Isotopes of hassium

{{Short description|none}} {{Infobox hassium isotopes}} Hassium (₁₀₈Hs) is a synthetic element, and thus a standard atomic weight cannot be given. Like all synthetic elements, it has no stable isotopes. The first isotope to be synthesized was ²⁶⁵Hs in 1984. There are 13 known isotopes from ²⁶³Hs to ²⁷⁷Hs and up to six isomers. The most stable known isotope is ²⁷¹Hs, with a half-life of about 46 seconds, though this assignment is not definite due to uncertainty arising from a low number of measurements. The isotopes ²⁶⁹Hs and ²⁷⁰Hs respectively have half-lives of about 13 seconds and 7.6 seconds. It is also possible that the isomer ^277mHs is more stable than these, but only one event of the decay of this isomer has been registered as of 2020.{{NUBASE2020|ref}}<ref>{{Cite web|title=Radioactive Elements|url=https://ciaaw.org/radioactive-elements.htm|date=2018|access-date=2020-09-20|website=Commission on Isotopic Abundances and Atomic Weights|language=en}}</ref>

== List of isotopes == {{Anchor|Hassium-263m|Hassium-274|Hassium-276|Hassium-278|Hassium-279|Hassium-280}}

<!--Please delete anchor(s) from the list above or table below if adding a dedicated isotope section(s).-->

{{Isotopes table |symbol=Hs |refs=NUBASE2020, AME2020 II, <!-- was updated to NUBASE2016, AMER2016 II? 2019-07-14 --> IsotopeFRIB, IsomerFRIB |notes=m, unc(), mass#, spin#, SF, discoveryname }} |-id=Hassium-263 | ²⁶³Hs | style="text-align:right" | 108 | style="text-align:right" | 155 | 263.12848(21)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/263.pdf 2009] | {{val|0.74|0.48|0.21|u=ms}}<br />[{{val|0.9|(4)|u=ms}}] | α | ²⁵⁹Sg | 3/2+# |-id=Hassium-264 | rowspan=2|²⁶⁴Hs | rowspan=2 style="text-align:right" | 108 | rowspan=2 style="text-align:right" | 156 | rowspan=2|264.12836(3) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/264.pdf 1986] | rowspan=2|{{val|0.63|0.34|0.16|u=s}}<br />[{{val|0.7|(3)|u=s}}] | α (70%) | ²⁶⁰Sg | rowspan=2|0+ |- | SF (30%) | (various) |-id=Hassium-265 | ²⁶⁵Hs | style="text-align:right" | 108 | style="text-align:right" | 157 | 265.129792(26) | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/265.pdf 1984] | {{val|1.96|(16)|u=ms}} | α | ²⁶¹Sg | 9/2+# |-id=Hassium-265m | style="text-indent:1em" | ^265mHs | colspan="3" style="text-indent:2em" | 229(22)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/108/265Hs-1.pdf 2009] | {{val|300|200|100|u=us}}<br />[{{val|360|(150)|u=us}}] | α | ²⁶¹Sg | 3/2+# |-id=Hassium-266 | rowspan=2|²⁶⁶Hs<ref group=n>Not directly synthesized, occurs as decay product of ²⁷⁰Ds</ref> | rowspan=2 style="text-align:right" | 108 | rowspan=2 style="text-align:right" | 158 | rowspan=2| 266.130049(29) | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/266.pdf 2001] | rowspan=2|{{val|3.0|(6)|u=ms}} | α (76%) | ²⁶²Sg | rowspan=2|0+ |- | SF (24%) | (various) |-id=Hassium-266m | style="text-indent:1em" | ^266mHs | colspan="3" style="text-indent:2em" | 1100(90)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/108/266Hs-1.pdf 2015] | {{val|74|354|34|u=ms}}<br />[{{val|280|(220)|u=ms}}] | α | ²⁶²Sg | 9-# |-id=Hassium-267 | ²⁶⁷Hs | style="text-align:right" | 108 | style="text-align:right" | 159 | 267.13168(10)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/267.pdf 1995] | {{val|52|13|8|u=ms}}<br />[{{val|55|(11)|u=ms}}] | α | ²⁶³Sg | 5/2+# |-id=Hassium-267m | style="text-indent:1em" | ^267mHs<ref group=n name="ui">Existence of this isomer is unconfirmed</ref> | colspan="3" style="text-indent:2em" | 39(24)&nbsp;keV | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/108/267Hs-1.pdf 2004] | {{val|940|120|45|u=us}}<br />[{{val|990|(90)|u=us}}] | α | ²⁶³Sg | |-id=Hassium-268 | ²⁶⁸Hs | style="text-align:right" | 108 | style="text-align:right" | 160 | 268.13201(32)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/268.pdf 2010] | {{val|0.38|1.8|0.17|u=s}}<br />[{{val|1.4|(1.1)|u=s}}] | α | ²⁶⁴Sg | 0+ |-id=Hassium-269 | ²⁶⁹Hs | style="text-align:right" | 108 | style="text-align:right" | 161 | 269.13365(14)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/269.pdf 1996] | {{val|13|10|4|u=s}}<ref name=Ds2024/> | α | ²⁶⁵Sg | 9/2+# |-id=Hassium-269m | rowspan=2 style="text-indent:1em" | ^269mHs<ref name=Ds2024/> | rowspan=2 colspan="3" style="text-indent:2em" | 20&nbsp;keV# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/108/269Hs-1.pdf 2024] | rowspan=2|{{val|2.8|13.6|1.3|u=s}} | α | ^265mSg | rowspan=2|1/2# |- | IT | ²⁶⁹Hs |-id=Hassium-270 | ²⁷⁰Hs | style="text-align:right" | 108 | style="text-align:right" | 162 | 270.13431(27)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/270.pdf 2006] | {{val|7.6|4.9|2.2|u=s}}<br />[{{val|9|(4)|u=s}}] | α | ²⁶⁶Sg | 0+ |-id=Hassium-271 | ²⁷¹Hs | style="text-align:right" | 108 | style="text-align:right" | 163 | 271.13708(30)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/271.pdf 2008] | {{val|46|56|16|u=s}}<ref name=Ds2024>{{cite journal |last1=Oganessian |first1=Yu. Ts. |last2=Utyonkov |first2=V. K. |last3=Shumeiko |first3=M. V. |last4=Abdullin |first4=F. Sh. |last5=Adamian |first5=G. G. |last6=Dmitriev |first6=S. N. |last7=Ibadullayev |first7=D. |last8=Itkis |first8=M. G. |last9=Kovrizhnykh |first9=N. D. |last10=Kuznetsov |first10=D. A. |last11=Petrushkin |first11=O. V. |last12=Podshibiakin |first12=A. V. |last13=Polyakov |first13=A. N. |last14=Popeko |first14=A. G. |last15=Rogov |first15=I. S. |last16=Sagaidak |first16=R. N. |last17=Schlattauer |first17=L. |last18=Shubin |first18=V. D. |last19=Solovyev |first19=D. I. |last20=Tsyganov |first20=Yu. S. |last21=Voinov |first21=A. A. |last22=Subbotin |first22=V. G. |last23=Bublikova |first23=N. S. |last24=Voronyuk |first24=M. G. |last25=Sabelnikov |first25=A. V. |last26=Bodrov |first26=A. Yu. |last27=Aksenov |first27=N. V. |last28=Khalkin |first28=A. V. |last29=Gan |first29=Z. G. |last30=Zhang |first30=Z. Y. |last31=Huang |first31=M. H. |last32=Yang |first32=H. B. |display-authors=3 |title=Synthesis and decay properties of isotopes of element 110: Ds 273 and Ds 275 |journal=Physical Review C |date=6 May 2024 |volume=109 |issue=5 |article-number=054307 |doi=10.1103/PhysRevC.109.054307 |url=https://journals.aps.org/prc/pdf/10.1103/PhysRevC.109.054307 |access-date=11 May 2024 |language=en |issn=2469-9985|url-access=subscription }}</ref> | α | ²⁶⁷Sg | 11/2# |-id=Hassium-271m | rowspan=2 style="text-indent:1em" | ^271mHs<ref name=Ds2024/> | rowspan=2 colspan="3" style="text-indent:2em" | 20&nbsp;keV# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/108/271Hs-1.pdf 2024] | rowspan=2|{{val|7.1|8.4|2.5|u=s}} | α | ^267mSg | rowspan=2|3/2# |- | IT | ²⁷¹Hs |-id=Hassium-272 | ²⁷²Hs<ref group=n>Not directly synthesized, occurs in decay chain of ²⁷⁶Ds</ref><ref name="276Ds-2023">{{cite journal |title=New isotope ²⁷⁶Ds and its decay products ²⁷²Hs and ²⁶⁸Sg from the ²³²Th + ⁴⁸Ca reaction |last1=Oganessian |first1=Yu. Ts. |last2=Utyonkov |first2=V. K. |last3=Shumeiko |first3=M. V. |display-authors=et al. |date=2023 |journal=Physical Review C |volume=108 |number=24611 |article-number=024611 |doi=10.1103/PhysRevC.108.024611|bibcode=2023PhRvC.108b4611O |s2cid=261170871 }}</ref> | style="text-align:right" | 108 | style="text-align:right" | 164 | 272.13849(55)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/272.pdf 2023] | {{val|160|190|60|u=ms}} | α | ²⁶⁸Sg | 0+ |-id=Hassium-273 | ²⁷³Hs<ref group=n>Not directly synthesized, occurs in decay chain of ²⁸⁵Fl</ref> | style="text-align:right" | 108 | style="text-align:right" | 165 | 273.14146(40)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/273.pdf 2010] | {{val|0.68|0.30|0.16|u=s}}<ref name="288-289Lv">{{cite web |last1=Kovrizhnykh |first1=N.D. |title=On the way to the synthesis of new elements: 119 and 120 |url=https://indico.gsi.de/event/21160/contributions/85071/attachments/49852/75915/TASCA25_Contribution_Kovrizhnykh.pdf |access-date=1 June 2025}}</ref><br />[{{val|1.06|(50)|u=s}}] | α | ²⁶⁹Sg | 3/2+# |-id=Hassium-275 | rowspan=2|²⁷⁵Hs<ref group="n">Not directly synthesized, occurs in decay chain of ²⁸⁷Fl</ref> | rowspan=2 style="text-align:right" | 108 | rowspan=2 style="text-align:right" | 167 | rowspan=2|275.14653(64)# | rowspan=2 style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/275.pdf 2004] | rowspan=2|{{val|600|230|130|u=ms}}<ref name=PuCa2022>{{cite journal |title=Investigation of ⁴⁸Ca-induced reactions with ²⁴²Pu and ²³⁸U targets at the JINR Superheavy Element Factory |journal=Physical Review C |volume=106 |number=24612 |year=2022 |first1=Yu. Ts. |last1=Oganessian |first2=V. K. |last2=Utyonkov |first3=D. |last3=Ibadullayev |article-number=024612 |display-authors=et al. |doi= 10.1103/PhysRevC.106.024612|bibcode=2022PhRvC.106b4612O |osti=1883808 |s2cid=251759318 }}</ref> | α | ²⁷¹Sg | rowspan=2| |- | SF (<11%) | (various) |-id=Hassium-277 | ²⁷⁷Hs<ref group="n" name="q">Not directly synthesized, occurs in decay chain of ²⁸⁹Fl</ref> | style="text-align:right" | 108 | style="text-align:right" | 169 | 277.15177(48)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/277.pdf 2010] | {{val|18|25|7|u=ms}}<ref>{{cite journal |last1=Cox |first1=D. M. |last2=Såmark-Roth |first2=A. |last3=Rudolph |first3=D. |last4=Sarmiento |first4=L. G. |last5=Clark |first5=R. M. |last6=Egido |first6=J. L. |last7=Golubev |first7=P. |last8=Heery |first8=J. |last9=Yakushev |first9=A. |last10=Åberg |first10=S. |last11=Albers |first11=H. M. |last12=Albertsson |first12=M. |last13=Block |first13=M. |last14=Brand |first14=H. |last15=Calverley |first15=T. |last16=Cantemir |first16=R. |last17=Carlsson |first17=B. G. |last18=Düllmann |first18=Ch. E. |last19=Eberth |first19=J. |last20=Fahlander |first20=C. |last21=Forsberg |first21=U. |last22=Gates |first22=J. M. |last23=Giacoppo |first23=F. |last24=Götz |first24=M. |last25=Götz |first25=S. |last26=Herzberg |first26=R.-D. |last27=Hrabar |first27=Y. |last28=Jäger |first28=E. |last29=Judson |first29=D. |last30=Khuyagbaatar |first30=J. |last31=Kindler |first31=B. |last32=Kojouharov |first32=I. |last33=Kratz |first33=J. V. |last34=Krier |first34=J. |last35=Kurz |first35=N. |last36=Lens |first36=L. |last37=Ljungberg |first37=J. |last38=Lommel |first38=B. |last39=Louko |first39=J. |last40=Meyer |first40=C.-C. |last41=Mistry |first41=A. |last42=Mokry |first42=C. |last43=Papadakis |first43=P. |last44=Parr |first44=E. |last45=Pore |first45=J. L. |last46=Ragnarsson |first46=I. |last47=Runke |first47=J. |last48=Schädel |first48=M. |last49=Schaffner |first49=H. |last50=Schausten |first50=B. |last51=Shaughnessy |first51=D. A. |last52=Thörle-Pospiech |first52=P. |last53=Trautmann |first53=N. |last54=Uusitalo |first54=J. |title=Spectroscopy along flerovium decay chains. II. Fine structure in odd-A 289Fl |journal=Physical Review C |date=6 February 2023 |volume=107 |issue=2 |article-number=L021301 |doi=10.1103/PhysRevC.107.L021301 |bibcode=2023PhRvC.107b1301C |doi-access=free }}</ref> | SF | (various) | 3/2+# |-id=Hassium-277m | style="text-indent:.3em" | ^277mHs<ref group=n name="ui" /><ref group=n name="q" /> | colspan="3" style="text-indent:2em" | 100(100)&nbsp;keV# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/isomers/abstracts/108/277Hs-1.pdf 2012] | {{val|34|166|16|u=s}}<br />[{{val|130|(100)|u=s}}] | SF | (various) | |-id=Hassium-278 | ²⁷⁸Hs<ref group="n">Not directly synthesized, occurs in decay chain of ²⁹⁰Fl, unconfirmed</ref> | style="text-align:right" | 108 | style="text-align:right" | 170 | 278.15375(32)# | style="text-align:center" | [https://www.nndc.bnl.gov/discovery/abstracts/108/278.pdf (2016)] | | SF | (various) | 0+ {{Isotopes table/footer}}

