FTIR OVERTONE SPECTROSCOPY ON SURFACES - THE C-O MODE IN CHEMISORBED METHOXY ON NI(111)

We report the observation of a vibrational overtone for an adsorbate o n a single crystal surface by high-resolution vibrational spectroscopy . A very weak absorption band at 2017 cm-1 is identified as the first overtone of the C-O stretching fundamental (at 1027 cm-1) of CH3O-Ni ( 111). The anharmonic shift in the absence of dipole-dipole coupling an d mechanical renormalization is determined to be 8.5 +/- 2 cm-1, sligh tly smaller than that of the C-0 stretching vibration in methanol, 12. 5 cm-1. Surprisingly, no C-O bond weakening is found in CH3O-Ni (111) compared to gas-phase methanol.