Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

The production of (283)Cn in the hot fusion reaction of U-238(Ca-48,3n) was confirmed using a new gas-filled recoil ion separator GARIS-II. At the excitation energies of the compound nucleus E* = 34.5 MeV, two decay events from (283)Cn were observed, resulting in the cross section of sigma(3n) = 2.0(-1.3)(+2.7) pb. One is the spontaneous fission with decay time tau = 14.4 s. The other is the 9.45MeV alpha-decay with tau = 5.4 s, followed by the spontaneous fission of (279)Ds (154 ms).

DOI： 10.7566/jpsj.86.085001

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Fission and capture reactions were simultaneously measured in the neutron-induced reactions of Am-241 at the spallation neutron facility of the Japan Proton Accelerator Research Complex (J-PARC). Data for the neutron energy range of E-n=0.1-20 eV were taken with the TOF method. The fission events were observed by detecting prompt neutrons accompanied by fission using liquid organic scintillators. The capture reaction was measured by detecting gamma rays emitted in the deexcitation of the compound nuclei using the same detectors, where the prompt fission neutrons and capture gamma rays were separated by a pulse shape analysis. The cross sections were obtained by normalizing the relative yields at the first resonance to evaluations or other experimental data. The ratio of the fission to capture cross sections at each resonance is compared with those from an evaluated nuclear data library and other experimental data. Some differences were found between the present values and the library/literature values at several resonances.

DOI： 10.1016/j.nima.2016.12.021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.physletb.2016.08.010

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Publishing type：Research paper (international conference proceedings)   Publisher：Journal of the Physical Society of Japan  

DOI： 10.7566/jpscp.6.030107

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s10967-014-3706-9

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.apradiso.2014.03.014

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Physical Society (APS)  

Production cross sections of Rf isotopes in the Cm-248+O-18 reaction were measured at the beam energy range of 88.2 to 101.3 MeV by use of a gas-filled recoil ion separator. The excitation functions of (260)Rf, (261)Rfa, and (262)Rf were obtained together with those of spontaneously fissioning nuclides which have few-second half-lives and have been assigned to (261)Rf(b) and a longer-lived state of (262)Rf. The excitation function of few-second spontaneously fissioning nuclide exhibited the maximum cross section at the O-18 beam energy of 94.8 MeV. The shape of the excitation function was almost the same as that of (261)Rfa, whereas it was quite different from those of (260)Rf and (262)Rf. A few-second spontaneously fissioning nuclide previously reported as (261)Rfb and (262)Rf observed in Cm-248+O-18 reaction was identified as (261)Rf(b).

DOI： 10.1103/physrevc.88.024618

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

DOI： 10.7566/jpsj.82.024202

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An isotope of the 113th element, i.e., 278113, was produced in a nuclear reaction with a 70Zn beam on a 209Bi target. We observed six consecutive \alpha-decays following the implantation of a heavy particle in nearly the same position in the semiconductor detector under an extremely low background condition. The fifth and sixth decays are fully consistent with the sequential decays of 262Db and 258Lr in both decay energies and decay times. This indicates that the present decay chain consisted of 278113, 274Rg (Z=111), 270Mt (Z=109), 266Bh (Z=107), 262Db (Z=105), and 258Lr (Z=103) with firm connections. This result, together with previously reported results from 2004 and 2007, conclusively leads to the unambiguous production and identification of the isotope 278113 of the 113th element.

DOI： 10.1143/jpsj.81.103201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Walter de Gruyter GmbH  

<title>Abstract</title>
The cation-exchange behavior of ²⁶¹Rf (<italic>T</italic>
_1/2= 78 s) produced in the ²⁴⁸Cm(¹⁸O, 5<italic>n</italic>) reaction was studied on a “one-atom-at-a-time” scale in 0.15–0.69 M H₂SO₄/HNO₃ mixed solutions ([H⁺]=1.0 M) using an automated ion-exchange separation apparatus coupled with the detection system for alpha-spectroscopy (AIDA). It was found that adsorption probabilities ( decrease with an increase of [HSO₄
⁻], showing a successive formation of Rf sulfate complexes. Rf exhibits a weaker complex formation tendency compared to the lighter homologues Zr and Hf. This is in good agreement with theoretical predictions including relativistic effects.

