Reactivity of oxidized polonium towards quartz and α-Al₂O₃ surfaces

The chemistry of the radioelement polonium has attracted increasing attention owing to its formation in accelerator-driven systems and its high radiotoxicity. Being the lighter homologue of the superheavy element livermorium, whose chemistry is still unexplored, studies of polonium provide a benchmark for verifying the structure of the periodic table at the heavy-element frontier. While the reactivity of elemental polonium towards various surfaces in inert or reducing atmospheres has been investigated previously, the reactivity of oxidized polonium towards quartz has not been explored in detail. Here, we report on gas-solid thermochromatography studies of polonium on quartz glass and α-Al₂O₃ surfaces in helium, as well as in oxygen- and water-containing atmospheres in the atom-at-a-time regime. We found that polonium chemically reacts in an oxygen-containing atmosphere, forming two oxidized species, which are less volatile than elemental polonium. The chemical reaction is influenced by the water vapour concentration in the carrier gas and the applied temperature. The adsorption enthalpy of elemental polonium on α-Al₂O₃ in pure helium gas was determined to be -85+4-3 kJ mol^-1, which is identical to the adsorption enthalpy on quartz as reported earlier. The results of the reported measurements will support future experiments with the superheavy element livermorium.