ADSORPTION OF SO2 ON PD(100) STUDIED BY S-K-EDGE XAFS

Surface structure and an electronic property of SO2 adsorbed on Pd(100 ) were studied by S K-edge NEXAFS, SEXAFS and Sis XPS. The molecule wa s found by the polar-angle dependent NEXAFS to adsorb with the molecul ar plane normal to the Pd(100) surface. This is a clear contrast to th e SO2/Ni(100) case where the molecule lies flat on the surface. From t he peak position of XPS and the pi peak height of the NEXAFS spectra, we can deduce that the amount of the charge transfer from Pd to SOI i s smaller than that from Ni. The SEXAFS analysis indicates that the S atom of the molecule is located at the bridge site and that one O atom also directly interacts with the metal surface. The difference of the adsorbate structure between SO2/Pd and SO2/Ni can be explained in ter ms of chemical bonding between the substrate and SO2.