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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：11 Percentile：81.01(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.
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：43.41(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：45 Percentile：98.21(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.
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：24 Percentile：90.97(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.
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：61.87(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.
-spectroscopy at an intense cold neutron beam facilityJentschel, M.*; Blanc, A.*; de France, G.*; Kster, U.*; Leoni, S.*; Mutti, P.*; Simpson, G.*; Soldner, T.*; Ur, C.*; Urban, W.*; et al.
Journal of Instrumentation (Internet), 12(11), p.P11003_1 - P11003_33, 2017/11
Times Cited Count：38 Percentile：85.07(Instruments & Instrumentation)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：46.42(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.
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：0.90(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.
-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：94.21(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.
Hofmann, S.*; Heinz, S.*; Mann, R.*; Maurer, J.*; Mnzenberg, G.*; Antalic, S.*; Barth, W.*; Burkhard, K. G.*; Dahl, L.*; Eberhardt, K.*; et al.
European Physical Journal A, 52(6), p.180_1 - 180_34, 2016/06
Times Cited Count：171 Percentile：93.43(Physics, Nuclear)Hofmann, S.*; Heinz, S.*; Mann, R.*; Maurer, J.*; Mnzenberg, G.*; Antalic, S.*; Barth, W.*; Dahl, L.*; Eberhardt, K.*; Grzywacz, R.*; et al.
European Physical Journal A, 52(4), p.116_1 - 116_12, 2016/04
Times Cited Count：29 Percentile：87.47(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：109 Percentile：97.61(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.
Rudolph, D.*; Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L.-L.*; Di Nitto, A.*; Dllmann, Ch. E.*; Gates, J. M.*; Gregorich, K. E.*; et al.
Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1185 - 1190, 2015/02
Times Cited Count：7 Percentile：50.83(Chemistry, Analytical)Thirty correlated -decay chains of element 115 were observed, which were consistent with previous observations interpreted as the decay chain of 115. GEANT4 Monte-Carlo simulations were performed to reproduce high-resolution -photon coincidence results, which allows one to propose Q
values and excitation schemes of the superheavy nuclei with unprecedented precision.
Ca + Bk fusion reaction leading to element Z = 117; Long-lived -decaying 
Db and discovery of 
LrKhuyagbaatar, 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 Letters, 112(17), p.172501_1 - 172501_5, 2014/05
Times Cited Count：210 Percentile：98.42(Physics, Multidisciplinary)The superheavy element with atomic number 117 was produced in the Ca + Bk fusion reaction using the gas-filled recoil separator TASCA at GSI in Germany. This result verified the previous result of the discovery of new element 117 reported by Flerov Laboratory of Nuclear Reactions in Russia, which makes certain the synthesis and discovery of element 117 in human history. On the other hand, the last nucleus in the decay chain from the element 117 was assigned to be the unknown nucleus Lr instead of the previously reported Db, and Db was found to be the -decaying nucleus with very long half-life.
Forsberg, U.*; Rudolph, D.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L.-L.*; Di Nitto, A.*; Dllmann, Ch. E.*; Gates, J. M.*; Gregorich, K. E.*; et al.
EPJ Web of Conferences, 66, p.02036_1 - 02036_4, 2014/03
Times Cited Count：7 Percentile：88.63(Physics, Nuclear)A focal-plane Si detector setup applied to the spectroscopy of the element 115 -decay chains was reported. Results of the digital signal analysis for preamplifier signals and of the event-by-event -energy loss correction analysis were presented. The detectors consist of five double-sided Si strip detectors (DSSSD) arranged as a box, and signals from one side of the detector at the bottom of the box were digitally processed. Energy losses of particles detected by two Si detectors at the bottom and a side differs event-by-event, because each particle passed through two dead layers with a certain tilted angle. By correcting for the energy loss of each event using the angle of the -particle emission extracted from the detected positions, we succeeded in improving the energy resolution significantly.
Rudolph, D.*; Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L.-L.*; Di Nitto, A.*; Dllmann, Ch. E.*; Gates, J. M.*; Gregorich, K. E.*; et al.
Acta Physica Polonica B, 45(2), p.263 - 272, 2014/02
Times Cited Count：22 Percentile：75.00(Physics, Multidisciplinary)Produced in the reaction of Ca beam with an Am target, thirty correlated -decay chains were observed. Observed decay chains are consistent with a previously reported decay chain, which confirms the identification of the element 115. In addition, an -photon coincidence measurement was performed, and rays as well as X-ray candidates were observed in this decay chain. The -ray observation in the heaviest region of superheavy nuclei brings a big progress in the superheavy nuclear structure studies.
Yakushev, A.*; Gates, J. M.*; Trler, A.*; Schdel, M.; Dllmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; Block, M.*; Brchle, W.*; Dvorak, J.*; et al.
Inorganic Chemistry, 53(3), p.1624 - 1629, 2014/02
Times Cited Count：105 Percentile：98.87(Chemistry, Inorganic & Nuclear)We report on a gas-solid chromatography study of the adsorption of element 114 (flerovium, Fl) on a Au surface. Fl was produced in the nuclear fusion reaction 
Pu(Ca, 3-4n)
Fl and was isolated in-flight from the primary beam in a physical recoil separator. The adsorption behavior of Fl, its nuclear -decay product Cn, their lighter homologues in groups 14 and 12, i.e., Pb and Hg, and the noble gas Rn were studied simultaneously by isothermal gas chromatography and thermochromatography. Two Fl atoms were detected. They adsorbed on a Au surface at room temperature, but not as readily as Pb and Hg. The observed adsorption behavior of Fl points to a higher inertness compared to its nearest homologue in the group, Pb. However, the measured lower limit for the adsorption enthalpy of Fl on a Au surface points to the formation of a metal-metal bond of Fl with Au. Fl is the least reactive element in the group, but still a metal.
Rudolph, D.*; Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L. L.*; Di Nitto, A.*; Dllmann, Ch. E.*; Gates, J. M.*; Gregorich, K. E.*; et al.
Physical Review Letters, 111(11), p.112502_1 - 112502_5, 2013/09
Times Cited Count：125 Percentile：96.18(Physics, Multidisciplinary)Ca + Cm 
116
studied at the GSI-SHIPHofmann, S.*; Heinz, S.*; Mann, R.*; Maurer, J.*; Khuyagbaatar, J.*; Ackermann, D.*; Antalic, S.*; Barth, B.*; Block, M.*; Burkhard, H. G.*; et al.
European Physical Journal A, 48(5), p.62_1 - 62_23, 2012/05
Times Cited Count：167 Percentile：98.85(Physics, Nuclear)Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Jeppsson, J.*; Rudolph, D.*; Andersson, L.-L.*; Ackermann, D.*; Asai, Masato; Block, M.*; Eberhardt, K.*; et al.
Acta Physica Polonica B, 43(2), p.305 - 311, 2012/02
The atomic numbers and mass numbers of superheavy elements produced in the reactions of Ca beam with actinide targets have not been identified with direct experimental evidences. This causes a little doubt about a new element synthesis. The aim of this study is to identify the atomic numbers of those superheavy elements through characteristic X-ray measurements. To produce and separate superheavy elements, we employed a gas-filled separator TASCA at GSI, and constructed high-efficiency --electron multi-coincidence detector setup at the focal plane of TASCA. Transmission efficiencies and focusing abilities were tested experimentally, and compared with simulations. We achieved a good performance to realize X-ray measurement for the element 115.
