The Raman spectrum of carbon monoxide chemisorbed on silica-supported nickel

The Raman spectrum of carbon monoxide chemisorbed on silica-supported nickel has been investigated at pressures below 10 Torr. Two ν(CO) stretching vibrations are found and assigned to linearly and bridge-bonded CO molecules, respectively. With decreasing pressure a frequency shift from 2100 to 2065 cm−1 is observed for the linear species and from 1940 to 1770 cm−1 for the bridge-bonded species. At lower wavenumbers several bands are found, which are assigned to ν(NiC) stretching vibrations of the two chemisorbed species located on different lattice sites. The observed frequency of the δ(NiCO) deformation vibration agrees well with calculations based on the evaluation of electron energy loss spectroscopy data. For the assignment of the vibrational bands, an FG matrix calculation has been carried out.