[Show abstract][Hide abstract]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.
Full-text available · Article · Aug 2014 · Journal of Nuclear Science and Technology
[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.
Article · Aug 2014 · Journal of Nuclear Science and Technology
[Show abstract][Hide abstract]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
Article · Sep 2013 · Analytical and Bioanalytical Chemistry
[Show abstract][Hide abstract]ABSTRACT: Experimental verification and characterization of the two-mode fission are reviewed. The presence of two independent deformation-paths in low energy fission of actinides is demonstrated by studying correlation among saddle-point configurations, scission-point configurations, and mass-yield distributions; the elongated scission configuration is related with the fission process that goes over a higher threshold energy and results in a symmetric mass-division mode, while the compact scission configuration with the process that experiences a lower threshold ends up with an asymmetric mass-division mode. Based on an extensive systematic analysis of scission properties in a wide range of actinide fission, the bimodal fission observed in the spontaneous fission of the heavy actinides is interpreted as the result of the presence of two fission paths, namely, the ordinary asymmetric fission path and a strongly shell-influenced symmetric mode.
[Show abstract][Hide abstract]ABSTRACT: The IUPAC/IUPAP Joint Working Party (JWP) on the priority of claims to the discovery of new elements 113–116 and 118 has reviewed the relevant literature pertaining to several claims. In accordance with the criteria for the discovery of elements previously established by the 1992 IUPAC/IUPAP Transfermium Working Group (TWG), and reinforced in subsequent IUPAC/IUPAP JWP discussions, it was determined that the Dubna-Livermore collaborations share in the fulfillment of those criteria both for elements
[Show abstract][Hide abstract]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.
[Show abstract][Hide abstract]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.
[Show abstract][Hide abstract]ABSTRACT: The IUPAC/IUPAP Joint Working Party (JWP) on the priority of claims to the discovery of new elements has reviewed the relevant literature pertaining to several claims. In accordance with the criteria for the discovery of elements previously established by the 1992 IUPAC/IUPAP Transfermium Working Group (TWG), and reiterated by the 1999 and 2003 IUPAC/IUPAP JWPs, it was determined that the 1996 and 2002 claims by the Hofmann et al. research collaborations for the discovery of the element with atomic number 112 at Gesellschaft fur Schwerionenforschung (GSI) share in the fulfillment of those criteria. A synopsis of Z = 112 experiments and related efforts is presented. A subsequent report will address identification of higher-Z elements including those of odd atomic number.
[Show abstract][Hide abstract]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
Article · Dec 2008 · Journal of Radioanalytical and Nuclear Chemistry
[Show abstract][Hide abstract]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-).
Full-text available · Article · Jan 2008 · Radiochimica Acta
[Show abstract][Hide abstract]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.
[Show abstract][Hide abstract]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.
[Show abstract][Hide abstract]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 T
1/2 = 3.6(2) min and the (1-) state with T
1/2 = 2.9(2) min. The 1185.5 keV level in 236Pu was found to be the K isomer with K
π = 5- and t
1/2 = 1.2(3) μs. EC transitions from 236g, mAm to the 1185.5, 1311.5, and 1340.8 keV levels in 236Pu show small log ft values of 4.9, 5.3, and 4.8, respectively, indicating that the π5/2+ → ν5/2+ transition largely contributes to these transitions, and thus, the populated levels should be the π5/2-π5/2+ two-quasiparticle states. The K
π = 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.
[Show abstract][Hide abstract]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)]
[Show abstract][Hide abstract]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
[Show abstract][Hide abstract]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- configuration. The α-γ coincidence result has revealed that the π5/2- 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.
[Show abstract][Hide abstract]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.
[Show abstract][Hide abstract]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.
Full-text available · Article · May 2004 · Journal of the American Chemical Society
[Show abstract][Hide abstract]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.
[Show abstract][Hide abstract]ABSTRACT: The IUPAC/IUPAP Joint Working Party on the priority of claims to the discovery of new elements has reviewed the relevant literature pertaining to several claims. In accordance with the criteria for the discovery of elements, previously established by the 1992 IUPAC/IUPAP Transfermium Working Group, and reinforced by the 1999 IUPAC/IUPAP Joint Working Party, it was determined that the claim by the Hofmann et al. research collaboration for the discovery of element 111 at Gesellschaft für Schwerionenforschung (GSI) has fulfilled those criteria. For elements 112, 114, and 116, the collaborations of Hofmann et al. and of Oganessian et al. produced high-quality data with plausible interpretations. However, confirmation by further results is needed to assign priority of discovery for these elements. The working party was not persuaded that other collaborations have satisfied the discovery criteria.
Full-text available · Article · Jan 2003 · Pure and Applied Chemistry