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Journal Articles

Fusion reaction $$^{48}$$Ca+$$^{249}$$Bk leading to formation of the element Ts (Z=117)

Khuyagbaatar, J.*; Yakushev, A.*; D$"u$llmann, 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

We have performed an experiment to synthesize the element 117 (Ts) with the $$^{48}$$Ca+$$^{249}$$Bk fusion reaction. Four $$alpha$$-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 $$alpha$$ decay of $$^{294}$$Ts. The other two were short decay chains which are consistent with the one originating from the $$alpha$$ decay of $$^{293}$$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.

Journal Articles

Online chemical adsorption studies of Hg, Tl, and Pb on SiO$$_{2}$$ and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCA

Lens, L.*; Yakushev, A.*; D$"u$llmann, 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

 Percentile:100(Chemistry, Inorganic & Nuclear)

Online gas-solid adsorption studies with single atom quantities of Hg, Tl, and Pb on SiO$$_{2}$$ 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$$_{2}$$ or Au. The short-lived Tl and Pb were successfully measured by the Si detectors with the SiO$$_{2}$$ surface at room temperature. On the other hand, the Hg did not adsorb on the SiO$$_{2}$$ 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.

Journal Articles

Towards saturation of the electron-capture delayed fission probability; The New isotopes $$^{240}$$Es and $$^{236}$$Bk

Konki, J.*; Khuyagbaatar, J.*; Uusitalo, J.*; Greenlees, P. T.*; Auranen, K.*; Badran, H.*; Block, M.*; Briselet, R.*; Cox, D. M.*; Dasgupta, M.*; et al.

Physics Letters B, 764, p.265 - 270, 2017/01

 Times Cited Count:6 Percentile:18.72(Astronomy & Astrophysics)

Journal Articles

Recoil-$$alpha$$-fission and recoil-$$alpha$$-$$alpha$$-fission events observed in the reaction $$^{48}$$Ca + $$^{243}$$Am

Forsberg, U.*; Rudolph, D.*; Andersson, L.-L.*; Di Nitto, A.*; D$"u$llmann, 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:22 Percentile:4.76(Physics, Nuclear)

Alpha-decay chains observed in the element-115 production reactions of $$^{48}$$Ca + $$^{243}$$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-$$alpha$$-($$alpha$$)-fission type, fourteen of which were observed, and some of which were interpreted as the 2-neutron evaporation products $$^{289}$$Mc, have been reassigned. It is plausible that most of them were assigned to the 3-neutron evaporation products $$^{288}$$Mc whose decay chain would on the way have branches of EC decays followed by fission.

Journal Articles

In situ synthesis of volatile carbonyl complexes with short-lived nuclides

Even, J.*; Ackermann, D.*; Asai, Masato; Block, M.*; Brand, H.*; Di Nitto, A.*; D$"u$llmann, 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:6 Percentile:28.02(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.

Journal Articles

Selected spectroscopic results on element 115 decay chains

Rudolph, D.*; Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L.-L.*; Di Nitto, A.*; D$"u$llmann, 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:6 Percentile:28.02(Chemistry, Analytical)

Thirty correlated $$alpha$$-decay chains of element 115 were observed, which were consistent with previous observations interpreted as the decay chain of $$^{288}$$115. GEANT4 Monte-Carlo simulations were performed to reproduce high-resolution $$alpha$$-photon coincidence results, which allows one to propose Q$$_{alpha}$$ values and excitation schemes of the superheavy nuclei with unprecedented precision.

Journal Articles

$$^{48}$$Ca + $$^{249}$$Bk fusion reaction leading to element Z = 117; Long-lived $$alpha$$-decaying $$^{270}$$Db and discovery of $$^{266}$$Lr

Khuyagbaatar, J.*; Yakushev, A.*; D$"u$llmann, 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:131 Percentile:1.03(Physics, Multidisciplinary)

The superheavy element with atomic number 117 was produced in the $$^{48}$$Ca + $$^{249}$$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 $$alpha$$ decay chain from the element 117 was assigned to be the unknown nucleus $$^{266}$$Lr instead of the previously reported $$^{270}$$Db, and $$^{270}$$Db was found to be the $$alpha$$-decaying nucleus with very long half-life.