==Isotopes and nuclear properties==

===Target-projectile combinations leading to ''Z''=108 compound nuclei===

{| class="wikitable" style="text-align:center" !Target!!Projectile!!CN!!Attempt result |--

!¹³⁶Xe |¹³⁶Xe||²⁷²Hs||{{no|Failure to date}} |- !¹⁹⁸Pt |⁷⁰Zn||²⁶⁸Hs||{{no|Failure to date<ref>{{cite web |url=http://www.nupecc.org/ecos/sh_0710.pdf |title=Archived copy |website=www.nupecc.org |access-date=11 January 2022 |archive-url=https://web.archive.org/web/20070823154030/http://www.nupecc.org/ecos/sh_0710.pdf |archive-date=23 August 2007 }}</ref>}} |- !²⁰⁸Pb |⁵⁸Fe||²⁶⁶Hs||{{yes|Successful reaction}} |- !²⁰⁷Pb |⁵⁸Fe||²⁶⁵Hs||{{yes|Successful reaction}} |- !²⁰⁸Pb |⁵⁶Fe||²⁶⁴Hs||{{yes|Successful reaction}} |- !²⁰⁷Pb |⁵⁶Fe||²⁶³Hs||{{unk|Reaction yet to be attempted}} |- !²⁰⁶Pb |⁵⁸Fe||²⁶⁴Hs||{{yes|Successful reaction}} |- !²⁰⁹Bi |⁵⁵Mn||²⁶⁴Hs||{{no|Failure to date}} |- !²²⁶Ra |⁴⁸Ca||²⁷⁴Hs||{{yes|Successful reaction}} |- !²³²Th |⁴⁰Ar||²⁷²Hs||{{unk|Reaction yet to be attempted}} |- !²³⁸U |³⁶S||²⁷⁴Hs||{{yes|Successful reaction}} |- !²³⁸U |³⁴S||²⁷²Hs||{{yes|Successful reaction}} |- !²⁴⁴Pu |³⁰Si||²⁷⁴Hs||{{unk|Reaction yet to be attempted}} |- !²⁴⁸Cm |²⁶Mg||²⁷⁴Hs||{{yes|Successful reaction}} |- !²⁴⁸Cm |²⁵Mg||²⁷³Hs||{{no|Failure to date}} |- !²⁵⁰Cm |²⁶Mg||²⁷⁶Hs||{{unk|Reaction yet to be attempted}} |- !²⁴⁹Cf |²²Ne||²⁷¹Hs||{{yes|Successful reaction}} |- |}

