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Journal Articles

Extraction behavior of rutherfordium as a cationic fluoride complex with a TTA chelate extractant from HF/HNO $$_{3}$$ acidic solutions

Yokoyama, Akihiko*; Kitayama, Yuta*; Fukuda, Yoshiki*; Kikunaga, Hidetoshi*; Murakami, Masashi*; Komori, Yukiko*; Yano, Shinya*; Haba, Hiromitsu*; Tsukada, Kazuaki; Toyoshima, Atsushi*

Radiochimica Acta, 107(1), p.27 - 32, 2019/01

 Percentile:100(Chemistry, Inorganic & Nuclear)

Journal Articles

Electron-tracking Compton camera imaging of technetium-95m

Hatsukawa, Yuichi*; Hayakawa, Takehito*; Tsukada, Kazuaki; Hashimoto, Kazuyuki*; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Tanimori, Toru*; Sonoda, Shinya*; Kabuki, Shigeto*; et al.

PLoS ONE (Internet), 13(12), p.e0208909_1 - e0208909_12, 2018/12

 Percentile:100(Multidisciplinary Sciences)

Imaging of $$^{95m}$$Tc radioisotope was conducted using an electron tracking-Compton camera (ETCC). $$^{95m}$$Tc emits 204, 582, and 835 keV $$gamma$$ rays, and was produced in the $$^{95}$$Mo(p,n)$$^{95m}$$Tc reaction with a $$^{95}$$Mo-enriched target. The recycling of the $$^{95}$$Mo-enriched molybdenum trioxide was investigated, and the recycled yield of $$^{95}$$Mo was achieved to be 70% - 90%. The images were obtained with each of the three $$gamma$$ rays. Results showed that the spatial resolution increases with increasing $$gamma$$-ray energy, and suggested that the ETCC with high-energy $$gamma$$-ray emitters such as $$^{95m}$$Tc is useful for the medical imaging of deep tissue and organs in the human body.

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:4 Percentile:21.13(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

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 (Internet), 163, p.00041_1 - 00041_6, 2017/11

 Percentile:100

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 (Internet), 131, p.05001_1 - 05001_6, 2016/12

 Percentile:100

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

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 (Internet), 131, p.07005_1 - 07005_7, 2016/12

 Percentile:100

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

Vacuum chromatography of Tl on SiO$$_{2}$$ at the single-atom level

Steinegger, P.*; Asai, Masato; Dressler, R.*; Eichler, R.*; Kaneya, Yusuke*; Mitsukai, Akina*; Nagame, Yuichiro; Piguet, D.*; Sato, Tetsuya; Sch$"a$del, M.; et al.

Journal of Physical Chemistry C, 120(13), p.7122 - 7132, 2016/04

 Times Cited Count:8 Percentile:42.61(Chemistry, Physical)

A new experimental method "vacuum chromatography" has been developed to measure adsorption enthalpy of superheavy elements, and its feasibility has been examined using short-lived thallium isotopes. The short-lived thallium isotopes were produced at the JAEA tandem accelerator. The thallium ion beam prepared with an on-line isotope separator which ionized and mass-separated the thallium isotopes was injected into an isothermal vacuum chromatography apparatus. A temperature-dependent adsorption property of thallium atom on SiO$$_{2}$$ surface were measured. The adsorption enthalpy of thallium was determined to be 158 kJ/mol. The thallium is a homolog of element 113. Thus, the vacuum chromatography developed in this study enables us to perform chemical experiments for short-lived superheavy elements with half-lives of a order of one second.

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:8 Percentile:10.94(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

Production and separation of astatine isotopes in the $$^7$$Li + $$^{nat}$$Pb reaction

Nishinaka, Ichiro; Yokoyama, Akihiko*; Washiyama, Koshin*; Maeda, Eita*; Watanabe, Shigeki; Hashimoto, Kazuyuki; Ishioka, Noriko; Makii, Hiroyuki; Toyoshima, Atsushi; Yamada, Norihiro*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 304(3), p.1077 - 1083, 2015/06

 Times Cited Count:3 Percentile:53.75(Chemistry, Analytical)

Production cross sections of astatine isotopes $$^{207-211}$$At in the 29-57 MeV $$^7$$Li induced reaction with $$^{nat}$$Pb target have been measured by $$alpha$$- and $$gamma$$-ray spectrometry. Excitation functions of production cross sections have been compared with a statistical model calculation to study the reaction mechanism of $$^7$$Li + $$^{nat}$$Pb. Considerably small experimental cross sections of $$^{210}$$At and $$^{209}$$At compared with the calculation were clearly observed at incident energies higher than 44 MeV, indicating that the effects of breakup reaction play a role. A chemical separation of astatine from an irradiated lead target has been studied with a dry-distillation method. A complementary way to produce astatine isotopes has been developed.

