/openbook.php?isbn=0309070384 |title = Executive Summary |publisher = nap.edu |access-date = 2008-07-20 |archive-url = https://web.archive.org/web/20080327004306/http://www.nap.edu/openbook.php?isbn=0309070384 |archive-date = 2008-03-27 |url-status = live |doi = 10.17226/9860 |year = 2000 |isbn = 978-0-309-07038-6 }}</ref>

Helium produced between 1930 and 1945 was about 98.3% pure (2% nitrogen), which was adequate for airships. In 1945, a small amount of 99.9% helium was produced for welding use. By 1949, commercial quantities of Grade A 99.95% helium were available.<ref>{{Cite book|publisher=Bureau of Mines / Minerals yearbook 1949|date=1951|last1=Mullins|first1=P. V.|last2=Goodling|first2=R. M.|title=Helium|pages=599–602|url=http://digicoll.library.wisc.edu/cgi-bin/EcoNatRes/EcoNatRes-idx?type=div&did=ECONATRES.MINYB1949.PVMULLINS&isize=text|access-date=2008-07-20|archive-url=https://web.archive.org/web/20081206011210/http://digicoll.library.wisc.edu/cgi-bin/EcoNatRes/EcoNatRes-idx?type=div&did=ECONATRES.MINYB1949.PVMULLINS&isize=text|archive-date=2008-12-06|url-status=live}}</ref>

For many years, the United States produced more than 90% of commercially usable helium in the world, while extraction plants in Canada, Poland, Russia, and other nations produced the remainder. In the mid-1990s, a new plant in [[Arzew]], Algeria, producing {{convert|17|e6m3|e6ft3|abbr=off}} began operation, with enough production to cover all of Europe's demand. Meanwhile, by 2000, the consumption of helium within the U.S. had risen to more than 15 million kg per year.<ref>{{cite web|url=http://minerals.usgs.gov/ds/2005/140/helium-use.pdf|title=Helium End User Statistic|access-date=2008-07-20|publisher=U.S. Geological Survey|archive-url=https://web.archive.org/web/20080921114913/http://minerals.usgs.gov/ds/2005/140/helium-use.pdf|archive-date=2008-09-21|url-status=live}}</ref> In 2004–2006, additional plants in [[Ras Laffan Industrial City|Ras Laffan]], [[Qatar]], and [[Skikda]], Algeria were built. Algeria quickly became the second leading producer of helium.<ref name="wwsupply">{{Cite journal
 |title=Challenges to the Worldwide Supply of Helium in the Next Decade |last1=Smith|first1=E. M. |last2=Goodwin|first2=T. W. |last3=Schillinger|first3=J. |journal=Advances in Cryogenic Engineering |volume=A |issue=710 |pages=119–138
 |series=49
 |date=2003 |doi=10.1063/1.1774674 |bibcode=2004AIPC..710..119S|s2cid=109060534}}</ref> Through this time, both helium consumption and the costs of producing helium increased.<ref name="Kaplan2007">{{cite journal
 |last=Kaplan |first=Karen H. |date = June 2007|title=Helium shortage hampers research and industry
 |periodical=[[Physics Today]] |publisher=[[American Institute of Physics]]
 |volume=60 |issue=6 |pages=31–32
 |doi=10.1063/1.2754594
|bibcode = 2007PhT....60f..31K }}</ref> From 2002 to 2007 helium prices doubled.<ref name="Basu2007">{{Cite news |last=Basu |first=Sourish |editor-last=Yam |editor-first=Philip |date=October 2007 |title=Updates: Into Thin Air |access-date=2008-08-04 |periodical=Scientific American |publisher=Scientific American, Inc. |volume=297 |issue=4 |page=18 |url=http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ARTICLEID_CHAR=E0D18FB2-3048-8A5E-104115527CB01ADB |archive-url=https://web.archive.org/web/20081206032004/http://www.sciamdigital.com/index.cfm?fa=Products.ViewIssuePreview&ARTICLEID_CHAR=E0D18FB2-3048-8A5E-104115527CB01ADB |archive-date=2008-12-06 |url-status=dead }}</ref>

