Hiromitsu Haba

Experiment on the Synthesis of Element 113 in the Reaction 209Bi(70Zn,n)278113

The convincing candidate event of the isotope of the 113th element, 278 113, and its daughter nuclei, 274 111 and 270 Mt, were observed, for the first time, in the 209 Bi + 70 Zn reaction at a beam energy of 349.0 MeV with a total dose of 1.7 ×10 19 . Alpha decay energies and decay times of the candidates, 278 113, 274 111, and 270 Mt, were (11.68 ±0.04 MeV, 0.344 ms), (11.15 ±0.07 MeV, 9.26 ms), and (10.03 ±0.07 MeV, 7.16 ms), respectively. The production cross section of the isotope was deduced to be 55 +150 -45 fb (10 -39 cm 2 ).

Observation of Second Decay Chain from 278113

RIKEN (The Institute of Physical and Chemical Research), Wako, Saitama 351-0198 Department of Physics, Saitama University, Saitama 338-8570 Center for Instrumental Analysis, Niigata University, Niigata 950-2181 Center for Nuclear Study, University of Tokyo, Wako, Saitama 351-0198 Japan Atomic Energy Agency, Tokai, Ibaraki 319-1195 Department of Chemistry, Niigata University, Niigata 950-2181 University of Tsukuba, Tsukuba, Ibaraki 305-8571 Department of Physics, Tohoku University, Sendai 980-8578 Department of Physics, Yamagata University, Yamagata 990-8560

New Result in the Production and Decay of an Isotope, 278113, of the 113th Element

An isotope of the 113th element, i.e., 278 113, was produced in a nuclear reaction with a 70 Zn beam on a 209 Bi target. We observed six consecutive α-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 262 Db and 258 Lr in both decay energies and decay times. This indicates that the present decay chain consisted of 278 113, 274 Rg ( Z =111), 270 Mt ( Z =109), 266 Bh ( Z =107), 262 Db ( Z =105), and 258 Lr ( 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 278 113 of the 113th element.

Experiment on Synthesis of an Isotope 277112 by 208Pb+70Zn Reaction

The production and decay of 277 112 have been investigated using a gas-filled recoil ion separator in irradiations of 208 Pb targets with a 70 Zn beam at 349.5 MeV. We have observed two α-decay chains that can be assigned to subsequent decays from 277 112 produced in the 208 Pb( 70 Zn,n) reaction. After emitting four consecutive α-particles, both the chains terminate by spontaneous fission decays of 261 Rf, and the decay energies and decay times of both the chains obtained in the present work agree well with those reported by a group at Gesellschaft fur Schwerionenforschung (GSI), Germany. The present result gives the first clear confirmation of the discovery of 277 112 and its α-decay product 273 Ds reported previously.

A Possible Novel Magnetic Ordering in SmRu4P12

We have carried out X-ray absorption spectroscopy, 149 Sm nuclear resonant forward scattering, and 99 Ru Mossbauer spectroscopy of SmRu 4 P 12 . The X-ray absorption spectra indicate that the Sm ions are trivalent up to 14 K. The quantum beats due to magnetic dipolar ordering are observed at 4.5 K in 149 Sm nuclear resonant forward scattering. The temperature dependence of time-integrated intensity in 149 Sm nuclear forward scattering suggests that the magnetic dipolar ordering occurs just below the metal–insulator transition temperature. No significant changes in the parameters are observed between 77 and 5 K in 99 Ru Mossbauer spectroscopy. The present result suggests a magnetic ordering accompanied by a magnetic dipole moment at the metal–insulator transition temperature in SmRu 4 P 12 in spite of the proposal of the magnetic ordering accompanied by a T β -type octupole.

Gamma-Ray Compton Imaging of Multitracer in Biological Samples Using Strip Germanium Telescope

The feasibility of using a Compton camera for multitracer imaging has been demonstrated with the results of two biological sample imaging experiments. The distribution of the multitracer administered to a soybean sample and a tumor-bearing mouse has been visualized for each nuclide simultaneously. Three-dimensional images of the multitracer have been obtained even though the samples were measured from a fixed direction.

Production and decay properties of 272111 and its daughter nuclei

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

Chemical studies on rutherfordium (Rf) at JAERI

Summary Chemical studies on element 104, rutherfordium (Rf), at JAERI (Japan Atomic Energy Research Institute) are reviewed. The transactinide nuclide 261Rf has been produced in the reaction 248Cm(18O, 5n) 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 HNO3 solutions 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.

Hexafluoro complex of rutherfordium in mixed HF/HNO3 solutions

Summary Formation of anionic fluoride-complexes of element 104, rutherfordium, produced in the 248Cm(18O,5n) 261Rf reaction was studied by anion-exchange on an atom-at-a-time scale. It was found that the hexafluoro complex of Rf, [RfF6]2−, was formed in the studied fluoride ion concentrations of 0.0005–0.013 M. Formation of [RfF6]2− was significantly different from that of the homologues Zr and Hf, [ZrF6]2− and [HfF6]2−; the evaluated formation constant of [RfF6]2− is at least one-order of magnitude smaller than those of [ZrF6]2− and [HfF6]2−.

Multiple molecular simultaneous imaging in a live mouse using semiconductor Compton camera

We have demonstrated the feasibility of semiconductor Compton cameras for multiple molecular imaging in nuclear medicine. The Compton camera used in this work comprises two double-sided orthogonal-strip germanium detectors, and their excellent energy resolution enabled discrimination of the nuclides and accurate determination of the scattering angle for γ rays in wide energy range. Three radioactive tracers of 65ZnCl2, 85SrCl2, and iodinated (131I) methylnorcholestenol were injected to a living mouse and were measured simultaneously. Both two- and three-dimensional images of each tracer were obtained by a fixed-angle imaging with a single Compton camera, which reflected the different in vivo behavior of them.