Berlin 2005 – wissenschaftliches Programm
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O: Oberflächenphysik
O 15: Postersitzung (Adsorption an Oberfl
ächen, Epitaxie und Wachstum, Organische Dünnschichten, Oxide und Isolatoren, Rastersondentechniken, Zeitaufgelöste Spektroskopie, Methoden)
O 15.3: Poster
Freitag, 4. März 2005, 17:00–20:00, Poster TU D
Interaction of Formic Acid with Surfaces of Solid Water between 80 and 200K — •S. Bahr1, O. Höfft1, A. Borodin1, V. Kempter1, F. Borget2, T. Chiavassa2, and A. Allouche2 — 1Institut für Physik und Physikalische Technologien, TU Clausthal, Leibnizstr. 4, D–38678 Clausthal–Zellerfeld — 2Physique des Interactions Ioniques et Moléculaires, CNRS-UMR6633 Université de Provence, Campus St. Jérôme, Marseille France
The interaction of formic acid (HCOOH) with solid water, deposited on tungsten at 80K, was studied witch metastable impact electron spectroscopy (MIES), UPS(HeI and II), IR-Spectroscopy and TPD. In MIES and UPS the emission from the outermost 1b1, 3a1, 1b2 MOs of water and the weakest–bonded π– and σ–type MOs of formic acid (FA) were monitored. The results are interpreted witch the help of cluster DFT calculations. FA/water interfaces were prepared at 80K, namely FA layers on thin films of solid water and H2O adlayers on thin FA films; they were annealed between 80 and 200K. It is concluded that an H–bonded FA–network forms on the solid water surface, suggesting that the lateral interaction between FA species is stronger that between FA and water. In the entire studied temperature range the FA species remain in the surface layer although a partial solvation takes place above 120K. After the desorption of water (155K TPD peak maximum), weak features of FA can be seen up to about 170K. Under the studied conditions no de–protonation of FA can be detected. Results for the deposition for H2O on FA films at 80K will also be presented.