Ethene adsorbed on Cu(110): A combined photoemission and photoelectron diffraction study

The adsorption geometry of ethene on Cu(110) has been investigated using photoelectron diffraction (PhD) in the scanned energy mode as well as angle-resolved valence level photoemission. Two best fit PhD geometries have been found, both of which are compatible with the photoemission data: the molecule is adsorbed either in an atop site on the close-packed Cu rows at a perpendicular height of 2.08+/-0.02 Angstrom with a C-C bond length of 1.32+/-0.09 Angstrom, or in a short bridge site on the Cu rows at a perpendicular height of 2.09+/-0.02 Angstrom with a C-C bond length of 1.53+/-0.13 Angstrom. In each case the molecular plane is parallel to the surface, but the C-C axis can be twisted azimuthally out of the [1(1) over bar0$] direction by as much as 24 degrees.