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

Element 105 / Transition metal group V / Chemical properties / Bromides / Volatility / Gas chromatography AbstractThe retention behavior of volatile bromide molecules of shortlived isotopes of tantalum and element 105 in KCl coated quartz columns was studied using continuous isothermal gas chromatography. HBr and HBr saturated with BBrs vapor were used as reactive gases. The isotopes were produced in the fusion reactions ^°Ne+"" Eu and ^^O + ^^^Bk, respectively. The reaction producta were transported from the accelerator to the chromatography set-up with a gas-jet system using an aerosol with He as carrier gas and KCl as transporting particles. The measured retention times are compared to those of "'Nb bromides from a previous study. The retention times of niobium and tantalum bromides are very similar, in agreement with expectations based on the nearly identical Sublimation enthalpies of NbBrj and TaBr;. For the bromides of element 105, higher retention times are found, indicating a lower volatility of lOSBrs than of NbBrs and TaBrs. On the basis of empirical systematics, a Sublimation enthalpy of 138± 15 kJ/mol can be estimated for 105Br5 from the experimental data.

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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Element 105 / Chemicalproperties / Complexation with OL-hydroxyisobutyrate / Pentavalent oxidation State / Nuclear decay of^^^-^^^Ha AbstractStudies of the complexation of element 105 by unbuffered ahydroxyisobutyric acid (a-HiB) and its elution from strongly acidic cation exchange resin were performed on a mixture of 34-s ^"Ha and 27-s "'Ha produced in the and reactions at a beam energy of 99 MeV. The Ha isotopes were detected by measuring the spontaneous fission and a-activities associated with their decay, and the a-decays of their daughters, 4-s and 6-s ^"Lr. Time-correlated pairs of parent and daughter a-particles were also registered. The experiments were performed on a one-minute time scale with the computer-controlled hquid chromatography system ARCA II. In 0.05 M a-HiB, element 105 was found to be eluted within 4 s from 1.6x8 mm columns together with the pentavalent Nb-, Ta-, and Pa-ions, while tetravalent Zr-and trivalent Eu-ions were strongly retained on the columns. This is independent proof that the most stable oxidation State of element 105 in aqueous Solution is + 5. This very efficient Separation of 262,263^^2 was also used, for the first time, to demonstrate that their a-and spontaneous fission decays can be registered from a «23 um thin aqueous layer in contact with a large-area passivated ionimplanted planar Silicon detector. In addition, the a-HiB separations were instrumental in the successful Identification of the hitherto undiscovered isotope produced at an '®0 beam energy of 93 MeV.

Element 105 / Chemical properties / Halide complex formation / Extraction into a secondary alcohol SummaryStudies of the extraction of element 105 into diisobutylcarbinol (DIBC) from aqueous HBr and HCl solutions wcre performed on "^Ha and "^Ha produced in the "'Bk("0,5n) and reactions at a beam energy of 99 MeV. The Ha isotopes were detected by measuring the fission and a activities associated with their decay and the a-decays of their daughters, 4-s and 6-s ^''Lr. Complete extraction-elution cycles were performed on a one-minute time scale by the computer-controlled liquid chromatography apparatus, ARCA II, using reversed-phase micro-chromatographic columns incorporating DIBC on an inert support. Stimulated by the previously observed similarity of the aqueous-phase chemistry of element 105 to that of niobium and protactinium, the extraction, from concentrated HBr, was followed by the elution of a Nb fraction in 6 M HCl/ 0.0002 M HF, and a Pa fraction in 0.5 M HCl. The number of 262,263j^^ dccays observed in the Nb fraction indicated that less than 45% of the Ha was extracted into DIBC from concentrated HBr. This was confirmed in a series of experiments in which, after the extraction, the DIBC along with all extracted species was stripped from the columns with acetone. It is concluded that, in the present chemical system, the extraction behaviour of element 105 is closer to that of niobium than to that of protactinium. The decreasing extractability from HBr (Pa > Nb > Ha) is likely to be due to an increasing tendency of these Clements to form non-extractable polynegative complex species in concentrated HBr in the sequence Pa < Nb < Ha.