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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：4 Percentile：57.86(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.
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：20 Percentile：95.44(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.
Bh in the 
Cm(
Na,5
)Bh reaction and its decay propertiesHaba, Hiromitsu*; Fan, F.*; Kaji, Daiya*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Komori, Yukiko*; Kondo, Narumi*; Kudo, Hisaaki*; Morimoto, Koji*; Morita, Kosuke*; et al.
Physical Review C, 102(2), p.024625_1 - 024625_12, 2020/08
Times Cited Count：5 Percentile：56.79(Physics, Nuclear)
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：18 Percentile：90.88(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：6 Percentile：52.69(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.
-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：39 Percentile：93.7(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.
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：54.99(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：193 Percentile：98.57(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：6 Percentile：87.15A 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：21 Percentile：75(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：94 Percentile：98.73(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：118 Percentile：96.43(Physics, Multidisciplinary)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.
Even, J.*; Ballof, J.*; Brchle, W.*; Buda, R. A.*; Dllmann, Ch. E.*; Eberhardt, K.*; Gorshkov, A.*; Gromm, E.*; Hild, D.*; Jger, E.*; et al.
Nuclear Instruments and Methods in Physics Research A, 638(1), p.157 - 164, 2011/03
Times Cited Count：24 Percentile：86.94(Instruments & Instrumentation)
U(
S, 3-5)
Hs reaction leading to the observation of HsGraeger, R.*; Ackermann, D.*; Chelnokov, M.*; Chepigin, V.*; Dllmann, C. E.*; Dvorak, J.*; Even, J.*; Gorshkov, A.*; He
berger, F. P.*; Hild, D.*; et al.
Physical Review C, 81(6), p.061601_1 - 061601_5, 2010/06
Times Cited Count：43 Percentile：90.76(Physics, Nuclear)Toyoshima, Atsushi; Oe, Kazuhiro; Asai, Masato; Miyashita, Sunao; Sato, Tetsuya; Sato, Nozomi; Kaneya, Yusuke*; Kitatsuji, Yoshihiro; Tsukada, Kazuaki; Nagame, Yuichiro; et al.
no journal, ,
Miyashita, Sunao; Toyoshima, Atsushi; Oe, Kazuhiro; Asai, Masato; Sato, Tetsuya; Kitatsuji, Yoshihiro; Tsukada, Kazuaki; Nagame, Yuichiro; Schdel, M.; Omtvedt, J. P.*; et al.
no journal, ,
For determination of the redox potentials of seaborgium (Sg), we plan to carry out rapid continuous experiments using a new system combined with a flow electrolytic column and the rapid liquid-liquid extraction apparatus SISAK. For the experiments of redox potentials of Sg, fast separation between different oxidation states of Sg is required. In this study, solvent extraction of W and Mo, as the lighter homologues of Sg, from 0.10 mol/L hydrochloric acid solution into di-(2-ethylhexyl)phosphoric acid (HDEHP), 1-phenyl-3-metyl-4-benzoyl-5-pyrazolone (PMBP) and 3-isopropyl-tropolone (HT) in toluene was investigated. A synergistic effect by tributylphosphate (TBP) was also examined.
Toyoshima, Atsushi; Miyashita, Sunao; Oe, Kazuhiro; Asai, Masato; Sato, Tetsuya; Tsukada, Kazuaki; Kitatsuji, Yoshihiro; Nagame, Yuichiro; Schdel, M.; Omtvedt, J. P.*; et al.
no journal, ,
We plan to determine the redox potential of seaborgium (Sg) in continuous experiments with a flow electrolytic column and a continuous solvent extraction SISAK. In this study, reduction experiments of its lighter homologues, Mo and W, were performed using the flow electrolytic column apparatus. After 200 
L of the 
W radiotracer in 0.1 M HCl was introduced into the apparatus, 1000 L of 0.1 M HCl was fed into the electrode on which an potential was applied between -0.8 and 0.6 V. 1000 L was taken from the effluent from the electrode and was then mixed with 10
M hinokitiol in toluene with the same volume. After shaking for 1 min and then centrifuging for 30 s, 800 L was taken from each phase, which was then separately subjected to -ray spectrometry. As a result, the extraction yield of W was constant against the variation of the applied potential. It seems that once reduced W was again oxidized to the +6 state in the extraction procedure.
Oe, Kazuhiro; Tsukada, Kazuaki; Asai, Masato; Sato, Tetsuya; Toyoshima, Atsushi; Miyashita, Sunao; Nagame, Yuichiro; Schdel, M.; Kaneya, Yusuke*; Lerum, H. V.*; et al.
no journal, ,
We are planning to investigate the redox potentials of element 106, seaborgium, with a combination of the rapid liquid-liquid extraction apparatus SISAK and a flow electrolytic column. In order to combine these two apparatuses, we need to reduce the liquid flow-rate of the SISAK system. In this study, a new degasser, which works with a lower flow rate, was developed for SISAK. It separates the gas-liquid mixture using a hydrophobic Teflon membrane (only the gas can go through the membrane). Using this new degasser, dissolution efficiencies of gas-jet transported products were measured. At the typical flow rate for the SISAK system (0.4 mL/s), a dissolution efficiency of approximately 80% was obtained. A high yield of around 80% was also observed at a flow rate of 0.1 mL/s with a mixer for the gas-liquid mixing.
Omtvedt, J. P.*; Oe, Kazuhiro; Lerum, H. V.*; Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Kratz, J. V.*; Nagame, Yuichiro; Schdel, M.
no journal, ,
We are planning to investigate the redox potentials of element 106, seaborgium, with a combination of the automated liquid-liquid extraction system SISAK and a flow electrolytic column. In order to combine these two apparatuses, we need to reduce the liquid flow-rate of the SISAK system. In this study, a new degasser, which works with a lower flow rate, was developed for SISAK. It separates the gas-liquid mixture using a hydrophobic Teflon membrane (only the gas can go through the membrane). Using this new degasser, dissolution efficiencies of gas-jet transported products were measured. A high yield of around 80% was observed at a flow rate of 0.1 mL/s with a mixer for the gas-liquid mixing. This result has never been achieved with the conventional SISAK degasser. This is an important step forward with respect to combining the SISAK system with a flow electrolytic column for performing redox experiments on Sg.