DOI： 10.1524/ract.2012.1898

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Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

DOI： 10.1246/bcsj.20110126

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Walter de Gruyter GmbH  

<title>Abstract</title>Production cross sections of fission product ⁹⁹Mo produced in the reaction of <italic />¹⁹F + ²⁰⁹Bi<italic /> have been measured at the incident energies 135–83 MeV near and below the fusion barrier by radiochemical methods. The excitation function for the fusion-fission cross sections in this reaction were deduced down to 80 μb from the measured production cross sections. A systematic analysis of the fusion-fission excitation function shows that sub-barrier fusion hindrance in the heavy mass system <italic />¹⁹F + ²⁰⁹Bi<italic /> is different from that in the medium-heavy mass systems but similar to that in the medium-light mass system and in the heavy mass system. This work is the first radiochemical study of sub-barrier fusion hindrance in heavy mass systems.

DOI： 10.1524/rcpr.2011.0021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

DOI： 10.14494/jnrs.11.7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

We report on the characteristic anion-exchange behavior of the superheavly element dubnium (Db) with atomic number Z = 105 in HF/HNO3 Solution at the fluoride ion concentration [F-] = 0.003 M. The result clearly demonstrates that the fluoro complex formation of Db is significantly different from that of the group-5 homologue Ta in the 6th period of the periodic table while the behavior of Db is similar to that of the lighter homologue Nb in the 5th period.

DOI： 10.1246/cl.2009.1084

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Decay properties of an isotope 266Bh and its daughter nucleus 262Db produced by the 248Cm(23Na,5n) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. 266Bh was clearly identified from the correlation of the known nuclide, 262Db. The obtained decay properties of 266Bh and 262Db are consistent with those observed in the 278113 chain, which provided further confirmation of the discovery of 278113.

DOI： 10.1143/jpsj.78.064201

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Anion-exchange chromatography of element 105, dubnium (Db), produced in the Cm-248(F-19, 5n)(262)Db reaction is investigated together with the homologues Nb and Ta, and the pseudo-homologue Pa in 13.9 M hydrofluoiic acid (HF) solution. The distribution coefficient (K-d) of Db on an anion-exchange resin is successfully determined by running cycles of 1702 chromatographic column separations. The result clearly indicates that the adsorption of Db on the resin is significantly different from that of the homologues and that the adsorption of anionic fluoro complexes of these elements decreases in the sequence of Ta approximate to Nb > Db >= Pa.

DOI： 10.1524/ract.2009.1577

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DOI： 10.1016/j.nima.2008.02.090

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Chemical Society of Japan  

We report on new and much more precise cation-exchange data of element 104, rutherfordium (Rf), in the fluoride ion concentration [F<SUP>−</SUP>] range of 5.29×10<SUP>−5</SUP>−1.04×10<SUP>−3</SUP> M. The result based on one-atom-at-a-time chemistry clearly demonstrates that the distribution coefficients (<I>K</I><SUB>d</SUB>) decrease with increasing [F<SUP>−</SUP>], suggesting successive fluoride complexation of Rf. The complexation of Rf is briefly discussed in terms of fully relativistic density functional calculation theory.

DOI： 10.1246/cl.2008.288

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Walter de Gruyter GmbH  

DOI： 10.1524/ract.2008.1474

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Language：English   Publishing type：Research paper (international conference proceedings)  

DOI： 10.1016/j.nuclphysa.2008.02.149

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Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

DOI： 10.1143/jpsj.76.045001

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Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

DOI： 10.1143/jpsj.76.043201

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Walter de Gruyter GmbH  

The extraction behavior of rutherfordium (Rf) into tributylphosphate (TBP) from hydrochloric acid (HCl) has been studied together with those of the lighter group-4 elements Zr and Hf. The extractability of²⁶¹Rf,¹⁶⁹Hf, and⁸⁵Zr into TBP was investigated under identical conditions in 7.2–8.0 M HCl by on-line reversed-phase extraction chromatography. The percent extractions of Rf, Hf, and Zr into the TBP resin increase steeply with increasing HCl concentration, and the order of extraction is Zr &gt; Hf ≈ Rf. By considering the order of chloride complexation among these elements, it is suggested that the stability of the TBP complex of Rf tetrachloride is lower than those of Zr and Hf.

