J. Phys. IV France
Volume 7, Numéro C2, Avril 1997
Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure
Page(s) C2-469 - C2-470
Proceedings of the 9th International Conference on X-Ray Absorption Fine Structure

J. Phys. IV France 7 (1997) C2-469-C2-470

DOI: 10.1051/jp4/1997058

New Opportunities in the Soft X-Ray Absorption to Characterize the Adsorbate Bonding

K. Babersehke, H. Wende, P. Srivastava and R. Chauvistré

Institut für Experimentalphysik, Freie Universität Berlin, Arnimallee 14,14195 Berlin, Germany

One of the important applications of XAS in the soft X-ray regime is the ability to measure the EXAFS of light elements, like carbon, nitrogen, etc. up to sulfur and chlorine. These elements, adsorbed on metal surfaces, are the most important constituents for the investigation of gas-metal interactions. One decade ago, the surface EXAFS "world was harmonic", the nearest neighbor distances were determined within the harmonic approximation, R did not change with temperature, and the coordination number N was determined from measurements at a single temperature. Recently, SEXAFS data were taken as a function of T and at various angles of X-ray incidence. This advance, in combination with multiple scattering analysis and full simulation computer codes, allows to routinely determine the pair distribution function up to the third moment. We relate in general terms the Einstein temperature, the local static disorder and thermal expansion to the ionic versus covalent bonding, shape of effective pair potentials and adsórbate induced surface reconstruction. Furthermore, these low Z systems are ideal candidates to detect unambiguously the photoelectron backscattering by interstitial charge densities (AXAFS).

© EDP Sciences 1997