Editing Module:Superheavy element (section)

=== Synthesis of superheavy nuclei ===
{{see also|Nucleosynthesis|Nuclear reaction}}
[[File:Deuterium-tritium fusion.svg|alt=A graphic depiction of a nuclear fusion reaction|left|thumb|A graphic depiction of a [[nuclear fusion]] reaction. Two nuclei fuse into one, emitting a [[neutron]]. Reactions that created new elements to this moment were similar, with the only possible difference that several singular neutrons sometimes were released, or none at all.]]

A superheavy{{efn|In [[nuclear physics]], an element is called [[heavy element|heavy]] if its atomic number is high; [[lead]] (element&nbsp;82) is one example of such a heavy element. The term "superheavy elements" typically refers to elements with atomic number greater than [[lawrencium|103]] (although there are other definitions, such as atomic number greater than [[fermium|100]]<ref>{{Cite web|url=https://www.chemistryworld.com/news/explainer-superheavy-elements/1010345.article|title=Explainer: superheavy elements|last=Krämer|first=K.|date=2016|website=[[Chemistry World]]|language=en|access-date=2020-03-15}}</ref> or [[copernicium|112]];<ref>{{Cite web|archive-url=https://web.archive.org/web/20150911081623/https://pls.llnl.gov/research-and-development/nuclear-science/project-highlights/livermorium/elements-113-and-115|url=https://pls.llnl.gov/research-and-development/nuclear-science/project-highlights/livermorium/elements-113-and-115|title=Discovery of Elements 113 and 115|publisher=[[Lawrence Livermore National Laboratory]]|archive-date=2015-09-11|access-date=2020-03-15}}</ref> sometimes, the term is presented an equivalent to the term "transactinide", which puts an upper limit before the beginning of the hypothetical [[superactinide]] series).<ref>{{cite encyclopedia|last1=Eliav|first1=E.|title=Electronic Structure of the Transactinide Atoms|date=2018|encyclopedia=Encyclopedia of Inorganic and Bioinorganic Chemistry|pages=1–16|editor-last=Scott|editor-first=R. A.|publisher=[[John Wiley & Sons]]|language=en|doi=10.1002/9781119951438.eibc2632|isbn=978-1-119-95143-8|last2=Kaldor|first2=U.|last3=Borschevsky|first3=A.| s2cid=127060181 }}</ref> Terms "heavy isotopes" (of a given element) and "heavy nuclei" mean what could be understood in the common language—isotopes of high mass (for the given element) and nuclei of high mass, respectively.}} [[atomic nucleus]] is created in a nuclear reaction that combines two other nuclei of unequal size{{Efn|In 2009, a team at the JINR led by Oganessian published results of their attempt to create hassium in a symmetric <sup>136</sup>Xe&nbsp;+&nbsp;<sup>136</sup>Xe reaction. They failed to observe a single atom in such a reaction, putting the upper limit on the cross section, the measure of probability of a nuclear reaction, as 2.5&nbsp;[[picobarn|pb]].<ref>{{Cite journal|last1=Oganessian|first1=Yu. Ts.|author-link=Yuri Oganessian|last2=Dmitriev|first2=S. N.|last3=Yeremin|first3=A. V.|last4=Aksenov|first4=N. V.|last5=Bozhikov|first5=G. A.|last6=Chepigin|first6=V. I.|last7=Chelnokov|first7=M. L.|last8=Lebedev|first8=V. Ya.|last9=Malyshev|first9=O. N.|last10=Petrushkin|first10=O. V.|last11=Shishkin|first11=S. V.|display-authors=3|date=2009|title=Attempt to produce the isotopes of element 108 in the fusion reaction <sup>136</sup>Xe + <sup>136</sup>Xe |journal=[[Physical Review C]]|language=en|volume=79|issue=2|page=024608|doi=10.1103/PhysRevC.79.024608|issn=0556-2813}}</ref> In comparison, the reaction that resulted in hassium discovery, <sup>208</sup>Pb + <sup>58</sup>Fe, had a cross section of ~20&nbsp;pb (more specifically, 19{{su|p=+19|b=-11}}&nbsp;pb), as estimated by the discoverers.<ref name="84Mu01">{{cite journal|last1=Münzenberg|first1=G.|author-link=Gottfried Münzenberg|last2=Armbruster|first2=P.|author-link2=Peter Armbruster|last3=Folger|first3=H.|last4=Heßberger|first4=F. P.|last5=Hofmann|first5=S.|last6=Keller|first6=J.|last7=Poppensieker|first7=K.|last8=Reisdorf|first8=W.|last9=Schmidt|first9=K.-H.|display-authors=3|date=1984|title=The identification of element 108|url=http://www.gsi-heavy-ion-researchcenter.org/forschung/kp/kp2/ship/108-discovery.pdf|journal=Zeitschrift für Physik A|volume=317|issue=2|pages=235–236|bibcode=1984ZPhyA.317..235M|doi=10.1007/BF01421260|archive-url=https://web.archive.org/web/20150607124040/http://www.gsi-heavy-ion-researchcenter.org/forschung/kp/kp2/ship/108-discovery.pdf|archive-date=7 June 2015|access-date=20 October 2012|first10=H.-J.|last10=Schött|first11=M. E.|last11=Leino|first12=R.|last12=Hingmann| s2cid=123288075 }}</ref>}} into one; roughly, the more unequal the two nuclei in terms of [[mass]], the greater the possibility that the two react.<ref name="Bloomberg">{{Cite news|last=Subramanian|first=S.|author-link=Samanth Subramanian|url=https://www.bloomberg.com/news/features/2019-08-28/making-new-elements-doesn-t-pay-just-ask-this-berkeley-scientist|title=Making New Elements Doesn't Pay. Just Ask This Berkeley Scientist|website=[[Bloomberg Businessweek]]| date=28 August 2019 |access-date=2020-01-18}}</ref> The material made of the heavier nuclei is made into a target, which is then bombarded by the [[Particle beam|beam]] of lighter nuclei. Two nuclei can only [[nuclear fusion|fuse]] into one if they approach each other closely enough; normally, nuclei (all positively charged) repel each other due to [[Coulomb's law|electrostatic repulsion]]. The [[strong interaction]] can overcome this repulsion but only within a very short distance from a nucleus; beam nuclei are thus greatly [[particle accelerator|accelerated]] in order to make such repulsion insignificant compared to the velocity of the beam nucleus.<ref name="n+1">{{Cite web|url=https://nplus1.ru/material/2019/03/25/120-element|title=Сверхтяжелые шаги в неизвестное|last=Ivanov|first=D.|date=2019|website=nplus1.ru|language=ru|trans-title=Superheavy steps into the unknown|access-date=2020-02-02}}</ref> The energy applied to the beam nuclei to accelerate them can cause them to reach speeds as high as one-tenth of the [[speed of light]]. However, if too much energy is applied, the beam nucleus can fall apart.<ref name="n+1"/>