DOI： 10.1524/ract.2007.95.1.1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

At the Institute of Physical and Chemical Research (RIKEN) a series of experiments studying the productions and their decays of the heaviest elements have been performed by using a gas-filled recoil ion separator GARIS. Results on the isotope of the 112th element, (277)112, and on that of the 113th element (278)113, are reviewed. Tow decay chains which are assigned to be ones originating from the isotope (277)112 were observed in the Pb-201(Zn-70, n) reaction. Both chains consisted of four consecutive alpha decays followed by a spontaneous fission. The results provide a confirmation of the production and decay of the isotope (277)112 reported by a research group at Gesellschaft fur Schwerionenforschung (GSI), Germany, produced via the same reaction by using a velocity filter. Tow decay chains, both consisted of four consecutive alpha decays followed by a spontaneous fission, were observed also in the reaction Bi-209(Zn-70, n). Those are assigned to be the convincing candidate events of the decays of the isotope of the 113th element (278)113, and its daughter nuclei, (274)Rg, (270)Mt, (266)Bh, and (262)Db.

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DOI： 10.1103/physrevc.73.067301

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

Chemical properties of the transactinide element, rutherfordium (Rf), produced in the reaction Cm-248(O-18, 5n) have been studied based on an atom-at-a-time scale. Ion-exchange chromatographic experiments on Rf together with the lighter homologues in the periodic table of the elements, group-4 elements Zr and Hf, in hydrofluoric acid solutions have been conducted with a rapid chemical separation apparatus. From the systematic study of the anion-exchange behavior of Rf, we have observed unexpected chemical behavior of Rf; the fluoride complex formation of Rf is significantly different from those of the homologues. Characteristics of the complexing strength of the Rf fluoride are briefly discussed by comparing with those of the homologues and with theoretical predictions by relativistic molecular density-functional calculations.

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

In the Institute of Physical and Chemical Research (RIKEN), using high intensity heavy ion beams from the RIKEN Linear Accelerator, productions and decays of isotopes of the heaviest elements have been investigated by using the gas-filled recoil separator, GARIS. The isotopes studied were (HS)-H-265, (DS)-D-271, (272)Rg, (277)112, and (278)113, respectively. Based on the observed decay chains consisting of consecutive alpha decays connected to the previously known alpha decays or spontaneous fissions, assignments of the initially produced isotopes were done. Our data with the atomic number from 108 to 112, agree well with the data previously taken. The production cross section of the isotope (278)113 of the 113th element have reached around 32 fb which shows the simple decrease of the cross section with the increase of the atomic number. The isotopes were produced, for the first time in the In evaporation channel from heavy-ion induced fusion reaction.

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In the Institute of Physical and Chemical Research (RIKEN), using high intensity heavy ion beams from the RIKEN Linear Accelerator, productions and decays of isotopes of the heaviest elements have been investigated by using the gas-filled recoil separator, GARIS. The isotopes studied were (265)Hs, (271)Ds, (272)Rg, (271)112, and (278)113, respectively. Based on the observed decay chains consisting of consecutive alpha decays connected to the previously known alpha decays or spontaneous fissions, assignments of the initially produced isotopes were done. Our data with the atomic number from 108 to 112, agree well with the data previously taken. The production cross section of the isotope (278)113 of the 113th element have reached around 32 fb which shows the simple decrease of the cross section with the increase of the atomic number. The isotopes were produced, for the first time in the In evaporation channel from heavy-ion induced fusion reaction.

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<title>Summary</title>Chemical studies on element 104, rutherfordium (Rf), at JAERI (Japan Atomic Energy Research Institute) are reviewed. The transactinide nuclide²⁶¹Rf has been produced in the reaction²⁴⁸Cm(¹⁸O, 5<italic>n</italic>) at the JAERI tandem accelerator with the production cross section of about 13 nb. On-line anion-exchange experiments on Rf together with the lighter homologues, group-4 elements Zr and Hf, in acidic solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, it has been found that the properties of Rf in HCl and HNO₃solutions are quite similar to those of Zr and Hf, definitely confirming that Rf is a member of the group-4 elements. However, we have observed an unexpected chemical behavior of Rf in HF solutions; the fluoride complex formation of Rf is significantly different from those of the homologues. Prospects of extending chemical studies on transactinide elements in the near future at JAERI are briefly considered.

