H. Nakahara

Tokyo Metropolitan University, Edo, Tōkyō, Japan

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Publications (174)282.09 Total impact

  • [Show abstract] [Hide abstract]
    ABSTRACT: Three fimdamental types (named A-, B- and O-type) in the fragment mass-yield distribution and three independent types of the scission deformation (β~1.65, 1.53 and 1.33) for actinide nuclei in fission process are experimentally observed. The correlations between the final shapes of fissioning nuclei and the shapes of the fragment mass-yield distributions are hence revealed and presented. A-type: deformation path with β~1.65 resulting in a typical FWHM of >20 u; B-type: deformation path with β~1.53 leading to a typical FWHM of ~15 u; O-type: deformation path with β~1.33 producing a FWHM of ~9 u.
    Journal of Nuclear Science and Technology 08/2014; 39(sup3):30-33. DOI:10.1080/00223131.2002.10875402
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    ABSTRACT: Nuclear decay properties of the neutron-deficient actinide isotopes 233,234,235,236Am and 237,238Cm have been investigated using a gas-jet coupled on-line isotope separator at the JAERI tandem accelerator facility. Alpha-decays of 233,235,236Am and 237,238Cm produced in the 6Li-induced reactions on 233,235U and 237Np targets have been observed with unambiguous mass identification, and the new isotopes 233Am and 237Cm have been identified for the first time. Alpha-particle energies, Qα values, half-lives and α-branching intensities were determined and the observed α decays of 233Am and 235Am are regarded as the favored transition.
    Journal of Nuclear Science and Technology 08/2014; 39(sup3):34-37. DOI:10.1080/00223131.2002.10875403
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    ABSTRACT: Prompt gamma-ray neutron activation analysis (PGNAA) using the internal mono-standard method was tested for its applicability to analyzing large solid samples including irregularly shaped meteorite samples. For evaluating the accuracy and precision of the method, large quantities of the Geological Survey of Japan standardized rock powders (JB-1a, JG-1a, and JP-1) were analyzed and 12 elements (B, Na, Mg, Al, Cl, K, Ca, Ti, Mn, Fe, Sm, and Gd) were determined by using Si as an internal standard element. Analytical results were mostly in agreement with literature values within 10 %. The precision of the method was also shown to be within 10 % (1σ) for most of these elements. The analytical procedure was then applied to four stony meteorites (Allende, Kimble County, Leedey, Lake Labyrinth) and four iron meteorites (Canyon Diablo, Toluca (Mexico), Toluca (Xiquipilco), Squaw Creek) consisting of large chunks or single slabs. For stony meteorites, major elements (Mg, Al, Si, S, Ca, and Ni), minor elements (Na and Mn) and trace element (B, Cl, K, Ti, Co, and Sm) were determined with adequate accuracy. For iron meteorites, results for the Co and Ni mass fractions determined are all consistent with corresponding literature values. After the analysis, it was confirmed that the residual radioactivity remaining in the sample after PGNAAwas very low and decreased down to the background level. This study shows that PGNAAwith the internal monostandard method is highly practical for determining the elemental composition of large, irregularly shaped solid samples including meteorites.
    Analytical and Bioanalytical Chemistry 09/2013; 405(27):8749-8759. DOI:10.1007/s00216-013-7331-1
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    ABSTRACT: . The primary and the secondary fragment mass yields and neutron multiplicity in the 11.5MeV proton-induced fission of 233U were determined by a double time-of-flight method. The most probable charges of the secondary fragments in the isobaric chains with A = 126 , 127, 129, 132, and 136 have been derived from the secondary mass yields together with the literature values of the fractional cumulative and independent yields measured radiochemically. The nuclear-charge polarization of primary fragments at scission was obtained by correcting the secondary fragment mass for neutron evaporation. The results show that the nuclear-charge polarization is mostly determined by the minimum potential energy of nuclei at scission and that this behavior is nearly independent not only of mass and excitation energy but also of neutron-to-proton ratios of the fissioning nuclei.
    European Physical Journal A 01/2011; 47(1):1-8. DOI:10.1140/epja/i2011-11009-4