{{as of|2012}}, the [[National Helium Reserve|United States National Helium Reserve]] accounted for 30 percent of the world's helium.<ref name="Newcomb">{{cite magazine|first=Tim|last=Newcomb|url=https://newsfeed.time.com/2012/08/23/theres-a-helium-shortage-on-and-its-affecting-more-than-just-balloons/|title=There's a Helium Shortage On—and It's Affecting More than Just Balloons|magazine=[[Time (magazine)|Time]]|date=21 August 2012|access-date=2013-09-16|archive-url=https://web.archive.org/web/20131229061210/http://newsfeed.time.com/2012/08/23/theres-a-helium-shortage-on-and-its-affecting-more-than-just-balloons/|archive-date=29 December 2013|url-status=live}}</ref> The reserve was expected to run out of helium in 2018.<ref name="Newcomb" /> Despite that, a proposed bill in the [[United States Senate]] would allow the reserve to continue to sell the gas. Other large reserves were in the [[Hugoton Natural Gas Area|Hugoton]] in [[Kansas]], United States, and nearby gas fields of Kansas and the [[panhandles]] of [[Texas]] and [[Oklahoma]]. New helium plants were scheduled to open in 2012 in [[Qatar]], Russia, and the US state of [[Wyoming]], but they were not expected to ease the shortage.<ref name="Newcomb" />

In 2013, Qatar started up the world's largest helium unit,<ref>{{cite web |url=http://www.airliquide.com/en/qatar-start-up-of-worlds-largest-helium-unit.html |title=Air Liquide {{pipe}} the world leader in gases, technologies and services for Industry and Health |access-date=2015-05-25 |url-status=dead |archive-url=https://web.archive.org/web/20140914141342/http://www.airliquide.com/en/qatar-start-up-of-worlds-largest-helium-unit.html |archive-date=2014-09-14 |date=19 February 2015 }} Air Liquide Press Release.</ref> although the [[2017 Qatar diplomatic crisis]] severely affected helium production there.<ref>{{Cite news|url=https://www.washingtonpost.com/news/wonk/wp/2017/06/26/middle-east-turmoil-is-disrupting-a-vital-resource-for-nuclear-energy-space-flight-and-birthday-balloons|title=Middle East turmoil is disrupting a vital resource for nuclear energy, space flight and birthday balloons|date=26 June 2017|work=washingtonpost.com|access-date=26 June 2017|archive-url=https://web.archive.org/web/20170626211653/https://www.washingtonpost.com/news/wonk/wp/2017/06/26/middle-east-turmoil-is-disrupting-a-vital-resource-for-nuclear-energy-space-flight-and-birthday-balloons/|archive-date=26 June 2017|url-status=live}}</ref> 2014 was widely acknowledged to be a year of over-supply in the helium business, following years of renowned shortages.<ref>{{cite web |url=http://www.gasworld.com/2015-what-lies-ahead-part-1/2004706.article |url-status=live |archive-url=https://web.archive.org/web/20150117012529/http://www.gasworld.com/2015-what-lies-ahead-part-1/2004706.article |archive-date=2015-01-17 |work=Gasworld |date=25 December 2014 |title=2015 – What lies ahead? Part 1 |last=Cockerill |first=Rob |access-date=15 September 2021}}</ref> Nasdaq reported (2015) that for [[Air Products]], an international corporation that sells gases for industrial use, helium volumes remain under economic pressure due to feedstock supply constraints.<ref>{{Cite web|url=https://www.nasdaq.com/article/will-air-products-apd-earnings-surprise-estimates-in-q2-analyst-blog-cm470472|title=Will Air Products' (APD) Earnings Surprise Estimates in Q2? - Analyst Blog|date=April 28, 2015|website=NASDAQ.com|access-date=August 4, 2019|archive-url=https://web.archive.org/web/20190715085145/https://www.nasdaq.com/article/will-air-products-apd-earnings-surprise-estimates-in-q2-analyst-blog-cm470472|archive-date=July 15, 2019|url-status=live}}</ref>