AVS 53rd International Symposium
    Surface Science Tuesday Sessions
       Session SS2-TuA

Paper SS2-TuA8
Adsorption and Desorption Kinetics on a Porous Solid: N@sub 2@ on Amorphous Solid Water

Tuesday, November 14, 2006, 4:20 pm, Room 2004

Session: Water-Surface Interactions on Metals
Presenter: T. Zubkov, Pacific Northwest National Laboratory
Authors: T. Zubkov, Pacific Northwest National Laboratory
T.R. Engstrom, University of Texas at Austin
R.S. Smith, Pacific Northwest National Laboratory
B.D. Kay, Pacific Northwest National Laboratory
Correspondent: Click to Email
Desorption of a weakly bound adsorbate from a porous solid was studied for the case of molecular nitrogen on amorphous solid water (ASW). Porous ASW films of different thickness were grown on Pt(111) by ballistic deposition. N@sub 2@ adsorption and desorption kinetics were monitored mass-spectrometrically. Temperature programmed desorption spectra show that with the increasing film thickness, the N@sub 2@ desorption peak systematically shifts to higher temperatures. The results are explained and quantitatively reproduced by a simple model, which assumes that the N@sub 2@ transport within the film is faster than the depletion rate to vacuum. The local coverage at the pore mouth determines the desorption rate. For thick ASW films (>1 µm), the assumption of the fast equilibration within the film is shown to be no longer valid due to diffusion limitations. The mechanisms of the adsorbate transport are discussed.* @FootnoteText@ *Pacific Northwest National Laboratory is operated by Battelle for the U.S. Department of Energy.