Journal Articles

Production of $$^{88}$$Nb and $$^{170}$$Ta for chemical studies of element 105, Db, using the GARIS gas-jet system

Huang, M.*; Haba, Hiromitsu*; Murakami, Masashi*; Asai, Masato; Kaji, Daiya*; Kanaya, Jumpei*; Kasamatsu, Yoshitaka*; Kikunaga, Hidetoshi*; Kikutani, Yuki*; Komori, Yukiko*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 304(2), p.845 - 849, 2015/05

 Times Cited Count:3 Percentile:66.76(Chemistry, Analytical)

A technique to utilize radioisotopes of Nb and Ta was developed for chemical studies of element 105, Db, by coupling a gas-jet transport system to the RIKEN gas-filled recoil ion separator (GARIS). The short-lived $$^{88}$$Nb and $$^{170}$$Ta were produced with nuclear reactions using a $$^{19}$$F beam whose energy was the same as that to produce $$^{262}$$Db. Then, they were separated with GARIS and extracted to a chemistry laboratory with the gas-jet transport system. By changing only magnetic field of GARIS and inserting an energy degrader and a shutter for recoil ions, we could deliver the $$^{88}$$Nb and $$^{170}$$Ta to a chemistry device for $$^{262}$$Db without changing other experimental conditions.

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:59 Percentile:1.63(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: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

Production of $$^{rm 95m}$$Tc for Compton camera imaging

Hatsukawa, Yuichi; Hashimoto, Kazuyuki; Tsukada, Kazuaki; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Nagai, Yasuki; Tanimori, Toru*; Sonoda, Shinya*; Kabuki, Shigeto*; et al.

Journal of Radioanalytical and Nuclear Chemistry, 303(2), p.1283 - 1285, 2015/02

 Times Cited Count:2 Percentile:66.76(Chemistry, Analytical)

Technetium-99m ($$^{rm 99m}$$Tc) is used in radioactive medical diagonostic tests, for example as a radioactive tracer that medical equipment can detect in the human body. It is well suited to the role because it emits readily detectable 141 keV $$gamma$$ rays, and its half-life is 6.01 hours (meaning that about 94% of it decays to technetium-99 in 24 hours). There are at least 31 commonly used radiopharmaceuticals based on technetium-99m for imaging and functional studies of the brain, myocardium, thyroid, lungs, liver, gallbladder, kidneys, skeleton, blood, and tumors. Recent years, with the develop-ment of the Compton camera which can realize high position resolution, technetium isotopes emitting high energy $$gamma$$-rays are required. In this study, technetium-95m which emits some $$gamma$$ rays around 800 keV was produced by the $$^{95}$$Mo(p,n)$$^{rm 95m}$$Tc reaction.

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:5 Percentile:43.49(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.

Journal Articles

Synthesis and detection of a Seaborgium carbonyl complex

Even, J.*; Yakushev, A.*; D$"u$llmann, Ch. E.*; Haba, Hiromitsu*; Asai, Masato; Sato, Tetsuya; Brand, H.*; Di Nitto, A.*; Eichler, R.*; Fan, F. L.*; et al.

Science, 345(6203), p.1491 - 1493, 2014/09

 Times Cited Count:35 Percentile:17.05(Multidisciplinary Sciences)

A new superheavy element complex, a seaborgium carbonyl, has been successfully synthesized, and its adsorption property has been studied using a cryo-thermochromatography and $$alpha$$-detection apparatus COMPACT. Nuclear reaction products of short-lived $$^{265}$$Sg preseparated with a gas-filled recoil ion separator GARIS at RIKEN were directly injected into a gas cell filled with He/CO mixture gas, and chemical reaction products of volatile carbonyl complexes were trasported to COMPACT. The Sg carbonyl complex detected with COMPACT was found to be very volatile with adsorption enthalpy of $$-$$50 kJ/mol, from which we have concluded that this complex should be a Sg hexacarbonyl Sg(CO)$$_{6}$$. This is the first synthesis of organometallic compounds of transactinide elements for which only simple inorganic comounds have been synthesized so far.

Journal Articles

Radiochemical studies of the heaviest elements at JAEA

Nagame, Yuichiro; Toyoshima, Atsushi; Tsukada, Kazuaki; Asai, Masato; Sato, Tetsuya; Sch$"a$del, M.

Journal of Radioanalytical and Nuclear Chemistry, 300(1), p.77 - 88, 2014/04

 Times Cited Count:3 Percentile:61.51(Chemistry, Analytical)

Journal Articles

Production of $$^{256}$$Lr in the $$^{249,250,251}$$Cf + $$^{11}$$B, $$^{243}$$Am + $$^{18}$$O, and $$^{248}$$Cm + $$^{14}$$N reactions

Sato, Nozomi; Sato, Tetsuya; Asai, Masato; Toyoshima, Atsushi; Tsukada, Kazuaki; Li, Z.*; Nishio, Katsuhisa; Nagame, Yuichiro; Sch$"a$del, M.; Haba, Hiromitsu*; et al.