DOI： 10.1524/ract.2005.93.9-10.519

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DOI： 10.1140/epja/i2004-10096-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

<SUP>85</SUP>Zr, <SUP>169</SUP>Hf, and <SUP>261</SUP>Rf were produced simultaneously from <SUP>nat</SUP>Ge (<SUP>18</SUP>O, xn), <SUP>nat</SUP>Gd (<SUP>18</SUP>O, xn), and <SUP>248</SUP>Cm (<SUP>18</SUP>O, 5n) reactions, respectively, and the volatility of their chlorides was examined using an isothermal gas chromatographic system. The observed gas chromatogram indicated that ZrCl<SUB>4</SUB>, HfCl<SUB>4</SUB>, and RfCl<SUB>4</SUB> had almost similar volatility.

DOI： 10.14494/jnrs2000.6.2_n1

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：WORLD SCIENTIFIC PUBL CO PTE LTD  

Chemical properties of the transactinide element, rutherfordium (Rf), produced in the reaction Cm-248(O-18,5n) have been studied at an atom-at-a-time scale. Ion-exchange experiments of Rf together with the lighter homologues in the periodic table of the elements, group-4 elements Zr and Hf, in hydrofluoric acid solutions have been conducted with a rapid ion-exchange separation apparatus. From the systematic study of the anion-exchange behavior of Rf, we have observed an unexpected chemical behavior of Rf; the fluoride complex formation of Rf is significantly different from those of the homologues. Characteristics of the complexing strength of the Rf fluoride are briefly discussed by comparing with those of Zr and Hf and also with theoretical predictions by relativistic molecular density-functional calculations.

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DOI： 10.1140/epja/i2004-10044-6

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Physical Society of Japan  

The convincing candidate event of the isotope of the 113th element, 278113, and its daughter nuclei, 274111 and 270Mt, were observed, for the first time, in the $\text{$^{209}$Bi} + \text{$^{70}$Zn}$ reaction at a beam energy of 349.0 MeV with a total dose of $1.7 \times 10^{19}$. Alpha decay energies and decay times of the candidates, 278113, 274111, and 270Mt, were ($11.68 \pm 0.04$ MeV, 0.344 ms), ($11.15 \pm 0.07$ MeV, 9.26 ms), and ($10.03 \pm 0.07$ MeV, 7.16 ms), respectively. The production cross section of the isotope was deduced to be 55$^{+150}_{-45}$ fb (10-39 cm2).

DOI： 10.1143/jpsj.73.2593

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The production and decay of $^{272}111$ has been investigated using a gas-filled recoil ion separator in irradiations of 209Bi targets with 64Ni beam at 320, 323 and 326 MeV. We have observed 14 $\alpha$-decay chains in total, that can be assigned, on the basis of their time correlations, to subsequent decays from $^{272}111$ produced in the 209Bi(64Ni,1n) reaction. The present result is the first clear confirmation for the discovery of $^{272}111$ and its $\alpha$-decay products, 264Bh and 268Mt, reported previously by a GSI group. New information on their half-lives and decay energies as well as the excitation function is presented.

DOI： 10.1143/jpsj.73.1738

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：ELSEVIER SCIENCE BV  

A gas-filled recoil separator GARIS for heavy element research was installed at an experimental hall of the RIKEN linear Accelerator (RILAC) facility. One of the interesting applications of the separator is the discovery of nuclei of superheavy elements whose atomic number are grater then 110. We performed experiments to study productions and decays of heavy nuclei, (271)Ds and (272)111, which were produced with Pb-208 + Ni-64 --&gt; (271)Ds + n and Bi-209 + Ni-64 --&gt; (272)111 + it reactions. Fourteen atoms of (271)Ds and the same number of (272)111 were detected and identified. Existence of an isomeric state in (271)Ds was confirmed. In the decay chains of (272)111, spontaneous fission decays were observed in decay of (264)Bh and (260)Db.

DOI： 10.1016/j.nuclphysa.2004.04.021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.nuclphysa.2004.01.019

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Elsevier BV  

DOI： 10.1016/j.nuclphysa.2004.01.021

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：American Chemical Society (ACS)  

Fluoride complexation of element 104, rutherfordium (Rf), produced in the (CM)-C-248(O-18,5n)(261)Rf 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 O-18-induced reactions on Ge and Gel 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.

