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{{short description|Isotopes of super-heavy elements theorized to be much more stable than others}} {{for|the speech by Jimmy Carter|Island of Stability (speech)}} {{Use American English|date=October 2019}} {{use dmy dates|date=November 2019}} In ], the '''island of stability''' is a predicted set of ]s of ]s that may have considerably longer ] than known isotopes of these elements. It is predicted to appear as an "island" in the ], separated from known ] and long-lived ]s. Its theoretical existence is attributed to stabilizing effects of predicted ] of ]s and ]s in the superheavy mass region.<ref>{{cite news |last1=Moskowitz |first1=C. |title=Superheavy Element 117 Points to Fabled "Island of Stability" on Periodic Table |url=https://www.scientificamerican.com/article/superheavy-element-117-island-of-stability/ |accessdate=20 April 2019 |work=Scientific American |date=2014}}</ref><ref name="NYT-20190827">{{cite news |last=Roberts |first=S. |title=Is It Time to Upend the Periodic Table? – The iconic chart of elements has served chemistry well for 150 years. But it's not the only option out there, and scientists are pushing its limits |url=https://www.nytimes.com/2019/08/27/science/periodic-table-elements-chemistry.html |date=2019 |work=] |accessdate=27 August 2019 }}</ref> ] showing the measured (boxed) and predicted ] of superheavy ], ordered by number of protons and neutrons. The expected location of the island of stability around ''Z'' = 112 is circled.<ref name=ZagrebaevPPT>{{cite conference |url=http://cyclotron.tamu.edu/nn2012/Slides/Plenary/NNC_2012_Zagrebaev.ppt |title=Opportunities for synthesis of new superheavy nuclei (What really can be done within the next few years) |first=V. |last=Zagrebaev |date=2012 |conference=11th International Conference on Nucleus-Nucleus Collisions (NN2012) |pages=24–28 |archive-url=https://web.archive.org/web/20160303235203/http://cyclotron.tamu.edu/nn2012/Slides/Plenary/NNC_2012_Zagrebaev.ppt |archive-date=3 March 2016 |location=San Antonio, Texas, US }}</ref><ref name=KarpovSHE/>]] {{Nuclear physics}} Several predictions have been made regarding the exact location of the island of stability, though it is generally thought to center near ] and ] isotopes in the vicinity of the predicted closed neutron ] at ''N'' = 184.<ref name=KarpovSHE>{{cite journal|last=Karpov|first=A. V. |last2=Zagrebaev|first2=V. I. |last3=Palenzuela|first3=Y. M. |last4=Ruiz|first4=L. F. |last5=Greiner|first5=W. |title=Decay properties and stability of the heaviest elements |journal=International Journal of Modern Physics E|date=2012|volume=21|issue=2|pages=1250013-1–1250013-20<!-- Deny Citation Bot-->|doi=10.1142/S0218301312500139 |url=http://nrv.jinr.ru/karpov/publications/Karpov12_IJMPE.pdf|bibcode=2012IJMPE..2150013K |displayauthors=3}}</ref> These models strongly suggest that the closed shell will confer further stability towards ] and ]. While these effects are expected to be greatest near ] ''Z'' = 114 and ''N'' = 184, the region of increased stability is expected to encompass several neighboring elements, and there may also be additional islands of stability around heavier nuclei that are ] (having magic numbers of both protons and neutrons). Estimates of the stability of the elements on the island are usually around a half-life of minutes or days; some estimates predict half-lives of millions of years.<ref name=physorg>{{cite web |url=http://newscenter.lbl.gov/2009/09/24/114-confirmed/ |title=Superheavy Element 114 Confirmed: A Stepping Stone to the Island of Stability |date=2009 |accessdate=23 October 2019 |publisher=]}}</ref> Although the nuclear shell model predicting magic numbers has existed since the 1940s, the existence of long-lived superheavy nuclides has not been definitively demonstrated. Like the rest of the superheavy elements, the nuclides on the island of stability have never been found in nature; thus, they must be created artificially in a ] to be studied. Scientists have not found a way to carry out such a reaction, for it is likely that new types of reactions will be needed to populate nuclei near the center of the island. Nevertheless, the successful synthesis of superheavy elements up to ''Z'' = 118 (]) with up to 177 neutrons demonstrates a slight stabilizing effect around elements ] to 114 that may continue in unknown isotopes, supporting the existence of the island of stability.<ref name=KarpovSHE /><ref name=beachhead /> ==Introduction== ===Nuclide stability=== {{see also|Valley of stability}} ] The composition of a ] (]) is defined by the ] ''Z'' and the ] ''N'', which sum to ] ''A''. Proton number ''Z'', also named the atomic number, determines the position of an ] in the ]. The approximately 3300 known nuclides<ref name=thoennesweb>{{cite web |last=Thoennessen |first=M. |title=Discovery of Nuclides Project |url=https://people.nscl.msu.edu/~thoennes/isotopes/index.html |date=2018 |accessdate=13 September 2019}}</ref> are commonly represented in a ] with ''Z'' and ''N'' for its axes and the ] for ] indicated for each unstable nuclide (see figure).<ref>{{harvnb|Podgorsak|2016|p=512}}</ref> {{As of|2019}}, 252 nuclides are observed to be ] (having never been observed to decay);<ref>{{cite web |date=2017 |title=Atomic structure |url=https://www.arpansa.gov.au/understanding-radiation/what-is-radiation/ionising-radiation/atomic-structure |website=Australian Radiation Protection and Nuclear Safety Agency |publisher=Commonwealth of Australia |accessdate=16 February 2019}}</ref> generally, as the number of protons increases, stable nuclei have a higher ] (more neutrons per proton). The last element in the periodic table that has a stable ] is ] (''Z'' = 82),{{efn|The heaviest stable element was believed to be bismuth (atomic number 83) until 2003, when its only stable isotope, ], was observed to undergo alpha decay.<ref>{{cite journal|last = Marcillac|first = P.|last2=Coron |first2=N. |last3=Dambier |first3=G. |last4=Leblanc |first4=J. |last5=Moalic |first5=J.-P. |date=2003 |displayauthors=3 |title = Experimental detection of α-particles from the radioactive decay of natural bismuth|journal = Nature|volume = 422|pages = 876–878|pmid=12712201|doi = 10.1038/nature01541|issue = 6934|bibcode = 2003Natur.422..876D}}</ref>}}{{efn|It is theoretically possible for other ] nuclides to decay, though their predicted half-lives are so long that this process has never been observed.<ref name=bellidecay>{{cite journal |last1=Belli |first1=P. |last2=Bernabei |first2=R. |last3=Danevich |first3=F. A. |last4=Incicchitti |first4=A. |last5=Tretyak |first5=V. I. |displayauthors=3 |title=Experimental searches for rare alpha and beta decays |journal=European Physical Journal A |date=2019 |volume=55 |issue=8 |pages=140-1–140-7 |doi=10.1140/epja/i2019-12823-2 |issn=1434-601X |arxiv=1908.11458|bibcode=2019EPJA...55..140B }}</ref>}} with stability (i.e. half-lives of the longest lived isotopes) generally decreasing in heavier elements.{{efn|A region of increased stability encompasses ] (''Z'' = 90) and ] (''Z'' = 92) whose half-lives are comparable to the ]. Elements intermediate between bismuth and thorium have shorter half-lives, and heavier nuclei beyond uranium become more unstable with increasing atomic number.<ref name=greinerVP/>}}<ref name=greinerVP>{{cite journal |last=Greiner |first=W. |date=2012 |title=Heavy into Stability |journal=Physics |volume=5 |pages=115-1–115-3 <!-- Deny Citation Bot-->|doi=10.1103/Physics.5.115|bibcode=2012PhyOJ...5..115G }}</ref> The half-lives of nuclei also decrease when there is a lopsided neutron–proton ratio, such that the resulting nuclei have too few or too many neutrons to be stable.<ref name=CN14>{{cite web|url=https://wwwndc.jaea.go.jp/CN14/ |title=Chart of the Nuclides |last=Koura |first=H. |last2=Katakura |first2=J. |last3=Tachibana |first3=T. |last4=Minato |first4=F. |date=2015 |publisher=Japan Atomic Energy Agency |access-date=12 April 2019}}</ref> The stability of a nucleus is determined by its ], higher binding energy conferring greater stability. The binding energy per nucleon increases with atomic number to a broad plateau around ''A'' = 60, then declines.<ref>{{harvnb|Podgorsak|2016|p=33}}</ref> If a nucleus can be split into two parts that have a lower total energy (a consequence of the ] resulting from greater binding energy), it is unstable. The nucleus can hold together for a finite time because there is a ] opposing the split, but this barrier can be crossed by ]. The lower the barrier and the masses of the ], the greater the probability per unit time of a split.