Interaction of alkali halides and organic molecules with amorphous solid water

COMP 378

S. Bahr, stephan.bahr@tu-clausthal.de, O. Höfft, oliver.hoefft@tu-clausthal.de, and V. Kempter, v.kempter@pe.tu-clausthal.de. Institut für Physik und Physikalische Technologien, TU Clausthal, Leibnizstr. 4, 38678 Clausthal-Zellerfeld, Germany
Surface segregation is studied by a combination of MIES, UPS(HeI) and TPD of ASW exposed to alkali halide vapour. The results are compared with MD simulations of the corresponding aqueous salt solutions. Our results provide direct evidence for the presence of iodide at aqueous surfaces, and confirm the structural similarity between ASW and liquid water. For the study of the interaction of benzene and pyridine with ASW, RAIRS was added to the techniques listed above. The orientation of the molecules with respect to ASW is different, reflecting the different bonding interactions, the formation of a pi - hydrogen bond (benzene) and competitive bonding via the nitrogen lone pair (pyridine). For benzene larger exposures induce a tilt of the initially flat first adlayer. As a consequence, molecules from the supporting ice film become embedded into the benzene adlayer.