[en] A gas-jet transport system has been coupled to the RIKEN gas-filled recoil ion separator GARIS to startup superheavy element (SHE) chemistry at RIKEN. The performance of the system was appraised using an isotope of element 104, ²⁶¹Rf, produced in the ²⁴⁸Cm(¹⁸O,5n)²⁶¹Rf reaction. Alpha-particles of ²⁶¹Rf separated with GARIS and extracted to a chemistry laboratory were successfully identified with a rotating wheel apparatus for α spectrometry. The setting parameters such as the magnetic field of the separator and the gas-jet conditions were optimized. The present results suggest that the GARIS/gas-jet system is a promising approach for exploring new frontiers in SHE chemistry: (i) the background radioactivities of unwanted reaction products are strongly suppressed, (ii) the intense beam is absent in the gas-jet chamber and hence high gas-jet efficiency is achieved, and (iii) the beam-free condition also allows for investigations of new chemical systems.

No abstract available

[en] The decay properties of ²⁶⁴Hs and ²⁶⁵Hs produced in the ^207,208Pb(⁵⁸Fe,xn) (x=1,2) reactions were studied using a gas-filled recoil ion separator at the linear accelerator facility of RIKEN. A total of six decay chains were assigned to ²⁶⁴Hs. The cross sections of ²⁶⁴Hs produced in the ²⁰⁸Pb(⁵⁸Fe,2n) and ²⁰⁷Pb(⁵⁸Fe,n) reactions were measured to be 2.8_-2.3^+6.5 and 6.9_-3.1^+4.4 pb, respectively. The isotope ²⁶⁴Hs decayed by α-particle emission (five events) and spontaneous fission (one event). The α-particle energy of ²⁶⁴Hs was observed at 10.61 ± 0.04 and 10.80 ± 0.08 MeV. (author)

[en] 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. (author)

[en] We report on the characteristic anion-exchange behavior of the superheavy 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. (author)

[en] 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 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 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. (author)