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

The effect of electric fields of electrochemical strength on the vibra tional relaxation of CO on Cu(100) is studied by first principles mole cular orbital calculations on cluster models. The effect of the field on the lifetimes of excited vibrations, as well as on other observable s such as vibrational frequencies and infrared intensities, is consist ent with the chemical nature of the metal-molecule bond changing in th e presence of the field. Additionally the charge distributions and mol ecular 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 demonstratin g that similar chemical effects are implicit within that theory.