<ref>{{cite book |last1=Blatt |first1=J. M. |last2=Weisskopf |first2=V. F. |title=Theoretical nuclear physics |date=2012 |publisher=Dover Publications |isbn=978-0-486-13950-0 |pages=7–9}}</ref> Protons in a nucleus are bound together by the ], which counterbalances the ] between positively ] protons. In heavier nuclei, larger numbers of uncharged neutrons are needed to reduce repulsion and confer additional stability. Even so, as physicists started to ] elements that are not found in nature, they found the stability decreased as the nuclei became heavier.<ref name=Sacks>{{cite news |last1=Sacks |first1=O. |title=Greetings From the Island of Stability |url=https://www.nytimes.com/2004/02/08/opinion/greetings-from-the-island-of-stability.html |accessdate=16 February 2019 |work=The New York Times |date=2004 |url-status=dead |archiveurl=https://web.archive.org/web/20180704182825/https://www.nytimes.com/2004/02/08/opinion/greetings-from-the-island-of-stability.html |archivedate=4 July 2018}}</ref> Thus, they speculated that the periodic table might come to an end. The discoverers of ] (element 94) considered naming it "ultimium", thinking it was the last.<ref>{{harvnb|Hoffman|2000|p=34}}</ref> Following the discoveries of heavier elements, of which some decayed in microseconds, it then seemed that instability with respect to ] would limit the existence of heavier elements. In 1939, an upper limit of potential element synthesis was estimated around ],<ref name=liquiddrop /> and following the first discoveries of ]s in the early 1960s, this upper limit prediction was extended to ].<ref name=Sacks/> {{clear}} ] ===Magic numbers=== As early as 1914, the possible existence of ]s with atomic numbers well beyond that of uranium—then the heaviest known element—was suggested, when German physicist ] proposed that superheavy elements around ''Z'' = 108 were a source of radiation in ]. Although he did not make any definitive observations, he hypothesized in 1931 that ]s around ''Z'' = 100 or ''Z'' = 108 may be relatively long-lived and possibly exist in nature.<ref name=swinne>{{harvnb|Kragh|2018|pages=9–10}}</ref> In 1955, American physicist ] also proposed the existence of these elements;<ref name=ghiorso1>{{harvnb|Hoffman|2000|p=400}}</ref> he is credited with the first usage of the term "superheavy element" in a 1958 paper published with Frederick Werner.<ref name=LBL665>{{cite report |last=Thompson |first=S. G. |last2=Tsang |first2=C. F. |title=Superheavy elements |date=1972 |publisher=] |id=LBL-665 |page=28 |url=https://escholarship.org/content/qt4qh151mc/qt4qh151mc.pdf}}</ref> This idea did not attract wide interest until a decade later, after improvements in the ]. In this model, the atomic nucleus is built up in "shells", analogous to ]s in atoms. Independently of each other, neutrons and protons have ]s that are normally close together, but after a given shell is filled, it takes substantially more energy to start filling the next. Thus, the binding energy per nucleon reaches a local maximum and nuclei with filled shells are more stable than those without.<ref>{{cite web |last=Nave |first=R. |date=|title=Shell Model of Nucleus |work=] |publisher=Department of Physics and Astronomy, ] |url=http://hyperphysics.phy-astr.gsu.edu/hbase/Nuclear/shell.html |accessdate=22 January 2007 }}</ref> This theory of a nuclear shell model originates in the 1930s, but it was not until 1949 that German physicists ] and ] ''et al.'' independently devised the correct formulation.<ref name=shellview>{{cite journal |last=Caurier |first=E. |last2=Martínez-Pinedo |first2=G. |last3=Nowacki |first3=F. |last4=Poves |first4=A. |last5=Zuker |first5=A. P. |displayauthors=3 |date=2005 |title=The shell model as a unified view of nuclear structure |journal=Reviews of Modern Physics |volume=77 |issue=2 |page=428 |doi=10.1103/RevModPhys.77.427 |arxiv=nucl-th/0402046|bibcode=2005RvMP...77..427C }}</ref> The numbers of nucleons for which shells are filled are called ]. Magic numbers of 2, 8, 20, 28, 50, 82 and 126 have been observed for neutrons, and the next number is predicted to be 184.<ref name=beachhead /><ref>{{cite book |last1=Satake |first1=M. |title=Introduction to nuclear chemistry. |date=2010 |publisher=Discovery Publishing House |isbn=978-81-7141-277-8 |page=36}}</ref> Protons share the first six of these magic numbers,<ref>{{cite book |last1=Ebbing |first1=D. |last2=Gammon |first2=S. D. |title=General chemistry |date=2007 |publisher=Houghton Mifflin |isbn=978-0-618-73879-3 |page=858 |edition=8th}}</ref> and 126 has been predicted as a magic proton number since the 1940s.<ref name=Kragh>{{harvnb|Kragh|2018|p=22}}</ref> Nuclides with a magic number of each—such as ] (''Z'' = 8, ''N'' = 8), ¹³²Sn (''Z'' = 50, ''N'' = 82), and ²⁰⁸Pb (''Z'' = 82, ''N'' = 126)—are referred to as "doubly magic" and are more stable than nearby nuclides as a result of greater binding energies.<ref>{{cite news |last1=Dumé |first1=B. |title="Magic" numbers remain magic |url=https://physicsworld.com/a/magic-numbers-remain-magic/ |accessdate=17 February 2019 |work=Physics World |publisher=IOP Publishing |date=2005}}</ref><ref name=DoublyMagic>{{cite journal |last=Blank |first=B. |last2=Regan |first2=P. H. |title=Magic and Doubly-Magic Nuclei |date=2000 |journal=Nuclear Physics News |volume=10 |issue=4 |pages=20–27 |url=https://www.researchgate.net/publication/232899048 |doi=10.1080/10506890109411553}}</ref> In the late 1960s, more sophisticated shell models were formulated by American physicist William Myers<!--don't link, this William Myers does not have an article--> and Polish physicist ], and independently by German physicist ]. With these models, taking into account Coulomb repulsion, Meldner predicted that the next proton magic number may be 114 instead of 126.<ref name=quest>{{cite journal|last=Bemis|first=C. E.|last2=Nix|first2=J. R.|date=1977|title=Superheavy elements – the quest in perspective|journal=Comments on Nuclear and Particle Physics|volume=7|issue=3|pages=65–78|url=http://inspirehep.net/record/1382449/files/v7-n3-p65.pdf|issn=0010-2709}}</ref> Myers and Świątecki appear to have coined the term "island of stability", and American chemist ], later a discoverer of many of the superheavy elements, quickly adopted the term and promoted it.<ref name=Kragh/><ref name=Kragh17>{{cite arxiv |title=The Search for Superheavy Elements: Historical and Philosophical Perspectives |pages=8–9 |eprint=1708.04064 |date=2017|last1=Kragh |first1=H.|class=physics.hist-ph }}</ref> Myers and Świątecki also proposed that some superheavy nuclei would be longer-lived as a consequence of higher ]s. Further improvements in the nuclear shell model by Soviet physicist ] led to the emergence of the macroscopic-microscopic method, a nuclear mass model that takes into consideration both smooth trends characteristic of the ] and local fluctuations such as shell effects. This approach enabled Swedish physicist ] ''et al.'', as well as other groups, to make the first detailed calculations of the stability of nuclei within the island.<ref name=quest/> With the emergence of this model, Strutinsky, Nilsson, and other groups argued for the existence of the doubly magic nuclide ²⁹⁸Fl (''Z'' = 114, ''N'' = 184), rather than ³¹⁰] (''Z'' = 126, ''N'' = 184) which was predicted to be doubly magic as early as 1957.<ref name=quest /> Subsequently, estimates of the proton magic number have ranged from 114 to 126, and there is still no consensus.<ref name=beachhead /><ref name=magickoura>{{cite journal|last=Koura|first=H.|last2=Chiba|first2=S.|date=2013|title=Single-Particle Levels of Spherical Nuclei in the Superheavy and Extremely Superheavy Mass Region|journal=Journal of the Physical Society of Japan|volume=82|issue=1|pages=014201-1–014201-5<!-- Deny Citation Bot-->|url=https://www.researchgate.net/publication/258799250 |doi=10.7566/JPSJ.82.014201|bibcode=2013JPSJ...82a4201K}}</ref><ref name=newsci10/> ==Discoveries== {|class="wikitable sortable" style="float:left; margin-right:1em; font-size:85%;" |+Most stable isotopes of superheavy elements (''Z'' ≥ 104) |- !rowspan=2|Element !rowspan=2|Atomic<br />number !rowspan=2|Most<br />stable<br />isotope !colspan=2|Half-life{{efn|Different sources give different values for half-lives; the most recently published values in the literature and NUBASE are both listed for reference.}} |- !Publications<br /><ref>{{harvnb|Emsley|2011|p=566}}</ref><ref name=shesummary>{{cite journal |last=Oganessian |first=Yu. Ts. |last2=Utyonkov |first2=V. K. |date=2015 |title=Super-heavy element research |url=https://www.researchgate.net/publication/273327193 |journal=Reports on Progress in Physics |volume=78 |issue=3 |pages=036301-14–036301-15 <!