DOI： 10.1021/ja031824u

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DOI： 10.1103/physrevc.69.014308

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

An elution curve of element 104, rutherfordium (Rf), in anion-exchange chromatography has been obtained for the first time on an atom-at-a-time basis. The distribution coefficient in 5.4 M hydrofluoric acid solution has been determined to be 28±6 mL/g from the observed peak volume of the elution curve.

DOI： 10.14494/jnrs2000.5.45

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Production and decay of an isotope (271)110 of the 110th element were studied. The isotope was produced by Pb-208 + Ni-64 --&gt; (271)110 + n reaction. Fourteen cc-decay chains have been assigned to be the decays originating from the isotope (271)110. The excitation function of the production cross section was measured. The results have provided a good confirmation of production and decay of the (271)110 reported by GSI group. The presence of an isomeric state in (271)110 has also been confirmed. Possible isomeric state in (267)Hs has also been presented. The production and decay of (272)111 has been also investigated in irradiations of Bi-209 targets with Ni-64 beam. We have observed 14 a-decay chains in total, that can be assigned, on the basis of their time correlations, to subsequent decays from (272)111.

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Authorship：Lead author   Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1023/a:1022271529219

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：MAIK NAUKA/INTERPERIODICA PUBL  

The present status of heavy element nuclear chemistry research at JAERI (Japan Atomic Energy Research Institute) is reviewed. Production of the transactinide nuclei (216)Rf and (212)Db via the reactions of Cm-248(O-18,5n) and Cm-248(F-19,5n), 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. (C) 2003 MAIK "Nauka/Interperiodica".

DOI： 10.1134/1.1586427

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DOI： 10.1103/physrevc.67.014604

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DOI： 10.1023/a:1022571813231

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1023/a:1022577409113

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1023/a:1022505104512

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1023/a:1022520113173

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1023/a:1022219512380

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：INST PHYSICS ACAD SCI CZECH REPUBLIC  

The present status of transactinide nuclear chemistry research at JAERI (Japan Atomic Energy Research Institute) is reviewed. Successful production of the transactinide nuclei, (261)Rf and (262)Db in the reactions Of Cm-248(O-18,5n) and Cm-248(F-19,5n), respectively, at the JAERI tandem accelerator is reported. Aqueous chemistry of element 104, Rf, is being performed with a newly developed rapid ion-exchange separation apparatus. Anion-exchange behaviour of Rf in acidic solutions is outlined. Research plans for the near future are briefly discussed.

DOI： 10.1007/s10582-003-0038-3

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Language：English   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

The charge distributions of fission products in proton-induced fission of <SUP>238</SUP>U and <SUP>232</SUP>Th were measured in a wide mass range. The most probable charges lay on the proton-rich side in the light fragment region and on the proton-deficient side in the heavy one compared with the unchanged charge distribution hypothesis. This result implies that the charge polarization occurs in the fission process. The charge polarization was examined with respect to the ground-state Q values. The estimations by the Q values fairly well reproduced the experimental most probable charges. These results suggest that the fission path to the most favorable charge division may go through the most energetically favorable path at scission point.

DOI： 10.14494/jnrs2000.3.2_7

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/00223131.2002.10875403

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Informa UK Limited  

DOI： 10.1080/00223131.2002.10875143

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

The transactinide nuclei, <SUP>261</SUP>Rf and <SUP>262</SUP>Db, have been produced in the <SUP>248</SUP>Cm (<SUP>18</SUP>O, 5n) reaction at beam energies of 91, 94, and 99 MeV, and in the <SUP>248</SUP>Cm (<SUP>19</SUP>F, 5n) reaction at 106 MeV, respectively. The production cross sections are evaluated from the mother-daughter correlations of α energies between <SUP>261</SUP>Rf and <SUP>257</SUP>No, and <SUP>262</SUP>Db and <SUP>258</SUP>Lr. The maximum cross section of the <SUP>248</SUP>Cm (<SUP>18</SUP>O, 5n) reaction is measured to be 13±3 nb at around 94 MeV, while the production cross section of <SUP>262</SUP>Db in <SUP>248</SUP>Cm (<SUP>19</SUP>F, 5n) is 1.3±0.4 nb at 106 MeV.

