Berlin 2005 – scientific programme
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O: Oberflächenphysik
O 54: Adsorption an Oberfl
ächen VI
O 54.9: Talk
Wednesday, March 9, 2005, 12:45–13:00, TU EB202
Adsorption isotherms and capillary waves of molecularly thin liquid films - an x-ray reflectivity study — •Michael Paulus1, Christian Gutt2, Michael Sprung3, Christoph Krywka1, and Metin Tolan1 — 1Experimentelle Physik I, Universität Dortmund, Maria-Goeppert-Mayer Str. 2, 44227 Dortmund — 2Department of Physics 0350, University of California, San Diego, 9500 Gilman Drive, La Jolla, CA 92093-0350, USA — 3c/o 8ID/IMMY-XOR-CAT, APS/ANL, Argonne, IL, 60439, USA
We present an x-ray reflectivity study of molecularly thin films of liquid iso-butane adsorbed on bulk liquid glycerol. The glycerol-isobutan interface serves as a model system to study the influence of the substrate-adsorbate interactions on both adsorption isotherms and capillary wave fluctuations. The low condensation pressure of isobutane (approximately 1.6bar at 288K) allows to adsorb thin liquid isobutane layers on the glycerol surface. The layer thickness is adjustable between monolayer coverages and 2-3 nm by varying the gas pressure at constant temperature. A special sample cell has been designed which guarantees the high degree of pressure and temperature stability needed for these experiments. From the x-ray reflectivity data film thickness and the capillary wave induced surface roughness as a function of pressure have been determined. A strong coupling between the first monolayers of isobutan and the glycerol surface leads nearly to a complete suppression of capillary waves in the monolayer.