-- Deny Citation Bot-->|doi=10.1088/0034-4885/78/3/036301 |pmid=25746203 |bibcode=2015RPPh...78c6301O |ref=harv}}</ref> !NUBASE 2016<br /><ref name=nubase>{{cite journal |title=The NUBASE2016 evaluation of nuclear properties |doi=10.1088/1674-1137/41/3/030001 |last1=Audi |first1=G. |last2=Kondev |first2=F. G. |last3=Wang |first3=M. |last4=Huang |first4=W. J. |last5=Naimi |first5=S. |journal=Chinese Physics C |volume=41 |issue=3 |pages=030001-134–030001-138 <!-- Deny Citation Bot-->|year=2017 |url=https://www-nds.iaea.org/amdc/ame2016NUBASE2016.pdf |bibcode=2017ChPhC..41c0001A |displayauthors=3}}<!--for consistency and specific pages, do not replace with {{NUBASE2016}}--></ref> |- |]||104||]||data-sort-value=4680|1.3 h||data-sort-value=9000|2.5 h |- |]||105||]||data-sort-value=104400|1.2 d||data-sort-value=93600|1.1 d |- |]||106||]||data-sort-value=840|14 min<ref name=PuCa2017 />||data-sort-value=300|5 min |- |]||107||]{{efn|The unconfirmed ²⁷⁸Bh may have a longer half-life of 11.5 minutes.<ref name=Hofmann2016 />}}||data-sort-value=61|1 min||data-sort-value=228|3.8 min |- |]||108||]||data-sort-value=9.7|9.7 s<ref name=chemHs>{{cite journal |last=Schädel |first=M. |date=2015 |title=Chemistry of the superheavy elements |journal=Philosophical Transactions of the Royal Society A |volume=373 |issue=2037 |pages=20140191–9 |doi=10.1098/rsta.2014.0191 |pmid=25666065 |bibcode=2015RSPTA.37340191S |url=https://pdfs.semanticscholar.org/81b4/dad92c6af938cc552e5ef8fb511fb45e0ca6.pdf}}</ref>||data-sort-value=16|16 s |- |]||109||]{{efn|name=X|For elements 109–118, the longest-lived known isotope is always the heaviest discovered thus far. This makes it seem likely that there are longer-lived undiscovered isotopes among the even heavier ones.<ref name=48Ca />}}{{efn|The unconfirmed ²⁸²Mt may have a longer half-life of 1.1 minutes.<ref name=Hofmann2016 />}}||data-sort-value=4.5|4.5 s||data-sort-value=7|7 s |- |]||110||]{{efn|name=X}}||data-sort-value=12.7|12.7 s||data-sort-value=14|14 s |- |]||111||]{{efn|name=X}}{{efn|The unconfirmed ²⁸⁶Rg may have a longer half-life of 10.7 minutes.<ref name=Hofmann2016 />}}||data-sort-value=100|1.7 min||data-sort-value=96|1.6 min |- |]||112||]{{efn|name=X}}||data-sort-value=28|28 s||data-sort-value=32|32 s |- |]||113||]{{efn|name=X}}||data-sort-value=9.5|9.5 s||data-sort-value=7|7 s |- |]||114||]{{efn|name=X}}{{efn|The unconfirmed ²⁹⁰Fl may have a longer half-life of 19 seconds.<ref name=Hofmann2016 />}}||data-sort-value=1.9|1.9 s||data-sort-value=2.4|2.4 s |- |]||115||]{{efn|name=X}}||data-sort-value=0.65|650 ms||data-sort-value=0.41|410 ms |- |]||116||]{{efn|name=X}}||data-sort-value=0.057|57 ms||data-sort-value=0.08|80 ms |- |]||117||]{{efn|name=X}}||data-sort-value=0.051|51 ms||data-sort-value=0.07|70 ms |- |]||118||]{{efn|name=X}}{{efn|The unconfirmed ²⁹⁵Og may have a longer half-life of 181 milliseconds.<ref name=Hofmann2016 />}}||data-sort-value=0.00069|690 µs||data-sort-value=0.00115|1.15 ms |} Interest in a possible island of stability grew throughout the 1960s, as some calculations suggested that it might contain nuclides with half-lives of billions of years.<ref name=lodhi11>{{harvnb|Lodhi|1978|p=11}}</ref><ref name=nuclei>{{cite journal |last=Oganessian |first=Yu. Ts. |year=2012 |title=Nuclei in the "Island of Stability" of Superheavy Elements |journal=] |volume=337 |issue=1 |page=012005 |bibcode=2012JPhCS.337a2005O |doi=10.1088/1742-6596/337/1/012005}}</ref> They were also predicted to be especially stable against spontaneous fission in spite of their high atomic mass.<ref name=quest /><ref name="Cwiok">{{cite journal |last1=Ćwiok |first1=S. |last2=Heenen |first2=P.-H. |last3=Nazarewicz |first3=W. |year=2005 |title=Shape coexistence and triaxiality in the superheavy nuclei |url=http://www.phys.utk.edu/witek/fission/utk/Papers/natureSHE.pdf |journal=] |volume=433 |issue=7027 |pages=705–709 |bibcode=2005Natur.433..705C |doi=10.1038/nature03336 |pmid=15716943 |url-status=dead |archiveurl=https://web.archive.org/web/20100623081932/http://www.phys.utk.edu/witek/fission/utk/Papers/natureSHE.pdf |archivedate=2010-06-23 }}</ref> It was thought that if such elements exist and are sufficiently long-lived, there may be several novel applications as a consequence of their nuclear and chemical properties. These include use in ]s as ]s, in ]s as a consequence of their predicted low ]es and high number of neutrons emitted per fission,<ref>{{cite book |last1=Gsponer |first1=A. |last2=Hurni |first2=J.-P. |year=2009 |title=Fourth Generation Nuclear Weapons: The physical principles of thermonuclear explosives, inertial confinement fusion, and the quest for fourth generation nuclear weapons |edition=3rd printing of the 7th |pages=110–115 |url=https://cryptome.org/2014/06/wmd-4th-gen-quest.pdf}}</ref> and as ] to power space missions.<ref name=newsci10>{{cite news |last=Courtland |first=R. |title=Weight scale for atoms could map 'island of stability' |date=2010 |accessdate=4 July 2019 |publisher=NewScientist |url=https://www.newscientist.com/article/dn18510-weight-scale-for-atoms-could-map-island-of-stability/}}</ref> These speculations led many researchers to conduct searches for superheavy elements in the 1960s and 1970s, both in nature and through ] in particle accelerators.<ref name=ghiorso1 /> During the 1970s, many searches for long-lived superheavy nuclei were conducted. Experiments aimed at synthesizing elements ranging in atomic number from 110 to 127 were conducted at laboratories around the world.<ref name=LodhiTable>{{harvnb|Lodhi|1978|p=35}}</ref><ref name=emsley>{{harvnb|Emsley|2011|p=588}}</ref> These elements were sought in fusion-evaporation reactions, in which a heavy target made of one nuclide is ] by accelerated ions of another in a ], and new nuclides are produced after these nuclei ] and the resulting excited system releases energy by evaporating several particles (usually protons, neutrons, or alpha particles). These reactions are divided into "cold" and "hot" fusion, which respectively create systems with lower and higher ] energies; this affects the yield of the reaction.<ref name=JK17>{{cite journal |last=Khuyagbaatar |first=J. |date=2017 |title=The cross sections of fusion-evaporation reactions: the most promising route to superheavy elements beyond ''Z'' = 118 |journal=EPJ Web of Conferences |volume=163 |pages=00030-1–00030-5 <!-- Deny Citation Bot-->|doi=10.1051/epjconf/201716300030 |url=https://www.researchgate.net/publication/321229825}}</ref> For example, the reaction between ²⁴⁸Cm and ⁴⁰Ar was expected to yield isotopes of element 114, and that between ²³²Th and ⁸⁴Kr was expected to yield isotopes of element 126.<ref name=H404>{{harvnb|Hoffman|2000|p=404}}</ref> None of these attempts were successful,<ref name=LodhiTable/><ref name=emsley>{{harvnb|Emsley|2011|p=588}}</ref> indicating that such experiments may have been insufficiently sensitive if reaction ] were low—resulting in lower yields—or that any nuclei reachable via such fusion-evaporation reactions might be too short-lived for detection.{{efn|name=microsec}} Subsequent successful experiments reveal that half-lives and cross sections indeed decrease with increasing atomic number, resulting in the synthesis of only a few short-lived atoms of the heaviest elements in each experiment.<ref name="Karpov2015">{{cite web<!--Citation bot deny--> |url=https://cyclotron.tamu.edu/she2015/assets/pdfs/presentations/Karpov_SHE_2015_TAMU.pdf |title=Superheavy Nuclei: Which regions of nuclear map are accessible in the nearest studies? |last=Karpov |first=A. |last2=Zagrebaev |first2=V. |last3=Greiner |first3=W. |date=2015 |pages=1–16 |work=SHE-2015 |access-date=30 October 2018}}</ref> Similar searches in nature were also unsuccessful, suggesting that if superheavy elements do exist in nature, their abundance is less than 10⁻¹⁴ ] of superheavy elements per mole of ore.<ref>{{harvnb|Hoffman|2000|p=403}}</ref> Despite these unsuccessful attempts to observe long-lived superheavy nuclei,<ref name=quest /> new superheavy elements were synthesized ] in laboratories through ] and cold fusion{{efn|This is a distinct concept from hypothestical fusion near room temperature (]); it instead refers to fusion reactions with lower excitation energy.}} reactions; rutherfordium, the first ], was discovered in 1969, and copernicium, eight protons closer to the island of stability predicted at ''Z'' = 114, was reached by 1996. Even though the half-lives of these nuclei are very short (on the order of ]s),<ref name=nubase/> the very existence of elements heavier than rutherfordium is indicative of stabilizing effects thought to be caused by closed shells; a ] would forbid the existence of these elements due to rapid spontaneous fission.