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    ABSTRACT: Fragment mass yields and the average neutron multiplicity in the proton-induced fission of 232Th and 233U were measured by a double time-of-flight method. The most probable charges of secondary fragments were evaluated from the fragment mass yields measured and the fractional cumulative yields reported. The nuclear charge polarization of primary fragments at scission was obtained by correcting the most probable charge of secondary fragments for neutron evaporation. The results show that the nuclear-charge polarization at scission is associated with the liquid-drop properties of nuclei and the proton shell effect with Z = 50 of heavy fragments and that it is practically insensitive to mass and excitation energy of the fissioning nucleus in the region of light actinides.
    03/2009; 1098(1). DOI:10.1063/1.3108846
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    ABSTRACT: In Japan, cosmetics claiming hormesis effect are available through Internet. Although these cosmetics show the contents, they never mention the minor elements and radioactive sources. The existence of radioisotopes, however, was observed by measurements of the gamma-rays with a HPGe detector. In this study, in order to clarify the contents of trace elements, the hormesis cosmetics including radioactive sources were analyzed using INAA, PGAA and NAA with multiple gamma-ray detection (NAAMG). Nineteen elements were analyzed quantitatively in hormesis cosmetics by INAA, PGAA and NAAMG and 16 elements were detected qualitatively by SEM-EPMA.
    Journal of Radioanalytical and Nuclear Chemistry 12/2008; 278(3):553-557. DOI:10.1007/s10967-008-1004-0
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    ABSTRACT: Formation of anionic fluoride-complexes of element 104, rutherfordium, produced in the Cm-248(O-18, 5n)(261)Rf reaction was studied by anion-exchange 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, [ZrF6](2-) and [HfF6](2-); the evaluated formation constant of [RfF(6)](2-) is at least one-order of magnitude smaller than those of [ZrF6](2-) and [HfF6](2-).
    Radiochimica Acta 01/2008; 96(3). DOI:10.1524/ract.2008.1474
  • I. Nishinaka, H. Nakahara, Y. Nagame
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    ABSTRACT: The most probable charges of secondary fragments, produced after neutron evaporation from primary fragments, have been evaluated using fractional cumulative and mass yields in the 12MeV proton-induced fission of 232Th . The nuclear-charge polarization of primary fragments at scission has been obtained by correcting the most probable charge of secondary fragments for neutron evaporation. The fragment mass dependence of the nuclear-charge polarization at scission shows good agreement with that for thermal neutron-induced fission of 235U , indicating that the nuclear-charge polarization is nearly insensitive to mass and excitation energy of the fissioning nucleus for asymmetric fission in the actinide region.
    European Physical Journal A 07/2007; 33(2):231-236. DOI:10.1140/epja/i2007-10437-y
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    ABSTRACT: Existence of two kinds of scission configurations associated with symmet- ric and asymmetric fission modes is pointed out in the fission of actinides: elongated and compact configurations. Each scission property is discussed in terms of shape elongation evaluated from fragment total kinetic energy (TKE). Fragment deformation at scission is also discussed based on neutron multiplicity measurements. From the systematic study of the scission properties in a wide range of actinides, the bimodal fission observed in the spontaneous fission (SF) of the heavy actinides would be interpreted as the result of the presence of the two fission paths; the ordinary asymmetric fission path is still exiting while the symmetric one is bifurcated by strongly shell-influenced effects.
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    ABSTRACT: The EC decay of 236Am has been studied using a gas-jet coupled on-line isotope separator. A half-life analysis revealed that there are two EC-decaying states in 236Am: the 5- state with T1/2 = 3.6(2) min and the (1-) state with T1/2 = 2.9(2) min. The 1185.5 keV level in 236Pu was found to be the K isomer with K = 5- and t1/2 = 1.2(3) s. EC transitions from 236g, mAm to the 1185.5, 1311.5, and 1340.8 keV levels in 236Pu show small logft values of 4.9, 5.3, and 4.8, respectively, indicating that the 5/2+[642] 5/2+[633] transition largely contributes to these transitions, and thus, the populated levels should be the 5/2-[523]5/2+[642] two-quasiparticle states. The K = 0- octupole band established in 236Pu is located at higher energy than those in 238,240Pu, which implies that the octupole correlations become weak at 236Pu.
