No atoms were detected, providing a limit of 1.6 pb for the cross section at the energy provided. The GSI repeated the experiment with higher sensitivity in three separate runs in April–May 2007, January–March 2008, and September–October 2008, all with negative results, reaching a cross section limit of 90 fb.[4]
244Pu(58Fe,xn)302-xUbn
Following their success in obtaining oganesson by the reaction between 249Cf and 48Ca in 2006, the team at the Joint Institute for Nuclear Research (JINR) in Dubna started experiments in March–April 2007 to attempt to create unbinilium with a 58Fe beam and a 244Pu target.[5][6] Initial analysis revealed that no atoms of unbinilium were produced, providing a limit of 400 fb for the cross section at the energy studied.[7]
244 94Pu + 58 26Fe → 302 120Ubn * → no atoms
The Russian team planned to upgrade their facilities before attempting the reaction again.[7]
245Cm(54Cr,xn)299-xUbn
There are indications that this reaction may be tried by the JINR in the future. The expected products of the 3n and 4n channels, 296Ubn and 295Ubn, could undergo five alpha decays to reach the darmstadtium isotopes 276Ds and 275Ds respectively; these darmstadtium isotopes were synthesised at the JINR in 2022 and 2023 respectively, both in the 232Th+48Ca reaction.[2][8]
248Cm(54Cr,xn)302-xUbn
In 2011, after upgrading their equipment to allow the use of more radioactive targets, scientists at the GSI attempted the rather asymmetrical fusion reaction:[9]
248 96Cm + 54 24Cr → 302 120Ubn * → no atoms
It was expected that the change in reaction would quintuple the probability of synthesizing unbinilium,[10] as the yield of such reactions is strongly dependent on their asymmetry.[11] Although this reaction is less asymmetric than the 249Cf+50Ti reaction, it also creates more neutron-rich unbinilium isotopes that should receive increased stability from their proximity to the shell closure at N = 184.[12] Three signals were observed in May 2011; a possible assignment to 299Ubn and its daughters was considered,[13] but could not be confirmed,[14][15][12] and a different analysis suggested that what was observed was simply a random sequence of events.[16]
In March 2022, Yuri Oganessian gave a seminar at the JINR considering how one could synthesise element 120 in the 248Cm+54Cr reaction.[17] In 2023, the director of the JINR, Grigory Trubnikov, stated that he hoped that the experiments to synthesise element 120 will begin in 2025.[18]
249Cf(50Ti,xn)299-xUbn
In August–October 2011, a different team at the GSI using the TASCA facility tried a new, even more asymmetrical reaction:[9][19]
249 98Cf + 50 22Ti → 299 120Ubn * → no atoms
Because of its asymmetry,[20] the reaction between 249Cf and 50Ti was predicted to be the most favorable practical reaction for synthesizing unbinilium, although it is also somewhat cold, and is further away from the neutron shell closure at N = 184 than any of the other three reactions attempted. No unbinilium atoms were identified, implying a limiting cross section of 200 fb.[19] Jens Volker Kratz predicted the actual maximum cross section for producing unbinilium by any of the four reactions 238U+64Ni, 244Pu+58Fe, 248Cm+54Cr, or 249Cf+50Ti to be around 0.1 fb;[21] in comparison, the world record for the smallest cross section of a successful reaction was 30 fb for the reaction 209Bi(70Zn,n)278Nh,[11] and Kratz predicted a maximum cross section of 20 fb for producing ununennium.[21] If these predictions are accurate, then synthesizing ununennium would be at the limits of current technology, and synthesizing unbinilium would require new methods.[21]
This reaction was investigated again in April to September 2012 at the GSI. This experiment used a 249Bk target and a 50Ti beam to produce element 119, but since 249Bk decays to 249Cf with a half-life of about 327 days, both elements 119 and 120 could be searched for simultaneously:
249 97Bk + 50 22Ti → 299 119Uue * → no atoms
249 98Cf + 50 22Ti → 299 120Ubn * → no atoms
Neither element 119 nor element 120 was observed. This implied a limiting cross section of 65 fb for producing element 119 in these reactions, and 200 fb for element 120.[22]
In May 2021, the JINR announced plans to investigate the 249Cf+50Ti reaction in their new facility.[23] The 249Cf target would have been produced by the Oak Ridge National Laboratory in Oak Ridge, Tennessee, United States; the 50Ti beam would be produced by the Hubert Curien Pluridisciplinary Institute in Strasbourg, Alsace, France.[24] However, after the Russian invasion of Ukraine began in 2022, collaboration between the JINR and other institutes completely ceased due to sanctions.[25] Thus, the JINR's plans have since shifted to the 248Cm+54Cr reaction, where the target and projectile beam could both be made in Russia.[24][26]
Starting from 2022,[27] plans began to be made to use the 88-inch cyclotron in the Lawrence Berkeley National Laboratory (LBNL) in Berkeley, California, United States to attempt to make new elements using 50Ti projectiles. The plan was to first test them on a plutonium target to create livermorium (element 116), which was successful in 2024. Thus, an attempt to make element 120 in the 249Cf+50Ti reaction is now planned for 2025.[28][29]
^Hofmann, S.; Heinz, S.; Mann, R.; 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.
^Heßberger, F. P.; Ackermann, D. (2017). "Some critical remarks on a sequence of events interpreted to possibly originate from a decay chain of an element 120 isotope". The European Physical Journal A. 53 (123): 123. Bibcode:2017EPJA...53..123H. doi:10.1140/epja/i2017-12307-5. S2CID125886824.
^Mayer, Anastasiya (31 May 2023). ""Большинство наших партнеров гораздо мудрее политиков"" ["Most of our partners are much wiser than politicians"]. Vedomosti (in Russian). Retrieved 15 August 2023. В этом году мы фактически завершаем подготовительную серию экспериментов по отладке всех режимов ускорителя и масс-спектрометров для синтеза 120-го элемента. Научились получать высокие интенсивности ускоренного хрома и титана. Научились детектировать сверхтяжелые одиночные атомы в реакциях с минимальным сечением. Теперь ждем, когда закончится наработка материала для мишени на реакторах и сепараторах у наших партнеров в «Росатоме» и в США: кюрий, берклий, калифорний. Надеюсь, что в 2025 г. мы полноценно приступим к синтезу 120-го элемента.
^Siwek-Wilczyńska, K.; Cap, T.; Wilczyński, J. (April 2010). "How can one synthesize the element Z = 120?". International Journal of Modern Physics E. 19 (4): 500. Bibcode:2010IJMPE..19..500S. doi:10.1142/S021830131001490X.
^Sokolova, Svetlana; Popeko, Andrei (24 May 2021). "How are new chemical elements born?". jinr.ru. JINR. Retrieved 4 November 2021. Previously, we worked mainly with calcium. This is element 20 in the Periodic Table. It was used to bombard the target. And the heaviest element that can be used to make a target is californium, 98. Accordingly, 98 + 20 is 118. That is, to get element 120, we need to proceed to the next particle. This is most likely titanium: 22 + 98 = 120.
There is still much work to adjust the system. I don't want to get ahead of myself, but if we can successfully conduct all the model experiments, then the first experiments on the synthesis of element 120 will probably start this year.
^"В ЛЯР ОИЯИ впервые в мире синтезирован ливерморий-288" [Livermorium-288 was synthesized for the first time in the world at FLNR JINR] (in Russian). Joint Institute for Nuclear Research. 23 October 2023. Retrieved 18 November 2023.
