Nihonium (113Nh) is asynthetic element. Being synthetic, astandard atomic weight cannot be given and like all artificial elements, it has nostable isotopes. The firstisotope to be synthesized was284Nh as adecay product of288Mc in 2003. The first isotope to be directly synthesized was278Nh in 2004. There are 6 knownradioisotopes from278Nh to286Nh, along with the unconfirmed287Nh and290Nh. The longest-lived isotope is286Nh with ahalf-life of 9.5 seconds.
^( ) – Uncertainty (1σ) is given in concise form in parentheses after the corresponding last digits.
^# – Atomic mass marked #: value and uncertainty derived not from purely experimental data, but at least partly from trends from the Mass Surface (TMS).
Super-heavy elements such as nihonium are produced by bombarding lighter elements inparticle accelerators that inducefusion reactions. Whereas most of the isotopes of nihonium can be synthesized directly this way, some heavier ones have only been observed as decay products of elements with higheratomic numbers.[6]
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 MeV) that may either fission or evaporate several (3 to 5) neutrons.[7] In cold fusion reactions, the produced fused nuclei have a relatively low excitation energy (~10–20 MeV), which decreases the probability that these products will undergo fission reactions. As the fused nuclei cool to theground state, they require emission of only one or two neutrons, and thus, allows for the generation of more neutron-rich products.[6] The latter is a distinct concept from that of where nuclear fusion claimed to be achieved at room temperature conditions (seecold fusion).[8]
Before the synthesis of nihonium by the RIKEN team, scientists at theInstitute for Heavy Ion Research (Gesellschaft für Schwerionenforschung) inDarmstadt, Germany also tried to synthesize nihonium by bombarding bismuth-209 with zinc-70 in 1998. No nihonium atoms were identified in two separate runs of the reaction.[9] They repeated the experiment in 2003 again without success.[9] In late 2003, the emerging team atRIKEN using their efficient apparatus GARIS attempted the reaction and reached a limit of 140 fb. In December 2003 – August 2004, they resorted to "brute force" and carried out the reaction for a period of eight months. They were able to detect a single atom of278Nh.[10] They repeated the reaction in several runs in 2005 and were able to synthesize a second atom,[11] followed by a third in 2012.[12]
The table below contains various combinations of targets and projectiles which could be used to form compound nuclei with Z=113.
In June 2006, the Dubna-Livermore team synthesised nihonium directly by bombarding aneptunium-237 target with acceleratedcalcium-48 nuclei, in a search for the lighter isotopes281Nh and282Nh and their decay products, to provide insight into the stabilizing effects of the closed neutron shells atN = 162 andN = 184:[13]
Nihonium has been observed as a decay product ofmoscovium (via alpha decay). Moscovium currently has five known isotopes; all of them undergo alpha decays to become nihonium nuclei, with mass numbers between 282 and 286. Parent moscovium nuclei can be themselves decay products oftennessine. It may also occur as a decay product of flerovium (via electron capture), and parent flerovium nuclei can be themselves decay products oflivermorium.[16] For example, in January 2010, the Dubna team (JINR) identified nihonium-286 as a product in the decay of tennessine via an alpha decay sequence:[14]
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.
^abcHofmann, S.; Heinz, S.; Mann, R.; Maurer, J.; Münzenberg, G.; Antalic, S.; Barth, W.; et al. (2016). "Remarks on the Fission Barriers of SHN and Search for Element 120". In Peninozhkevich, Yu. E.; Sobolev, Yu. G. (eds.).Exotic Nuclei: EXON-2016 Proceedings of the International Symposium on Exotic Nuclei. Exotic Nuclei. pp. 155–164.ISBN9789813226555.
^abHofmann, S.; Heinz, S.; Mann, R.; Maurer, J.; Münzenberg, G.; Antalic, S.; Barth, W.; et al. (2016). "Review of even element super-heavy nuclei and search for element 120".The European Physics Journal A.2016 (52).doi:10.1140/epja/i2016-16180-4.
^Wang, Meng; Huang, W.J.; Kondev, F.G.; Audi, G.; Naimi, S. (2021). "The AME 2020 atomic mass evaluation (II). Tables, graphs and references*".Chinese Physics C.45 (3) 030003.doi:10.1088/1674-1137/abddaf.
^Fleischmann, Martin; Pons, Stanley (1989). "Electrochemically induced nuclear fusion of deuterium".Journal of Electroanalytical Chemistry and Interfacial Electrochemistry.261 (2):301–308.doi:10.1016/0022-0728(89)80006-3.
^Morita, Kosuke; Morimoto, Kouji; Kaji, Daiya; Akiyama, Takahiro; Goto, Sin-Ichi; Haba, Hiromitsu; Ideguchi, Eiji; Kanungo, Rituparna; et al. (2004). "Experiment on the Synthesis of Element 113 in the Reaction209Bi(70Zn, n)278113".Journal of the Physical Society of Japan.73 (10):2593–2596.Bibcode:2004JPSJ...73.2593M.doi:10.1143/JPSJ.73.2593.
^K. Morita; Morimoto, Kouji; Kaji, Daiya; Haba, Hiromitsu; Ozeki, Kazutaka; Kudou, Yuki; Sumita, Takayuki; Wakabayashi, Yasuo; Yoneda, Akira; Tanaka, Kengo; et al. (2012). "New Results in the Production and Decay of an Isotope,278113, of the 113th Element".Journal of the Physical Society of Japan.81 (10) 103201.arXiv:1209.6431.Bibcode:2012JPSJ...81j3201M.doi:10.1143/JPSJ.81.103201.S2CID119217928.
^abOganessian, Yu. Ts.; Penionzhkevich, Yu. E.; Cherepanov, E. A. (2007). "Heaviest Nuclei Produced in48Ca-induced Reactions (Synthesis and Decay Properties)".AIP Conference Proceedings. Vol. 912. pp. 235–246.doi:10.1063/1.2746600.
^Sonzogni, Alejandro."Interactive Chart of Nuclides". National Nuclear Data Center: Brookhaven National Laboratory. Archived fromthe original on 2007-08-07. Retrieved2008-06-06.
