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O: Fachverband Oberflächenphysik

O 48: Poster Session IV: Surface dynamics II: Phase transitions and elementary processes

O 48.5: Poster

Dienstag, 2. März 2021, 13:30–15:30, P

Interfacial phase transition in multiphase systems of environmental relevance — •Thorsten Bartels-Rausch, Xiangrui Kong, Fabrizio Orlando, Luca Artiglia, Astrid Waldner, Thomas Huthwelker, and Markus Ammann — Paul Scherrer Institut, Villigen PSI, Switzerland

Laboratory experiments are presented on the phase change at the surface of sodium chloride - water mixtures at temperatures between 259 K and 240 K. A high selectivity to the upper few nanometres of the frozen solution - air interface is achieved by using electron yield near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. We find that sodium chloride at the interface of frozen solutions, which mimic sea-salt deposits in snow, remain as supercooled liquid down to 240 K. Below this temperature, hydrohalite exclusively precipitates, anhydrous sodium chloride is not detected. In this work, we present the first NEXAFS spectrum of hydrohalite.

Experiments were performed at the PHOENIX beam line of the Swiss Light Source (SLS) at the Paul Scherrer Institute using the Near Ambient Pressure Photoemission (NAPP) set-up. In this work, we focus on the sample environment an in particular the ability to accurately monitor and set temperature and partial pressure of water. The importance of precise knowledge the trajectories, or history of, relative humidity and temperature that the sample have been exposed to are discussed.