a Near Edge X Ray Absorption Fine Structure Spectroscopy Study of the Structure and Bonding of Small Molecules and Reactive Intermediates on Silver and Carburized Tungsten Surfaces.
CO bonds with its bond axis normal to the surface with a bond length of 1.13 A on W(100)-(5 times 1)-C. The perturbed nitrile intermediate of HCN/W(100) -(5 times 1)-C bonds with its C-N axis parallel to the surface. The C-N bond has a length of 1.39 A indicating that the bond has undergone significant rehybridization. The C-N bond of the HCNH intermediate is also rehybridized with a bond length of 1.34 A. Its C-N axis is inclined at an angle of 60^ circ from the surface normal. C_2 H_2 and CH_3 CN are bound parallel to the surface and are unrehybridized on Ag(110). Two distinct C_2 intermediates are found with bond lengths of 1.27 and 1.39 A. Their C-C bond axes are parallel to the surface and aligned along the close-packed direction. For CH_2CN bond lengths of 1.49 and 1.11 A are determined for the C-C and CequivN bonds which are parallel to the surface and perpendicular to the close-packed direction on Ag(110). There is evidence of pi -donation from the pi orbital with p-lobes perpendicular to the surface. HCOO is bonded with its molecular plane randomly oriented azimuthally on Ag(110). The data is explained with a static tilt of the molecular plane at 30^circ from the surface normal or an oscillation of the molecular plane about the surface normal with a displacement of 50^ circ. These results suggest that the finite tilt angles determined for other species be reevaluated with a dynamic model of the bonding.
- Pub Date:
- Physics: Molecular; Physics: Condensed Matter