    European Physical Journal A 02/2005; 23(3):395-400. DOI:10.1140/epja/i2004-10096-6
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    ABSTRACT: The fluoride complex formation of the first transactinide element, rutherfordium (104Rf), was studied through an anion-exchange method. The short-lived nuclide, 261Rf, was produced in the 248Cm(18O,5n) reaction at the JAERI tandem accelerator. The distribution coeffs. (Kd values) of Rf on an anion-exchange resin in hydrofluoric acid (HF) / nitric acid (HNO3) mixed solns. were obtained together with those of the group-4 homologues, Zr and Hf, using a rapid chem. app. The Kd values of Rf under a const. concn. of fluoride ion (F-, 3texttimes10-3 M) are entirely smaller than those of Zr and Hf and decrease with increase of the concn. of nitrate ion (NO3-). On the other hand, the Kd values of Rf under the const. concn. of NO3- (0.01, 0.015 M) increase with increasing F concn. around at 10-3-10-2 M. This increase of the Kd values was obsd. in approx. two orders of magnitude higher F- concn. than those of Zr and Hf. From a slope anal. of the logKd-log[NO3-] plot, it was found that a complex of Rf with a charge of -2 is exchanged with the counter ion, NO3-, on the anion-exchange resin. Assuming the consecutive formation reactions of the fluoride complexes of Rf, it was found that a hexafluoro complex of Rf, [RfF6]2- which is the same species as well-known [ZrF6]2- and [HfF6]2- is formed in the soln. and the formation of [RfF6]2- is much weaker than those of [ZrF6]2- and [HfF6]2-. [on SciFinder(R)]
  • Y. Nagame, M. Hirata, H. Nakahara
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    ABSTRACT: This chapter reviews the historical perspective of transuranium elements and the recent progress in the production and study of nuclear properties of transuranium nuclei. Exotic decay properties of heavy nuclei are also introduced. Chemical properties of transuranium elements in aqueous and solid states are summarized based on the actinide concept. For new application of studying transuranium elements, an X-ray absorption fine structure (XAFS) method and computational chemistry are surveyed.
    ChemInform 12/2004; 35(51). DOI:10.1002/chin.200451198
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    ABSTRACT: Primary and secondary fragment mass and fragment total kinetic energy were measured by the time-of-flight technique in the 12 MeV proton induced fission of 232Th. The average neutron multiplicity was obtained from the difference of the primary fragment mass and the secondary one as a function of mass and total kinetic energy of fission fragments. Simulation calculations were applied for correction of observed fission data affected by instrumental fluctuations in measurements of flight time and kinetic energies of fragments. Anomalous behaviors of the average neutron multiplicity as a function of total kinetic energy in the mass region of 98–107 for the lighter fragment and 126–135 for the heavier were observed and they were found to correlate with two fission modes, symmetric and asymmetric fission. The overall trend of the average neutron multiplicity was discussed in terms of the two fission modes. Partition of the total excitation energy between fragment pairs deduced from the neutron multiplicity data was evaluated for each fission mode for the first time.
    Physical Review C 07/2004; 70(1). DOI:10.1103/PhysRevC.70.014609
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    ABSTRACT: Fluoride complexation of element 104, rutherfordium (Rf), produced in the 248Cm(18O,5n)261Rf reaction has been studied by anion-exchange chromatography on an atom-at-a-time scale. The anion-exchange chromatographic 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 18O-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 effects on the fluoride complexation of Rf.
    Journal of the American Chemical Society 05/2004; 126(16):5219-24. DOI:10.1021/ja031824u
