Vacuum Chromatography of Tl on SiO₂ at the Single-Atom Level

An isothermal vacuum chromatography setup for superheavy element chemistry studies was developed and tested online at the one-atom-at-a-time level. As a model system, the adsorption behavior of thallium on quartz was chosen with respect to a future chemical characterization of its superheavy homologue, element 113 (E113, Z = 113), using the described setup. Short-lived ¹⁸⁴Tl (t_1/2 = 10.1(5) s) was produced in the reaction ¹⁵²Gd(³⁵Cl, 3n)¹⁸⁴Tl and delivered as a mass-separated ion beam to the chemistry experiment: A subsurface implantation and a subsequent fast thermal release from a metal matrix was followed by isothermal vacuum chromatography as the chemical separation stage. Single atomic species passing this chromatographic separation were finally identified by time- and energy-resolved event-by-event α-spectroscopy using a diamond-based solid-state detector. The derived adsorption enthalpy of -ΔH_ads^SiO2(Tl) = 158 ± 3 kJ·mol^-1 significantly exceeds available data but correlates well with the adsorption of other elements studied on the same surface. The described technique enables chemical experiments with short-lived transactinide elements (t_1/2 < 1 s), surpassing the rapidity of today's state-of-the-art gas-phase experiments by at least 1 order of magnitude. (Figure Presented).