ELECTRIC-FIELD EFFECTS ON CHEMISORPTION AND VIBRATIONAL-RELAXATION OF CO ON CU(100)

The effect of electric fields of electrochemical strength on the vibrational relaxation of CO on Cu(100) is studied by first principles molecular orbital calculations on cluster models. The effect of the field on the lifetimes of excited vibrations, as well as on other observables such as vibrational frequencies and infrared intensities, is consistent with the chemical nature of the metal-molecule bond changing in the presence of the field. Additionally the charge distributions and molecular orbitals obtained from the calculations are analyzed in detail to show the changes that occur. The validity of the alternative Stark effect interpretation of the field's role is explained by demonstrating that similar chemical effects are implicit within that theory.