<ref name=liquiddrop>{{cite journal |last=Möller |first=P. |date=2016 |title=The limits of the nuclear chart set by fission and alpha decay |journal=EPJ Web of Conferences |volume=131 |pages=03002-1–03002-8<!-- Deny Citation Bot--> |url=http://inspirehep.net/record/1502715/files/epjconf-NS160-03002.pdf |doi=10.1051/epjconf/201613103002 |bibcode=2016EPJWC.13103002M}}</ref> Flerovium, with the expected magic 114 protons, was first synthesized in 1998 at the ] in ], Russia, by a group of physicists led by ]. A single atom of element 114 was detected, with a lifetime of 30.4 seconds, and its ]s had half-lives measurable in minutes.<ref name="99Og01">{{cite journal |last1=Oganessian |first1=Yu. Ts. |last2=Utyonkov |first2=V. K. |last3=Lobanov |first3=Yu. V. |display-authors=etal |date=1999 |title=Synthesis of Superheavy Nuclei in the ⁴⁸Ca + ²⁴⁴Pu Reaction |url=http://flerovlab.jinr.ru/linkc/flnr_presentations/articles/synthesis_of_Element_114_1999.pdf |journal=] |volume=83 |issue=16 |page=3154 |bibcode=1999PhRvL..83.3154O |doi=10.1103/PhysRevLett.83.3154}}</ref> Because the produced nuclei underwent alpha decay rather than fission, and the half-lives were several ] longer than those previously predicted{{efn|Oganessian stated that element 114 would have a half-life on the order of 10⁻¹⁹ s in the absence of stabilizing effects in the vicinity of the theorized island.<ref name=whatittakes>{{cite web |last=Chapman |first=K. |date=2016 |title=What it takes to make a new element |url=https://www.chemistryworld.com/what-it-takes-to-make-a-new-element/1017677.article |publisher=] |accessdate=16 January 2020}}</ref>}} or observed for superheavy elements,<ref name="99Og01"/> this event was seen as a "textbook example" of a decay chain characteristic of the island of stability, providing strong evidence for the existence of the island of stability in this region.<ref>{{harvnb|Hoffman|2000|p=426}}</ref> Even though the original 1998 chain was not observed again, and its assignment remains uncertain,<ref name=Hofmann2016/> further successful experiments in the next two decades led to the discovery of all elements up to ], whose half-lives were found to exceed initially predicted values; these decay properties further support the presence of the island of stability.<ref name=beachhead>{{cite journal |last=Oganessian |first=Yu. Ts. |last2=Rykaczewski |first2=K. |title=A beachhead on the island of stability |date=2015 |journal=Physics Today |volume=68 |issue=8 |pages=32–38 |doi=10.1063/PT.3.2880 |url=https://www.researchgate.net/publication/282806685 |bibcode=2015PhT....68h..32O|osti=1337838 }}</ref><ref name=48Ca>{{cite journal |last=Oganessian |first=Yu. Ts. |title=Heaviest nuclei from ⁴⁸Ca-induced reactions |date=2007 |journal=Journal of Physics G: Nuclear and Particle Physics |volume=34 |issue=4 |pages=R233 |doi=10.1088/0954-3899/34/4/R01 |url=https://www.nucleonica.com/images/4/41/Oganessian.pdf |bibcode=2007JPhG...34R.165O}}</ref><ref name="117s">{{cite journal|last1=Oganessian |first1=Yu. Ts.|last2=Abdullin |first2=F. Sh.|last3=Bailey |first3=P. D. |last4=Benker |first4=D. E.|last5=Bennett |first5=M. E.|last6=Dmitriev |first6=S. N.|last7=Ezold |first7=J. G.|last8=Hamilton |first8=J. H.|last9=Henderson |first9=R. A. | first10=M. G. |last10=Itkis | first11=Yuri V. |last11=Lobanov | first12=A. N. |last12=Mezentsev | first13=K. J. |last13=Moody | first14=S. L. |last14=Nelson | first15=A. N. |last15=Polyakov | first16=C. E. |last16=Porter | first17=A. V. |last17=Ramayya | first18=F. D. |last18=Riley | first19=J. B.|last19=Roberto | first20=M. A. |last20=Ryabinin | first21=K. P. |last21=Rykaczewski | first22=R. N. |last22=Sagaidak | first23=D. A. |last23=Shaughnessy | first24=I. V. |last24=Shirokovsky | first25=M. A. |last25=Stoyer | first26=V. G. |last26=Subbotin | first27=R. |last27=Sudowe | first28=A. M. |last28=Sukhov | first29=Yu. S. |last29=Tsyganov | first30=Vladimir K. |last30=Utyonkov | first31=A. A. |last31=Voinov | first32=G. K. |last32=Vostokin | first33=P. A. |last33=Wilk|title=Synthesis of a New Element with Atomic Number ''Z'' = 117 |year=2010 |journal=Physical Review Letters |volume=104 |issue=14 |pages=142502-1–142502-4 <!-- Deny Citation Bot-->|doi=10.1103/PhysRevLett.104.142502 |pmid=20481935 |bibcode=2010PhRvL.104n2502O |url=https://www.researchgate.net/publication/44610795 |displayauthors=3 }}</ref> Although known nuclei still fall several neutrons short of ''N'' = 184 where maximum stability is expected (the most neutron-rich confirmed nuclei, ²⁹³Lv and ²⁹⁴Ts, only reach ''N'' = 177), and the exact location of the center of the island remains unknown,<ref name=physorg/><ref name=beachhead /> the trend of increasing stability closer to ''N'' = 184 has been demonstrated. For example, the isotope ²⁸⁵Cn, with eight more neutrons than ²⁷⁷Cn, has a half-life almost five orders of magnitude longer. This trend is expected to continue into unknown heavier isotopes.<ref name=Zagrebaev /> ] ===Deformed nuclei=== Though nuclei within the island of stability around ''N'' = 184 are predicted to be ], studies from the early 1990s—beginning with Polish physicists Zygmunt Patyk and Adam Sobiczewski in 1991<ref>{{Cite journal|last=Patyk|first=Z.|last2=Sobiczewski|first2=A.|date=1991|title=Ground-state properties of the heaviest nuclei analyzed in a multidimensional deformation space|journal=Nuclear Physics A|language=en|volume=533|issue=1|page=150|bibcode=1991NuPhA.533..132P|doi=10.1016/0375-9474(91)90823-O}}</ref>—suggest that some superheavy elements do not have perfectly spherical nuclei.<ref name=structure>{{cite journal |title=Structure of Odd-''N'' Superheavy Elements |journal=Physical Review Letters |volume=83 |issue=6 |pages=1108–1111 |year=1999 |doi=10.1103/PhysRevLett.83.1108 |last1=Ćwiok |first1=S. |last2=Nazarewicz |first2=W. |last3=Heenen |first3=P. H. |bibcode=1999PhRvL..83.1108C }}</ref><ref name=zaioo>{{cite journal |last=Zagrebaev |first=V. I. |last2=Aritomo |first2=Y. |last3=Itkis |first3=M. G. |last4=Oganessian |first4=Yu. Ts. |last5=Ohta |first5=N. |displayauthors=3 |title=Synthesis of superheavy nuclei: How accurately can we describe it and calculate the cross sections? |date=2001 |journal=Physical Review C |volume=65 |issue=1 |pages=014607-1–014607-14 <!-- Deny Citation Bot-->|doi=10.1103/PhysRevC.65.014607 |url=http://nrv.jinr.ru/pdf_file/zaioo.pdf}}</ref> A change in the shape of the nucleus changes the position of neutrons and protons in the shell. Research indicates that large nuclei farther from spherical magic numbers are ],<ref name=zaioo/> causing magic numbers to shift or new magic numbers to appear. Current theoretical investigation indicates that in the region ''Z'' = 106–108 and ''N'' ≈ 160–164, nuclei may be more resistant to fission as a consequence of shell effects for deformed nuclei; thus, such superheavy nuclei would only undergo alpha decay.<ref name="predictions" /><ref name="longlived" /><ref name="nuclear" /> Hassium-270 is now believed to be a doubly magic deformed nucleus, with deformed magic numbers ''Z'' = 108 and ''N'' = 162.<ref name=270Hs01>{{Cite journal |first1=J. |last1=Dvořák |first2 =W. |last2= Brüchle |first3= M. |last3= Chelnokov |first4= R. |last4= Dressler |first5= Ch. E. |last5= Düllmann |first6= K. |last6= Eberhardt |first7= V. |last7= Gorshkov |first8= E. |last8= Jäger |first9= R. |last9= Krücken |first10= A. |last10= Kuznetsov |first11= Y. |last11= Nagame |first12= F. |last12= Nebel |first13= Z. |last13= Novackova |first14= Z. |last14= Qin |first15= M. |last15= Schädel |first16= B. |last16= Schausten |first17= E. |last17= Schimpf |first18= A. |last18= Semchenkov |first19= P. |last19= Thörle |first20= A. |last20= Türler |first21= M. |last21= Wegrzecki |first22= B. |last22= Wierczinski |first23= A. |last23= Yakushev |first24= A. |last24= Yeremin |displayauthors=3 |year=2006 |title=Doubly Magic Nucleus {{su|p=270|b=108}}Hs{{su|b=162}} |journal=] |volume=97 |issue=24 |pages=242501-1–242501-4 <!-- Deny Citation Bot-->|bibcode=2006PhRvL..97x2501D |doi=10.1103/PhysRevLett.97.242501 |pmid=17280272|url=https://www.dora.lib4ri.ch/psi/islandora/object/psi%3A16351 }}</ref> It has a half-life of 9 seconds.<ref name=nubase/> This is consistent with models that take into account the deformed nature of nuclei intermediate between the actinides and island of stability near ''N'' = 184, in which a stability "peninsula" emerges at deformed magic numbers ''Z'' = 108 and ''N'' = 162.