Coming close enough alone is not enough for two nuclei to fuse: when two nuclei approach each other, they usually remain together for about 10{{sup|−20}}&nbsp;seconds and then part ways (not necessarily in the same composition as before the reaction) rather than form a single nucleus.<ref name="n+1" /><ref>{{Cite web|url=http://theconversation.com/something-new-and-superheavy-at-the-periodic-table-26286|title=Something new and superheavy at the periodic table|last=Hinde|first=D.|date=2017|website=[[The Conversation (website)|The Conversation]]|language=en|access-date=2020-01-30}}</ref> This happens because during the attempted formation of a single nucleus, electrostatic repulsion tears apart the nucleus that is being formed.<ref name="n+1" /> Each pair of a target and a beam is characterized by its [[cross section (physics)|cross section]]—the probability that fusion will occur if two nuclei approach one another expressed in terms of the transverse area that the incident particle must hit in order for the fusion to occur.{{Efn|The amount of energy applied to the beam particle to accelerate it can also influence the value of cross section. For example, in the {{nuclide|silicon|28}} + {{Physics particle|n|TL=1|BL=0}} → {{nuclide|aluminium|28}} + {{Physics particle|p|TL=1|BL=1}} reaction, cross section changes smoothly from 370&nbsp;mb at 12.3 MeV to 160&nbsp;mb at 18.3 MeV, with a broad peak at 13.5&nbsp;MeV with the maximum value of 380&nbsp;mb.<ref>{{Cite journal |last1=Kern |first1=B. D. |last2=Thompson |first2=W. E. |last3=Ferguson |first3=J. M. |date=1959 |title=Cross sections for some (n, p) and (n, α) reactions |journal=Nuclear Physics |language=en |volume=10 |pages=226–234 |doi=10.1016/0029-5582(59)90211-1|bibcode=1959NucPh..10..226K }}</ref>}} This fusion may occur as a result of the quantum effect in which nuclei can [[Quantum tunnelling#Nuclear fusion|tunnel]] through electrostatic repulsion. If the two nuclei can stay close  past that phase, multiple nuclear interactions result in redistribution of energy and an energy equilibrium.<ref name="n+1" />