===Nucleosynthesis=== Superheavy elements such as hassium are produced by bombarding lighter elements in particle accelerators that induce fusion reactions. Whereas most of the isotopes of hassium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higher atomic numbers.<ref name="AM89">{{Cite journal |first1=Peter |last1=Armbruster |name-list-style=amp|first2=Gottfried|last2=Münzenberg |title=Creating superheavy elements |journal=Scientific American |volume=34 |pages=36–42 |year=1989}}</ref>

Depending on the energies involved, the former are separated into "hot" and "cold". In hot fusion reactions, very light, high-energy projectiles are accelerated toward very heavy targets (actinides), giving rise to compound nuclei at high excitation energy (~40–50&nbsp;MeV) that may either fission or evaporate several (3 to 5) neutrons.<ref name="fusion">{{cite journal |last1=Barber |first1=Robert C. |last2=Gäggeler |first2=Heinz W. |last3=Karol |first3=Paul J. |last4=Nakahara |first4=Hiromichi |last5=Vardaci |first5=Emanuele |last6=Vogt |first6=Erich |title=Discovery of the element with atomic number 112 (IUPAC Technical Report) |journal=Pure and Applied Chemistry |volume=81 |issue=7 |page=1331 |year=2009 |doi=10.1351/PAC-REP-08-03-05|doi-access=free }}</ref> In cold fusion reactions, the produced fused nuclei have a relatively low excitation energy (~10–20&nbsp;MeV), which decreases the probability that these products will undergo fission reactions. As the fused nuclei cool to the ground state, they require emission of only one or two neutrons, and thus, allows for the generation of more neutron-rich products.<ref name="AM89"/> The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (see cold fusion).<ref>{{cite journal |last1=Fleischmann |first1=Martin |last2=Pons |first2=Stanley |year=1989 |title=Electrochemically induced nuclear fusion of deuterium |journal=Journal of Electroanalytical Chemistry and Interfacial Electrochemistry |volume=261 |issue=2 |pages=301–308 |doi=10.1016/0022-0728(89)80006-3}}</ref>

====Cold fusion==== Before the first successful synthesis of hassium in 1984 by the GSI team, scientists at the Joint Institute for Nuclear Research (JINR) in Dubna, Russia also tried to synthesize hassium by bombarding lead-208 with iron-58 in 1978. No hassium atoms were identified. They repeated the experiment in 1984 and were able to detect a spontaneous fission activity assigned to ²⁶⁰Sg, the daughter of ²⁶⁴Hs.<ref>{{Cite journal|doi=10.1007/BF01415635|title=On the stability of the nuclei of element 108 with A=263–265|year=1984|last1=Oganessian |first1=Yu Ts|journal=Zeitschrift für Physik A|volume=319|pages=215–217|last2=Demin|first2=A. G.|last3=Hussonnois|first3=M.|last4=Tretyakova|first4=S. P.|last5=Kharitonov|first5=Yu P.|last6=Utyonkov|first6=V. K.|last7=Shirokovsky|first7=I. V.|last8=Constantinescu|first8=O.|last9=Bruchertseifer|first9=H.|last10=Korotkin|first10=Yu S.|bibcode = 1984ZPhyA.319..215O|issue=2 |s2cid = 123170572|display-authors=8}}</ref> Later that year, they tried the experiment again, and tried to chemically identify the decay products of hassium to provide support to their synthesis of element 108. They were able to detect several alpha decays of ²⁵³Es and ²⁵³Fm, decay products of ²⁶⁵Hs.<ref name="93TWG">{{Cite journal|doi=10.1351/pac199365081757|title=Discovery of the transfermium elements. Part II: Introduction to discovery profiles. Part III: Discovery profiles of the transfermium elements (Note: for Part I see Pure Appl. Chem., Vol. 63, No. 6, pp. 879–886, 1991)|year=1993|last1=Barber |first1=R. C.|journal=Pure and Applied Chemistry|volume=65|page=1757|last2=Greenwood|first2=N. N.|last3=Hrynkiewicz|first3=A. Z.|last4=Jeannin|first4=Y. P.|last5=Lefort|first5=M.|last6=Sakai|first6=M.|last7=Ulehla|first7=I.|last8=Wapstra|first8=A. P.|last9=Wilkinson|first9=D. H.|issue=8|s2cid=195819585|doi-access=free}}</ref>

In the official discovery of the element in 1984, the team at GSI studied the same reaction using the alpha decay genetic correlation method and were able to positively identify 3 atoms of ²⁶⁵Hs.<ref name="84Mu01">{{cite journal |last1=Münzenberg |first1=G. |last2=Armbruster |first2=P. |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. |last10=Schött |first10=H. -J. |last11=Leino |first11=M. E. |last12=Hingmann |first12=R. |year=1984 |title=The identification of element 108 |journal=Zeitschrift für Physik A |volume=317 |issue=2 |pages=235–236 |doi=10.1007/BF01421260 |bibcode = 1984ZPhyA.317..235M |s2cid=123288075 |display-authors=8 }}</ref> After an upgrade of their facilities in 1993, the team repeated the experiment in 1994 and detected 75 atoms of ²⁶⁵Hs and 2 atoms of ²⁶⁴Hs, during the measurement of a partial excitation function for the 1n neutron evaporation channel.<ref>{{Cite journal|doi=10.1088/0034-4885/61/6/002|year=1998|last=Hofmann |first=S. |journal=Reports on Progress in Physics|volume=61|pages=639–689|bibcode = 1998RPPh...61..639H|title=New elements – approaching|issue=6 |s2cid=250756383 }}</ref> A further run of the reaction was conducted in late 1997 in which a further 20 atoms were detected.<ref>{{Cite journal|doi=10.1007/s002180050343|title=Excitation function for the production of 265 108 and 266 109|year=1997|last1=Hofmann |first1=S.| journal=Zeitschrift für Physik A|volume=358|pages=377–378|last2=Heßberger|first2=F.P.|last3=Ninov|first3=V.|last4=Armbruster|first4=P.|last5=Münzenberg|first5=G.|last6=Stodel|first6=C.|last7=Popeko|first7=A.G.|last8=Yeremin|first8=A.V.|last9=Saro|first9=S.|last10=Leino|first10=M.|bibcode = 1997ZPhyA.358..377H|issue=4 |s2cid=124304673|display-authors=8}}</ref> This discovery experiment was successfully repeated in 2002 at RIKEN (10 atoms) and in 2003 at GANIL (7 atoms). The team at RIKEN further studied the reaction in 2008 in order to conduct the first spectroscopic studies of the even-even nucleus ²⁶⁴Hs. They were also able to detect a further 29 atoms of ²⁶⁵Hs.

The team at Dubna also conducted the analogous reaction with a lead-207 target instead of a lead-208 target in 1984:

:{{nuclide|link=yes|lead|207}} + {{nuclide|link=yes|iron|58}} → {{nuclide|link=yes|hassium|264}} + {{SubatomicParticle|link=yes|neutron}}

They were able to detect the same spontaneous fission activity as observed in the reaction with a lead-208 target and once again assigned it to ²⁶⁰Sg, daughter of ²⁶⁴Hs.<ref name="93TWG" /> The team at GSI first studied the reaction in 1986 using the method of genetic correlation of alpha decays and identified a single atom of ²⁶⁴Hs with a cross section of 3.2&nbsp;pb.<ref name="264Hs">{{Cite journal|doi=10.1007/BF01290935|title=Evidence for264108, the heaviest known even-even isotope|year=1986|last1=Münzenberg |first1=G.|journal=Zeitschrift für Physik A|volume=324|pages=489–490|last2=Armbruster|first2=P.|last3=Berthes|first3=G.|last4=Folger|first4=H.|last5=Heßberger|first5=F. P.|last6=Hofmann|first6=S.|last7=Poppensieker|first7=K.|last8=Reisdorf|first8=W.|last9=Quint|first9=B.|last10=Schmidt|first10=K. -H.|last11=Schött |first11=H. -J. |last12=Sümmerer |first12=K.|last13=Zychor|first13=I.|last14=Leino|first14=M. E.|last15=Gollerthan|first15=U.|last16=Hanelt|first16=E.|bibcode = 1986ZPhyA.324..489M|issue=4 |s2cid=121616566|display-authors=8}}</ref> The reaction was repeated in 1994 and the team were able to measure both alpha decay and spontaneous fission for ²⁶⁴Hs. This reaction was also studied in 2008 at RIKEN in order to conduct the first spectroscopic studies of the even-even nucleus ²⁶⁴Hs. The team detected 11 atoms of ²⁶⁴Hs.