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    ABSTRACT: EC and α decays of 235Am have been studied using a gas-jet coupled on-line isotope separator. Excited states in 235Pu have been established for the first time by means of γ-ray spectroscopy following the EC decay of 235Am. The deduced log ft value suggests that the ground state of 235Am should have the π5/2-[523] configuration. The α-γ coincidence result has revealed that the π5/2-[523] state in 231Np populated by the favored α transition of 235Am is located at < 15 keV, which allows us to precisely determine the Q α value of 235Am.
    European Physical Journal A 01/2004; 22(3). DOI:10.1140/epja/i2004-10044-6
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    ABSTRACT: The present status of heavy element nuclear chemistry research at JAERI (Japan Atomic Energy Research Institute) is reviewed. Production of the transactinide nuclei 261Rf and 262Db via the reactions of 248Cm(18O,5n) and 248Cm(19F, 5n), respectively, at the JAERI tandem accelerator is reported. Study of the aqueous chemistry of Rf is being carried out with a newly developed rapid ion-exchange separation apparatus. Anion-exchange behavior of Rf in acidic solution is briefly discussed. Recent experimental results on decay studies of neutron-deficient actinide nuclei using the gas-jet coupled JAERI-ISOL are given. We also discuss characteristics of nuclear deformation properties at scission in symmetric and asymmetric fission of actinides. Prospects for studies in the near future are briefly considered.
    Physics of Atomic Nuclei 05/2003; 66(6):1131-1136. DOI:10.1134/1.1586427
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    ABSTRACT: The authors made systematic studies of lanthanide metallofullerenes on the following three properties using the radiochem. method: (1) the relative prodn. yields of metallofullerene species, (2) variation of the HPLC retention time among M(III)@C82 species, and (3) the effects of the reactor irradn. on the survival yields of each metallofullerene species. The prodn. yields of M@C82 relative to La@C82 decrease as the at. no. of M became larger and as the no. of atom ratio, M/C, in the carbon rod became larger. However, the prodn. yields of M1M2@C82, relative to that of LuM@C82 increase for the larger at. no. The retention time for the M(III)@C82 species in the Buckyprep column was found to become slightly longer for the larger at. no. but it becomes abruptly larger for Gd, and Tb by ∼5%. The overall effects of the reactor irradn. on the survival yields (or retention yields) of M@C82 species are (19.7 textpm 2.1)%. [on SciFinder(R)]
    01/2003; 255(1):159-164.
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    ABSTRACT: We have, previously, reported on the HPLC elution behavior of the Th, Pa, U, Np, and Am metallofullerenes and the UV/vis/NIR absorption spectra of the Th@C84 and U@C82 species. In this paper, the followings are reported: (1) Pu metallofullerenes were produced and their HPLC elution behavior was investigated using a radiotracer technique. The HPLC chromatogram of this metallofullerene was found to be almost the same as that of the Np and Am metallofullerenes. (2) The oxidation states of Th@C84 and U@C82 produced in macroscopic quantities were examined by XANES (X-ray absorption near edge structure) measurements. The oxidation state of the U atom in the C82 fullerene cage was estimated to be 3+ with the formal charge of the ionic molecule being U3+@C82 3-.
    Journal of Radioanalytical and Nuclear Chemistry 01/2003; 255(1):155-158. DOI:10.1023/A:1022204503720
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    ABSTRACT: The elution behavior of metallofullerenes encapsulating Ac atoms was studied using HPLC. The component of the dominant elution peak is Ac@C82. [on SciFinder(R)]
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    ABSTRACT: The encapsulated stable actinide elements with fullerene are sepd. by HPLC and the oxidn. states are studied. [on SciFinder(R)]

Publication Stats

1k Citations
282.09 Total Impact Points

Institutions

  • 1977–2013
    • Tokyo Metropolitan University
      • Department of Chemistry
      Edo, Tōkyō, Japan
  • 1995
    • Tokyo Institute of Technology
      • Chemistry Department
      Tokyo, Tokyo-to, Japan
  • 1986
    • Tsurumi University
      • School of Dental Medicine
      Yokohama, Kanagawa, Japan
    • Toho University
      • Department of Chemistry
      Edo, Tōkyō, Japan
  • 1974–1976
    • Niigata University
      • Department of Chemistry
      Niahi-niigata, Niigata, Japan