BONDING ON SURFACES - THE SEXAFS POINT-OF-VIEW

The temperature dependent Surface EXAFS of O and N on Ni(100) and O on Cu(100) is analyzed. The first moments of the Pair Distribution Funct ion (PDF) are determined, including anharmonic contributions. From a s ystematic analysis of the pair potentials it is proposed that for the reconstructed surfaces the bond is more covalent, for the unreconstruc ted ones more ionic. The value of the charge transfer to the adatom is found to be approximately 0.63 electrons for the ionic cases. Upon th e reconstruction of the Cu(100) surface the static part of the disorde r is found to increase. The dissociation process Of O2 molecules on Cu (100) is studied. The -differences in the PDF moments between the diff erent adsorption states are shown to correlate to the strength of chem isorption.