<ref name=Moller97>{{cite journal |last=Möller |first=P. |last2=Nix |first2=J. R. |title=Stability and Production of Superheavy Nuclei |date=1998 |journal=AIP Conference Proceedings |volume=425 |issue=1 |pages=75 |doi=10.1063/1.55136 |arxiv=nucl-th/9709016|bibcode=1998AIPC..425...75M }}</ref><ref name=270Hs2020>{{cite journal |last=Meng |first=X. |last2=Lu |first2=B.-N. |last3=Zhou |first3=S.-G. |title=Ground state properties and potential energy surfaces of ²⁷⁰Hs from multidimensionally constrained relativistic mean field model |date=2020 |journal=Science China Physics, Mechanics & Astronomy |volume=63 |issue=1 |pages=212011-1–212011-9 <!-- Deny Citation Bot-->|doi=10.1007/s11433-019-9422-1 |arxiv=1910.10552|bibcode=2020SCPMA..6312011M }}</ref> Determination of the decay properties of neighboring hassium and seaborgium isotopes near ''N'' = 162 provides further strong evidence for this region of relative stability in deformed nuclei.<ref name="Cwiok" /> This also strongly suggests that the island of stability (for spherical nuclei) is not completely isolated from the region of stable nuclei, but rather that both regions are instead linked through an isthmus of relatively stable deformed nuclei.<ref name=Moller97 /><ref name=kjmoody>{{cite book |editor-last=Schädel |editor-first=M. |editor-last2=Shaughnessy |editor-first2=D. |title=The Chemistry of Superheavy Elements |year=2014 |edition=2nd |publisher=Springer |page=3 |chapter=Synthesis of Superheavy Elements |last=Moody |first=K. J. |isbn=978-3-642-37466-1}}</ref> ==Predicted decay properties== ] (β) or ] (EC) branches may appear closest to the center of the island around ²⁹¹Cn and ²⁹³Cn.<ref name=KarpovSHE />]] The ] of nuclei in the island of stability itself are unknown since none of the nuclides that would be "on the island" have been observed. Many physicists believe that the half-lives of these nuclei are relatively short, on the order of minutes or days.<ref name=physorg /> Some theoretical calculations indicate that their half-lives may be long, on the order of 100 years,<ref name=KarpovSHE /><ref name="Karpov2015" /> or possibly as long as 10⁹ years.<ref name=nuclei /> The shell closure at ''N'' = 184 is predicted to result in longer ] for alpha decay and spontaneous fission.<ref name=KarpovSHE /> It is believed that the shell closure will result in higher fission barriers for nuclei around ²⁹⁸Fl, strongly hindering fission and perhaps resulting in fission half-lives 30 orders of magnitude greater than those of nuclei unaffected by the shell closure.<ref name=quest /><ref name=SHlimit>{{cite conference|last=Koura|first=H.|date=2011|title=Decay modes and a limit of existence of nuclei in the superheavy mass region|url=http://tan11.jinr.ru/pdf/10_Sep/S_2/05_Koura.pdf|conference=4th International Conference on the Chemistry and Physics of the Transactinide Elements|accessdate=18 November 2018}}</ref> For example, the neutron-deficient isotope ] (with ''N'' = 170) undergoes fission with a half-life of 2.5 milliseconds, and is thought to be one of the most neutron-deficient nuclides with increased stability in the vicinity of the ''N'' = 184 shell closure.<ref name=PuCa2017>{{cite journal |last1=Utyonkov |first1=V. K. |last2=Brewer |first2=N. T. |first3=Yu. Ts. |last3=Oganessian |first4=K. P. |last4=Rykaczewski |first5=F. Sh. |last5=Abdullin |first6=S. N. |last6=Dimitriev |first7=R. K. |last7=Grzywacz |first8=M. G. |last8=Itkis |first9=K. |last9=Miernik |first10=A. N. |last10=Polyakov |first11=J. B. |last11=Roberto |first12=R. N. |last12=Sagaidak |first13=I. V. |last13=Shirokovsky |first14=M. V. |last14=Shumeiko |first15=Yu. S. |last15=Tsyganov |first16=A. A. |last16=Voinov |first17=V. G. |last17=Subbotin |first18=A. M. |last18=Sukhov |first19=A. V. |last19=Karpov |first20=A. G. |last20=Popeko |first21=A. V. |last21=Sabel'nikov |first22=A. I. |last22=Svirikhin |first23=G. K. |last23=Vostokin |first24=J. H. |last24=Hamilton |first25=N. D. |last25=Kovrinzhykh |first26=L. |last26=Schlattauer |first27=M. A. |last27=Stoyer |first28=Z. |last28=Gan |first29=W. X. |last29=Huang |first30=L. |last30=Ma |displayauthors=3 |date=2018 |title=Neutron-deficient superheavy nuclei obtained in the ²⁴⁰Pu + ⁴⁸Ca reaction |journal=Physical Review C |volume=97 |issue=1 |pages=014320-1–014320-10 <!-- Deny Citation Bot-->|doi=10.1103/PhysRevC.97.014320|bibcode=2018PhRvC..97a4320U |url=https://www.researchgate.net/publication/322812255}}</ref> Beyond this point, some undiscovered isotopes are predicted to undergo fission with still shorter half-lives, limiting the existence{{efn|The ] (IUPAC) defines the limit of nuclear existence at a half-life of 10⁻¹⁴ seconds; this is approximately the time required for nucleons to arrange themselves into nuclear shells and thus form a nuclide.<ref>{{harvnb|Emsley|2011|p=590}}</ref>}} and possible observation{{efn|name=microsec|While such nuclei may be synthesized and a ] of decay signals may be registered, decays faster than one microsecond may pile up with subsequent signals and thus be indistinguishable, especially when multiple uncharacterized nuclei may be formed and emit a series of similar alpha particles.<ref name=Np223>{{cite journal |title=New short-lived isotope ²²³Np and the absence of the ''Z'' = 92 subshell closure near ''N'' = 126 |first=M. D. |last=Sun |first2=Z. |last2=Liu |first3=T. H. |last3=Huang |display-authors=et al. |journal=Physics Letters B |volume=771 |date=2017 |pages=303–308 |doi=10.1016/j.physletb.2017.03.074 |url=https://www.researchgate.net/publication/317142406|bibcode=2017PhLB..771..303S }}</ref> The main difficulty is thus attributing the decays to the correct ], as a superheavy atom that decays before reaching the detector will not be registered at all.<ref name=Palenzuela/>}} of superheavy nuclei far from the island of stability (namely for ''N'' < 170 as well as for ''Z'' > 120 and ''N'' > 184).<ref name=CN14/><ref name=liquiddrop /> These nuclei may undergo alpha decay or spontaneous fission in microseconds or less, with some fission half-lives estimated on the order of 10⁻²⁰ seconds in the absence of fission barriers.<ref name="predictions" /><ref name="longlived" /><ref name="nuclear" /><ref name=SHlimit/> In contrast, ²⁹⁸Fl (predicted to lie within the region of maximum shell effects) may have a much longer spontaneous fission half-life, possibly on the order of 10¹⁹ years.<ref name=quest /> In the center of the island, there may be competition between alpha decay and spontaneous fission, though the exact ratio is model-dependent.<ref name=KarpovSHE /> The alpha decay half-lives of 1700 nuclei with 100 ≤ ''Z'' ≤ 130 have been calculated in a quantum tunneling model with both experimental and theoretical alpha decay ], and are in agreement with observed half-lives for some of the heaviest isotopes.<ref name="predictions">{{Cite journal |last1=Samanta |first1=C. |last2=Chowdhury |first2=P. R. |last3=Basu |first3=D. N. |year=2007 |title=Predictions of alpha decay half lives of heavy and superheavy elements |journal=] |volume=789 |issue= 1–4|pages=142–154 |arxiv=nucl-th/0703086 |bibcode=2007NuPhA.789..142S |doi=10.1016/j.nuclphysa.2007.04.001|citeseerx=10.1.1.264.8177 }}</ref><ref name="longlived">{{Cite journal |last=Chowdhury |first=P. R. |last2=Samanta |first2=C. |last3=Basu |first3=D. N. |year=2008 |title=Search for long lived heaviest nuclei beyond the valley of stability |journal=] |volume=77 |issue=4 |pages=044603-1–044603-14 <!-- Deny Citation Bot-->|arxiv=0802.3837 |bibcode=2008PhRvC..77d4603C |doi=10.1103/PhysRevC.77.044603}}</ref><ref name="nuclear">{{Cite journal |last=Chowdhury |first=P. R. |last2=Samanta |first2=C. |last3=Basu |first3=D. N. |year=2008 |title=Nuclear half-lives for α-radioactivity of elements with 100 ≤ ''Z'' ≤ 130 |journal=] |volume=94 |issue=6 |pages=781–806 |arxiv=0802.4161 |bibcode=2008ADNDT..94..781C |doi=10.1016/j.adt.2008.01.003}}</ref><ref name="half-lifesall">{{Cite journal |last=Chowdhury |first=P. R. |last2=Samanta |first2=C. |last3=Basu |first3=D. N. |year=2006 |title=α decay half-lives of new superheavy elements |journal=] |volume=73 |issue= 1|pages=014612-1–014612-7 <!-- Deny Citation Bot-->|arxiv=nucl-th/0507054 |bibcode=2006PhRvC..73a4612C |doi=10.1103/PhysRevC.73.014612}}</ref><ref name="decaychains">{{Cite journal |last=Chowdhury |first=P. R. |last2=Basu |first2=D. N. |last3=Samanta |first3=C. |date=2007 |title=α decay chains from element 113 |journal=] |volume=75 |issue=4 |pages=047306-1–047306-3 <!-- Deny Citation Bot-->|arxiv=0704.3927 |bibcode=2007PhRvC..75d7306C |doi=10.1103/PhysRevC.75.047306}}</ref><ref name="tunneling">{{Cite journal |last1=Samanta |first1=C. |last2=Basu |first2=D. N. |last3=Chowdhury |first3=P. R. |year=2007 |title=Quantum tunneling in ²⁷⁷112 and its alpha-decay chain |journal=] |volume=76 |issue=12 |pages=124201-1–124201-4 <!