Condensed phase matter in the atmosphere is of paramount importance for hydrology, biogeochemical cycles, climate, ecosystems and human health. Ice in snow and cirrus clouds, aqueous solutions in aerosol particles and clouds, and salt, organics and mineral oxides in other particulate matter suspended in the air are some examples. Increased interest about chemical and physical processes at or near the condensed phase – air interface has led to in situ techniques capable of probing relevant surfaces at the molecular scale (at depths of a few nanometer at most) and the interior of atmospheric particles with submicron resolution. Atmospheric material properties are a strong function of the water vapor partial pressure in the mbar range, while most chemically relevant trace gases are in the 10-6 mbar range and below. Therefore, in situ techniques must provide chemical selectivity and either sensitivity for the surface or high spatial resolution, while at the same time being able to cope with a high water vapor pressure. For the purpose of addressing interfacial chemistry we have recently developed an in situ cell for ambient pressure X-ray photoelectron spectroscopy (AP-XPS) to study the interaction of trace gases with ice, mineral oxides and aqueous solutions that allows equilibrating these materials at relevant relative humidity and at the same time features fast response times to sticky trace gases. For the purpose of addressing the internal physical and chemical structure of aerosol particles, we have used an environmental cell in conjunction with scanning transmission X-ray microspectroscopy (STXM) to investigate the behavior of authentic and proxy aerosol particles in response to chemical or photochemical stimuli that induce changes in morphology and chemical composition. Recent results obtained with both techniques will be presented.
Alpert, P. A., Ciuraru, R., Rossignol, S., Passananti, M., Tinel, L., Perrier, S., Dupart, Y., Steimer, S. S., Ammann, M., Donaldson, D. J., and George, C.: Fatty Acid Surfactant Photochemistry Results in New Particle Formation, Scientific Reports, 7, 12693, 2017.
Artiglia, L., Edebeli, J., Orlando, F., Chen, S., Lee, M.-T., Corral Arroyo, P., Gilgen, A., Bartels-Rausch, T., Kleibert, A., Vazdar, M., Andres Carignano, M., Francisco, J. S., Shepson, P. B., Gladich, I., and Ammann, M.: A surface-stabilized ozonide triggers bromide oxidation at the aqueous solution-vapour interface, Nature Communications, 8, 700, 2017.
Kong, X., Waldner, A., Orlando, F., Artiglia, L., Huthwelker, T., Ammann, M., and Bartels-Rausch, T.: Coexistence of Physisorbed and Solvated HCl at Warm Ice Surfaces, The Journal of Physical Chemistry Letters, 4757-4762, 2017.