THE ADSORPTION OF PYRIDINE AT CLEAN, OXIDIZED AND HYDROXYLATED CU(111) SURFACES

The adsorption of pyridine at clean, partially oxidised and hydroxylated Cu(111) surfaces has been investigated by X-ray photoelectron and vibrational electron energy loss spectroscopies. At the clean surface at 190 K adsorption is molecular, desorption occurring by 240 K. The VEEL spectra indicate that under these conditions the molecule adsorbs with its C-2 axis parallel to the surface. In contrast in the presence of chemisorbed oxygen pyridine desorption does not occur until ca. 370 K, and the C-2 axis of the molecule is found to be perpendicular to the surface. XP spectra suggest that pyridine interacts directly with the surface oxygen rather than the metal cation, forming a species analogous to a pyridine oxide.