NEXAFS and EELS study of the orientation of sulfur dioxide on Ag(110)

Abstract

The angular dependence of the b1* resonance in the near-edge X-ray absorption fine-structure (NEXAFS) spectra indicates that the plane of the SO2 molecule is perpendicular to the plane of the surface and perpendicular to the close-packed direction of the Ag(110) surface ([110] azimuth). SO2 forms a π-acceptor bond between the 3b1 molecular orbital of SO2 and the Ag(110) surface, and the b1* resonance corresponds to transitions into the antibonding combination of this π-acceptor bond while still retaining its strong angular dependence on the orientation of the E + (combining right arrow above sign) vector. This antbonding combination lies 531.9 eV above the O(1s) level. Off-specular electron energy loss spectroscopy (EELS) measurements confirm the dipole activity of the observed vibrational modes and show that the C2v axis of the SO2 molecule must be oriented along the surface normal. © 1991 American Chemical Society.