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Journal Articles

Urban factors and mental health symptoms in children of the Tokyo Early Adolescence Survey; Impact of proximity to railway stations

Davies, S. J. C.*; Bolea-Alamanac, B.*; Endo, Kaori*; Yamamoto, Yu*; Yamasaki, Shudo*; Malins, A.; Evans, J.*; Sullivan, S.*; Ando, Shuntaro*; Nishida, Atsushi*; et al.

Journal of Transport & Health, 28, p.101564_1 - 101564_11, 2023/01

Journal Articles

On the adsorption and reactivity of element 114, flerovium

Yakushev, A.*; Lens, L.*; D$"u$llmann, Ch. E.*; Khuyagbaatar, J.*; J$"a$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:8 Percentile:81.08(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.

Journal Articles

Application of a novel gas phase synthesis approach to carbonyl complexes of accelerator-produced 5d transition metals

G$"o$tz, M.*; Yakushev, A.*; G$"o$tz, S.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; Asai, Masato; Kindler, B.*; Krier, J.*; Lommel, B.*; Nagame, Yuichiro*; et al.

Radiochimica Acta, 110(2), p.75 - 86, 2022/02

 Times Cited Count:2 Percentile:32.89(Chemistry, Inorganic & Nuclear)

The study of volatile superheavy element carbonyl complexes requires more efficient methods because the yield of transactinide elements decreases with increasing atomic number. This is achieved by using a newly developed double chamber system to separate the recoil chamber and the reaction one, thereby avoiding the decomposition of reactive molecules by the projectile ion beam, which hinders the synthesis of carbonyl complexes. The feasibility of this method was verified by synthesizing 5d metal short-lived isotopes as homologous element isotopes of the light transactinide elements Sg, Bh, Hs, and Mt at the Japan Atomic Energy Agency tandem accelerator and conducting model experiments.

Journal Articles

Search for elements 119 and 120

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, 102(6), p.064602_1 - 064602_9, 2020/12

 Times Cited Count:30 Percentile:97.96(Physics, Nuclear)

A search for production of the superheavy elements with atomic numbers 119 and 120 was performed in the $$^{50}$$Ti+$$^{249}$$Bk and $$^{50}$$Ti+$$^{249}$$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.

Journal Articles

First online operation of TRIGA-TRAP

Grund, J.*; Asai, Masato; Blaum, K.*; Block, M.*; Chenmarev, S.*; D$"u$llmann, Ch. E.*; Eberhardt, K.*; Lohse, S.*; Nagame, Yuichiro*; Nagy, Sz.*; et al.

Nuclear Instruments and Methods in Physics Research A, 972, p.164013_1 - 164013_8, 2020/08

 Times Cited Count:5 Percentile:54.54(Instruments & Instrumentation)

We report on the successful coupling of the Penning-trap mass spectrometry setup TRIGA-TRAP to the research reactor TRIGA Mainz. This offers the possibility to perform direct high-precision mass measurements of short-lived nuclei produced in neutron-induced fission of a $$^{235}$$U target located near the reactor core. An aerosol-based gas-jet system is used for efficient transport of short-lived neutron-rich nuclei from the target chamber to a surface ion source. In conjunction with new ion optics and extended beam monitoring capabilities, the experimental setup has been fully commissioned. The design of the surface ion source, efficiency studies and first results are presented.

Journal Articles

New excited 2$$^+$$ and 3$$^-$$ two-proton states in $$_{84}^{210}$$Po$$_{126}$$ populated by two-proton transfer

Dupont, E.*; Astier, A.*; Petrache, C. M.*; Lv, B. F.*; Deloncle, I.*; Kiener, J.*; Orlandi, R.; Makii, Hiroyuki; Nishio, Katsuhisa; Hirose, Kentaro; et al.

Physical Review C, 101(1), p.014309_1 - 014309_6, 2020/01

 Times Cited Count:1 Percentile:14.01(Physics, Nuclear)

Journal Articles

Search for $$alpha$$ decay of $$^{104}$$Te with a novel recoil-decay scintillation detector

Xiao, Y.*; Go, S.*; Grzywacz, R.*; Orlandi, R.; Andreyev, A. N.; Asai, Masato; Bentley, M. A.*; de Angelis, G.*; Gross, C. J.*; Hausladen, P.*; et al.

