Dr. Thorsten Bartels-Rausch

This line of research deals with the characterization of the hydrogen-bonding network structure of adsorbed water at the surface of environmentally relevant mineral surfaces by Near Ambient Pressure X-ray excited electron spectroscopy at the Swiss Light Source of PSI (SLS). The studies revealed liquid-like features of adsorbed water at sub-freezing temperatures with an impact on the ability to act as ice nuclei and to drive atmospheric chemistry. A unique feature of the SLS endstation is the precise temperature (80°C to -80°C) and water vapor pressure (up to 6 mbar) regulation allowing to probe any condition in the phase diagram of aerosol and ice.

Taking full advantage of surface-sensitive X-ray absorption spectroscopy and X-ray photoemission spectroscopy at near ambient pressure, this research has provided direct experimental evidence on how acidic trace gases, such as HCl, modify the hydrogen bonding network at the ice surface. The evolving picture is that acidic trace gases form liquid-like solvation shells in an elsewise ice-like interfacial region upon adsorption. This finding raises open questions on the impact of photochemistry and heterogeneous chemistry at the interfacial region of ice and snow in the environment, given the importance of multiphase chemistry of snow and ice clouds for Earth’s geochemical cycles and climate system. 

Research over the past decades has provided an impressive observational basis for large scale effects of multiphase chemistry in snow, such as substantial modification of the composition and of the chemical reactivity of the lowermost atmosphere in polar regions and the ability of toxins to enter the marine food web. This fundamental laboratory based research investigates the chemical reactivity of solutes and reactants embedded at different locations in snow. Questions tackled are the impact of complex composition, of microphysical properties, and of phase changes on the reactivity. In cooperation with the Schneebeli group in Davos, we further investigated how snow metamorphism influences multiphase chemistry at snow surfaces. 

I contribute to developing  X-ray excited electron spectroscopy for atmospheric research at the  ISS endstation at the Swiss Light Source. The approach is to bring our established know-how in dosing and detecting atmospheric trace gases to this Near Ambient Pressure Photoemission facility. This development work also includes going further in open and fair data management by establishing FAIR data processing routines and workflows for the above research and by introducing ETH's data management system openBIS to PSI.