Reactivity of polonium towards quartz surfaces

Beyond the (quasi)stable and abundant elements lead and bismuth, all elements are radioactive, with polonium being the first of a series of radioelements up to primordial uranium. Interest in understanding its chemical behavior is increasing, not least due to its co-production in accelerator-driven systems and high radiotoxicity. Polonium is also the lighter homologue of the superheavy element livermorium, which has not been studied chemically to date. Polonium therefore acts as a benchmark to verify the structure of the periodic table at the heavy-element frontier. Here, we report on gas-solid thermochromatography studies of polonium in the atom-at-a-time regime under helium and hydrogen gas atmospheres. Quartz surfaces with different degrees of hydroxylation were used as a stationary phase. On quartz glass with low OH-concentrations, a volatile species interacting with an adsorption enthalpy of -85+3-2 kJ mol^-1 was found and assigned to elemental polonium. On more highly hydroxylated quartz glass, an additional deposition zone due to a species with an adsorption enthalpy of -139+6-5 kJ mol^-1 was observed and attributed to a polonium species formed by chemical reactions with the surface. Under our experimental conditions, chemical reactions of polonium in the solid phase dominate over reactions in the gas phase. Thus, the nature of the surface should be considered as an important parameter in future gas chromatography studies.