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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.

In fusion reactions of 4~ with isotopes of Ho, Tm, Yb, Lu, Hf and Ta, cross sections for the production of proton-rich evaporation-residues near the 126 neutron shell were measured. This first comprehensive study of very fissile spherical residues reveals a surprisingly low stabilizing influence of the spherical N=126 shell on the survival probability. The experimental results are compared with evaporation calculations. Conclusions for the production of superheavy nuclei are drawn.

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