DOI： 10.14494/jnrs2000.3.85

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

A short review is given on our current anion-exchange studies of element 104, rutherfordium (Rf), in HCl and HNO<SUB>3</SUB> solutions. The distribution coefficients of the Rf homologues Zr, Hf, and Th (IV), and Pu (IV) on an anion-exchange resin were measured in 1.0-11.5 M HCl and 1.1-13.1 M HNO<SUB>3</SUB> with a batch method using the radiotracers <SUP>88</SUP>Zr, <SUP>175</SUP>Hf, <SUP>234</SUP>Th, and <SUP>237</SUP>Pu. In experiments for the short-lived <SUP>261</SUP>Rf, the isotopes <SUP>85</SUP>Zr, <SUP>169</SUP>Hf, and <SUP>169</SUP>Rf were produced in the <SUP>18</SUP>O-induced reactions on <SUP>nat</SUP>Ge, <SUP>248</SUP>Gd, and <SUP>248</SUP>Cm targets, respectively, and their anion-exchange behavior in 4.0-11.5 M HCl and 8.0 M HNO<SUB>3</SUB> was investigated using the Automated Ion-exchange separation apparatus coupled with the Detection system for Alpha spectroscopy (AIDA). In the HCl system, the percent adsorption of Rf on the anion-exchange resin increases steeply with increasing HCl concentration from 7.0 M to 11.5 M. This adsorption behavior is similar to that of the group-4 elements Zr and Hf, and is quite different from that of the pseudo-homologue Th (IV). The percent adsorption decreases in the order Rf>Zr>Hf. In the HNO<SUB>3</SUB> system, Rf behaves like Zr and Hf in 8.0 M HNO<SUB>3</SUB> but not like Pu (IV) and Th (IV), implying the formation of cationic or neutral species.

DOI： 10.14494/jnrs2000.3.143

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

The present status of heavy element nuclear chemistry research at JAERI (Japan Atomic Energy Research Institute) is reviewed. Successful production of the transactinide nuclei, <SUP>261</SUP>Rf and <SUP>262</SUP>Db via the reactions of <SUP>248</SUP>Cm (<SUP>18</SUP>O, 5n) and <SUP>248</SUP>Cm (<SUP>19</SUP>F, 5n), respectively at the JAERI tandem accelerator is presented. Aqueous chemistry of Rf is being carried out with a newly developed rapid ion-exchange separation apparatus. Anion-exchange behavior of Rf in HCl solution is shortly discussed. Recent experimental results on decay studies of neutron-deficient actinide nuclei using the gas-jet coupled JAERI-ISOL are also given. Prospects for the near future studies are briefly considered.

DOI： 10.14494/jnrs2000.3.129

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

An anion exchange in mineral acid and methanol system was examined in view of rapid chemical separation. An elution behavior of Bk in hydrochloric acid-methanol system was obtained using <SUP>250</SUP>Bk. An elution behavior of Bk in nitric acid-methanol system was predicted from the relationship between an elution position and an ionic radius . The separation was completed for nitric acid-methanol system and for hydrochloric-methanol system within 40 and 25 min, respectively.

DOI： 10.14494/jnrs2000.3.155

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

The deformation properties of heavy nuclei undergoing the individual fission paths are studied. To understand the nuclear mass division process at low energy, fission events for the symmetric and asymmetric fission paths are analyzed from the overall fission events. The fragment mass-yield distributions for the symmetric and asymmetric fission paths in the fission processes of <SUP>210</SUP>Po, <SUP>227</SUP>Ac, <SUP>233</SUP>Pa, <SUP>249</SUP>Bk, and <SUP>259</SUP>Md are systematically studied. Fission characteristics including the deformation of the fissioning nucleus at the scission configuration, the fragment massyield distributions, and the total kinetic energy release for individual fission paths are presented.

DOI： 10.14494/jnrs2000.3.103

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：The Japan Society of Nuclear and Radiochemical Sciences  

The EC and α decays of neutron-deficient Am and Cm nuclei have been studied using a gas-jet coupled on-line isotope separator. Decay schemes of the EC decay of <SUP>235, 236</SUP>Am have been constructed, and weak α decays of <SUP>233, 235, 236</SUP>Am and <SUP>237, 238</SUP>Cm have been observed. The efficiency of the on-line mass separation of Bk nuclei was measured to be ∼1%. The Q<SUB>α</SUB> values, α-decay partial half-lives, and proton-neutron configurations are discussed.

