Adsorbate-substrate bonding and dynamics as determined by SEXAFS

Abstract

A review is given of surface extended X-ray absorption fine structure (SEXAFS) data taken at the N and O K-edges of atomic and molecular adsorbates on Cu and Ni surfaces. The theory of the dynamic analysis of SEXAFS data is briefly presented. We conclude that a dynamic analysis is also necessary in many cases for a reliable structural determination. This result is particularly important in the case of reconstructed surfaces where the structural and dynamic contributions in the SEXAFS amplitude and phase can be of comparable strength. An analysis of the dynamic part of the disorder allows one to distinguish between reconstructed and unreconstructed systems. Furthermore, the use of model pair potentials allows for a discussion of surface reconstruction in terms of simple physical parameters. Finally a short discussion is given of the photon flux and stability required for a state of the art SEXAFS experiment, in view of the availability of the improved third generation soft X-ray sources.