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Journal Articles

Extraction of chromatographic behavior of Rf, Zr, and Hf in HCl solution with styrenedivinylbenzene copolymer resin modified by TOPO (trioctylphosphine oxide)

Toyoshima, Atsushi; Kasamatsu, Yoshitaka*; Tsukada, Kazuaki; Asai, Masato; Ishii, Yasuo; Tome, Hayato*; Nishinaka, Ichiro; Sato, Tetsuya; Nagame, Yuichiro; Sch$"a$del, M.; et al.

Journal of Nuclear and Radiochemical Sciences, 11(1), p.7 - 11, 2010/06

The extraction behavior of rutherfordium (Rf) into trioctylphosphine oxide (TOPO) from 2.0 - 7.0 M HCl solution was studied together with that of the homologues Zr and Hf. The extracted yields of Rf, Zr, and Hf increased with an increase of HCl concentration, and the sequence of their extraction was Zr $$>$$ Hf $$geq$$ Rf. It is suggested that the stability of the RfCl$$_{4}$$$$cdot$$2(TOPO) complex is lower than that of the corresponding species of the homologues.

Journal Articles

An Attempt for determining $$^{235}$$U/$$^{238}$$U ratio for a trace amount of uranium: Search for an extinct radionuclide $$^{247}$$Cm in the early solar system

Chai, J.; Miyamoto, Yutaka; Kokubu, Yoko; Magara, Masaaki; Sakurai, Satoshi; Usuda, Shigekazu; Oura, Yasuji*; Ebihara, Mitsuru*

Journal of Radioanalytical and Nuclear Chemistry, 272(2), p.397 - 401, 2007/05

 Times Cited Count:2 Percentile:79.36(Chemistry, Analytical)

$$^{247}$$Cm is an important nuclide because it has the next-shortest half-life (1.6$$cdot$$10$$^{7}$$ yr) from $$^{244}$$Pu among the transuranic nuclides. The disintegration of $$^{247}$$Cm to $$^{235}$$U by three $$alpha$$ decays and two $$beta$$ decays and the chemical fractionation between Cm and U during the formation of solid materials in early solar system lead to changes in the ratios of $$^{235}$$U to $$^{238}$$U. This variation may provide strict constraints on the time interval between the last r-process nucleosynthetic event and the formation of the solar system. It is important to develop a practical analysis protocol to determine the isotope ratio of trace uranium in geochemical and environment samples. As uranium is the least abundant element in our solar system, analytical techniques with high sensitivity and precision are required. In this study, a double focusing inductively coupled plasma mass spectory was applied to measure isotopic ratio of uranium. By one set data obtained from the EDTA phase of the Jilin meteorite sample, the upper limit of $$^{247}$$Cm in the early solar system was calculated and $$^{247}$$Cm/$$^{235}$$U $$<$$ 0.003 was obtained.

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:60 Percentile:11.44(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

Magnetic excitations in the heavy-fermion superconductor PrOs$$_4$$Sb$$_{12}$$

Raymond, S.*; Flouquet, J.*; Kuwahara, Keitaro*; Iwasa, Kazuaki*; Kogi, Masafumi*; Kaneko, Koji; Metoki, Naoto; Sugawara, Hitoshi*; Aoki, Yuji*; Sato, Hideyuki*

Physica B; Condensed Matter, 359-361, p.898 - 900, 2005/06

 Times Cited Count:2 Percentile:87.36(Physics, Condensed Matter)

The low lying magnetic excitations of the unconventional heavy fermion superconductor PrOs$$_4$$Sb$$_{12}$$ were studied by inelastic neutron scattering on single crystalline sample. The crystal field excitation first evidenced at 0.7 meV on powder samples is found to have a minimum of energy at the zone boundary corresponding to the wavevector of antiferro-quadrupolar instability. The evolution of the magnetic excitation spectrum under magnetic field confirms the singlet ground state.

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:33.56(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

Development of multiple prompt $$gamma$$-ray analysis

Oshima, Masumi; Toh, Yosuke

Hamon, 15(1), p.86 - 89, 2005/01

A new beam line for multiple prompt $$gamma$$-ray analysis(MPGA) has been constructed at JRR-3 neutron guide hall. The expected performance for MPGA is presented. This facility will be used for nuclear data and nuclear structure studies also.