-- Deny Citation Bot-->|arxiv=0708.4355 |bibcode=2007JPSJ...76l4201S |doi=10.1143/JPSJ.76.124201}}</ref> The longest-lived nuclides are also predicted to lie on the ], for ] is predicted to compete with the other decay modes near the predicted center of the island, especially for isotopes of elements 111–115. Unlike other decay modes predicted for these nuclides, beta decay does not change the mass number. Instead, a neutron is converted into a proton or vice versa, producing an adjacent ] closer to the center of stability (the isobar with the lowest ]). For example, significant beta decay branches may exist in nuclides such as ²⁹¹Fl and ²⁹¹Nh; these nuclides have only a few more neutrons than known nuclides, and might decay via a "narrow pathway" towards the center of the island of stability.<ref name=ZagrebaevPPT/><ref name=KarpovSHE /> The possible role of beta decay is highly uncertain, as some isotopes of these elements (such as ²⁹⁰Fl and ²⁹³Mc) are predicted to have shorter partial half-lives for alpha decay. Beta decay would reduce competition and would result in alpha decay remaining the dominant decay channel, unless additional stability towards alpha decay exists in ] isomers of these nuclides.<ref name=sarriguren>{{cite journal |last=Sarriguren |first=P. |title=Microscopic calculations of weak decays in superheavy nuclei |date=2019 |journal=Physical Review C |volume=100 |issue=1 |pages=014309-1–014309-12 <!-- Deny Citation Bot-->|doi=10.1103/PhysRevC.100.014309 |arxiv=1907.06877|bibcode=2019PhRvC.100a4309S }}</ref> Considering all decay modes, various models indicate a shift of the center of the island (i.e. the longest-living nuclide) from ²⁹⁸Fl to a lower atomic number, and competition between alpha decay and spontaneous fission in these nuclides;<ref name="Nilsson1969">{{cite journal |last1=Nilsson |first1=S. G. |last2=Tsang |first2=C. F. |last3=Sobiczewski |first3=A. |display-authors=etal |year=1969 |title=On the nuclear structure and stability of heavy and superheavy elements |journal=] |volume=131 |issue=1 |pages=53–55 |bibcode = 1969NuPhA.131....1N |doi=10.1016/0375-9474(69)90809-4|url=http://www.escholarship.org/uc/item/0d8319f2 |type=Submitted manuscript }}</ref> these include 100-year half-lives for ²⁹¹Cn and ²⁹³Cn,<ref name="Karpov2015" /><ref name=Palenzuela>{{cite journal|last=Palenzuela|first=Y. M.|last2=Ruiz|first2=L. F.|last3=Karpov|first3=A.|last4=Greiner|first4=W.|year=2012|title=Systematic Study of Decay Properties of Heaviest Elements|journal=Bulletin of the Russian Academy of Sciences: Physics|volume=76|issue=11|pages=1165–1171|issn=1062-8738|url=http://nrv.jinr.ru/karpov/publications/Palenzuela12_BRAS.pdf|doi=10.3103/S1062873812110172|bibcode=2012BRASP..76.1165P}}</ref> a 1000-year half-life for ²⁹⁶Cn,<ref name="Karpov2015" /> and a 300-year half-life for ²⁹⁴Ds,<ref name=SHlimit /> the latter two exactly at the ''N'' = 184 shell closure. It has also been posited that this region of enhanced stability for elements with 112 ≤ ''Z'' ≤ 118 may instead be a consequence of nuclear deformation, and that the true center of the island of stability for spherical superheavy nuclei lies around ³⁰⁶] (''Z'' = 122, ''N'' = 184).<ref name=Kratz>{{cite conference |last1=Kratz |first1=J. V. |date=2011 |title=The Impact of Superheavy Elements on the Chemical and Physical Sciences |url=http://tan11.jinr.ru/pdf/06_Sep/S_1/02_Kratz.pdf |pages=30–37 |conference=4th International Conference on the Chemistry and Physics of the Transactinide Elements |accessdate=27 August 2013}}</ref> This model defines the island of stability as the region with the greatest resistance to fission rather than the longest total half-lives;<ref name=Kratz/> the nuclide ³⁰⁶Ubb is still predicted to have a short half-life with respect to alpha decay.<ref name=KarpovSHE/><ref name="nuclear"/> Another potentially significant decay mode for the heaviest superheavy elements was proposed to be ] by Romanian physicists ] and Radu A. Gherghescu and German physicist ]. Its ] relative to alpha decay is expected to increase with atomic number such that it may compete with alpha decay around ''Z'' = 120, and perhaps become the dominant decay mode for heavier nuclides around ''Z'' = 124. As such, it is expected to play a larger role beyond the center of the island of stability (though still influenced by shell effects), unless the center of the island lies at a higher atomic number than predicted.<ref name="cldec">{{Cite journal |last1=Poenaru |first1=D. N. |last2=Gherghescu |first2=R. A. |last3=Greiner |first3=W. |year=2011 |title=Heavy-Particle Radioactivity of Superheavy Nuclei |journal=] |volume=107 |issue=6 |pages=062503-1–062503-4 <!-- Deny Citation Bot-->|arxiv=1106.3271 |bibcode=2011PhRvL.107f2503P |doi=10.1103/PhysRevLett.107.062503 |pmid=21902317}}</ref> ==Possible natural occurrence== ] = 178 and ] = 112]] Even though half-lives of hundreds or thousands of years would be relatively long for superheavy elements, they are far too short for any such nuclides to exist ] on Earth. Additionally, instability of nuclei intermediate between primordial actinides (], ], and ]) and the island of stability may inhibit production of nuclei within the island in ] nucleosynthesis. Various models suggest that spontaneous fission will be the dominant decay mode of nuclei with ''A'' > 280, and that neutron-induced or beta-delayed ]—respectively neutron capture and beta decay immediately followed by fission—will become the primary reaction channels. As a result, beta decay towards the island of stability may only occur within a very narrow path or may be entirely blocked by fission, thus precluding the synthesis of nuclides within the island.<ref name=natural>{{cite journal|last=Petermann |first=I|last2=Langanke|first2=K.|last3=Martínez-Pinedo|first3=G.|last4=Panov|first4=I. V. |last5=Reinhard|first5=P. G.|last6=Thielemann|first6=F. K. |displayauthors=3 |date=2012|title=Have superheavy elements been produced in nature?|journal=European Physical Journal A|volume=48|issue=122|pages=122|url=https://www.researchgate.net/publication/229156774|doi=10.1140/epja/i2012-12122-6|arxiv=1207.3432|bibcode=2012EPJA...48..122P}}</ref> The non-observation of superheavy nuclides such as ²⁹²Hs and ²⁹⁸Fl in nature is thought to be a consequence of a low yield in the ''r''-process resulting from this mechanism, as well as half-lives too short to allow measurable quantities to persist in nature.<ref name=spectrometry>{{cite journal| last=Ludwig |first=P. |last2=Faestermann |first2=T. |last3=Korschinek |first3=G. |last4=Rugel |first4=G. |last5=Dillmann |first5=I. |last6=Fimiani |first6=L. |last7=Bishop |first7=S. |last8=Kumar |first8=P. |displayauthors=3 |title=Search for superheavy elements with 292 ≤ ''A'' ≤ 310 in nature with accelerator mass spectrometry |date=2012 |journal=Physical Review C |volume=85 |issue=2 |pages=024315-1–024315-8 <!-- Deny Citation Bot-->|doi=10.1103/PhysRevC.85.024315 |url=https://www.nucastro.ph.tum.de/fileadmin/tuphena/www/pubs/e024315.pdf |archive-url=https://web.archive.org/web/20181228223425/https://www.nucastro.ph.tum.de/fileadmin/tuphena/www/pubs/e024315.pdf |archive-date=28 December 2018 |url-status=live}}</ref>{{efn|The observation of long-lived isotopes of ] and ] in nature has been claimed by Israeli physicist ] ''et al.'',<ref name="rg2009">{{cite journal |last1=Marinov |first1=A. |last2=Rodushkin |first2=I. |last3=Pape |first3=A. |last4=Kashiv |first4=Y. |last5=Kolb |first5=D. |last6=Brandt |first6=R. |last7=Gentry |first7=R. V. |last8=Miller |first8=H. W. |last9=Halicz |first9=L. |first10=I. |last10=Segal |year=2009 |displayauthors=3 |title=Existence of Long-Lived Isotopes of a Superheavy Element in Natural Au |journal=] |volume=18 |number=3 |pages=621–629 |publisher=] |doi=10.1142/S021830130901280X |url=http://www.phys.huji.ac.il/~marinov/publications/Au_paper_IJMPE_73.pdf |accessdate=12 February 2012 |arxiv=nucl-ex/0702051 |bibcode=2009IJMPE..18..621M |archive-url=https://web.archive.org/web/20140714210340/http://www.phys.huji.ac.il/~marinov/publications/Au_paper_IJMPE_73.pdf |archive-date=14 July 2014 |url-status=dead }}</ref><ref name=arxiv122>{{cite journal |last=Marinov |first=A. |author2=Rodushkin, I.|author3= Kolb, D.|author4= Pape, A.|author5= Kashiv, Y.|author6= Brandt, R.|author7= Gentry, R. V.|author8= Miller, H. W. |displayauthors=3 |title=Evidence for a long-lived superheavy nucleus with atomic mass number A = 292 and atomic number Z =~ 122 in natural Th |journal= International Journal of Modern Physics E|year=2010 |arxiv=0804.3869 |bibcode = 2010IJMPE..19..131M |doi = 10.1142/S0218301310014662 |volume=19 |issue=1 |pages=131–140 }}</ref> though evaluations of the technique used and subsequent unsuccessful searches cast considerable doubt on these results.