LINEWIDTH OF INTRAMOLECULAR VIBRATIONS OF CARBON-MONOXIDE ADSORBATE ON METAL-SURFACES - A POSSIBLE MECHANISM

In this paper, we study the relaxation of intramolecular vibrations of a diatomic molecule adsorbed on metal surfaces at low coverage. Using a simple model that include the coupling between the adsorbate-surfac e vibrational mode omega(0) and the intraadmolecular vibrational mode Omega, we present a mechanism for the dephasing process of the intramo lecular vibrational mode Omega via the relaxation of adsorbate-surface vibrational mode omega(0). We propose that this relaxation (dephasing ) process may have a significant contribution to the linewidth of the intramolecular vibrations in certain surface systems. Explicit calcula tions are carried out for CO adsorbed on Pt and on Ni. For the CO/Pt c ase, our results are in good agreement with experimental data.