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Journal Articles

Chemical characterization of a volatile dubnium compound, DbOCl$$_3$$

Chiera, N. M.*; Sato, Tetsuya; Eichler, R.*; Tomitsuka, Tomohiro; Asai, Masato; Adachi, Sadia*; Dressler, R.*; Hirose, Kentaro; Inoue, Hiroki*; Ito, Yuta; et al.

Angewandte Chemie; International Edition, 60(33), p.17871 - 17874, 2021/08

 Times Cited Count:0 Percentile:0(Chemistry, Multidisciplinary)

The formation and the chemical characterization of single atoms of dubnium (Db, element 105), in the form of its volatile oxychloride, was investigated using the on-line gas phase chromatography technique, in the temperature range 350 - 600 $$^circ$$C. Under the exact same chemical conditions, comparative studies with the lighter homologs of group-5 in the Periodic Table clearly indicate the volatility sequence being NbOCl$$_3 > $$ TaOCl$$_3 geq$$ DbOCl$$_3$$. From the obtained experimental results, thermochemical data for DbOCl$$_3$$ were derived. The present study delivers reliable experimental information for theoretical calculations on the chemical properties of transactinides.

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:16 Percentile:70.21(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

Ground-state configuration of the $$N=157$$ nucleus $$^{259}$$No

Asai, Masato; Tsukada, Kazuaki; Sakama, Minoru*; Haba, Hiromitsu*; Ichikawa, Takatoshi*; Ishii, Yasuo; Toyoshima, Atsushi; Ishii, Tetsuro; Nishinaka, Ichiro; Nagame, Yuichiro; et al.

Physical Review C, 87(1), p.014332_1 - 014332_6, 2013/01

 Times Cited Count:4 Percentile:36.33(Physics, Nuclear)

The spin-parity and neutron configuration of the ground state of $$^{259}$$No have been identified through $$alpha$$-decay spectroscopy. The $$^{259}$$No is the nucleus with the largest neutron number whose spin-parities and single-particle configurations have ever been identified. The neutron 9/2$$^{+}$$[615] configuration was assigned to the ground state of $$^{259}$$No as well as to the 231.4 keV level in $$^{255}$$Fm. This allowed us to establish energy spacings and order of the neutron single-particle orbitals in such heaviest nuclear region. The appearance of the 9/2$$^{+}$$[615] ground state at $$N$$=157 implies that the order of the neutron orbitals between the $$N$$=152 and 162 deformed shell gaps should change considerably with increasing neutron number.

Journal Articles

Hexafluoro complex of rutherfordium in mixed HF/HNO$$_{3}$$ solutions

Toyoshima, Atsushi; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Akiyama, Kazuhiko*; Goto, Shinichi*; Ishii, Yasuo; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; et al.

Radiochimica Acta, 96(3), p.125 - 134, 2008/03

 Times Cited Count:27 Percentile:86.74(Chemistry, Inorganic & Nuclear)

Formation of an anionic fluoride-complex of element 104, rutherfordium (Rf) produced in the $$^{248}$$Cm($$^{18}$$O,5n)$$^{261}$$Rf reaction was studied by an anion-exchange method based on an atom-at-a-time scale. It was found that the hexafluoro complex of Rf, [RfF$$_{6}$$]$$^{2-}$$, was formed in the studied fluoride ion concentrations of 0.0005 - 0.013 M. Formation of [RfF$$_{6}$$]$$^{2-}$$ was significantly different from that of the homologues Zr and Hf, [ZrF$$_{6}$$]$$^{2-}$$ and [HfF$$_{6}$$]$$^{2-}$$; the evaluated formation constant of [RfF$$_{6}$$]$$^{2-}$$ is at least one-order of magnitude smaller than those of [ZrF$$_{6}$$]$$^{2-}$$ and [HfF$$_{6}$$]$$^{2-}$$.

Journal Articles

$$alpha$$ decay of $$^{238}$$Cm and the new isotope $$^{237}$$Cm

Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Sakama, Minoru*; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

Physical Review C, 73(6), p.067301_1 - 067301_4, 2006/06

 Times Cited Count:21 Percentile:77.62(Physics, Nuclear)

no abstracts in English

Journal Articles

Experimental identification of spin-parities and single-particle configurations in $$^{257}$$No and its $$alpha$$-decay daughter $$^{253}$$Fm

Asai, Masato; Tsukada, Kazuaki; Sakama, Minoru*; Ichikawa, Shinichi; Ishii, Tetsuro; Nagame, Yuichiro; Nishinaka, Ichiro; Akiyama, Kazuhiko; Osa, Akihiko; Oura, Yasuji*; et al.

