Fermi resonance coupling in a surface adsorbate: The C–H stretch in methoxy adsorbed on Cu(100) calculations and experiments

The C–H stretch spectrum of methoxy adsorbed on Cu(100) has been measured using Fourier transform infrared spectroscopy. Fermi resonance coupling constants in methoxy are calculated using a normal mode model where the unperturbed modes were either experimentally determined or inferred from ab initio calculations performed for a methoxy-Mo model complex. The measured frequency shifts and intensity redistribution observed in the C–H stretch region are qualitatively reproduced by the calculations.