Radiochimica Acta, 102(3), p.211 - 219, 2014/03

 Times Cited Count:6 Percentile:43.1(Chemistry, Inorganic & Nuclear)

Production cross-sections of the isotope $$^{256}$$Lr in the $$^{249,250,251}$$Cf + $$^{11}$$B, $$^{243}$$Am + $$^{18}$$O, and $$^{248}$$Cm + $$^{14}$$N reactions were measured using a He/KCl gas-jet transport system and a rotating wheel $$alpha$$-particle detection apparatus. The $$alpha$$-particle energy of $$^{256}$$Lr was distributed from 8.3 to 8.7 MeV and its half-life, $$T_{1/2}$$, was measured to be $$28 pm 1$$ s. The maximum cross sections in the $$^{249}$$Cf($$^{11}$$B, 4$$n$$)$$^{256}$$Lr and $$^{243}$$Am($$^{18}$$O, 5$$n$$)$$^{256}$$Lr reactions were determined to be $$122 pm 6$$ nb at the beam energy of 63 MeV and $$26 pm 3$$ nb at 96 MeV, respectively. In the $$^{248}$$Cm($$^{14}$$N, 6$$n$$)$$^{256}$$Lr reaction, the cross section was measured to be $$27 pm 1$$ nb at 91 MeV.

Journal Articles

Production of $$^{262}$$Db in the $$^{248}$$Cm($$^{19}$$F,5$$n$$)$$^{262}$$Db reaction and decay properties of $$^{262}$$Db and $$^{258}$$Lr

Haba, Hiromitsu*; Huang, M.*; Kaji, Daiya*; Kanaya, Jumpei*; Kudo, Yuki*; Morimoto, Koji*; Morita, Kosuke*; Murakami, Masashi*; Ozeki, Kazutaka*; Sakai, Ryutaro*; et al.

Physical Review C, 89(2), p.024618_1 - 024618_11, 2014/02

 Times Cited Count:16 Percentile:17.81(Physics, Nuclear)

Journal Articles

Measurement of the Md$$^{3+}$$/Md$$^{2+}$$ reduction potential studied with flow electrolytic chromatography

Toyoshima, Atsushi; Li, Z.*; Asai, Masato; Sato, Nozomi; Sato, Tetsuya; Kikuchi, Takahiro; Kaneya, Yusuke; Kitatsuji, Yoshihiro; Tsukada, Kazuaki; Nagame, Yuichiro; et al.

Inorganic Chemistry, 52(21), p.12311 - 12313, 2013/11

 Times Cited Count:3 Percentile:78.65(Chemistry, Inorganic & Nuclear)

The reduction behavior of mendelevium (Md) was studied using a flow electrolytic chromatography apparatus. By applying appropriate potentials on the chromatography column, the more stable Md$$^{3+}$$ is reduced to Md$$^{2+}$$. The reduction potential of the Md$$^{3+}$$ + e$$^{-}$$ $$rightarrow$$ Md$$^{2+}$$ couple was determined to be -0.16$$pm$$0.05 V vs. a normal hydrogen electrode.

Journal Articles

Adsorption behavior of $$^{95}$$Nb and $$^{179}$$Ta as homologues of element 105, Db, on cation exchanger in HF/HNO$$_{3}$$ solution

Kasamatsu, Yoshitaka*; Toyoshima, Atsushi; Tome, Hayato*; Tsukada, Kazuaki; Asai, Masato; Haba, Hiromitsu*; Nagame, Yuichiro

Journal of Nuclear and Radiochemical Sciences (Internet), 13(1), p.9 - 12, 2013/06

Adsorption behavior of the group-5 elements, $$^{95}$$Nb and $$^{179}$$Ta, on cation-exchange resin was studied in mixed solution of HF and HNO$$_{3}$$ as a model experiment of their heavier homologue, element 105 (dubnium, Db). Chemical reactions of these elements in the cation exchange rapidly reached the equilibrium. It was found that distribution coefficients of Nb and Ta decrease with increasing the fluoride ion concentration in the studied range of 10$$^{-7}$$ - 10$$^{-5}$$ M. Clear difference between Nb and Ta was observed in the variations of the distribution coefficients against the fluoride ion concentration. This would originate from their different chemical species of fluoride complexes. We propose the cation-exchange experiment of Db based on the present experimental results to understand its fluoride complex formation.

233 (Records 1-20 displayed on this page)