Vibrational study of a combination band and the effects of inhomogeneous broadening: CO on Pt(111)

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Abstract
The combination band of the Pt-CO and the C-O stretch vibrational modes of carbon monoxide chemisorbed on a Pt(111) surface has been studied by infrared spectroscopy. The width of this combination band is much larger than the sum of that of the two fundamental modes. By studies of the width of the C-O stretch mode in the dilution limit of isotopic mixtures, it is found that the effects from surface imperfections are negligible. This indicates that the large width of the combination band at low temperatures is caused by the dispersion of the C-O stretch mode and at high temperatures by inhomogeneous broadening.