Studies of the halide complexation of element 105 in aqueous solution were performed on 34-s 262 Ha produced in the 249 Bk( ls O,5n) reaction. The 262 Ha was detected by measuring the fission and alpha activities associated with its decay and the alpha decays of its daughter, 4.3-s 258 Lr. Time-correlated pairs of parent and daughter alpha particles provided a unique identification of the presence of 262 Ha. About 1600 anion exchange separations of 262 Ha from HCl and mixed HC1/HF solutions were performed on a one-minute time scale. Reversed-phase micro-chromatographic columns incorporating triisooctyl amine (TIOA) on an inert support were used in the computer-controlled liquid chromatography apparatus, ARCA II. -.

The microcomputer controlled Automated Rapid Chemistry Apparatus, ARCA, is described in its newly designed version for the study of chemical properties of element 105 in aqueous solutions. This improved version, ARCA II, is adapted to the needs of fast and repetitive separations to be carried out in a chemically inert automated micro high performance liquid chromatography system. As an example, the separation of several group HIB, IVB, and VB elements in the system triisooctylamine/hydrochloric acid within 30 s is demonstrated. Furthermore, a new method for the fast preparation of samples for α-particle spectroscopy by evaporation of the aqueous effluent with an intense light source is presented.

A new nuclide 'Ha was produced in the bombardment of a Bk target with 93-MeV "0 ions. It was detected via spontaneous fission counting and was shown to have a half-life of about 0.5 min. This activity was also separated from the reaction products by automated rapid chemical separations using cation-exchange chromatography in 0.05M a-hydroxyisobutyric acid. After chemical separation, ' 'Ha was found to decay by spontaneous fission (57+i'd%) and by a emission (E =8.35 MeV, 43%) with a half-life of 27+7 s. The spontaneous fission fragment energy spectrum is compatible with an average total kinetic energy of about 200 MeV.PACS number(s): 23.90.+w, 25.70.Jj, 25.85.Ca, 27.90.+b

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Previous studies of the halide complex formation of element 105 and its anion exchange with triisooctyl amine (TIOA) were continued. The experiments were performed on a one-minute time scale with the computer-controlled liquid chromatography system ARCA II on a mixture of 34-s 262 Ha and 27-s 263 Ha produced in the 249 Bk( 18 0,5n) and 249 Bk( 18 0,4n) reactions at a beam energy of 99 MeV. The Ha isotopes were detected by measuring the spontaneous fission and α-activities associated with their decay, and the α-decays of their daughters, 4-s 258 Lr, and 6-s 259 Lr. Time-correlated pairs of parent and daughter α-particles were also registered. 262,263 Ha was absorbed on the TIOA columns from either 12 M HCl/0.01 M HF or 10 M HCl, and was subsequently eluted in 0.5 M HCl/0.01 M HF like its homolog niobium, and the pseudohomolog protactinium, and unlike the closest homolog, tantalum, which remains in the amine phase under these conditions. The effluent was divided into an early Pa fraction and a subsequent Nb fraction. By varying the cut between the Pa fraction and the Nb fraction in rough steps, it was shown that the elution of element 105 occurs closer to the Pa elution position, i.e., earlier than the elution of Nb. These results confirm the non-tantalum like behavior of element 105 in 0.5 M HCl/0.01 M HF, and corroborate previously suggested structural differences between the halide complexes of element 105, niobium, and protactinium, on the one hand, and those of tantalum on the other hand.

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Production cross sections for targetqike transfer products in reactions of 4~ with 233,235,238 U at the barrier were determined using radiochemical techniques. The heaviest products detected are isotopes of californium (Z= 98). In addition to the quasi-elastic component of the isotopic distributions observed in the vicinity of uranium, there are also relaxed contributions throughout the entire region. The peak positions of the isotope distributions of this component for fixed atomic number, after the transfer of > 3 charges, approach closely the minimum of the potential energy surfaces (PES). The experimental results thus indicate the cold formation of the reaction products. A search for long-lived heavy actinides produced, by fusion-evaporation, via isotopes of element 110 and their subsequent decay through e-decay chains, remained unsuccessful at a cross section limit of 21 pb.