Online chemical adsorption studies of Hg, Tl, and Pb on SiO₂ and Au surfaces in preparation for chemical investigations on Cn, Nh, and Fl at TASCA

Abstract

Online gas-solid adsorption studies with single-atom quantities of Hg, Tl, and Pb, the lighter homologs of the superheavy elements (SHE) copernicium (Cn, Z=112), nihonium (Nh, Z=113), and flerovium (Fl, Z=114), were carried out using short-lived radioisotopes. The interaction with Au and SiO2 surfaces was studied and the overall chemical yield was determined. Suitable radioisotopes were produced in fusion-evaporation reactions, isolated in the gas-filled recoil separator TASCA, and flushed rapidly to an adjacent setup of two gas chromatography detector arrays covered with SiO2 (first array) and Au (second array). While Tl and Pb adsorbed on the SiO2 surface, Hg interacts only weakly and reached the Au-covered array. Our results contribute to elucidating the influence of relativistic effects on chemical properties of the heaviest elements by providing experimental data on these lighter homologs.

First Study on Nihonium (Nh, Element 113) Chemistry at TASCA

“…Due to the small α -decay branches of the produced Tl isotopes, no quantitative evaluation of the chemical yield for Tl was possible. However, the chemical yield estimated for Tl should not exceed that of Pb ( Lens et al, 2018 ).…”

“…Prior to the Nh chemistry experiment at GSI, adsorption studies of the non-volatile metals Tl and Pb and the volatile metal Hg were performed behind TASCA with a setup similar to that shown in Figure 1C , using a SiO 2 -covered and a Au-covered detector array ( Lens et al, 2018 ). Short-lived Tl and Pb isotopes were produced in nuclear fusion reactions with 50 Ti or 48 Ca ion beams bombarding 141 Pr and 144 Sm targets, respectively.…”

“…Reaction products were separated in TASCA, and thermalized inside the RTC. The diffusion-controlled deposition of both Tl and Pb was observed in the first SiO 2 detector channel, whereas Hg passed the first detector array and adsorbed on Au ( Lens et al, 2018 ). A diffusion-controlled deposition was observed in both detector arrays: for Pb and Tl isotopes on the SiO 2 detector surface and for Hg isotopes on the Au detector surface.…”

“…A diffusion-controlled deposition was observed in both detector arrays: for Pb and Tl isotopes on the SiO 2 detector surface and for Hg isotopes on the Au detector surface. A lower limit of the adsorption enthalpy of −ΔH ads ≥ 67 kJ/mol ( Lens et al, 2018 ) was determined for Tl and Pb on a SiO 2 surface and for Hg on a Au surface through Monte Carlo (MC) simulations using the mobile adsorption mechanism ( Zvára, 1985 ). A transport efficiency from the RTC into the Cryo Online Multidetector for Physics And Chemistry of Transactinides (COMPACT) of 25% was obtained for Pb isotopes, while 62% was found for the less reactive Hg ( Lens et al, 2018 ).…”

“…A lower limit of the adsorption enthalpy of −ΔH ads ≥ 67 kJ/mol ( Lens et al, 2018 ) was determined for Tl and Pb on a SiO 2 surface and for Hg on a Au surface through Monte Carlo (MC) simulations using the mobile adsorption mechanism ( Zvára, 1985 ). A transport efficiency from the RTC into the Cryo Online Multidetector for Physics And Chemistry of Transactinides (COMPACT) of 25% was obtained for Pb isotopes, while 62% was found for the less reactive Hg ( Lens et al, 2018 ). This difference points at larger adsorption losses inside the RTC and the connecting tube for Pb compared to Hg.…”