In 2008, the team at RIKEN conducted the analogous reaction with a lead-206 target for the first time:

:{{nuclide|link=yes|lead|206}} + {{nuclide|link=yes|iron|58}} → {{nuclide|link=yes|hassium|263}} + {{SubatomicParticle|link=yes|neutron}}

They were able to identify 8 atoms of the new isotope ²⁶³Hs.<ref>[http://159.93.28.88/linkc/flnr_presentations/Mendeleev%20simposium/Morita.ppt Mendeleev Symposium. Morita] {{webarchive |url=https://web.archive.org/web/20110927212405/http://159.93.28.88/linkc/flnr_presentations/Mendeleev%20simposium/Morita.ppt |date=September 27, 2011 }}</ref>

In 2008, the team at the Lawrence Berkeley National Laboratory (LBNL) studied the analogous reaction with iron-56 projectiles for the first time:

:{{nuclide|link=yes|lead|208}} + {{nuclide|link=yes|iron|56}} → {{nuclide|link=yes|hassium|263}} + {{SubatomicParticle|link=yes|neutron}}

They were able to produce and identify six atoms of the new isotope ²⁶³Hs.<ref name="263Hs">{{Cite journal|doi=10.1103/PhysRevC.79.011602|title=New Isotope ²⁶³108|year=2009 |last1=Dragojević |first1=I. |journal=Physical Review C|volume=79|issue=1|article-number=011602|last2=Gregorich|first2=K.|last3=Düllmann|first3=Ch.|last4=Dvorak|first4=J.|last5=Ellison|first5=P.|last6=Gates|first6=J.|last7=Nelson|first7=S.|last8=Stavsetra|first8=L.|last9=Nitsche|first9=H.|bibcode = 2009PhRvC..79a1602D }}</ref> A few months later, the RIKEN team also published their results on the same reaction.<ref>{{Cite journal|doi=10.1143/JPSJ.78.035003|title=Production and Decay Properties of ²⁶³108|year=2009 |last1=Kaji |first1=Daiya |journal=Journal of the Physical Society of Japan |volume=78 |article-number=035003 |last2=Morimoto |first2=Kouji |last3=Sato |first3=Nozomi |last4=Ichikawa |first4=Takatoshi |last5=Ideguchi |first5=Eiji |last6=Ozeki |first6=Kazutaka |last7=Haba |first7=Hiromitsu |last8=Koura |first8=Hiroyuki |last9=Kudou |first9=Yuki |last10=Ozawa |first10=Akira |last11=Sumita |first11=Takayuki |last12=Yamaguchi |first12=Takayuki |last13=Yoneda |first13=Akira |last14=Yoshida |first14=Atsushi |last15=Morita |first15=Kosuke |bibcode = 2009JPSJ...78c5003K |issue=3 |display-authors=8}}</ref>

Further attempts to synthesise nuclei of hassium were performed the team at Dubna in 1983 using the cold fusion reaction between a bismuth-209 target and manganese-55 projectiles:

:{{nuclide|link=yes|bismuth|209}} + {{nuclide|link=yes|manganese|55}} → {{nuclide|hassium|264−x}} + x {{SubatomicParticle|link=yes|Neutron}} (x = 1 or 2)

They were able to detect a spontaneous fission activity assigned to ²⁵⁵Rf, a product of the ²⁶³Hs decay chain. Identical results were measured in a repeat run in 1984.<ref name="93TWG" /> In a subsequent experiment in 1983, they applied the method of chemical identification of a descendant to provide support to the synthesis of hassium. They were able to detect alpha decays from fermium isotopes, assigned as descendants of the decay of ²⁶²Hs. This reaction has not been tried since and ²⁶²Hs is currently unconfirmed.<ref name="93TWG" />

====Hot fusion==== Under the leadership of Yuri Oganessian, the team at the Joint Institute for Nuclear Research studied the hot fusion reaction between calcium-48 projectiles and radium-226 targets in 1978:

:{{nuclide|link=yes|radium|226}} + {{nuclide|link=yes|calcium|48}} → {{nuclide|link=yes|hassium|270}} + 4 {{SubatomicParticle|link=yes|Neutron}}

However, results are not available in the literature.<ref name="93TWG" /> The reaction was repeated at the JINR in June 2008 and 4 atoms of the isotope ²⁷⁰Hs were detected.<ref>{{cite web |url=http://www1.jinr.ru/Reports/2008/english/06_flnr_e.pdf |title=Flerov Laboratory of Nuclear Reactions}}{{page needed|date=October 2015}}</ref> In January 2009, the team repeated the experiment and a further 2 atoms of ²⁷⁰Hs were detected.<ref>{{cite web |url=http://www.np.ph.bham.ac.uk/iop09/iop_talks/07_04_09_Parallel_2/Y%20Tsyganov.ppt |title=Results of ²²⁶Ra+⁴⁸Ca Experiment |last1=Tsyganov |first1=Yu. |last2=Oganessian |first2=Yu. |last3=Utyonkov |first3=V. |last4=Lobanov |first4=Yu. |last5=Abdullin |first5=F. |last6=Shirokovsky |first6=I. |last7=Polyakov |first7=A. |last8=Subbotin |first8=V. |last9=Sukhov |first9=A. |date=2009-04-07 |access-date=2012-12-25 }}{{dead link|date=July 2020|bot=medic}}{{cbignore|bot=medic}} [http://www.powershow.com/view1/1ac3df-ODU4Z/Results_of_226Ra_48Ca_Experiment_YuTsyganov_YuOganessian_VUtyonkov_YuLobanov_FAbdullin_IS_powerpoint_ppt_presentation Alt URL]</ref>

The team at Dubna studied the reaction between californium-249 targets and neon-22 projectiles in 1983 by detecting spontaneous fission activities:

:{{nuclide|link=yes|californium|249}} + {{nuclide|link=yes|neon|22}} → {{nuclide|hassium|271−x}} + x {{SubatomicParticle|link=yes|Neutron}}

Several short spontaneous fission activities were found, indicating the formation of nuclei of hassium.<ref name="93TWG" />

The hot fusion reaction between uranium-238 targets and projectiles of the rare and expensive isotope sulfur-36 was conducted at the GSI in April–May 2008:

:{{nuclide|link=yes|uranium|238}} + {{nuclide|link=yes|sulfur|36}} → {{nuclide|link=yes|hassium|270}} + 4 {{SubatomicParticle|link=yes|Neutron}}

Preliminary results show that a single atom of ²⁷⁰Hs was detected. This experiment confirmed the decay properties of the isotopes ²⁷⁰Hs and ²⁶⁶Sg.<ref>[http://www.gsi.de/informationen/wti/library/scientificreport2008/PAPERS/NUSTAR-SHE-02.pdf Observation of ²⁷⁰Hs in the complete fusion reaction ³⁶S+²³⁸U*] {{webarchive|url=https://web.archive.org/web/20120303012421/http://www.gsi.de/informationen/wti/library/scientificreport2008/PAPERS/NUSTAR-SHE-02.pdf |date=2012-03-03 }} R. Graeger et al., GSI Report 2008</ref>

In March 1994, the team at Dubna led by the late Yuri Lazarev attempted the analogous reaction with sulfur-34 projectiles:

:{{nuclide|link=yes|uranium|238}} + {{nuclide|link=yes|sulfur|34}} → {{nuclide|hassium|272−x}} + x {{SubatomicParticle|link=yes|Neutron}} (x = 4 or 5)