Physical Review Letters, 95(10), p.102502_1 - 102502_4, 2005/09

 Times Cited Count:62 Percentile:88.35(Physics, Multidisciplinary)

Excited states in $$^{253}$$Fm fed by the $$alpha$$ decay of $$^{257}$$No have been established through $$alpha$$-$$gamma$$ and $$alpha$$-electron coincidence spectroscopy using a gas-jet transport system and an on-line isotope separator. The spin-parity of the 124.1 keV level in $$^{253}$$Fm has been identified on the basis of the measured internal conversion coefficients. The $$nu 3/2^{+}[622]$$ configuration has been assigned to the ground state of $$^{257}$$No as well as to the 124.1 keV level. It was found that the ground state configuration of $$^{257}$$No is different from that of lighter $$N=155$$ isotones.

Journal Articles

$$beta$$-decay half-lives of new neutron-rich rare-earth isotopes $$^{159}$$Pm, $$^{162}$$Sm, and $$^{166}$$Gd

Ichikawa, Shinichi; Asai, Masato; Tsukada, Kazuaki; Haba, Hiromitsu*; Nagame, Yuichiro; Shibata, Michihiro*; Sakama, Minoru*; Kojima, Yasuaki*

Physical Review C, 71(6), p.067302_1 - 067302_4, 2005/06

 Times Cited Count:18 Percentile:75.56(Physics, Nuclear)

The new neutron-rich raer-earth isotopes $$^{159}$$Pm, $$^{162}$$Sm, and $$^{166}$$Gd produced in the proton-induced fission of 238U were identified using the JAERI on-line isotope separator (JAERI-ISOL) coupled to a gas-jet transport sysetm. The half-lives of $$^{159}$$Pm, $$^{162}$$Sm, and $$^{166}$$Gd were determined to be 1.5$$pm$$0.2s, 2.4$$pm$$0.5s, and 4.8$$pm$$1.0s, respectively. The partial decay scheme of $$^{166}$$Gd wes constructed for $$gamma$$-$$gamma$$ coincidence data. The improved half-life values of 25.6$$pm$$2.2s wes obtained for the previously identified isotope $$^{166}$$Tb. The half-lives measured in the present study are in good agreement with the theoretical predictions calculated by the second generation of the gross theory with the atomic masses evaluated by the Audei and Wapstra.

Journal Articles

Proton-neutron configurations in $$^{236g,m}$$Am and its EC-decay daughter $$^{236}$$Pu

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

European Physical Journal A, 23(3), p.395 - 400, 2005/02

 Times Cited Count:12 Percentile:65.45(Physics, Nuclear)

The EC decay of $$^{236}$$Am has been studied through $$gamma$$-ray spectroscopy. Two EC-decaying states have been found in $$^{236}$$Am with half-lives of 3.6 min and 2.9 min. In $$^{236}$$Pu, we have found the $$K^{pi}=0^{-}$$ octupole band and two-quasiparticle states one of which is a $$K$$ isomer with a 1.2 $$mu$$s half-life. The EC transitions from $$^{236g,m}$$Am to the two-quasiparticle states in $$^{236}$$Pu show small $$log ft$$ values of 4.8--5.3, which allowed us to assign proton-neutron configurations of $$^{236g,m}$$Am and the two-quasiparticle states.

Journal Articles

Chemical studies on rutherfordium (Rf) at JAERI

Nagame, Yuichiro; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko; Ishii, Yasuo; Sato, Tetsuya; Hirata, Masaru; Nishinaka, Ichiro; Ichikawa, Shinichi; et al.

Radiochimica Acta, 93(9-10), p.519 - 526, 2005/00

 Times Cited Count:29 Percentile:88.24(Chemistry, Inorganic & Nuclear)

no abstracts in English

Journal Articles

EC and $$alpha$$ decays of $$^{235}$$Am

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu*; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Kojima, Yasuaki*; Oura, Yasuji*; et al.