{{external media|width=230px|float=left|video1=[https://www.youtube.com/watch?v=YovAFlzFtzg Visualization] of unsuccessful nuclear fusion, based on calculations from the [[Australian National University]]<ref>{{Cite journal|last1=Wakhle|first1=A.|last2=Simenel|first2=C.|last3=Hinde|first3=D. J.|display-authors=3|last4=Dasgupta|first4=M.|last5=Evers|first5=M.|last6=Luong|first6=D. H.|last7=du Rietz|first7=R.|date=2015|editor-last=Simenel|editor-first=C.|editor2-last=Gomes|editor2-first=P. R. S.|editor3-last=Hinde|editor3-first=D. J.|display-editors=3|editor4-last=Madhavan|editor4-first=N.|editor5-last=Navin|editor5-first=A.|editor6-last=Rehm|editor6-first=K. E.|title=Comparing Experimental and Theoretical Quasifission Mass Angle Distributions|journal=[[European Physical Journal WOC|European Physical Journal Web of Conferences]]|volume=86|page=00061|doi=10.1051/epjconf/20158600061| bibcode=2015EPJWC..8600061W |issn=2100-014X|doi-access=free|hdl=1885/148847|hdl-access=free}}</ref>}}

The resulting merger is an [[excited state]]<ref>{{cite web |url=http://oregonstate.edu/instruct/ch374/ch418518/Chapter%2010%20NUCLEAR%20REACTIONS.pdf |access-date=2020-01-27 |pages=7–8 |title=Nuclear Reactions}} Published as {{cite book|last1=Loveland|first1=W. D.|last2=Morrissey|first2=D. J.|last3=Seaborg|first3=G. T.|author-link3=Glenn T. Seaborg|title=Modern Nuclear Chemistry|date=2005|pages=249–297|chapter=Nuclear Reactions|publisher=[[John Wiley & Sons, Inc.]]|language=en|doi=10.1002/0471768626.ch10|isbn=978-0-471-76862-3}}</ref>—termed a [[Nuclear reaction#Compound nuclear reactions|compound nucleus]]—and thus it is very unstable.<ref name="n+1" /> To reach a more stable state, the temporary merger may [[Nuclear fission|fission]] without formation of a more stable nucleus.<ref name="CzechNuclear"/> Alternatively, the compound nucleus may eject a few [[neutron]]s, which would carry away the excitation energy; if the latter is not sufficient for a neutron expulsion, the merger would produce a [[gamma ray]]. This happens in about 10{{sup|−16}}&nbsp;seconds after the initial nuclear collision and results in creation of a more stable nucleus.<ref name="CzechNuclear">{{cite journal|title=Neutron Sources for ADS|last=Krása|first=A.|s2cid=28796927|date=2010|journal=Faculty of Nuclear Sciences and Physical Engineering|publisher=[[Czech Technical University in Prague]]|pages=4–8}}</ref> The definition by the [[IUPAC/IUPAP Joint Working Party]] (JWP) states that a [[chemical element]] can only be recognized as discovered if a nucleus of it has not [[Radioactive decay|decayed]] within 10{{sup|−14}} seconds. This value was chosen as an estimate of how long it takes a nucleus to acquire [[electron]]s and thus display its chemical properties.<ref>{{Cite journal|last=Wapstra|first=A. H.|author-link=Aaldert Wapstra|date=1991|title=Criteria that must be satisfied for the discovery of a new chemical element to be recognized|url=http://publications.iupac.org/pac/pdf/1991/pdf/6306x0879.pdf|journal=[[Pure and Applied Chemistry]]|volume=63|issue=6|page=883|doi=10.1351/pac199163060879| s2cid=95737691 |issn=1365-3075}}</ref>{{efn|This figure also marks the generally accepted upper limit for lifetime of a compound nucleus.<ref name=BerkeleyNoSF>{{Cite journal|last1=Hyde|first1=E. K.|last2=Hoffman|first2=D. C.|author-link2=Darleane C. Hoffman|last3=Keller|first3=O. L.|date=1987|title=A History and Analysis of the Discovery of Elements 104 and 105|journal=Radiochimica Acta|volume=42|issue=2|doi=10.1524/ract.1987.42.2.57|issn=2193-3405|pages=67–68| s2cid=99193729 |url=http://www.escholarship.org/uc/item/05x8w9h7}}</ref>}}