Editing Island of stability (section)

==Synthesis and difficulties==
[[File:Island of Stability.svg|alt=A 3D graph of stability of elements vs. number of protons Z and neutrons N, showing a "mountain chain" running diagonally through the graph from the low to high numbers, as well as an "island of stability" at high N and Z.|thumb|left|upright=2|Three-dimensional rendering of the island of stability around [[neutron number|''N'']]&nbsp;=&nbsp;178 and [[atomic number|''Z'']]&nbsp;=&nbsp;112]]
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 <sup>44</sup>S) in combination with actinide targets (such as <sup>248</sup>[[Curium|Cm]]) 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 <sup>250</sup>Cm and <sup>254</sup>[[Einsteinium|Es]] 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 |book-title=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 [[calcium-48|<sup>48</sup>Ca]]-induced fusion-evaporation reactions that populate the most neutron-rich known isotopes, namely those at a lower [[excited state|excitation]] energy (resulting in fewer neutrons being emitted during de-excitation), or those involving evaporation of charged particles (''pxn'', evaporating a proton and several neutrons, or ''αxn'', evaporating an [[alpha particle]] and several neutrons).<ref name=Yerevan2023PPT>{{cite conference |url=https://indico.jinr.ru/event/3622/contributions/20021/attachments/15292/25806/Yerevan2023.pdf |title=Interesting fusion reactions in superheavy region |first1=J. |last1=Hong |first2=G. G. |last2=Adamian |first3=N. V. |last3=Antonenko |first4=P. |last4=Jachimowicz |first5=M. |last5=Kowal |conference=IUPAP Conference "Heaviest nuclei and atoms" |publisher=Joint Institute for Nuclear Research |date=26 April 2023 |access-date=30 July 2023}}</ref> 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&nbsp;[[barn (unit)|fb]], smaller than when only neutrons are evaporated (''xn'' channels), it may still be possible to generate otherwise unreachable isotopes of superheavy elements in these reactions.<ref name=Yerevan2023PPT/><ref name=pxn>{{cite journal |last1=Hong |first1=J. |last2=Adamian |first2=G. G. |last3=Antonenko |first3=N. V. |date=2017 |title=Ways to produce new superheavy isotopes with ''Z''&nbsp;=&nbsp;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|doi-access=free }}</ref><ref name=xsection>{{cite journal |last1=Siwek-Wilczyńska |first1=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-->|s2cid=155404097 }}</ref> Some of these heavier isotopes (such as <sup>291</sup>Mc, <sup>291</sup>Fl, and <sup>291</sup>Nh) may also undergo [[electron capture]] (converting a proton into a neutron) in addition to alpha decay with relatively long half-lives, decaying to nuclei such as <sup>291</sup>Cn 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 /> In 2024, a team of researchers at the JINR observed one decay chain of the known isotope <sup>289</sup>Mc as a product in the ''p2n'' channel of the reaction between <sup>242</sup>Pu and <sup>50</sup>Ti, an experiment targeting neutron-deficient [[isotopes of livermorium|livermorium isotopes]]. This was the first successful report of a charged-particle exit channel in a hot fusion reaction between an actinide target and a projectile with ''Z''&nbsp;≥&nbsp;20.<ref name=jinr2024>{{Cite web |url=https://indico.jinr.ru/event/4343/contributions/28663/attachments/20748/36083/U%20+%20Cr%20AYSS%202024.pptx |title=Synthesis and study of the decay properties of isotopes of superheavy element Lv in Reactions <sup>238</sup>U + <sup>54</sup>Cr and <sup>242</sup>Pu + <sup>50</sup>Ti |last=Ibadullayev |first=Dastan |date=2024 |website=jinr.ru |publisher=[[Joint Institute for Nuclear Research]] |access-date=2 November 2024 |quote=}}</ref>

The process of slow [[neutron capture]] used to produce nuclides as heavy as <sup>257</sup>[[fermium|Fm]] is blocked by short-lived [[isotopes of fermium]] that undergo spontaneous fission (for example, <sup>258</sup>Fm has a half-life of 370&nbsp;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''&nbsp;=&nbsp;275 and ''Z''&nbsp;=&nbsp;104–108, in a series of controlled nuclear explosions with a higher [[neutron flux]] (about a thousand 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/>

[[File:Nuclear chart from KTUY model.svg|thumb|right|upright=2.2|alt=JAEA chart of nuclides up to ''Z''&nbsp;=&nbsp;149 and ''N''&nbsp;=&nbsp;256 showing predicted decay modes and the beta-stability line|This chart of nuclides used by the Japan Atomic Energy Agency shows known (boxed) and predicted decay modes of nuclei up to ''Z''&nbsp;=&nbsp;149 and ''N''&nbsp;=&nbsp;256. Regions of increased stability are visible around the predicted shell closures at ''N''&nbsp;=&nbsp;184 (<sup>294</sup>Ds–<sup>298</sup>Fl) and ''N''&nbsp;=&nbsp;228 (<sup>354</sup>126), separated by a gap of short-lived fissioning nuclei (''t''<sub>1/2</sub>&nbsp;<&nbsp;1&nbsp;ns; not colored in the chart).<ref name=SHlimit />]]

It may also be possible to generate isotopes in the island of stability such as <sup>298</sup>Fl in multi-nucleon [[Nuclear reaction#Transfer reactions|transfer reactions]] in low-energy collisions of [[actinide]] nuclei (such as <sup>238</sup>U and <sup>248</sup>Cm).<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-->|s2cid=73729050 |doi-access=free }}</ref> may provide a path to the island of stability if shell effects around ''Z''&nbsp;=&nbsp;114 are sufficiently strong, though lighter elements such as [[nobelium]] and seaborgium (''Z''&nbsp;=&nbsp;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=[[Physical Review C]] |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 <sup>238</sup>U&nbsp;+&nbsp;<sup>238</sup>U and <sup>238</sup>U&nbsp;+&nbsp;<sup>248</sup>Cm transfer reactions have failed to produce elements heavier than [[mendelevium]] (''Z''&nbsp;=&nbsp;101), though the increased yield in the latter reaction suggests that the use of even heavier targets such as <sup>254</sup>Es (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|doi-access=free }}</ref> This result is supported by a later calculation suggesting that the yield of superheavy nuclides (with ''Z''&nbsp;≤&nbsp;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 |s2cid=209932076 |url=http://hepnp.ihep.ac.cn/fileZGWLC/journal/article/zgwlc/newcreate/CPC-2019-0269.pdf |access-date=3 November 2019 |archive-date=3 November 2019 |archive-url=https://web.archive.org/web/20191103005211/http://hepnp.ihep.ac.cn/fileZGWLC/journal/article/zgwlc/newcreate/CPC-2019-0269.pdf |url-status=dead }}</ref> A 2018 study of the <sup>238</sup>U&nbsp;+&nbsp;<sup>232</sup>Th reaction at the [[Texas A&M]] 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&nbsp;<&nbsp;''Z''&nbsp;<&nbsp;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. |display-authors=3 |title=An experimental survey of the production of alpha decaying heavy elements in the reactions of <sup>238</sup>U + <sup>232</sup>Th at 7.5-6.1&nbsp;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 |bibcode=2018PhRvC..97f4602W|s2cid=67767157 }}</ref>