They announced the detection of 3 atoms of ²⁶⁷Hs from the 5n neutron evaporation channel.<ref name="267Hs">{{Cite journal|title=New Nuclide ²⁶⁷108 Produced by the ²³⁸U + ³⁴S Reaction|doi=10.1103/PhysRevLett.75.1903|year=1995|last1=Lazarev |first1=Yu. A. |journal=Physical Review Letters |volume=75 |pages=1903–1906 |pmid=10059158 |last2=Lobanov |first2=YV |last3=Oganessian |first3=YT |last4=Tsyganov |first4=YS |last5=Utyonkov |first5=VK |last6=Abdullin |first6=FS |last7=Iliev |first7=S |last8=Polyakov |first8=AN |last9=Rigol |first9=J |last10=Shirokovsky |first10=I. |last11=Subbotin |first11=V. |last12=Sukhov |first12=A. |last13=Buklanov |first13=G. |last14=Gikal |first14=B. |last15=Kutner |first15=V. |last16=Mezentsev |first16=A. |last17=Sedykh |first17=I. |last18=Vakatov |first18=D. |last19=Lougheed |first19=R. |last20=Wild |first20=J. |last21=Moody |first21=K. |last22=Hulet |first22=E. |issue=10 |bibcode=1995PhRvL..75.1903L |display-authors=8|url=https://cds.cern.ch/record/284096/files/SCAN-9507002.pdf }}</ref> The decay properties were confirmed by the team at GSI in their simultaneous study of darmstadtium. The reaction was repeated at the GSI in January–February 2009 in order to search for the new isotope ²⁶⁸Hs. The team, led by Prof. Nishio, detected a single atom each of both ²⁶⁸Hs and ²⁶⁷Hs. The new isotope ²⁶⁸Hs underwent alpha decay to the previously known isotope ²⁶⁴Sg.

Between May 2001 and August 2005, a GSI–PSI (Paul Scherrer Institute) collaboration studied the nuclear reaction between curium-248 targets and magnesium-26 projectiles:

:{{nuclide|link=yes|curium|248}} + {{nuclide|link=yes|magnesium|26}} → {{nuclide|hassium|274−x}} + x {{SubatomicParticle|link=yes|Neutron}} (x = 3, 4, or 5)

The team studied the excitation function of the 3n, 4n, and 5n evaporation channels leading to the isotopes ²⁶⁹Hs, ²⁷⁰Hs, and ²⁷¹Hs.<ref name="270Hs">[http://lch.web.psi.ch/files/anrep01/B-01heavies.pdf "Decay properties of ²⁶⁹Hs and evidence for the new nuclide ²⁷⁰Hs"] {{webarchive|url=https://www.webcitation.org/6CGIR6Ekz?url=http://lch.web.psi.ch/files/anrep01/B-01heavies.pdf |date=2012-11-18 }}, Turler et al., ''GSI Annual Report 2001''. Retrieved 2008-03-01.</ref><ref name="271Hs">{{cite web |url=http://www2.ha.physik.uni-muenchen.de/heaviest_atoms/talks/Dvorak.pdf |title=On the production and chemical separation of Hs (element 108) |last1=Dvorak |first1=Jan |date=2006-09-25 |publisher=Technical University of Munich |archive-url=https://web.archive.org/web/20090225155329/http://www2.ha.physik.uni-muenchen.de/heaviest_atoms/talks/Dvorak.pdf |archive-date=2009-02-25 |access-date=2012-12-23}}</ref> The synthesis of the doubly magic isotope ²⁷⁰Hs was published in December 2006 by the team of scientists from the Technical University of Munich.<ref>[http://www.gsi.de/informationen/wti/library/scientificreport2006/PAPERS/NUSTAR-SHE-06.pdf "Doubly magic ²⁷⁰Hs"] {{webarchive|url=https://web.archive.org/web/20120303012501/http://www.gsi.de/informationen/wti/library/scientificreport2006/PAPERS/NUSTAR-SHE-06.pdf |date=2012-03-03 }}, Turler et al., ''GSI report'', 2006. Retrieved 2008-03-01.</ref> It was reported that this isotope decayed by emission of an alpha particle with an energy of 8.83&nbsp;MeV and a half-life of ~22&nbsp;s. This figure has since been revised to 3.6&nbsp;s.<ref name="nuclidetable"/>