European Physical Journal A, 22(3), p.411 - 416, 2004/12

 Times Cited Count:8 Percentile:49.41(Physics, Nuclear)

EC and $$alpha$$ decays of $$^{235}$$Am have been studied by means of $$gamma$$-ray spectroscopy. Excited states in $$^{235}$$Pu have been established for the first time, and tentative spin-parity and Nilsson assignments were given to these levels. The ground state of $$^{235}$$Am was evaluated to be the $$pi 5/2^{-}[523]$$ state from the experimental results. It was found that the $$pi 5/2^{-}[523]$$ state in $$^{231}$$Np is located at $$<$$15~keV, which allowed us to determine the $$Q_{alpha}$$ value of $$^{235}$$Am as 6569$$^{+27}_{-12}$$~keV, in combination with the measured $$alpha$$-particle energy.

Journal Articles

Fluoride complexation of element 104, rutherfordium

Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Akiyama, Kazuhiko; Nishinaka, Ichiro; Hirata, Masaru; Yaita, Tsuyoshi; Ichikawa, Shinichi; Nagame, Yuichiro; et al.

Journal of the American Chemical Society, 126(16), p.5219 - 5224, 2004/04

 Times Cited Count:42 Percentile:73.39(Chemistry, Multidisciplinary)

Fluoride complexation of element 104, rutherfordium (Rf), produced in the $$^{248}$$Cm($$^{18}$$O,5n)$$^{261}$$Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchangechromatographic behavior of Rf was investigated in 1.9-13.9 M hydrofluoric acid together with those of the group-4 elements Zr and Hf produced in the $$^{18}$$O-induced reactions on Ge and Gd targets, respectively. It was found that the adsorption behavior of Rf on anion-exchange resin is quite different from those of Zr and Hf, suggesting the influence of relativistic effect on the fluoride complexation of Rf.

Journal Articles

Chemical studies of the heaviest elements

Nagame, Yuichiro; Haba, Hiromitsu*; Tsukada, Kazuaki; Asai, Masato; Toyoshima, Atsushi; Goto, Shinichi*; Akiyama, Kazuhiko; Kaneko, Tetsuya; Sakama, Minoru*; Hirata, Masaru; et al.

Nuclear Physics A, 734, p.124 - 135, 2004/04

 Times Cited Count:11 Percentile:58.28(Physics, Nuclear)

no abstracts in English

Journal Articles

$$alpha$$-decays of neutron-deficient americium isotopes

Sakama, Minoru*; Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Nishinaka, Ichiro; Nagame, Yuichiro; Haba, Hiromitsu*; Goto, Shinichi*; Shibata, Michihiro*; Kawade, Kiyoshi*; et al.

Physical Review C, 69(1), p.014308_1 - 014308_11, 2004/01

 Times Cited Count:19 Percentile:72.76(Physics, Nuclear)

no abstracts in English

Journal Articles

Identification of the new isotope $$^{241}$$Bk

Asai, Masato; Tsukada, Kazuaki; Ichikawa, Shinichi; Sakama, Minoru*; Haba, Hiromitsu*; Nagame, Yuichiro; Nishinaka, Ichiro; Akiyama, Kazuhiko; Toyoshima, Atsushi; Kaneko, Tetsuya*; et al.

European Physical Journal A, 16(1), p.17 - 19, 2003/01

 Times Cited Count:8 Percentile:51.33(Physics, Nuclear)

The new isotope $$^{241}$$Bk has been identified for the first time using a gas-jet coupled on-line isotope separator at the JAERI tandem accelerator facility. Characteristic X rays and three $$gamma$$ transitions associated with the EC decay of $$^{241}$$Bk have been observed, and the half-life was determined to be 4.6 min. The half-life value and the observed $$gamma$$-ray energies and intensities can be consistently explained as a consequence of the allowed EC transition of $$pi 7/2^{+}[633]$$ $$rightarrow$$ $$nu 7/2^{+}[624]$$.

Journal Articles

Characteristics of asymmetric mass distribution in proton-induced fission of actinides

Goto, Shinichi*; Kaji, D.*; Nishinaka, Ichiro; Nagame, Yuichiro; Ichikawa, Shinichi; Tsukada, Kazuaki; Asai, Masato; Haba, Hiromitsu; Mitsuoka, Shinichi; Nishio, Katsuhisa; et al.

