CO VIBRATIONS ON A STEPPED NI SURFACE

Electron energy loss spectra (ELS) have been measured after CO adsorption on the stepped Ni[5(111) × (11̄0)] surface as function of substrate temperature and CO exposure. At 150 K and exposures below 0.5 L, only adsorption sites close to the step edges are occupied. Pronounced rearrangements of CO molecules over terrace sites occur by increasing the temperature to 300 K. The occupation of special step sites gives rise to an exceptionally low frequency C-O stretching vibration of 1520 cm-1. This frequency indicative of a weakened C-O bond is correlated with the previously found tendency for CO decomposition to occur on this surface during a flash desorption experiment. © 1979.