====As decay product==== <div style="float:right; margin:0; font-size:85%;"> {| class="wikitable" style="text-align:center" |+List of hassium isotopes observed by decay ! Evaporation residue !! Observed hassium isotope |- |²⁶⁷Ds || ²⁶³Hs<ref name="267Ds">{{cite journal|doi=10.1103/PhysRevC.51.R2293|pmid=9970386|title=Evidence for the possible synthesis of element 110 produced by the ⁵⁹Co+²⁰⁹Bi reaction|year=1995|last1=Ghiorso |first1=A.|journal=Physical Review C|volume=51|pages=R2293–R2297|last2=Lee|first2=D.|last3=Somerville|first3=L.|last4=Loveland|first4=W.|last5=Nitschke|first5=J.|last6=Ghiorso|first6=W.|last7=Seaborg|first7=G.|last8=Wilmarth|first8=P.|last9=Leres|first9=R.|last10=Wydler|first10=A.|last11=Nurmia|first11=M.|last12=Gregorich|first12=K.|last13=Czerwinski|first13=K.|last14=Gaylord|first14=R.|last15=Hamilton|first15=T.|last16=Hannink|first16=N.|last17=Hoffman|first17=D.|last18=Jarzynski|first18=C.|last19=Kacher|first19=C.|last20=Kadkhodayan|first20=B.|last21=Kreek|first21=S.|last22=Lane|first22=M.|last23=Lyon|first23=A.|last24=McMahan|first24=M.|last25=Neu|first25=M.|last26=Sikkeland|first26=T.|last27=Swiatecki|first27=W.|last28=Türler|first28=A.|last29=Walton|first29=J.|last30=Yashita|first30=S.|bibcode = 1995PhRvC..51.2293G|issue=5 |display-authors=8}}</ref> |- |²⁶⁹Ds ||²⁶⁵Hs<ref name="265Hs">{{cite journal|doi=10.1007/BF01291181|title=Production and decay of ²⁶⁹110|year=1995|last1=Hofmann |first1=S.|journal=Zeitschrift für Physik A |volume=350|pages=277–280|last2=Ninov|first2=V.|last3=Heßberger|first3=F. P.|last4=Armbruster|first4=P.|last5=Folger|first5=H.|last6=Münzenberg|first6=G.|last7=Schött|first7=H. J.|last8=Popeko|first8=A. G.|last9=Yeremin|first9=A. V.|last10=Andreyev|first10=A. N.|last11=Saro|first11=S.|last12=Janik|first12=R.|last13=Leino|first13=M.|bibcode = 1995ZPhyA.350..277H|issue=4 |s2cid=125020220}}</ref> |- |²⁷⁰Ds ||²⁶⁶Hs<ref name="266Hs">{{cite journal|url=http://www.dnp.fmph.uniba.sk/etext/68/text/Hofmann_et_al_EPJ_A10_(2001)_5.pdf|title=The new isotope ²⁷⁰110 and its decay products ²⁶⁶Hs and ²⁶²Sg|last1=Hofmann |first1=S. |last2=Heßberger |first2=F. P. |last3=Ackermann |first3=D. |last4=Antalic |first4=S. |last5=Cagarda |first5=P. |last6=Ćwiok |first6=S. |last7=Kindler |first7=B. |last8=Kojouharova |first8=J.|last9=Lommel |first9=B. |last10=Mann |first10=R. |last11=Münzenberg |first11=G. |last12=Popeko |first12=A. G. |last13=Saro |first13=S. |last14=Schött |first14=H. J. |last15=Yeremin |first15=A. V. |journal=The European Physical Journal A |volume=10 |issue=1|pages=5–10 |year=2001 |doi=10.1007/s100500170137 |bibcode = 2001EPJA...10....5H |s2cid=124240926}}</ref> |- |²⁷¹Ds || ²⁶⁷Hs<ref name="271Ds">{{cite journal|doi=10.1088/0034-4885/61/6/002|year=1998|last=Hofmann |first=S. |journal=Reports on Progress in Physics|volume=61|pages=639–689|bibcode = 1998RPPh...61..639H|title=New elements – approaching|issue=6 |s2cid=250756383 }}</ref> |- |²⁷⁷Cn, ²⁷³Ds||²⁶⁹Hs<ref name="269Hs">{{cite journal |last1=Hofmann |first1=S. |year=1996 |title=The new element 112 |journal=Zeitschrift für Physik A |volume=354 |issue=1 |pages=229–230 |bibcode= 1996ZPhyA.354..229H|doi=10.1007/BF02769517|s2cid=119975957 |display-authors=etal}}</ref> |- |²⁷⁶Ds||²⁷²Hs<ref name="276Ds-2023"/> |- |²⁸⁵Fl, ²⁸¹Cn, ²⁷⁷Ds||²⁷³Hs<ref name="273Hs">{{Cite news |author=Public Affairs Department |date=26 October 2010 |title=Six New Isotopes of the Superheavy Elements Discovered: Moving Closer to Understanding the Island of Stability |url=http://newscenter.lbl.gov/news-releases/2010/10/26/six-new-isotopes |publisher=Berkeley Lab |access-date=2011-04-25}}</ref> |- |²⁹¹Lv, ²⁸⁷Fl, ²⁸³Cn, ²⁷⁹Ds||²⁷⁵Hs<ref name="275Hs">{{cite journal|doi=10.1038/22281|title=Synthesis of nuclei of the superheavy element 114 in reactions induced by ⁴⁸Ca|year=1999|last1=Yeremin |first1=A. V.|journal=Nature|volume=400|pages=242–245|last2=Oganessian|first2=Yu. Ts.|last3=Popeko|first3=A. G.|last4=Bogomolov|first4=S. L.|last5=Buklanov|first5=G. V.|last6=Chelnokov|first6=M. L.|last7=Chepigin|first7=V. I.|last8=Gikal|first8=B. N.|last9=Gorshkov|first9=V. A.|last10=Gulbekian|first10=G. G.|last11=Itkis|first11=M. G.|last12=Kabachenko|first12=A. P.|last13=Lavrentev|first13=A. Yu.|last14=Malyshev|first14=O. N.|last15=Rohac|first15=J.|last16=Sagaidak|first16=R. N.|last17=Hofmann|first17=S.|last18=Saro|first18=S.|last19=Giardina|first19=G.|last20=Morita|first20=K.|bibcode = 1999Natur.400..242O|issue=6741|s2cid=4399615}}</ref> |- |²⁹³Lv, ²⁸⁹Fl, ²⁸⁵Cn, ²⁸¹Ds||²⁷⁷Hs<ref name="277Hs">{{Cite web|url=http://www-win.gsi.de/kernchemie/English/Research/Elements/Element_114_eng.htm|archive-url=https://archive.today/20130211042613/http://www-win.gsi.de/kernchemie/English/Research/Elements/Element_114_eng.htm|title=Element 114 – Heaviest Element at GSI Observed at TASCA|archive-date=February 11, 2013}}</ref><ref name="277mHs">{{cite journal|doi=10.1103/PhysRevLett.83.3154|title=Synthesis of Superheavy Nuclei in the ⁴⁸Ca+ ²⁴⁴Pu Reaction|year=1999|last1=Oganessian |first1=Yu. Ts.|journal=Physical Review Letters|volume=83|pages=3154–3157|bibcode=1999PhRvL..83.3154O|last2=Utyonkov|first2=V.|last3=Lobanov|first3=Yu.|last4=Abdullin|first4=F.|last5=Polyakov|first5=A.|last6=Shirokovsky|first6=I.|last7=Tsyganov|first7=Yu.|last8=Gulbekian|first8=G.|last9=Bogomolov|first9=S.|last10=Gikal|first10=B.|last11=Mezentsev|first11=A.|last12=Iliev|first12=S.|last13=Subbotin|first13=V.|last14=Sukhov|first14=A.|last15=Buklanov|first15=G.|last16=Subotic|first16=K.|last17=Itkis|first17=M.|last18=Moody|first18=K.|last19=Wild|first19=J.|last20=Stoyer|first20=N.|last21=Stoyer|first21=M.|last22=Lougheed|first22=R.|issue=16|s2cid=109929705|display-authors=8}}</ref><ref name="04Og01"> {{cite journal |last1=Oganessian |first1=Yu. Ts. |year=2004 |title=Measurements of cross sections for the fusion-evaporation reactions ²⁴⁴Pu(⁴⁸Ca,xn)^292−x114 and ²⁴⁵Cm(⁴⁸Ca,xn)^293−x116 |journal=Physical Review C |volume=69 |issue=5 |article-number=054607 |bibcode=2004PhRvC..69e4607O |doi=10.1103/PhysRevC.69.054607 |url=http://link.aps.org/abstract/PRC/V69/E054607/ |display-authors=etal|doi-access=free }}</ref> |}</div>

Hassium isotopes have been observed as decay products of darmstadtium. Darmstadtium currently has ten known isotopes, all but one of which have been shown to undergo alpha decays to become hassium nuclei with mass numbers between 263 and 277. Hassium isotopes with mass numbers 266, 272, 273, 275, and 277 to date have only been produced by decay of darmstadtium nuclei. Parent darmstadtium nuclei can be themselves decay products of copernicium, flerovium, or livermorium.<ref name="nuclidetable">{{cite web |url=http://www.nndc.bnl.gov/chart/reCenter.jsp?z=108&n=161 |title=Interactive Chart of Nuclides |publisher=Brookhaven National Laboratory |last=Sonzogni |first=Alejandro |location=National Nuclear Data Center |access-date=2008-06-06 |archive-date=2016-01-12 |archive-url=https://web.archive.org/web/20160112161051/http://www.nndc.bnl.gov/chart/reCenter.jsp?z=108&n=161 }}</ref> For example, in 2004, the Dubna team identified hassium-277 as a final product in the decay of livermorium-293 via an alpha decay sequence:<ref name="04Og01"/>

:{{nuclide|livermorium|293}} → {{nuclide|flerovium|289}} + {{nuclide|helium|4}} :{{nuclide|flerovium|289}} → {{nuclide|copernicium|285}} + {{nuclide|helium|4}} :{{nuclide|copernicium|285}} → {{nuclide|darmstadtium|281}} + {{nuclide|helium|4}} :{{nuclide|darmstadtium|281}} → {{nuclide|hassium|277}} + {{nuclide|helium|4}} {{clear}}

===Unconfirmed isotopes=== ;^277mHs An isotope assigned to ²⁷⁷Hs has been observed on one occasion decaying by SF with a long half-life of ~11 minutes.<ref>{{cite journal |title=Synthesis of superheavy nuclei in ⁴⁸Ca+²⁴⁴Pu interactions |author1=Yu. Ts. Oganessian |author2=V. K. Utyonkov |author3=Yu. V. Lobanov |author4=F. Sh. Abdullin |author5=A. N. Polyakov |author6=I. V. Shirokovsky |author7=Yu. S. Tsyganov |author8=G. G. Gulbekian |author9=S. L. Bogomolov |display-authors=etal |journal=Nuclei Experiment: Physics of Atomic Nuclei |date=October 2000 |volume=63 |issue=10 |pages=1679–1687 |doi=10.1134/1.1320137 |bibcode=2000PAN....63.1679O|s2cid=118044323 }}</ref> The isotope is not observed in the decay of the ground state of ²⁸¹Ds but is observed in the decay from a rare, as yet unconfirmed isomeric level, namely ^281mDs. The half-life is very long for the ground state and it is possible that it belongs to an isomeric level in ²⁷⁷Hs. It has also been suggested that this activity actually comes from ²⁷⁸Bh, formed as the great-great-granddaughter of ²⁹⁰Fl through one electron capture to ²⁹⁰Nh and three further alpha decays. Furthermore, in 2009, the team at the GSI observed a small alpha decay branch for ²⁸¹Ds producing the nuclide ²⁷⁷Hs decaying by SF in a short lifetime. The measured half-life is close to the expected value for ground state isomer, ²⁷⁷Hs. Further research is required to confirm the production of the isomer.

