Editing Nihonium (section)

=== Early indications ===
The syntheses of elements [[bohrium|107]] to [[copernicium|112]] were conducted at the [[GSI Helmholtz Centre for Heavy Ion Research]] in [[Darmstadt]], Germany, from 1981 to 1996. These elements were made by cold fusion{{efn|[[Transactinide element]]s, such as nihonium, are produced by [[nuclear fusion]]. These fusion reactions can be divided into "hot" and "cold" fusion, depending on the excitation energy of the compound nucleus produced. "Cold fusion" in the context of superheavy element synthesis is a distinct concept from the idea that nuclear fusion can be achieved under room temperature conditions.<ref>{{cite journal |doi=10.1016/0022-0728(89)80006-3 |title=Electrochemically induced nuclear fusion of deuterium |date=1989 |last1=Fleischmann |first1=Martin |last2=Pons |first2=Stanley |journal=Journal of Electroanalytical Chemistry and Interfacial Electrochemistry |volume=261 |issue=2 |pages=301–308}}</ref> In hot fusion reactions, light, high-energy projectiles are accelerated towards heavy targets ([[actinide]]s), creating compound nuclei at high excitation energy (~40–50&nbsp;[[electronvolt|MeV]]) that may fission, or alternatively emit several (3 to 5) neutrons.<ref name="fusion">{{cite journal |last1=Barber |first1=Robert C. |last2=Gäggeler |first2=Heinz W. |last3=Karol |first3=Paul J. |last4=Nakahara |first4=Hiromichi |last5=Vardaci |first5=Emanuele |last6=Vogt |first6=Erich |title=Discovery of the element with atomic number 112 (IUPAC Technical Report) |journal=Pure and Applied Chemistry |volume=81 |issue=7 |page=1331 |date=2009 |doi=10.1351/PAC-REP-08-03-05|doi-access=free }}</ref> Cold fusion reactions use heavier projectiles, typically from the [[period 4 element|fourth period]], and lighter targets, usually [[lead]] and [[bismuth]]. The fused nuclei produced have a relatively low excitation energy (~10–20&nbsp;MeV), which decreases the probability that they will undergo fission reactions. As the fused nuclei cool to the [[ground state]], they emit only one or two neutrons. Hot fusion produces more neutron-rich products because actinides have the highest neutron-to-proton ratios of any elements, and is currently the only method to produce the superheavy elements from [[flerovium]] (element 114) onwards.<ref name="AM89">{{Cite journal |first1=Peter |last1=Armbruster |first2=Gottfried |last2=Munzenberg |title=Creating superheavy elements |journal=Scientific American |volume=34 |pages=36–42 |date=1989}}</ref>}} reactions, in which targets made of [[lead]] and [[bismuth]], which are around the [[nuclear shell model|stable configuration]] of 82 protons, are bombarded with heavy ions of [[period 4 element]]s. This creates fused nuclei with low excitation energies due to the stability of the targets' nuclei, significantly increasing the yield of [[superheavy element]]s. Cold fusion was pioneered by [[Yuri Oganessian]] and his team in 1974 at the [[Joint Institute for Nuclear Research]] (JINR) in [[Dubna]], Soviet Union. Yields from cold fusion reactions were found to decrease significantly with increasing atomic number; the resulting nuclei were severely neutron-deficient and short-lived. The GSI team attempted to synthesise element 113 via cold fusion in 1998 and 2003, bombarding bismuth-209 with [[zinc]]-70; both attempts were unsuccessful.<ref name="Chapman" /><ref>{{cite conference |url=https://www.epj-conferences.org/articles/epjconf/pdf/2016/26/epjconf-NS160-06001.pdf |title=The discovery of elements 107 to 112 |last1=Hofmann |first1=Sigurd |date=2016 |conference=Nobel Symposium NS160 – Chemistry and Physics of Heavy and Superheavy Elements |doi=10.1051/epjconf/201613106001|doi-access=free }}</ref>

