in your element Targeting tennessine Liz Williams explores the synthesis of tennessine, a story in which elements in supporting roles play a crucial part.

ll experiments have their struggles. experimental set-up by trying to detect a In the quest to create new rare but known superheavy element. In Asuperheavy elements, there is a lot doing so, they confirmed3 the existence of of anxious waiting. Weeks, even months element 117 through independent synthesis, can go by without a single piece of evidence 249Bk and established that their observation of that an element exists. The time between nothing in the element 119 experiment was the first day of beam time and an initial simply a sign that the fusion cross-section promising event can feel like eternity. Is for this reaction was smaller than expected. the experiment set up properly? Were the A year after the GSI team published their calculations correct? results, element 117 — along with 113, The first few syntheses of element 117 48Ca 249Bk 297Ts 293,294Ts 115, and 118 — were officially welcomed were full of such moments. The penultimate onto the periodic table by the International element of the periodic table as we know Union of Pure and Applied Chemistry and it was first discovered by a Russian–US International Union of Pure and Applied collaboration at the Flerov Laboratory of During 70 days of beam time, the Physics joint working party. Nuclear Reactions (FLNR) at the Joint FLNR team saw evidence1,2 that six atoms When the FLNR team was asked to Institute for Nuclear Research in Russia1,2. of element 117 had been created by first propose a name for element 117, they made Their findings were later confirmed by forming tennessine-297, which rapidly an unconventional suggestion: tennessine, a GSI-led international collaboration at emitted three or four neutrons to form two whose suffix identifies the element as a the GSI Helmholtz Centre for Heavy Ion isotopes (pictured). This evidence came halogen, is rooted in the state of Tennessee, Research in Germany3. The independent in the form of α​-decay chains that went USA. Rather than the location of discovery, verification of an element by a different team down to dubnium and roentgenium. Cross- this name — approved by the IUPAC in may not carry the same prestige as its initial sections — a measure of the probability of 2016 — honours the place where some of synthesis, but for superheavy elements it is an creating a particular element for a given the FLNR collaborators came from, but important part of the discovery process. In reaction — are incredibly small, and the also where the berkelium-249 material the case of element 117, this second synthesis detection of only a handful of such chains had been crafted. The state’s Oak Ridge was also valuable in its own right, as it lifted makes an experiment a successful one. On National Laboratory had successfully taken some uncertainties in the GSI team’s quest a second run in 2012, the FLNR team saw on the herculean task of producing the for the even-heavier element 119. evidence for4,5 another seven atoms. Both berkelium-249 target so essential to the In 2009, the FLNR team was running experiments confirmed a rise in stability element’s discovery. ❐ an experiment using a technique called for elements with more than 110 protons, hot fusion, in which a radioactive actinide supporting the existence of the island Elizabeth Williams nucleus (in this case, berkelium-249, of stability. Department of Nuclear Physics, Australian National with 97 protons) reacts with, typically, Meanwhile, the GSI team had University, Canberra, Australia. calcium-48 (20 protons). Hot fusion embarked on a hunt for element 119 by e-mail: [email protected] reactions are capable of producing nuclei colliding titanium-50 (22 protons) with close to where we think we might find berkelium-249. They had put a lot of effort Published online: 19 October 2018 the ‘island of stability’ — a cluster of into refining their experimental set-up https://doi.org/10.1038/s41557-018-0160-2 relatively stable nuclei (in comparison to for this purpose by creating a very intense their neighbours) predicted to exist either titanium-50 beam, introducing a digital References around elements featuring 114, or between data acquisition system, and working to 1. Oganessian, T. S. et al. Phys. Rev. Lett. 104, 142502 (2010). 2. Oganessian, T. S. et al. Phys. Rev. C 83, 054315 (2011). 120 and 126 protons, and 184 neutrons. reduce background radiation. But, four 3. Khuyagbaatar, J. et al. Phys. Rev. Lett. 112, 172501 (2014). If it does indeed exist, the exact locations months into the experiment, element 119 4. Oganessian, T. S. et al. Phys. Rev. Lett. 109, 162501 (2012). and the decay properties of the island’s remained undiscovered. 5. Oganessian, T. S. et al. Phys. Rev. C 87, 054621 (2013). nuclei will be powerful tools for refining The radioactive berkelium target was our understanding of nuclear structure. decaying away and tension was running Competing interests high in the team, so in 2012 they switched The author collaborated with the GSI group on other to a calcium-48 beam to check their superheavy element research (not Z =​ 117 or 119).

Fl Mc Lv Ts Og 119 120 121 122 123 124125 126 127 128 129 130131 132 133 134

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