===Retracted isotopes=== ;²⁷³Hs In 1999, American scientists at the University of California, Berkeley, announced that they had succeeded in synthesizing three atoms of ²⁹³118.<ref name="Ninov1999">{{cite journal |last1=Ninov |first1=V. |year=1999 |title=Observation of Superheavy Nuclei Produced in the Reaction of {{SimpleNuclide|Krypton|86}} with {{SimpleNuclide|Lead|208}} |journal=Physical Review Letters |volume=83 |issue=6 |pages=1104–1107 |doi=10.1103/PhysRevLett.83.1104 |bibcode=1999PhRvL..83.1104N|url=https://zenodo.org/record/1233919 |display-authors=etal}}</ref> These parent nuclei were reported to have successively emitted three alpha particles to form hassium-273 nuclei, which were claimed to have undergone an alpha decay, emitting alpha particles with decay energies of 9.78 and 9.47&nbsp;MeV and half-life 1.2&nbsp;s, but their claim was retracted in 2001.<ref>{{Cite news |author=Public Affairs Department |date=21 July 2001 |title=Results of element 118 experiment retracted |url=http://enews.lbl.gov/Science-Articles/Archive/118-retraction.html |publisher=Berkeley Lab |access-date=2008-01-18 |archive-url=https://web.archive.org/web/20080129191344/http://enews.lbl.gov/Science-Articles/Archive/118-retraction.html |archive-date=29 January 2008 }}</ref> The isotope, however, was produced in 2010 by the same team. The new data matched the previous (fabricated)<ref name="NYT20021015">{{cite news |url=https://www.nytimes.com/2002/10/15/science/at-lawrence-berkeley-physicists-say-a-colleague-took-them-for-a-ride.html?scp=2&sq=victor%20ninov&st=cse&pagewanted=1 |title=At Lawrence Berkeley, Physicists Say a Colleague Took Them for a Ride |author=George Johnson |newspaper=The New York Times |date=15 October 2002}}</ref> data.<ref name="273Hs"/>

===²⁷⁰Hs: prospects for a deformed doubly magic nucleus=== According to macroscopic-microscopic (MM) theory, ''Z''&nbsp;=&nbsp;108 is a deformed proton magic number, in combination with the neutron shell at ''N''&nbsp;=&nbsp;162. This means that such nuclei are permanently deformed in their ground state but have high, narrow fission barriers to further deformation and hence relatively long SF partial half-lives. The SF half-lives in this region are typically reduced by a factor of 10⁹ in comparison with those in the vicinity of the spherical doubly magic nucleus ²⁹⁸Fl, caused by an increase in the probability of barrier penetration by quantum tunnelling, due to the narrower fission barrier. In addition, ''N''&nbsp;=&nbsp;162 has been calculated as a deformed neutron magic number and hence the nucleus ²⁷⁰Hs has promise as a deformed doubly magic nucleus. Experimental data from the decay of ''Z''&nbsp;=&nbsp;110 isotopes ²⁷¹Ds and ²⁷³Ds, provides strong evidence for the magic nature of the ''N''&nbsp;=&nbsp;162 sub-shell. The recent synthesis of ²⁶⁹Hs, ²⁷⁰Hs, and ²⁷¹Hs also fully support the assignment of ''N''&nbsp;=&nbsp;162 as a magic closed shell. In particular, the low decay energy for ²⁷⁰Hs is in complete agreement with calculations.<ref>{{Cite journal|title = Properties of the hypothetical spherical superheavy nuclei|author = Robert Smolanczuk|year = 1997 |journal=Physical Review C |volume=56|issue=2 |pages = 812–824 |doi= 10.1103/PhysRevC.56.812|bibcode = 1997PhRvC..56..812S }}</ref>

====Evidence for the ''Z''&nbsp;=&nbsp;108 deformed proton shell==== Evidence for the magicity of the ''Z''&nbsp;=&nbsp;108 proton shell can be deemed from two sources: # the variation in the partial spontaneous fission half-lives for isotones # the large gap in Q_α for isotonic pairs between ''Z''&nbsp;=&nbsp;108 and ''Z''&nbsp;=&nbsp;110.

For SF, it is necessary to measure the half-lives for the isotonic nuclei ²⁶⁸Sg, ²⁷⁰Hs and ²⁷²Ds. Since fission of ²⁷⁰Hs has not been measured, detailed data of ²⁶⁸Sg fission is not yet available,<ref name=276Ds-2023/> and ²⁷²Ds is still unknown, this method cannot be used to date to confirm the stabilizing nature of the ''Z''&nbsp;=&nbsp;108 shell. However, good evidence for the magicity of ''Z''&nbsp;=&nbsp;108 can be deemed from the large differences in the alpha decay energies measured for ²⁷⁰Hs, ²⁷¹Ds and ²⁷³Ds. More conclusive evidence would come from the determination of the decay energy of the yet-unknown nuclide ²⁷²Ds.

===Nuclear isomerism=== ;²⁷⁷Hs An isotope assigned to ²⁷⁷Hs has been observed on one occasion decaying by spontaneous fission with a long half-life of ~11&nbsp;minutes.<ref name="Ogan">{{cite journal|doi=10.1134/1.1320137|title=Synthesis of superheavy nuclei in 48Ca+244Pu interactions|year=2000|last1=Oganessian|first1=Yu. Ts.|last2=Utyonkov|first2=V. K.|last3=Lobanov|first3=Yu. V.|last4=Abdullin|first4=F. Sh.|last5=Polyakov|first5=A. N.|last6=Shirokovsky|first6=I. V.|last7=Tsyganov|first7=Yu. S.|last8=Gulbekian|first8=G. G.|last9=Bogomolov|first9=S. L.|last10=Gikal|first10=B. N.|last11=Mezentsev|first11=A. N.|last12=Iliev|first12=S.|last13=Subbotin|first13=V. G.|last14=Sukhov|first14=A. M.|last15=Ivanov|first15=O. V.|last16=Buklanov|first16=G. V.|last17=Subotic|first17=K.|last18=Itkis|first18=M. G.|last19=Moody|first19=K. J.|last20=Wild|first20=J. F.|last21=Stoyer|first21=N. J.|last22=Stoyer|first22=M. A.|last23=Lougheed|first23=R. W.|journal=Physics of Atomic Nuclei|volume=63|issue=10|pages=1679–1687|bibcode = 2000PAN....63.1679O |s2cid=118044323|display-authors=8}}</ref> The isotope is not observed in the decay of the most common isomer of ²⁸¹Ds but is observed in the decay from a rare, as yet unconfirmed isomeric level, namely ^281mDs. The half-life is very long for the ground state and it is possible that it belongs to an isomeric level in ²⁷⁷Hs. Furthermore, in 2009, the team at the GSI observed a small alpha decay branch for ²⁸¹Ds producing an isotope of ²⁷⁷Hs decaying by spontaneous fission with a short lifetime. The measured half-life is close to the expected value for ground state isomer, ²⁷⁷Hs. Further research is required to confirm the production of the isomer.<ref name="277Hs"/> A more recent study suggests that this observed activity may actually be from ²⁷⁸Bh.<ref name="Hofmann2016">{{cite journal |last1=Hofmann |first1=S. |last2=Heinz |first2=S. |first3=R. |last3=Mann |first4=J. |last4=Maurer |first5=G. |last5=Münzenberg |first6=S. |last6=Antalic |first7=W. |last7=Barth |first8=H. G. |last8=Burkhard |first9=L. |last9=Dahl |first10=K. |last10=Eberhardt |first11=R. |last11=Grzywacz |first12=J. H. |last12=Hamilton |first13=R. A. |last13=Henderson |first14=J. M. |last14=Kenneally |first15=B. |last15=Kindler |first16=I. |last16=Kojouharov |first17=R. |last17=Lang |first18=B. |last18=Lommel |first19=K. |last19=Miernik |first20=D. |last20=Miller |first21=K. J. |last21=Moody |first22=K. |last22=Morita |first23=K. |last23=Nishio |first24=A. G. |last24=Popeko |first25=J. B. |last25=Roberto |first26=J. |last26=Runke |first27=K. P. |last27=Rykaczewski |first28=S. |last28=Saro |first29=C. |last29=Scheidenberger |first30=H. J. |last30=Schött |first31=D. A. |last31=Shaughnessy |first32=M. A. |last32=Stoyer |first33=P. |last33=Thörle-Popiesch |first34=K. |last34=Tinschert |first35=N. |last35=Trautmann |first36=J. |last36=Uusitalo |first37=A. V. |last37=Yeremin |date=2016 |title=Review of even element super-heavy nuclei and search for element 120 |journal=The European Physical Journal A |volume=2016 |issue=52 |page=180 |doi=10.1140/epja/i2016-16180-4|bibcode=2016EPJA...52..180H |osti=1410078 |s2cid=124362890 |url=https://zenodo.org/record/897926 }}</ref>