Journal Articles

Spectroscopic tools applied to element Z = 115 decay chains

Forsberg, U.*; Rudolph, D.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L.-L.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; Gates, J. M.*; Gregorich, K. E.*; et al.

EPJ Web of Conferences (Internet), 66, p.02036_1 - 02036_4, 2014/03

 Times Cited Count:5 Percentile:9.47

A focal-plane Si detector setup applied to the spectroscopy of the element 115 $$alpha$$-decay chains was reported. Results of the digital signal analysis for preamplifier signals and of the event-by-event $$alpha$$-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 $$alpha$$ particles detected by two Si detectors at the bottom and a side differs event-by-event, because each $$alpha$$ particle passed through two dead layers with a certain tilted angle. By correcting for the energy loss of each $$alpha$$ event using the angle of the $$alpha$$-particle emission extracted from the detected positions, we succeeded in improving the $$alpha$$ energy resolution significantly.

Journal Articles

Alpha-photon coincidence spectroscopy along element 115 decay chains

Rudolph, D.*; Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L.-L.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; Gates, J. M.*; Gregorich, K. E.*; et al.

Acta Physica Polonica B, 45(2), p.263 - 272, 2014/02

 Times Cited Count:15 Percentile:21.56(Physics, Multidisciplinary)

Produced in the reaction of $$^{48}$$Ca beam with an $$^{243}$$Am target, thirty correlated $$alpha$$-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 $$alpha$$-photon coincidence measurement was performed, and $$gamma$$ rays as well as X-ray candidates were observed in this decay chain. The $$gamma$$-ray observation in the heaviest region of superheavy nuclei brings a big progress in the superheavy nuclear structure studies.

Journal Articles

Superheavy element flerovium (element 114) is a volatile metal

Yakushev, A.*; Gates, J. M.*; T$"u$rler, A.*; Sch$"a$del, M.; D$"u$llmann, Ch. E.*; Ackermann, D.*; Andersson, L.-L.*; Block, M.*; Br$"u$chle, W.*; Dvorak, J.*; et al.

Inorganic Chemistry, 53(3), p.1624 - 1629, 2014/02

 Times Cited Count:51 Percentile:1.81(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 $$^{244}$$Pu($$^{48}$$Ca, 3-4n)$$^{288,289}$$Fl and was isolated in-flight from the primary $$^{48}$$ beam in a physical recoil separator. The adsorption behavior of Fl, its nuclear $$alpha$$-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.

Journal Articles

Spectroscopy of element 115 decay chains

Rudolph, D.*; Forsberg, U.*; Golubev, P.*; Sarmiento, L. G.*; Yakushev, A.*; Andersson, L. L.*; Di Nitto, A.*; D$"u$llmann, 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:88 Percentile:2.76(Physics, Multidisciplinary)

Journal Articles

Evidence for hindrance in fusion between sulfur and lead nuclei

Khuyagbaatar, J.*; Nishio, Katsuhisa; Hofmann, S.*; Ackermann, D.*; Block, M.*; Heinz, S.*; He${ss}$berger, F. P.*; Hirose, Kentaro; Ikezoe, Hiroshi; Kindler, B.*; et al.

Physical Review C, 86(6), p.064602_1 - 064602_6, 2012/12

 Times Cited Count:11 Percentile:35.22(Physics, Nuclear)

Journal Articles

The Reaction $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$116$$^{*}$$ studied at the GSI-SHIP

Hofmann, 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:104 Percentile:1.27(Physics, Nuclear)

Journal Articles

First experiment at TASCA towards X-ray fingerprinting of element 115 decay chains

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 $$^{48}$$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 $$alpha$$-$$gamma$$-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.

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