Journal of Radioanalytical and Nuclear Chemistry, 255(1), p.73 - 76, 2003/01

 Times Cited Count:0 Percentile:0.01(Chemistry, Analytical)

no abstracts in English

Journal Articles

Nuclear decay properties of the neutron-deficient actinides

Sakama, Minoru*; Tsukada, Kazuaki; Asai, Masato; Ichikawa, Shinichi; Haba, Hiromitsu; Goto, Shinichi*; Nishinaka, Ichiro; Nagame, Yuichiro; Oura, Yasuji*; Kojima, Yasuaki*; et al.

Journal of Nuclear Science and Technology, 39(Suppl.3), p.34 - 37, 2002/11

no abstracts in English

Journal Articles

Measurements of EC and weak $$alpha$$ decays of neutron-deficient transuranium isotopes

Asai, Masato; Sakama, Minoru; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi; Kojima, Yasuaki*; Oura, Yasuji*; et al.

Journal of Nuclear Science and Technology, 39(Suppl.2), p.474 - 477, 2002/08

Neutron-deficient americium and curium isotopes with half-lives $$leq$$10 min have been produced with the tandem accelerator, and their EC and weak $$alpha$$ decays have been successfully measured through an on-line isotope separation. Decay schemes of $$^{235,236}$$Am have been established, and proton-neutron configurations in the parent and daughter nuclei have been determined. Observed $$alpha$$ transitions in $$^{233,235}$$Am were found to be the favored transitions between the $$pi 5/2^{-}[523]$$ Nilsson states. Information on nuclear structure, deformation, and atomic masses in this region were obtained.

Journal Articles

Decay studies of neutron-deficient Am, Cm, and Bk nuclei using an on-line isotope separator

Asai, Masato; Sakama, Minoru*; Tsukada, Kazuaki; Ichikawa, Shinichi; Haba, Hiromitsu; Nishinaka, Ichiro; Nagame, Yuichiro; Goto, Shinichi*; Akiyama, Kazuhiko; Toyoshima, Atsushi; et al.

Journal of Nuclear and Radiochemical Sciences, 3(1), p.187 - 190, 2002/06

EC and $$alpha$$ decays of neutron-deficient americium, curium, and berkelium nuclei have been studied using the JAERI on-line isotope separator. Decay schemes of $$^{235, 236}$$Am have been established for the first time, and proton-neutron configurations in $$^{235, 236}$$Am and $$^{235, 236}$$Pu have been determined. $$alpha$$ transitions observed in $$^{233, 235}$$Am were found to be the favored transitions between the $$pi 5/2^{-}[523]$$ Nilsson states. $$Q_{alpha}$$ values of $$^{237, 238}$$Cm have been determined. Nuclear structure, deformation, and atomic masses for these nuclei were discussed.

Journal Articles

Anion-exchange behavior of Rf in HCl and HNO$$_{3}$$ solutions

Haba, Hiromitsu; Tsukada, Kazuaki; Asai, Masato; Goto, Shinichi*; Toyoshima, Atsushi; Nishinaka, Ichiro; Akiyama, Kazuhiko; Hirata, Masaru; Ichikawa, Shinichi; Nagame, Yuichiro; et al.

Journal of Nuclear and Radiochemical Sciences, 3(1), p.143 - 146, 2002/06

We have investigated the sorption behavior of element 104 rutherfordium (Rf) on an anion exchange resin from HCl and HNO$$_{3}$$ solutions. In the HCl experiments, the distribution coefficients of Rf increase with an increase of HCl concentration from 7.0 M to 11.5 M, indicating that anionic species such as [Rf(OH)Cl$$_{5}$$]$$^{2-}$$ or [RfCl$$_{6}$$]$$^{2-}$$ are formed. This sorption behavior of Rf is typical of the group-4 elements Zr and Hf, and is quite different from that of the pseudo-homologue Th. It is also noted that the distribution coefficients decrease in the order Rf, Zr, Hf at 9.0 M HCl, which is consistent with the expected order of ionic radii. On the other hand, Rf appears to behave like Zr and Hf in 8 M HNO$$_{3}$$ not like Pu and Th.

Journal Articles

Status and prospects of Heavy element nuclear chemistry research at JAERI

Nagame, Yuichiro; Asai, Masato; Haba, Hiromitsu; Tsukada, Kazuaki; Goto, Shinichi; Sakama, Minoru; Nishinaka, Ichiro; Toyoshima, Atsushi; Akiyama, Kazuhiko; Ichikawa, Shinichi

Journal of Nuclear and Radiochemical Sciences, 3(1), p.129 - 132, 2002/06

no abstracts in English

63 (Records 1-20 displayed on this page)