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Yakushev, A.*; Lens, L.*; D
llmann, Ch. E.*; Khuyagbaatar, J.*; J
ger, E.*; Krier, J.*; Runke, J.*; Albers, H. M.*; Asai, Masato; Block, M.*; et al.
Frontiers in Chemistry (Internet), 10, p.976635_1 - 976635_11, 2022/08
Times Cited Count：9 Percentile：79.28(Chemistry, Multidisciplinary)Flerovium (Fl, element 114) is the heaviest element chemically studied so far. The first chemical experiment on Fl suggested that Fl is a noble-gas-like element, while the second studies suggested that Fl has a volatile-metal-like character. To obtain more reliable conclusion, we performed further experimental studies on Fl adsorption behavior on Si oxide and gold surfaces. The present results suggest that Fl is highly volatile and less reactive than the volatile metal, Hg, but has higher reactivity than the noble gas, Rn.
Be produced by the strongest solar proton event during the holoceneSpiegl, T. C.*; Yoden, Shigeo*; Langematz, U.*; Sato, Tatsuhiko; Chhin, R.*; Noda, Satoshi*; Miyake, Fusa*; Kusano, Kanya*; Schaar, K.*; Kunze, M.*
Journal of Geophysical Research; Atmospheres, 127(13), p.e2021JD035658_1 - e2021JD035658_21, 2022/07
Times Cited Count：3 Percentile：16.31(Meteorology & Atmospheric Sciences)The abundance of cosmogenic isotopes in natural archives carries important information about the complex pathways from their source in the upper atmosphere to their deposition via atmospheric transport processes. Here, we use a new modelling framework to (a) estimate the Be production yield for the 774 CE/775 event, (b) evaluate the performance of our model framework by comparing the model results to four ice core records and (c) investigate the atmospheric pathways with a state-of-the-art climate model in detail. The results give new constraints regarding the seasonal timing of the event, underpin the role of the background conditions in the stratosphere, and highlight regional variations in the cosmogenic surface flux.
G
tz, M.*; Gtz, S.*; Kratz, J.-V.*; Ballof, J.*; Dllmann, Ch. E.*; Eberhardt, K.*; Mokry, C.*; Renisch, D.*; Runke, J.*; Sato, Tetsuya; et al.
Radiochimica Acta, 109(3), p.153 - 165, 2021/03
Times Cited Count：3 Percentile：45.99(Chemistry, Inorganic & Nuclear)We report on a novel two-chamber approach for the synthesis of volatile complexes that allows spatial decoupling of thermalization and gas-phase carbonyl complex synthesis. Neutron induced fission on 
U and spontaneous fission of 
Cm were employed for the production of the fission products. These were stopped inside a gas volume behind the target and flushed with an inert-gas flow into a second chamber. This was flushed with carbon monoxide to allow the gas-phase synthesis of carbonyl complexes. Parameter studies of the transfer from the first into the second chamber as well as on the carbonyl complex formation and transport processes have been performed. High overall efficiencies of more than 50% were reached rendering this approach interesting for studies of superheavy elements. Our results show that carbonyl complex formation of thermalized fission products is a single-atom reaction, and not a hot-atom reaction.
Khuyagbaatar, J.*; Yakushev, A.*; Dllmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; Asai, Masato; Block, M.*; Boll, R. A.*; Brand, H.*; Cox, D. M.*; et al.
Physical Review C, 102(6), p.064602_1 - 064602_9, 2020/12
Times Cited Count：43 Percentile：98.01(Physics, Nuclear)A search for production of the superheavy elements with atomic numbers 119 and 120 was performed in the 
Ti+
Bk and Ti+Cf fusion-evaporation reactions, respectively, at the gas-filled recoil separator TASCA. Over four months of irradiation, neither was detected at cross-section sensitivity levels of 65 and 200 fb, respectively. The non-observation of elements 119 and 120 is discussed within the concept of fusion-evaporation reactions including various theoretical predictions on the fission-barrier heights of superheavy nuclei in the region of the island of stability.
Baron, P.*; Cornet, S. M.*; Collins, E. D.*; DeAngelis, G.*; Del Cul, G.*; Fedorov, Y.*; Glatz, J. P.*; Ignatiev, V.*; Inoue, Tadashi*; Khaperskaya, A.*; et al.
