Editing Hassium (section)

=== Cold fusion ===

Nuclear reactions used in the 1960s resulted in high excitation energies that required expulsion of four or five neutrons; these reactions used targets made of elements with high atomic numbers to maximize the size difference between the two nuclei in a reaction. While this increased the chance of fusion due to the lower electrostatic repulsion between target and projectile, the formed compound nuclei often broke apart and did not survive to form a new element. Moreover, fusion inevitably produces neutron-poor nuclei, as heavier elements need more neutrons per proton for stability;{{efn|Generally, heavier nuclei require more neutrons because as the number of protons increases, so does electrostatic repulsion between them. This repulsion is balanced by the binding energy generated by the strong interaction between quarks within nucleons; it is enough to hold the quarks together in a nucleon together and some of it is left for binding of different nucleons. The more nucleons in a nucleus, the more energy there is for binding the nucleons (greater total binding energy does not necessarily mean greater binding energy per nucleon).<ref>{{Cite web |date=2019 |url=https://inchemistry.acs.org/content/inchemistry/en/atomic-news/modern-alchemy-creating-superheavy-elements.html |last=Poole-Sawyer |first=J. |title=Modern Alchemy: Creating Superheavy Elements |website=[[inChemistry]] |publisher=[[American Chemical Society]] |access-date=2020-01-27 |archive-date=27 January 2020 |archive-url=https://web.archive.org/web/20200127134511/https://inchemistry.acs.org/content/inchemistry/en/atomic-news/modern-alchemy-creating-superheavy-elements.html |url-status=live }}</ref> However, having too many neutrons per proton, while decreasing electrostatic repulsion per nucleon, results in beta decay.<ref>{{Cite web|title=Beta Decay|url=https://www2.lbl.gov/abc/wallchart/chapters/03/2.html|access-date=2020-08-28|work=Guide to the Nuclear Wall Chart|publisher=[[Lawrence Berkeley National Laboratory]]|archive-date=16 December 2017|archive-url=https://web.archive.org/web/20171216223958/http://www2.lbl.gov/abc/wallchart/chapters/03/2.html|url-status=live}}</ref>}} therefore, the necessary ejection of neutrons results in final products that are typically shorter-lived. As such, light beams (six to ten protons) allowed synthesis of elements only up to [[Seaborgium|106]].<ref name="Oganessian122">{{Cite journal|last=Oganessian|first=Yu.|date=2012|title=Nuclei in the "Island of Stability" of Superheavy Elements|journal=Journal of Physics: Conference Series|volume=337|issue=1|pages=012005-1–012005-6|doi=10.1088/1742-6596/337/1/012005|bibcode=2012JPhCS.337a2005O|issn=1742-6596|doi-access=free}}</ref>

To advance to heavier elements, Soviet physicist [[Yuri Oganessian]] at [[Joint Institute for Nuclear Research]] (JINR) in [[Dubna]], [[Moscow Oblast]], [[Russian SFSR]], [[Soviet Union]], proposed a different mechanism, in which the bombarded nucleus would be lead-208, which has [[Magic number (physics)|magic numbers]] of protons and neutrons, or another nucleus close to it.<ref name="Oganessian04">{{Cite journal |last=Oganessian|first=Yu. Ts. |date=2004|title=Superheavy elements|journal=Pure and Applied Chemistry |volume=76|issue=9|pages=1717–1718|doi=10.1351/pac200476091715|issn=1365-3075|doi-access=free}}</ref> Each proton and neutron has a fixed [[rest energy]]; those of all protons are equal and so are those of all neutrons. In a nucleus, some of this energy is diverted to binding protons and neutrons; if a nucleus has a magic number of protons and/or neutrons, then even more of its rest energy is diverted, which makes the nuclide more stable. This additional stability requires more energy for an external nucleus to break the existing one and penetrate it.<ref name="coldfusion77">{{Cite web|url=http://n-t.ru/ri/ps/pb106.htm|title=Популярная библиотека химических элементов. Сиборгий (экавольфрам)|trans-title=Popular library of chemical elements. Seaborgium (eka-tungsten)|language=ru|website=n-t.ru|access-date=2020-01-07|archive-date=23 August 2011|archive-url=https://web.archive.org/web/20110823090114/http://n-t.ru/ri/ps/pb106.htm|url-status=live}} Reprinted from {{cite book|author=<!--none-->|date=1977|title=Популярная библиотека химических элементов. Серебро — Нильсборий и далее|chapter=Экавольфрам|trans-title=Popular library of chemical elements. Silver through nielsbohrium and beyond|trans-chapter=Eka-tungsten|language=ru|publisher=[[Nauka (publisher)|Nauka]]}}</ref> More energy diverted to binding nucleons means less rest energy, which in turn means less mass (mass is proportional to rest energy). More equal atomic numbers of the reacting nuclei result in greater electrostatic repulsion between them, but the lower [[mass excess]] of the target nucleus balances it.<ref name="Oganessian04" /> This leaves less excitation energy for the new compound nucleus, which necessitates fewer neutron ejections to reach a stable state.<ref name="coldfusion77" /> Due to this energy difference, the former mechanism became known as "hot fusion" and the latter as "cold fusion".<ref>{{Cite journal|last=Oganessian|first=Yu. Ts.|date=2000|title=Route to islands of stability of superheavy elements|journal=Physics of Atomic Nuclei |volume=63|issue=8|page=1320|doi=10.1134/1.1307456|bibcode=2000PAN....63.1315O|s2cid=121690628|issn=1063-7788}}</ref>

Cold fusion was first declared successful in 1974 at JINR, when it was tested for synthesis of the yet-undiscovered element{{spaces}}106.<ref name="coldfusion77" /> These new nuclei were projected to decay via spontaneous fission. The physicists at JINR concluded element 106 was produced in the experiment because no fissioning nucleus known at the time showed parameters of fission similar to what was observed during the experiment and because changing either of the two nuclei in the reactions negated the observed effects. Physicists at Lawrence Berkeley Laboratory (LBL; originally Radiation Laboratory, RL, and later [[Lawrence Berkeley National Laboratory]], LBNL) of the [[University of California, Berkeley|University of California]] in [[Berkeley, California|Berkeley]], [[California]], United States, also expressed great interest in the new technique.<ref name="coldfusion77" /> When asked about how far this new method could go and if lead targets were a physics' [[Klondike Gold Rush|Klondike]], Oganessian responded, "Klondike may be an exaggeration [...] But soon, we will try to get elements [[Bohrium|107]]{{spaces}}... 108 in these reactions."<ref name="coldfusion77" />