Online Gas Adsorption Chromatography with Tl on Fused Silica for Next-Generation Chemistry Experiments with Nh

Presented here are comprehensive online gas adsorption chromatography experiments with thallium on fused silica surfaces toward an unambiguous chemical characterization of nihonium (Nh, Z = 113). Short-lived ¹⁸⁴Tl (t1/2 = 10.1 ± 5 s), produced in the nuclear fusion-evaporation reaction ¹⁴¹Pr(⁴⁸Ti, 5n)¹⁸⁴Tl, was velocity-separated and introduced into the chemistry setup mounted in the focal plane of the separator. Isothermal gas adsorption chromatography experiments with a fused silica stationary phase at different dehydroxylation stages revealed a strong influence on the yield of transported Tl species. The evaluated adsorption enthalpies of the presumed monohydroxide TlOH of - ΔHadsd-SiO₂(TlOH) = 127 ± 3 kJ/mol (dehydroxylated SiO₂) and -ΔHadsh-SiO₂(TlOH) = 132 ± 12 kJ/mol (hydroxylated SiO₂) agree well with earlier offline experiments. In the case of a dehydroxylated stationary phase, the chemical speciation of Tl shifted from TlOH to less volatile species TlX2 with -ΔHadsd-SiO₂(TlX2) ≥197 kJ/mol. The presented findings highlight the central role of the fused silica stationary phase in order to promote the formation of a defined chemical species of heavy Group 13 elements Tl and potentially Nh. The outcome is compared to state-of-the-art theoretical predictions.