Progress in Nuclear Energy, 117, p.103091_1 - 103091_24, 2019/11
Times Cited Count：73 Percentile：94.03(Nuclear Science & Technology)The results of an international review of separation processes for spent nuclear fuel (SNF) recycling in future closed fuel cycles with the evaluation of Technology Readiness Level are reported. This study was made by the Expert Group on Fuel Recycling Chemistry (EGFRC) organised by the Nuclear Energy Agency (NEA) of the Organisation for Economic Co-operation and Development (OECD). A unique feature of this study was that processes were classified according to a hierarchy of separations aimed at different elements within spent fuel (uranium; uranium-plutonium co-recovery; minor actinides; high heat generating radionuclides) and also the Head-end processes, used to prepare the SNF for chemical separation, were included. Separation processes covered both wet (hydrometallurgical) and dry (pyro-chemical) processes.
Ca+Bk leading to formation of the element Ts (Z=117)Khuyagbaatar, J.*; Yakushev, A.*; Dllmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; Asai, Masato; Block, M.*; Boll, R. A.*; Brand, H.*; Cox, D. M.*; et al.
Physical Review C, 99(5), p.054306_1 - 054306_16, 2019/05
Times Cited Count：23 Percentile：90.91(Physics, Nuclear)We have performed an experiment to synthesize the element 117 (Ts) with the Ca+Bk fusion reaction. Four 
-decay chains attributed to the element 117 were observed. Two of them were long decay chains which can be assigned to the one originating from the decay of 
Ts. The other two were short decay chains which are consistent with the one originating from the decay of 
Ts. We have compared the present results with the literature data, and found that our present results mostly confirmed the literature data, leading to the firm confirmation of the synthesis of the element 117.
Atz, M.*; Salazar, A.*; Hirano, Fumio; Fratoni, M.*; Ahn, J.*
Annals of Nuclear Energy, 124, p.28 - 38, 2019/02
Times Cited Count：1 Percentile：11.15(Nuclear Science & Technology)The likelihood for criticality in the far field of a repository was evaluated for direct disposal of commercial light water reactor used nuclear fuel. Two models were used in combination for this evaluation: (1) a neutronics model to estimate the minimum critical masses of spherical, water-saturated depositions of fuel material; (2) a transport model to simulate the dissolution of fuel material from multiple canisters and the subsequent transport of the solutes through host rock to a single accumulation location. The results suggest that accumulation of a critical mass is possible under conservative conditions but that these conditions are unlikely to occur, especially in the vicinity of a carefully-arranged repository.
and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCALens, L.*; Yakushev, A.*; Dllmann, Ch. E.*; Asai, Masato; Ballof, J.*; Block, M.*; David, H. M.*; Despotopulos, J.*; Di Nitto, A.*; Eberhardt, K.*; et al.
Radiochimica Acta, 106(12), p.949 - 962, 2018/12
Times Cited Count：8 Percentile：62.99(Chemistry, Inorganic & Nuclear)Online gas-solid adsorption studies with single atom quantities of Hg, Tl, and Pb on SiO and Au surfaces were carried out using short-lived radioisotopes with half-lives in the range of 4-49 s. This is a model study to measure adsorption enthalpies of superheavy elements Cn, Nh, and Fl. The short-lived isotopes were produced and separated by the gas-filled recoil separator TASCA at GSI. The products were stopped in He gas, and flushed into gas chromatography columns made of Si detectors whose surfaces were covered by SiO or Au. The short-lived Tl and Pb were successfully measured by the Si detectors with the SiO surface at room temperature. On the other hand, the Hg did not adsorb on the SiO surface, but adsorbed on the Au surface. The results demonstrated that the adsorption properties of short-lived Hg, Tl, and Pb could be studied with this setup, and that this method is applicable to the experiment for Cn, Nh, and Fl.
Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Beerwerth, R.*; Kaneya, Yusuke*; Makii, Hiroyuki; Mitsukai, Akina*; Nagame, Yuichiro; Osa, Akihiko; Toyoshima, Atsushi; et al.