DOI： 10.14494/jnrs2000.3.187

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Language：English   Publishing type：Research paper (scientific journal)  

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&gt
-type: deformation path with β∼1.65 resulting in a typical FWHM of &gt
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. © 2014 Taylor and Francis Group, LLC.

DOI： 10.1080/00223131.2002.10875402

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Walter de Gruyter GmbH  

Characteristics of nuclear deformation properties at scission of two fission modes, symmetric and asymmetric, are reviewed. Existence of two kinds of scission configurations associated with the symmetric and asymmetric fission modes is pointed out: elongated and compact configurations. Each symmetric and asymmetric 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 data. From the systematic study of the scission properties in a wide range of actinide fission, the bimodal fission observed in spontaneous fission (SF) of the heavy actinides is interpreted as the result of the presence of the two fission paths of the ordinary asymmetric mode and a strongly shell-influenced symmetric one. The correlation between the fragment shell structures and the asymmetric mass-yield curves is described.

DOI： 10.1524/ract.2001.89.11-12.681

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Other Link： https://www.degruyter.com/document/doi/10.1524/ract.2001.89.11-12.681/xml

Publishing type：Research paper (scientific journal)   Publisher：Walter de Gruyter GmbH  

The transactinide nuclides²⁶¹Rf and²⁶²Db have been successfully produced in the²⁴⁸Cm(¹⁸O,5<italic>n</italic>) reaction at 99 MeV and in the²⁴⁸Cm(¹⁹F,5<italic>n</italic>) reaction at 100, 103, and 106 MeV, respectively, at the JAERI tandem accelerator. The on-line ion exchange experiments with an automated fast and repetitive liquid chromatography separation system were performed in the HNO₃/HF system using Rf homologues^89mZr and^167,165Hf produced in the⁸⁹Y(<italic>p,n</italic>) and¹⁵²Gd(¹⁸O,<italic>xn</italic>) reactions, respectively. The radiotracers⁸⁸Zr,¹⁷⁵Hf, and²³⁴Th were also prepared and the distribution coefficients on ion exchange resins were measured systematically in 1-11 M HCl and 1-14 M HNO₃with the batch method. It was found that anion exchange experiments of Rf in 8 M HNO₃and 9 M HCl provided information useful to extract the ionic radius of Rf and to verify the influence of relativistic effects.

DOI： 10.1524/ract.2001.89.11-12.733

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Other Link： https://www.degruyter.com/document/doi/10.1524/ract.2001.89.11-12.733/xml

DOI： 10.1556/APH.13.2001.1-3.13

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Language：English   Publishing type：Research paper (international conference proceedings)   Publisher：AMER INST PHYSICS  

EC and alpha decays of neutron-deficient nuclei Am233-236 have been studied using: a gas-jet coupled on-line isotope separator. A proton orbital of the ground state of Am-235 and neutron orbitals in Pu-235 have been estimated from a decay scheme of 235Am. The 5(-) ground state and the 1(-) EC decaying isomer in Am-236 and the configuration of two-quasiparticle states in Pu-236 have been established. Q alpha values of Am-233,Am-235,Am-236 have been determined from measured alpha -particle energies. It was found that evaluated Q alpha values were systematically overestimated by 100-200 keV in neutron-deficient Am nuclei.

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Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/s100500070013

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Other Link： http://link.springer.com/article/10.1007/s100500070013/fulltext.html

Language：English   Publishing type：Research paper (scientific journal)   Publisher：Springer Science and Business Media LLC  

DOI： 10.1007/bf02349537

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Other Link： http://link.springer.com/article/10.1007/BF02349537/fulltext.html

Language：English   Publisher：AMER INST PHYSICS  

Decay properties of an isotope (266)Bh and its daughter nucleus (262)Db produced by the Cm-248(Na-23 5n) reaction were studied by using a gas-filled recoil separator coupled with a position-sensitive semiconductor detector. (266)Bh was clearly identified from the correlation of the known nuclide, (262)Db. The obtained decay properties of (266)Bh and (262)Db are consistent with those observed in the (278)113 chain by RIKEN collaboration, which provided further confirmation of the discovery of (278)113.

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Language：English   Publishing type：Research paper, summary (international conference)   Publisher：AMER CHEMICAL SOC  

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