Faced with this problem, [[Yuri Oganessian|Oganessian]] and his team at the [[Joint Institute for Nuclear Research|JINR]] turned their renewed attention to the older hot fusion technique, in which heavy [[actinide]] targets were bombarded with lighter ions. [[Calcium-48]] was suggested as an ideal projectile, because it is very neutron-rich for a light element (combined with the already neutron-rich actinides) and would minimise the neutron deficiencies of the nuclides produced. Being [[doubly magic]], it would confer benefits in stability to the fused nuclei. In collaboration with the team at the [[Lawrence Livermore National Laboratory]] (LLNL) in [[Livermore, California]], United States, they made an attempt on [[flerovium|element 114]] (which was predicted to be a [[magic number (physics)|magic number]], closing a proton shell, and more stable than element 113).<ref name="Chapman" />

In 1998, the JINR–LLNL collaboration started their attempt on element 114, bombarding a target of [[plutonium-244]] with ions of calcium-48:<ref name="Chapman" />

:{{nuclide|plutonium|244}} + {{nuclide|calcium|48}} → <sup>292</sup>114* → <sup>290</sup>114 + 2 {{SubatomicParticle|neutron}} + e<sup>−</sup> → <sup>290</sup>113 + [[electron neutrino|ν<sub>e</sub>]] ?

A single [[atom]] was observed which was thought to be the isotope <sup>289</sup>114: the results were published in January 1999.<ref name="99Og01">{{cite journal |last1=Oganessian |first1=Yu. Ts. |display-authors=etal |date=1999 |title=Synthesis of Superheavy Nuclei in the <sup>48</sup>Ca + <sup>244</sup>Pu Reaction |url=http://flerovlab.jinr.ru/linkc/flnr_presentations/articles/synthesis_of_Element_114_1999.pdf |journal=[[Physical Review Letters]] |volume=83 |issue=16 |page=3154 |bibcode=1999PhRvL..83.3154O |doi=10.1103/PhysRevLett.83.3154 |access-date=5 April 2017 |archive-date=30 July 2020 |archive-url=https://web.archive.org/web/20200730232521/http://flerovlab.jinr.ru/linkc/flnr_presentations/articles/synthesis_of_Element_114_1999.pdf |url-status=dead }}</ref> Despite numerous attempts to repeat this reaction, an isotope with these decay properties has never again been found, and the exact identity of this activity is unknown.<ref name="04OgJINRPP">{{cite journal |last=Oganessian |first=Yu. Ts. |display-authors=etal |date=2004 |title=Measurements of cross sections and decay properties of the isotopes of elements 112, 114, and 116 produced in the fusion reactions <sup>233,238</sup>U, <sup>242</sup>Pu, and <sup>248</sup>Cm + <sup>48</sup>Ca |url=http://www.jinr.ru/publish/Preprints/2004/160(E7-2004-160).pdf |journal=[[Physical Review C]] |volume=70 |issue=6 |page=064609 |bibcode=2004PhRvC..70f4609O |doi=10.1103/PhysRevC.70.064609 |url-status=dead |archive-url=https://web.archive.org/web/20080528130343/http://www.jinr.ru/publish/Preprints/2004/160%28E7-2004-160%29.pdf |archive-date=28 May 2008 }}</ref> A 2016 paper by [[Sigurd Hofmann]] et al. considered that the most likely explanation of the 1998 result is that two neutrons were emitted by the produced compound nucleus, leading to <sup>290</sup>114 and [[electron capture]] to <sup>290</sup>113, while more neutrons were emitted in all other produced chains. This would have been the first report of a decay chain from an isotope of element 113, but it was not recognised at the time, and the assignment is still uncertain.<ref name="Hofmann2016" /> A similar long-lived activity observed by the JINR team in March 1999 in the <sup>242</sup>Pu + <sup>48</sup>Ca reaction may be due to the electron-capture daughter of <sup>287</sup>114, <sup>287</sup>113; this assignment is also tentative.<ref name="EXON" />