Physical Review C, 100(3), p.034315_1 - 034315_8, 2019/09

 Times Cited Count:15 Percentile:83.54(Physics, Nuclear)

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

AA2019-0039.pdf:5.03MB

 Times Cited Count:21 Percentile:90.63(Physics, Nuclear)

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

AA2018-0417.pdf:0.99MB

 Times Cited Count:6 Percentile:63.44(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

First ionization potentials of Fm, Md, No, and Lr; Verification of filling-up of 5f electrons and confirmation of the actinide series

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:69.82(Chemistry, Multidisciplinary)

The first ionization potential (IP$$_1$$) yields information on valence electronic structure of an atom. IP$$_1$$ 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$$_1$$ 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$$_1$$ among the actinide elements owing to its full-filled 5f and the 7s orbitals. In the present study, we have successfully determined IP$$_1$$ 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$$_1$$ value of heavy actinoids would increase monotonically with filling electrons up in the 5f orbital like heavy lanthanoids.

Journal Articles

Determination of fusion barrier distributions from quasielastic scattering cross sections towards superheavy nuclei synthesis

Tanaka, Taiki*; Narikiyo, Yoshihiro*; Morita, Kosuke*; Fujita, Kunihiro*; Kaji, Daiya*; Morimoto, Koji*; Yamaki, Sayaka*; Wakabayashi, Yasuo*; Tanaka, Kengo*; Takeyama, Mirei*; et al.

Journal of the Physical Society of Japan, 87(1), p.014201_1 - 014201_9, 2018/01

 Times Cited Count:16 Percentile:73.53(Physics, Multidisciplinary)

Excitation functions of quasielastic scattering cross sections for the $$^{48}$$Ca + $$^{208}$$Pb, $$^{50}$$Ti + $$^{208}$$Pb, and $$^{48}$$Ca + $$^{248}$$Cm reactions were successfully measured by using the gas-filled recoil-ion separator GARIS. Fusion barrier distributions were extracted from these data, and compared with the coupled-channels calculations. It was found that the peak energies of the barrier distributions for the $$^{48}$$Ca + $$^{208}$$Pb and $$^{50}$$Ti + $$^{208}$$Pb systems coincide with those of the 2n evaporation channel cross sections for the systems, while that of the $$^{48}$$Ca + $$^{248}$$Cm is located slightly below the 4n evaporation ones. This results provide us helpful information to predict the optimum beam energy to synthesize superheavy nuclei.

Journal Articles

Study of fission using multi-nucleon transfer reactions

Nishio, Katsuhisa; Hirose, Kentaro; Vermeulen, M. J.; Makii, Hiroyuki; Orlandi, R.; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Sato, Tetsuya; Nagame, Yuichiro; et al.

EPJ Web of Conferences, 163, p.00041_1 - 00041_6, 2017/11

 Times Cited Count:1 Percentile:61.28

Journal Articles

Study of the reaction $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$Lv$$^{ast}$$ at RIKEN-GARIS

Kaji, Daiya*; Morita, Kosuke*; Morimoto, Koji*; Haba, Hiromitsu*; Asai, Masato; Fujita, Kunihiro*; Gan, Z.*; Geissel, H.*; Hasebe, Hiroo*; Hofmann, S.*; et al.

Journal of the Physical Society of Japan, 86(3), p.034201_1 - 034201_7, 2017/03

 Times Cited Count:24 Percentile:81.66(Physics, Multidisciplinary)

The fusion reaction of $$^{48}$$Ca + $$^{248}$$Cm $$rightarrow$$ $$^{296}$$Lv$$^{ast}$$ was studied using the gas-filled recoil-ion separator GARIS at RIKEN. A total of seven $$alpha$$ and spontaneous-fission decay chains were observed, which would originate from the reaction products of the element 116, $$^{292}$$Lv and $$^{293}$$Lv. Decay properties observed in the chains are in good agreement with the previously published ones. However, one of the chains showed a discrepancy, indicating the new spontaneous-fission branch in $$^{285}$$Cn or the production of the new isotope $$^{294}$$Lv.