<ref name=emsley/>}} Despite these obstacles to their synthesis, a 2013 study published by a group of Russian physicists led by ] proposes that the longest-lived copernicium isotopes may occur at an abundance of 10⁻¹² relative to lead, whereby they may be detectable in ]s.<ref name=Zagrebaev /> Similarly, in a 2013 experiment, a group of Russian physicists led by Aleksandr Bagulya reported the possible observation of three ] superheavy nuclei in ] crystals in meteorites. The atomic number of these nuclei was estimated to be between 105 and 130, with one nucleus likely constrained between 113 and 129, and their lifetimes were estimated to be at least 3,000 years. Although this observation has yet to be confirmed in independent studies, it strongly suggests the existence of the island of stability, and is consistent with theoretical calculations of half-lives of these nuclides.<ref name=oly1>{{cite journal |last1=Bagulya |first1=A. V. |last2=Vladimirov |first2=M. S. |last3=Volkov |first3=A. E. |last4=Goncharova |first4=L. A. |last5=Gorbunov |first5=S. A. |last6=Kalinina |first6=G. V. |last7=Konovalova |first7=N. S. |last8=Okatyeva |first8=N. M. |last9=Pavolva |first9=T. A. |last10=Polukhina |first10=N. G. |last11=Starkov |first11=N. I. |last12=Soe |first12=T. N. |last13=Chernyavsky |first13=M. M. |last14=Shchedrina |first14=T. V. |display-authors=3 |title=Charge spectrum of superheavy nuclei of galactic cosmic rays obtained in the OLIMPIA experiment |journal=Bulletin of the Lebedev Physics Institute |date=2015 |volume=42 |issue=5 |pages=152–156 |doi=10.3103/S1068335615050073 |url=https://www.researchgate.net/publication/279166139|bibcode=2015BLPI...42..152B }}</ref><ref name=nats>{{cite arxiv |first=A. |last= Alexandrov |first2= V. |last2= Alexeev |first3= A. |last3= Bagulya |first4= A. |last4= Dashkina |first5= M. |last5= Chernyavsky |first6= A. |last6= Gippius |first7= L. |last7= Goncharova |first8= S. |last8= Gorbunov |first9= V. |last9= Grachev |first10= G. |last10= Kalinina |first11= N. |last11= Konovalova |first12= N. |last12= Okateva |first13= T. |last13= Pavlova |first14= N. |last14= Polukhina |first15= R. |last15= Rymzhanov |first16= N. |last16= Starkov |first17= T. N. |last17= Soe |first18= T. |last18= Shchedrina |first19= A. |last19= Volkov |display-authors=3 |title=Natural superheavy nuclei in astrophysical data |date=2019 |eprint=1908.02931 |class=nucl-ex }}</ref><ref name=19cq>{{cite journal |title=Superheavy elements: Oganesson and beyond |date=2019 |last=Giuliani |first=S. A. |last2=Matheson |first2=Z. |last3=Nazarewicz |first3=W. |display-authors=et al. |journal=Reviews of Modern Physics |volume=1 |issue=1 |pages=24–27 |doi=10.1103/RevModPhys.91.011001 |osti=1513815 }}</ref> ==Possible synthesis and difficulties== The manufacture of nuclei on the island of stability proves to be very difficult because the nuclei available as starting materials do not deliver the necessary sum of neutrons. Radioactive ion beams (such as ⁴⁴S) in combination with actinide targets (such as ²⁴⁸]) may allow the production of more neutron rich nuclei nearer to the center of the island of stability, though such beams are not currently available in the required intensities to conduct such experiments.<ref name=Zagrebaev /><ref name=Popeko>{{cite conference |last=Popeko |first=A. G. |title=Perspectives of SHE research at Dubna |date=2016 |conference=NUSTAR Annual Meeting 2016 |location=Helmholtzzentrum für Schwerionenforschung, Darmstadt, Germany |pages=22–28 |url=https://indico.gsi.de/event/3548/session/23/contribution/45/material/slides/}}</ref><ref name=Zhu19/> Several heavier isotopes such as ²⁵⁰Cm and ²⁵⁴] may still be usable as targets, allowing the production of isotopes with one or two more neutrons than known isotopes,<ref name=Zagrebaev>{{cite conference |last1=Zagrebaev |first1=V. |last2=Karpov |first2=A. |last3=Greiner |first3=W. |date=2013 |title=Future of superheavy element research: Which nuclei could be synthesized within the next few years? |publisher=IOP Science |booktitle=Journal of Physics: Conference Series |volume=420 |pages=1–15 |arxiv=1207.5700 |doi=10.1088/1757-899X/468/1/012012 }}</ref> though the production of several milligrams of these rare isotopes to create a target is difficult.<ref name=Roberto>{{cite web |url=https://cyclotron.tamu.edu/she2015/assets/pdfs/presentations/Roberto_SHE_2015_TAMU.pdf |title=Actinide Targets for Super-Heavy Element Research |last=Roberto |first=J. B. |date=2015 |website=cyclotron.tamu.edu |publisher=Texas A & M University |pages=3–6 |access-date=30 October 2018}}</ref> It may also be possible to probe alternative reaction channels in the same ]-induced fusion-evaporation reactions that populate the most neutron-rich known isotopes, namely the ''pxn'' and ''αxn'' (emission of a proton or ], respectively, followed by several neutrons) channels. This may allow the synthesis of neutron-enriched isotopes of elements 111–117.<ref name=pxn /> Although the predicted cross sections are on the order of 1–900 ], smaller than those in the ''xn'' (emission of neutrons only) channels, it may still be possible to generate otherwise unreachable isotopes of superheavy elements in these reactions.<ref name=pxn>{{cite journal |last=Hong |first=J. |last2=Adamian |first2=G. G. |last3=Antonenko |first3=N. V. |date=2017 |title=Ways to produce new superheavy isotopes with ''Z'' = 111–117 in charged particle evaporation channels |journal=Physics Letters B |volume=764 |pages=42–48 |doi=10.1016/j.physletb.2016.11.002 |bibcode=2017PhLB..764...42H}}</ref><ref name=xsection>{{cite journal |last=Siwek-Wilczyńska |first=K. |last2=Cap |first2=T. |last3=Kowal |first3=P. |date=2019 |title=How to produce new superheavy nuclei? |arxiv=1812.09522 |doi=10.1103/PhysRevC.99.054603 |journal=Physical Review C |volume=99 |issue=5 |pages=054603-1–054603-5<!-- Deny Citation Bot-->}}</ref> Some of these heavier isotopes (such as ²⁹¹Mc, ²⁹¹Fl, and ²⁹¹Nh) may also undergo ] (converting a proton into a neutron) in addition to alpha decay with relatively long half-lives, decaying to nuclei such as ²⁹¹Cn that are predicted to lie near the center of the island of stability. However, this remains largely hypothetical as no superheavy nuclei near the beta-stability line have yet been synthesized and predictions of their properties vary considerably across different models.<ref name=ZagrebaevPPT /><ref name=Zagrebaev /> The process of slow ] used to produce nuclides as heavy as ²⁵⁷] is blocked by short-lived ] that undergo spontaneous fission (for example, ²⁵⁸Fm has a half-life of 370 µs); this is known as the "fermium gap" and prevents the synthesis of heavier elements in such a reaction. It might be possible to bypass this gap, as well as another predicted region of instability around ''A'' = 275 and ''Z'' = 104–108, in a series of controlled nuclear explosions with a higher ] (~1000 times greater than fluxes in existing reactors) that mimics the astrophysical ''r''-process.<ref name=Zagrebaev/> First proposed in 1972 by Meldner, such a reaction might enable the production of macroscopic quantities of superheavy elements within the island of stability;<ref name=ZagrebaevPPT/> the role of fission in intermediate superheavy nuclides is highly uncertain, and may strongly influence the yield of such a reaction.<ref name=natural/> ] shows known (boxed) and predicted decay modes of nuclei up to ''Z'' = 149 and ''N'' = 256. Regions of increased stability are visible around the predicted shell closures at ''N'' = 184 (²⁹⁴Ds–²⁹⁸Fl) and ''N'' = 228 (³⁵⁴126), separated by a gap of short-lived fissioning nuclei (''t''_1/2 < 1 ns; not colored in the chart).<ref name=SHlimit />]] It may also be possible to generate isotopes in the island of stability such as ²⁹⁸Fl in multi-nucleon ] in low-energy collisions of ] nuclei (such as ²³⁸U and ²⁴⁸Cm).<ref name=Popeko /> This inverse quasifission (partial fusion followed by fission, with a shift away from mass equilibrium that results in more asymmetric products) mechanism<ref name=TDHF>{{cite journal |last=Sekizawa |first=K. |date=2019 |title=TDHF theory and its extensions for the multinucleon transfer reaction: A mini review |journal=Frontiers in Physics |volume=7 |number=20 |arxiv=1902.01616 |doi=10.3389/fphy.2019.00020 |bibcode=2019FrP.....7...20S |pages=1–6<!-- Deny Citation Bot-->}}</ref> may provide a path to the island of stability if shell effects around ''Z'' = 114 are sufficiently strong, though lighter elements such as ] and seaborgium (''Z'' = 102–106) are predicted to have higher yields.