Substrate modification in vibrational shifts induced by C-13 isotopic substitutions in adsorbed ethoxy determined by infrared spectroscopy and ab initio calculations: Cu(100) and W(110)

Vibrational shifts in ethoxy (CH3CH2O-) adsorbed on Cu(100) induced by thre e different C-13 isotopic substitutions are compared with previous experime ntal results for W(110) and ab initio calculations. In the calculations the metal surfaces were represented by a single molybdenum atom. It is demonst rated that even such a simple model is a significant improvement on the fre e ethanol molecule when determining vibrational shifts for the Cu(100) surf ace. The accuracy of the calculated vibrational C-13 shifts can be used as a powerful assignment tool in surface molecular spectroscopy of adsorbates on different metal surfaces. The implications of our results for adsorbate site symmetries are also discussed. (C) 1999 Elsevier Science B.V. All righ ts reserved.