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Chemical studies of the transactinide elements at JAEA
Y. Nagame
Advanced Science Research Center, Japan Atomic Energy Agency (JAEA)
Tokai, Ibaraki 319-1195, Japan
Studies on the chemical properties of the transactinide elements (Z  104) offer unique opportunities
to obtain information about trends in the periodic table of the elements at the limits of nuclear stability, and
to assess the magnitude of the influence of relativistic effects on chemical properties. From the calculations
of electron configurations of heavier elements, it is predicted that sudden changes in the structure of
electron shells may appear due to relativistic effects which originate from the increasingly strong Coulomb
field of the highly charged atomic nucleus. Thus, it is expected that heavier elements show a drastic
rearrangement of electrons in their atomic ground states, and as electron configurations are responsible for
chemical behavior of elements, such relativistic effects can lead to surprising chemical properties.
Increasing deviations from the periodicity of chemical properties based on extrapolation from lighter
homologues in the periodic table are consequently predicted.
The transactinide elements must be produced at accelerators using reactions of heavy-ion beams with
heavy target materials and must be identified by measurement of their decay or that of their known
daughter nuclei with unambiguous detection techniques. Both half-lives and production rates of nuclides of
heavier elements are rapidly decreasing, and so each atom produced decays before a new atom is
synthesized. This means any chemistry to be performed must be done on an "atom-at-a-time" basis.
To verify experimentally the influence of relativistic effects of electron shell structure, we are
studying chemical properties of the transactinide elements. The transactinide element, rutherfordium (Rf:
element 104), 261Rf (T1/2 = 68 s) was produced via the reaction of 248Cm(18O,5n) using the JAEA tandem
accelerator. The evaluated production cross section was about 10 nb, indicating that the production rate
was approximately 2 atoms per min. From the systematic study of chemical properties of Rf, it has been
found that the chemical behavior of Rf is quite similar to that of the group-4 elements in the periodic table,
Zr and Hf; the results show that Rf is the member of the group-4 elements. However, we have observed
unexpected chemical behavior of Rf. The fluoride complex formation of Rf is quite different from those of
the homologues Zr and Hf, which suggests the influence of relativistic effects on the fluoride complex
formation of Rf. In this report, the atom-at-a-time chemistry of Rf at JAEA is presented.
The present study has been carried out in collaboration with RIKEN, Niigata University, Osaka
University, Tokyo Metropolitan University, University of Tokushima, Kanazawa University, Tsukuba
University, Gesellschaft für Schwerionenforschung (GSI), and University of Mainz.