Journal of the American Chemical Society, 140(44), p.14609 - 14613, 2018/11
Times Cited Count：27 Percentile：69.46(Chemistry, Multidisciplinary)The first ionization potential (IP
) yields information on valence electronic structure of an atom. IP values of heavy actinides beyond einsteinium (Es, Z = 99), however, have not been determined experimentally so far due to the difficulty in obtaining these elements on scales of more than one atom at a time. Recently, we successfully measured IP of lawrencium (Lr, Z = 103) using a surface ionization method. The result suggests that Lr has a loosely-bound electron in the outermost orbital. In contrast to Lr, nobelium (No, Z = 102) is expected to have the highest IP among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP values of No as well as fermium (Fm, Z = 100) and mendelevium (Md, Z = 101) using the surface ionization method. The obtained results indicate that the IP value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.
Hayafune, Hiroki; Glatz, J.-P.*; Yang, H.*; Ruggieri, J.-M.*; Kim, Y.-I.*; Ashurko, Y.*; Hill, R.*
Proceedings of International Conference on Fast Reactors and Related Fuel Cycles; Next Generation Nuclear Systems for Sustainable Development (FR-17) (USB Flash Drive), 12 Pages, 2017/06
The SFR system arrangement Phase II became effective on 16 February 2016 by signatures of CEA, JAEA, KAERI, USDOE, and Rosatom, and was extended for additional 10 years. Collaboration of GIF SFR is growing adding new reactor concepts and related RDs. In 2015, a project arrangement on SFR System Integration and Assessment (SIA) has been signed by 7 members : China, EU, France, Japan, Korea, Russia and US. In the SIA project, RD needs from the SFR design will be shown to the RD project, and RD results from each RD project will be integrated into the designs.
Ca + Cm collisions 10% above the Coulomb barrierGtz, M.*; Gtz, S.*; Kratz, J. V.*; Dllmann, Ch. E.*; Mokry, Ch.*; Runke, J.*; Thrle-Pospiech, P.*; Wiehl, N.*; Schdel, M.; Ballof, J.*; et al.
Nuclear Physics A, 961, p.1 - 21, 2017/05
Times Cited Count：6 Percentile：47.01(Physics, Nuclear)The kinematics of multi-nucleon transfer reactions in the Ca + Cm collisions were investigated using a stacked-foil technique and radiochemical separations. In previous studies, isotopic distributions of the products of below-target isotopes were found to be broader than those of above-target isotopes, which had been interpreted as larger contributions of strongly dumped collisions in the productions of below-target isotopes than above-target ones. However, in the present study, the average total kinetic energy loss (TKEL), and thus, the average excitation energies were determined for both below-target and above-target isotopes, and they were found to be similar. This contradicts the previous interpretation, and thus, a new interpretation has been proposed; highly excited above-target products are lost by fission.
Atz, M.*; Liu, X.*; Fratoni, M.*; Ahn, J.*; Hirano, Fumio
Proceedings of 2017 International High-Level Radioactive Waste Management Conference (IHLRWM 2017) (CD-ROM), p.608 - 614, 2017/04
Nagame, Yuichiro; Kratz, J. V.*; Schdel, M.*
EPJ Web of Conferences, 131, p.07007_1 - 07007_8, 2016/12
Times Cited Count：3 Percentile：72.98(Chemistry, Inorganic & Nuclear)Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi*; Kaneya, Yusuke; Tsukada, Kazuaki; Dllmann, C. E.*; Eberhardt, K.*; Eliav, E.*; et al.
EPJ Web of Conferences, 131, p.05001_1 - 05001_6, 2016/12
Times Cited Count：0 Percentile：0.9(Chemistry, Inorganic & Nuclear)Ionization efficiency in a surface ionization process depends on the first ionization potential of the atom. Based on the dependence, the ionization potential of the atom can be determined. We measured ionization efficiencies of fermium, einsteinium, mendelevium, and lawrencium by using a newly developed gas-jet coupled surface ion-source. The ionization potential of the elements have not been determined so far due to their low production rates and/or their short half-lives. Based on a relationship between the ionization efficiency and the ionization potential obtained via measurements of short-lived lanthanide isotopes, the ionization potentials of these actinide elements have been successfully determined.
Eichler, R.*; Asai, Masato; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; Dllmann, Ch. E.*; Even, J.*; Fangli, F.*; Goetz, M.*; et al.
EPJ Web of Conferences, 131, p.07005_1 - 07005_7, 2016/12
Times Cited Count：3 Percentile：72.98(Chemistry, Inorganic & Nuclear)In recent years gas-phase chemical studies assisted by physical pre-separation allowed for the productions and investigations of fragile single molecular species of superheavy elements. The latest highlight is the formation of very volatile hexacarbonyl compound of element 106, Sg(CO)
. Following this success, second-generation experiments were performed to measure the first bond dissociation energy between the central metal atom and the surrounding ligand. The method using a tubular decomposition reactor was developed and successfully applied to short-lived Mo(CO), W(CO), and Sg(CO).
