Berlin 2008 – wissenschaftliches Programm
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O: Fachverband Oberflächenphysik
O 36: Surfaces and Films: Forces, Structure and Manipulation
O 36.7: Vortrag
Dienstag, 26. Februar 2008, 15:45–16:00, MA 041
Single crystal microcalorimetry: Measuring molecule-surface interactions — •Jan-Henrik Fischer1, Jason Farmer2, Jens Hartmann1, Swetlana Schauermann1 und Hans-Joachim Freund1 — 1Fritz-Haber-Institut der Max-Planck-Gesellschaft, Berlin — 2Department of Chemistry, University of Washington, Seattle
Determination of the strength of adsorbate-surface interaction is an important fundamental issue in surface science and an essential prerequisite for understanding real catalytic processes. The strength of adsorbate-surface bonding and of lateral adsorbate-adsorbate interactions can be addressed by measurement of heats of adsorption as a function of surface structure, coverage and presence of other co-adsorbates.
Traditional experimental techniques for probing the energetics of adsorption, such as e.g. thermal desorption spectroscopy, provide reliable results only for reversible adsorption systems and cannot be correctly applied for processes including dissociation, clustering, diffusion into the bulk or reaction with other coadsorbates. These restrictions can be overcome by using a direct calorimetric measurement of adsorption energies on surfaces. For this purpose we set up a new microcalorimetry experiment at Fritz-Haber-Institut, which is based on a method previously developed by King and Campbell [1]. The method relies on the measurement of a temperature change upon adsorption of gaseous molecules on ultrathin (1−10 µ m) single crystals, which is realized by application of a pyroelectric detector and an independent laser-based energy calibration.
[1] Campbell et al., Rev. Sci. Instr. 75, 11 (2004)