Journal Articles

First ionization potential of the heaviest actinide lawrencium, element 103

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi*; Kaneya, Yusuke; Tsukada, Kazuaki; D$"u$llmann, 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

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.

Journal Articles

Stability and synthesis of superheavy elements; Fighting the battle against fission - Example of $$^{254}$$No

Lopez-Martens, A.*; Henning, G.*; Khoo, T. L.*; Seweryniak, D.*; Alcorta, M.*; Asai, Masato; Back, B. B.*; Bertone, P. F.*; Boilley, D.*; Carpenter, M. P.*; et al.

EPJ Web of Conferences, 131, p.03001_1 - 03001_6, 2016/12

 Times Cited Count:1 Percentile:44

Fission barrier height and its angular-momentum dependence have been measured for the first time in the nucleus with the atomic number greater than 100. The entry distribution method, which can determine the excitation energy at which fission starts to dominate the decay process, was applied to $$^{254}$$No. The fission barrier of $$^{254}$$No was found to be 6.6 MeV at zero spin, indicating that the $$^{254}$$No is strongly stabilized by the nuclear shell effects.

Journal Articles

Complex chemistry with complex compounds

Eichler, R.*; Asai, Masato; Brand, H.*; Chiera, N. M.*; Di Nitto, A.*; Dressler, R.*; D$"u$llmann, 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:2 Percentile:73.04

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)$$_{6}$$. 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)$$_{6}$$, W(CO)$$_{6}$$, and Sg(CO)$$_{6}$$.

Journal Articles

Decomposition studies of group 6 hexacarbonyl complexes, 1; Production and decomposition of Mo(CO)$$_6$$ and W(CO)$$_6$$

Usoltsev, I.*; Eichler, R.*; Wang, Y.*; Even, J.*; Yakushev, A.*; Haba, Hiromitsu*; Asai, Masato; Brand, H.*; Di Nitto, A.*; D$"u$llmann, Ch. E.*; et al.

Radiochimica Acta, 104(3), p.141 - 151, 2016/03

 Times Cited Count:30 Percentile:94.8(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)$$_6$$. 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)$$_6$$ and W(CO)$$_6$$, indicating that the first bond dissociation energy of Sg(CO)$$_6$$ could be determined with this technique.

Journal Articles

Measurement of the first ionization potential of lawrencium, element 103

Sato, Tetsuya; Asai, Masato; Borschevsky, A.*; Stora, T.*; Sato, Nozomi; Kaneya, Yusuke; Tsukada, Kazuaki; D$"u$llmann, Ch. E.*; Eberhardt, K.*; Eliav, E.*; et al.

Nature, 520(7546), p.209 - 211, 2015/04

 Times Cited Count:104 Percentile:97.57(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, $$Z$$=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.

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:14 Percentile:77.78(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

Development of a He/CdI$$_{2}$$ gas-jet system coupled to a surface-ionization type ion-source in JAEA-ISOL; towards determination of the first ionization potential of Lr (Z = 103)

Sato, Tetsuya; Asai, Masato; Sato, Nozomi; Tsukada, Kazuaki; Toyoshima, Atsushi; Oe, Kazuhiro*; Miyashita, Sunao*; Kaneya, Yusuke; Osa, Akihiko; Sch$"a$del, M.; et al.

Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1253 - 1257, 2015/02

 Times Cited Count:8 Percentile:56.45(Chemistry, Analytical)

We have developed a surface-ionization ion-source coupled to the He/CdI$$_2$$ gas-jet transport system for the Isotope Separator On-Line (ISOL) at the JAEA tandem accelerator for experimental determination of the first ionization potential of lawrencium (Lr, $$Z = 103$$). We performed to ionize a short-lived Lr isotope and various lanthanide isotopes. We successfully observed mass-separated ions of $$^{256}$$Lr by using our present system at the first time. The first ionization potential of Lr was evaluated based on a correlation between of effective ionization potential and ionization efficiency of short-lived lanthanide isotopes in our system.

138 (Records 1-20 displayed on this page)