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:7 Percentile:53.34(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

$$alpha$$-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:17 Percentile:28.77(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:47.9(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

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

Photofission of $$^{209}$$Bi at intermediate energies

Haba, Hiromitsu; Kasaoka, Makoto*; Igarashi, Manabu*; Washiyama, Koshin*; Matsumura, Hiroshi*; Oura, Yasuji*; Shibata, Seiichi*; Sakamoto, Ko*; Furukawa, Michiaki*; Fujiwara, Ichiro*

Radiochimica Acta, 90(7), p.371 - 382, 2002/08

 Times Cited Count:2 Percentile:81.95(Chemistry, Inorganic & Nuclear)

The reaction yields of 63 radionuclides with the mass number A = 56-135 produced in the photofission of $$^{209}$$Bi by bremsstrahlung of end-point energies (E$$_{0}$$) from 450 to 1100 MeV have been measured using a catcher foil technique. The charge distribution was well reproduced by a Gaussian function with the most probable charge (Z$$_{p}$$) expressed by Z$$_{p}$$ = RA + S, and with the A-independent FWHME$$_{CD}$$. The charge distribution parameters R, S and FWHM$$_{CD}$$ were independent of E$$_{0}$$ above 600 MeV. The weighted mean values at E$$_{0}$$ $$geq$$ 600 MeV were R = 0.421 $$pm$$ 0.001, S = 0.6 $$pm$$ 0.1 and FWHM$$_{CD}$$ = 2.1 $$pm$$ 0.1 charge unit (c.u.). Based on the charge distribution parameters, the symmetric mass yield distributions with the most probable mass A$$_{p}$$ of 96 $$pm$$ 1 mass unit (m.u.) and the width FWHM$$_{MD}$$ of 33 $$pm$$ 1 m.u. were also obtained. The characteristics of the charge and mass yield distributions are discussed by referring to those for $$^{197}$$Au based on the results of calculations using PICA3/GEM.

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

Study of metallofullerenes encapsulating actinides

Akiyama, Kazuhiko; Sueki, Keisuke*; Tsukada, Kazuaki; Yaita, Tsuyoshi; Miyake, Yoko*; Haba, Hiromitsu*; Asai, Masato; Kodama, Takeshi*; Kikuchi, Koichi*; Otsuki, Tsutomu*; et al.

Journal of Nuclear and Radiochemical Sciences, 3(1), p.151 - 154, 2002/06

The oxidation state of actinide elements encapsulated in fullerenes is studied. HPLC elution behavior of actinide-fullerenes is classified into two groups; the elution behavior of the first group, encapsulating U, Np, and Am, is similar to that of the light lanthanide-fullerenes, such as La, Ce, Pr, and Nd, while the behavior of the second group, encapsulating Th and Pa, is quite different from that of any lanthanide-fullerenes. The chemical species in the main HPLC elution peak of each group were identified as M@C82 and M@C84 (M = metal atom) from the mass of the U and Th fullerenes, respectively. The oxidation states of the U and Th atoms in the fullerenes were deduced to be 3+ and 4+, respectively, from the UV/vis/NIR absorption and XANES spectroscopy.

Oral presentation

Nuclear-charge polarization at scission in proton-induced fission of light actinides

Nishinaka, Ichiro; Tanikawa, Masashi*; Nagame, Yuichiro; Nakahara, Hiromichi*

no journal, , 

In the 12 MeV proton-induced fission of $$^{232}$$Th and $$^{233}$$U, primary and secondary fragment mass yields as well as the average neutron multiplicity have been studied with a double time-of-flight technique. From these experimental data of fission fragments and the literature data of fission products, the nuclear-charge polarization at scission was derived. It was found that the nuclear charge polarization is characterized by the liquid-drop properties of nuclei and the proton shell effects $$Z$$ = 50 of heavy fragments. The fragment mass dependence of the nuclear-charge polarization in the present systems agrees with that in the thermal-neutron-induced fission of $$^{235}$$U, indicating that the nuclear-charge polarization is practically insensitive to mass and excitation energy of the fissioning nucleus for the asymmetric fission in the region of light actinides.

Oral presentation

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