-fission and recoil---fission events observed in the reaction Ca + 
AmForsberg, U.*; Rudolph, D.*; Andersson, L.-L.*; Di Nitto, A.*; Dllmann, Ch. E.*; Fahlander, C.*; Gates, J. M.*; Golubev, P.*; Gregorich, K. E.*; Gross, C. J.*; et al.
Nuclear Physics A, 953, p.117 - 138, 2016/09
Times Cited Count：46 Percentile：94.56(Physics, Nuclear)Alpha-decay chains observed in the element-115 production reactions of Ca + Am were investigated using a new data set consisting of our recently reported data obtained at GSI and previously reported ones at Dubna and LBNL. Short decay chains of recoil--()-fission type, fourteen of which were observed, and some of which were interpreted as the 2-neutron evaporation products 
Mc, have been reassigned. It is plausible that most of them were assigned to the 3-neutron evaporation products 
Mc whose decay chain would on the way have branches of EC decays followed by fission.
and W(CO)Usoltsev, I.*; Eichler, R.*; Wang, Y.*; Even, J.*; Yakushev, A.*; Haba, Hiromitsu*; Asai, Masato; Brand, H.*; Di Nitto, A.*; Dllmann, Ch. E.*; et al.
Radiochimica Acta, 104(3), p.141 - 151, 2016/03
Times Cited Count：31 Percentile：95.03(Chemistry, Inorganic & Nuclear)Conditions of the production and decomposition of hexacarbonyl complexes of short-lived Mo and W isotopes were investigated to study thermal stability of the heaviest group 6 hexacarbonyl complex Sg(CO). A tubular flow reactor was tested to decompose the hexacarbonyl complexes and to extract the first bond dissociation energies. A silver was found to be the most appropriate reaction surface to study the decomposition of the group 6 hexacarbonyl. It was found that the surface temperature at which the decomposition occurred was correlated to the first bond dissociation energy of Mo(CO) and W(CO), indicating that the first bond dissociation energy of Sg(CO) could be determined with this technique.
104 in liquid phaseNagame, Yuichiro; Kratz, J. V.*; Schdel, M.
Nuclear Physics A, 944, p.614 - 639, 2015/12
Times Cited Count：24 Percentile：81.68(Physics, Nuclear)Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi; Kaneya, Yusuke; Tsukada, Kazuaki; Dllmann, Ch. E.*; Eberhardt, K.*; Eliav, E.*; et al.
Nature, 520(7546), p.209 - 211, 2015/04
Times Cited Count：107 Percentile：97.49(Multidisciplinary Sciences)Ionization efficiency in a surface ionization process depends on the first ionization potential of the atom. Based on the dependence, the ionization potential of the atom can be determined. We successfully measured ionization efficiencies of lawrencium (Lr, 
=103) using a gas-jet coupled surface ion-source. The ionization potential of Lr has not been determined owing to its low production rate and its short half-life. Based on a relationship between the ionization efficiency and the ionization potential obtained via measurements of short-lived lanthanide isotopes, the ionization potential of Lr was determined.
Even, J.*; Ackermann, D.*; Asai, Masato; Block, M.*; Brand, H.*; Di Nitto, A.*; Dllmann, Ch. E.*; Eichler, R.*; Fan, F.*; Haba, Hiromitsu*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 303(3), p.2457 - 2466, 2015/03
Times Cited Count：15 Percentile：77.56(Chemistry, Analytical)Rapid In situ synthesis of metal carbonyl complexes has been demonstrated using short-lived isotopes produced in nuclear fission and fusion reactions. The short-lived isotopes with high recoil energy directly react with carbon-monoxides and form carbonyl complexes. Only highly volatile complexes were fast transported in a gas stream to counting and chemistry devices. Short-lived Mo, Tc, Ru, Rh, W, Re, Os, and Ir were found to form volatile carbonyl complexes, while no volataile complex of Hf and Ta were detected. This technique has been applied to a chemical investigation of the superheavy element Sg (atomic number 106), and will be applicable to various fields of nuclear science with short-lived transition metal isotopes.