;²⁶⁹Hs The direct synthesis of ²⁶⁹Hs has resulted in the observation of three alpha particles with energies 9.21, 9.10, and 8.94&nbsp;MeV emitted from ²⁶⁹Hs atoms. However, when this isotope is indirectly synthesized from the decay of ²⁷⁷Cn, only alpha particles with energy 9.21&nbsp;MeV have been observed, indicating that this decay occurs from an isomeric level. Further research is required to confirm this.<ref name="270Hs"/><ref name="269Hs"/>

;²⁶⁷Hs ²⁶⁷Hs is known to decay by alpha decay, emitting alpha particles with energies of 9.88, 9.83, and 9.75&nbsp;MeV. It has a half-life of 52&nbsp;ms. In the recent syntheses of ²⁷¹Ds and ^271mDs, additional activities have been observed. A 0.94&nbsp;ms activity emitting alpha particles with energy 9.83&nbsp;MeV has been observed in addition to longer lived ~0.8 s and ~6.0 s activities. Currently, none of these are assigned and confirmed and further research is required to positively identify them.<ref name="267Hs"/>

;²⁶⁵Hs The synthesis of ²⁶⁵Hs has also provided evidence for two isomeric levels. The ground state decays by emission of an alpha particle with energy 10.30&nbsp;MeV and has a half-life of 2.0&nbsp;ms. The isomeric state has 300&nbsp;keV of excess energy and decays by the emission of an alpha particle with energy 10.57&nbsp;MeV and has a half-life of 0.75&nbsp;ms.<ref name="84Mu01"/>

;Future experiments Scientists at the GSI are planning to search for isomers of ²⁷⁰Hs using the reaction ²²⁶Ra(⁴⁸Ca,4n) in 2010 using the new TASCA facility at the GSI.<ref>{{Cite web|url=http://www-win.gsi.de/tasca08/contributions/TASCA08_Cont_Andersson.pdf|archive-url=https://web.archive.org/web/20120305104908/http://www-win.gsi.de/tasca08/contributions/TASCA08_Cont_Andersson.pdf|title=TASCA in Small Image Mode Spectroscopy|archive-date=March 5, 2012}}</ref> In addition, they also hope to study the spectroscopy of ²⁶⁹Hs, ²⁶⁵Sg and ²⁶¹Rf, using the reaction ²⁴⁸Cm(²⁶Mg,5n) or ²²⁶Ra(⁴⁸Ca,5n). This will allow them to determine the level structure in ²⁶⁵Sg and ²⁶¹Rf and attempt to give spin and parity assignments to the various proposed isomers.<ref>[http://www-win.gsi.de/tasca08/contributions/TASCA08_Cont_Yakushev2.pdf Hassium spectroscopy experiments at TASCA], A. Yakushev {{webarchive |url=https://web.archive.org/web/20120305105000/http://www-win.gsi.de/tasca08/contributions/TASCA08_Cont_Yakushev2.pdf |date=March 5, 2012 }}</ref>

===Physical production yields=== The tables below provides cross-sections and excitation energies for nuclear reactions that produce isotopes of hassium directly. Data in bold represent maxima derived from excitation function measurements. + represents an observed exit channel.

====Cold fusion==== {| class="wikitable" |- !Projectile!!Target!!CN!!1n!!2n!!3n |- |⁵⁸Fe||²⁰⁸Pb||²⁶⁶Hs||'''69&nbsp;pb, 13.9&nbsp;MeV'''||4.5&nbsp;pb |- | ⁵⁸Fe|| ²⁰⁷Pb|| ²⁶⁵Hs||3.2&nbsp;pb |}

====Hot fusion==== {| class="wikitable" |- !Projectile!!Target!!CN!!3n!!4n!!5n |- |⁴⁸Ca||²²⁶Ra||²⁷⁴Hs|| || 9.0&nbsp;pb|| |- |³⁶S||²³⁸U||²⁷⁴Hs|| || 0.8&nbsp;pb|| |- |³⁴S||²³⁸U||²⁷²Hs|| || ||2.5&nbsp;pb, 50.0&nbsp;MeV |- |²⁶Mg||²⁴⁸Cm||²⁷⁴Hs||'''2.5&nbsp;pb'''||'''3.0&nbsp;pb'''||'''7.0&nbsp;pb''' |}

===Theoretical calculations===

====Evaporation residue cross sections==== The below table contains various targets-projectile combinations for which calculations have provided estimates for cross section yields from various neutron evaporation channels. The channel with the highest expected yield is given.

DNS = Di-nuclear system; σ = cross section

{| class="wikitable" style="text-align:center" |- ! Target !! Projectile !! CN !! Channel (product) !! σ _max !! Model !! Ref |- ! ¹³⁶Xe | ¹³⁶Xe ||²⁷²Hs || 1–4n (^271–268Hs) ||10⁻⁶&nbsp;pb ||DNS || <ref name="FengEntranceChannel">[https://arxiv.org/abs/0904.2994 Influence of entrance channels on formation of superheavy nuclei in massive fusion reactions], Zhao-Qing Feng, Jun-Qing Li, Gen-Ming Jin, April 2009</ref> |- ! ²³⁸U | ³⁴S ||²⁷²Hs || 4n (²⁶⁸Hs) ||10&nbsp;pb ||DNS || <ref name="FengEntranceChannel"/> |- ! ²³⁸U | ³⁶S ||²⁷⁴Hs || 4n (²⁷⁰Hs) ||42.97&nbsp;pb ||DNS || <ref name="Feng108114">{{cite journal|last1=Feng|first1=Z.|last2=Jin|first2=G.|last3=Li|first3=J.|title=Production of new superheavy Z=108–114 nuclei with ²³⁸U, ²⁴⁴Pu and ^248,250Cm targets|date=2009|arxiv=0912.4069|journal=Physical Review C|volume=80|article-number=057601|doi=10.1103/PhysRevC.80.057601|s2cid=118733755 }}</ref> |- ! ²⁴⁴Pu | ³⁰Si ||²⁷⁴Hs || 4n (²⁷⁰Hs) ||185.1&nbsp;pb ||DNS || <ref name="Feng108114"/> |- ! ²⁴⁸Cm | ²⁶Mg ||²⁷⁴Hs || 4n (²⁷⁰Hs) ||719.1&nbsp;pb ||DNS || <ref name="Feng108114"/> |- ! ²⁵⁰Cm | ²⁶Mg ||²⁷⁶Hs || 4n (²⁷²Hs) ||185.2&nbsp;pb ||DNS || <ref name="Feng108114"/> |}

== References == {{reflist}} *[http://www.nndc.bnl.gov/chart/reCenter.jsp?z=108&n=162 National Nuclear Data Center, Brookhaven National Laboratory] {{Webarchive|url=https://web.archive.org/web/20160112161051/http://www.nndc.bnl.gov/chart/reCenter.jsp?z=108&n=162 |date=2016-01-12 }}

Half-life, spin, and isomer data selected from: * {{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. |display-authors=3 |journal=Chinese Physics C |volume=41 |issue=3 <!--Citation bot deny-->|article-number=030001 |year=2017|bibcode=2017ChPhC..41c0001A |s2cid=126750783 |ref={{harvid|Audi et al.|2017}} |url=http://pdfs.semanticscholar.org/7c02/89532fe80c913edd952e8caffd555013f596.pdf |archive-url=https://web.archive.org/web/20200801004253/http://pdfs.semanticscholar.org/7c02/89532fe80c913edd952e8caffd555013f596.pdf |archive-date=2020-08-01 }}<!--for consistency and specific pages, do not replace with {{NUBASE2016}}--> *{{NUBASE 2012}} *{{NUBASE 2003}} *{{NNDC}} *{{CRC85|chapter=11}} *{{cite web |author=GSI |year=2011 |title=Superheavy Element Research at GSI |url=http://tan11.jinr.ru/pdf/08_Sep/S_1/01_Duellmann.pdf |publisher=GSI |access-date=20 August 2012 |archive-date=12 January 2016 |archive-url=https://web.archive.org/web/20160112161020/http://tan11.jinr.ru/pdf/08_Sep/S_1/01_Duellmann.pdf |url-status=dead }}

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Category:Isotopes of hassium Category:Hassium Hassium