Dresden 2003 – wissenschaftliches Programm

Bereiche | Tage | Auswahl | Suche | Downloads | Hilfe

O: Oberflächenphysik

O 10: Elektronische Struktur II

O 10.8: Vortrag

Montag, 24. März 2003, 16:45–17:00, FOE/ORG

Chemisorption of Xenon on Metals ? — •H. J. Jänsch, P. Gerhard, M. Koch, and D. Fick — Fachbereich Physik, Philipps Universtiät Marburg, 35032 Marburg

The distinction between chemisorption and physisorption is not easily made, as the recent discussion on the state of adsorption of this closed shell atom shows[1]. Xe certainly shows true chemical bonds as in compounds like XeF₂ but also physisorption as in the condensed phase or as adsorbate on diamagnetic molecules. The chemical shift in nuclear magnetic resonance of ¹²⁹Xe is a superb indicator of the bonding situation. Small shifts (0-300 ppm) are typical for physisorption, large shifts (2000-7500 ppm) chemisorption.

We show for the first time NMR experiments on sub monolayer ¹²⁹Xe on a single crystal surface, Ir(111) in this case. The very large shift (≈1400 ppm) and the substantial anisotropy between 0^o and 90^o orientation (≈500 ppm) reveal the very strong chemical nature of the adsorbed state. Two major contributions, Knight shift and proper chemical shift are discussed, with the latter one being dominant. These ground state properties present benchmark spectroscopic data for testing present all electron theories. Supported by the Deutsche Forschungsgemeinschaft (DFG), Bonn.

[1] P. S. Bagus et al., PRL 89(2002)096104; S. Clarke et al. PRB 63(2001)085416; A. E. Bencourt J. Phys.: Condens. Matt. 12(2000)7077.