<ref name=Zagrebaev /><ref name=ZG>{{cite journal |last1=Zagrebaev |first1=V. |last2=Greiner |first2=W. |year=2008 |title=Synthesis of superheavy nuclei: A search for new production reactions |journal=] |volume=78 |issue=3 |pages=034610-1–034610-12 <!-- Deny Citation Bot-->|arxiv=0807.2537 |bibcode=2008PhRvC..78c4610Z |doi=10.1103/PhysRevC.78.034610}}</ref> Preliminary studies of the ²³⁸U + ²³⁸U and ²³⁸U + ²⁴⁸Cm transfer reactions have failed to produce elements heavier than ] (''Z'' = 101), though the increased yield in the latter reaction suggests that the use of even heavier targets such as ²⁵⁴Es (if available) may enable production of superheavy elements.<ref name=Schadel>{{cite journal |last1=Schädel |first1=M. |title=Prospects of heavy and superheavy element production via inelastic nucleus-nucleus collisions – from {{sup|238}}U + {{sup|238}}U to {{sup|18}}O + {{sup|254}}Es |journal=EPJ Web of Conferences |date=2016 |volume=131 |pages=04001-1–04001-9 <!-- Deny Citation Bot-->|doi=10.1051/epjconf/201613104001 |url=https://inspirehep.net/record/1502716/files/epjconf-NS160-04001.pdf}}</ref> This result is supported by a later calculation suggesting that the yield of superheavy nuclides (with ''Z'' ≤ 109) will likely be higher in transfer reactions using heavier targets.<ref name=Zhu19>{{cite journal |last1=Zhu |first1=L. |title=Possibilities of producing superheavy nuclei in multinucleon transfer reac-tions based on radioactive targets |journal=Chinese Physics C |date=2019 |volume=43 |issue=12 |pages=124103-1–124103-4 <!-- Deny Citation Bot-->|doi=10.1088/1674-1137/43/12/124103 |bibcode=2019ChPhC..43l4103Z |url=http://hepnp.ihep.ac.cn/fileZGWLC/journal/article/zgwlc/newcreate/CPC-2019-0269.pdf}}</ref> A 2018 study of the ²³⁸U + ²³²Th reaction at the ] Cyclotron Institute by Sara Wuenschel ''et al.'' found several unknown alpha decays that may possibly be attributed to new, neutron-rich isotopes of superheavy elements with 104 < ''Z'' < 116, though further research is required to unambiguously determine the atomic number of the products.<ref name=Zhu19/><ref name=Wuenschel/> This result strongly suggests that shell effects have a significant influence on cross sections, and that the island of stability could possibly be reached in future experiments with transfer reactions.<ref name=Wuenschel>{{cite journal |last1=Wuenschel |first1=S. |last2=Hagel |first2=K. |last3=Barbui |first3=M. |last4=Gauthier |first4=J. |last5=Cao |first5=X. G. |last6=Wada |first6=R. |last7=Kim |first7=E. J. |last8=Majka |first8=Z. |last9=Planeta |first9=R. |last10=Sosin |first10=Z. |last11=Wieloch |first11=A. |last12=Zelga |first12=K. |last13=Kowalski |first13=S. |last14=Schmidt |first14=K. |last15=Ma |first15=C. |last16=Zhang |first16=G. |last17=Natowitz |first17=J. B. |displayauthors=3 |title=An experimental survey of the production of alpha decaying heavy elements in the reactions of ²³⁸U + ²³²Th at 7.5-6.1 MeV/nucleon |journal=Physical Review C |date=2018 |volume=97 |issue=6 |pages=064602-1–064602-12 <!-- Deny Citation Bot-->|doi=10.1103/PhysRevC.97.064602 |arxiv=1802.03091}}</ref> ==Other islands of stability== {{see also|Extended periodic table}} Further shell closures beyond the main island of stability in the vicinity of ''Z'' = 112–114 may give rise to additional islands of stability. Although predictions for the location of the next magic numbers vary considerably, two significant islands are thought to exist around heavier doubly magic nuclei; the first near ³⁵⁴126 (with 228 neutrons) and the second near ⁴⁷²164 or ⁴⁸²164 (with 308 or 318 neutrons).<ref name=quest /><ref name=SHlimit /><ref name=greinernuclei>{{cite journal|last=Greiner|first=W.|date=2013|title=Nuclei: superheavy-superneutronic-strange-and of antimatter|url=http://inspirehep.net/record/1221632/files/jpconf13_413_012002.pdf|journal=Journal of Physics: Conference Series|volume=413|issue=1|pages=012002-1–012002-9<!-- Deny Citation Bot-->|doi=10.1088/1742-6596/413/1/012002|bibcode=2013JPhCS.413a2002G}}</ref> Nuclides within these two islands of stability might be especially resistant to spontaneous fission and have alpha decay half-lives measurable in years, thus having comparable stability to elements in the vicinity of ].<ref name=quest /> Other regions of relative stability may also appear with weaker proton shell closures in beta-stable nuclides; such possibilities include regions near ³⁴²126<ref name=okunev/> and ⁴⁶²154.<ref name=fossilfission>{{cite web|last=Maly|first=J.|last2=Walz|first2=D. R.|title=Search for superheavy elements among fossil fission tracks in zircon|date=1980|url=http://www.slac.stanford.edu/pubs/slacpubs/2500/slac-pub-2554.pdf |citeseerx=10.1.1.382.8189 |page=15}}</ref> Substantially greater ] between protons in such heavy nuclei may greatly reduce their stability, and possibly restrict their existence to localized islands in the vicinity of shell effects.<ref name=aag>{{cite journal |last=Afanasjev |first=A. F. |last2=Agbemava |first2=S. E. |last3=Gyawali |first3=A. |title=Hyperheavy nuclei: Existence and stability |date=2018 |journal=Physics Letters B |volume=782 |pages=533–540 |doi=10.1016/j.physletb.2018.05.070 |arxiv=1804.06395 |bibcode=2018PhLB..782..533A |url=https://www.researchgate.net/publication/324584302}}</ref> This may have the consequence of isolating these islands from the main ], as intermediate nuclides and perhaps elements in a "sea of instability" would rapidly undergo fission and essentially be nonexistent.<ref name=greinernuclei /> It is also possible that beyond a region of relative stability around element 126, heavier nuclei would lie beyond a fission threshold given by the liquid drop model and thus undergo fission with very short lifetimes, rendering them essentially nonexistent even in the vicinity of greater magic numbers.<ref name=okunev>{{cite journal|last=Okunev|first=V. S.|date=2018|title=About islands of stability and limiting mass of the atomic nuclei|journal=IOP Conference Series: Materials Science and Engineering|volume=468|pages=012012-1–012012-13<!-- Deny Citation Bot-->|doi=10.1088/1757-899X/468/1/012012|url=https://www.researchgate.net/publication/329664372}}</ref> It has also been posited that in the region beyond ''A'' > 300, an entire "]" consisting of a hypothetical phase of stable ], comprising freely flowing ] and ] quarks rather than ]s bound into protons and neutrons, may exist. Such a form of matter is theorized to be a ground state of ] with a greater binding energy per ] than ], favoring the decay of nuclear matter beyond this mass threshold into quark matter. If this state of matter exists, it could possibly be synthesized in the same fusion reactions leading to normal superheavy nuclei, and would be stabilized against fission as a consequence of its stronger binding that is enough to overcome Coulomb repulsion.<ref name=udQM>{{cite journal |last=Holdom |first=B. |last2=Ren |first2=J. |last3=Zhang |first3=C. |title=Quark matter may not be strange |date=2018 |journal=Physical Review Letters |volume=120 |issue=1 |pages=222001-1–222001-6 <!-- Deny Citation Bot-->|doi=10.1103/PhysRevLett.120.222001|pmid=29906186 |arxiv=1707.06610 |bibcode=2018PhRvL.120v2001H }}</ref> == See also == {{Portal|Nuclear technology|physics}} * ] * ] ==Notes== {{notelist}} ==References== {{Reflist|colwidth=30em}} ===Bibliography=== {{Refbegin}} * {{cite book|last=Emsley|first=J.|title=Nature's Building Blocks: An A-Z Guide to the Elements|edition=New|year=2011|publisher=Oxford University Press|isbn=978-0-19-960563-7|ref=harv}} * {{cite book |last=Hoffman |first=D. C. |last2=Ghiorso |first2=A. |last3=Seaborg |first3=G. T. |title=The Transuranium People: The Inside Story |year=2000 |publisher=World Scientific |isbn=978-1-78-326244-1 |ref={{harvid|Hoffman|2000}}}} * {{cite book |last=Kragh |first=H. |year=2018 |title=From Transuranic to Superheavy Elements: A Story of Dispute and Creation |publisher=Springer |isbn=978-3-319-75813-8 |ref=harv}} * {{cite book |editor1-last=Lodhi |editor1-first=M. A. K. |title=Superheavy Elements: Proceedings of the International Symposium on Superheavy Elements |publisher=Pergamon Press |date=1978 |isbn=978-0-08-022946-1 |ref={{harvid|Lodhi|1978}}}} * {{cite book |last=Podgorsak |first=E. B. |title=Radiation physics for medical physicists |year=2016 |publisher=Springer |isbn=978-3-319-25382-4 |edition=3rd |ref=harv}} {{Refend}} == External links == * (''Nature'', 2006, with JINR diagram of heavy nuclides and predicted island of stability) * (2004 – "maybe") * (2001; nuclides with 116 protons and mass 292) * (1999; first few ''Z'' = 114 atoms) {{featured article}} ] ] ] ] ]