BEYOND THE CHEMICAL-SHIFT - VIBRATIONALLY RESOLVED CORE-LEVEL PHOTOELECTRON-SPECTRA OF ADSORBED CO

Vibrational fine structure has been observed in the Cls and O1s photoe lectron lines of CO adsorbed on Ni(100). This allows a detailed separa tion of vibrational and electronic contributions to the line profile. The main line is found to represent the fully screened final state. Th e width of the photoelectron lines is dominated by the intramolecular stretch mode, which strongly depends on the chemical start of the adso rbate. The identification of the adiabatic transition makes the determ ination of chemical shifts more precise. The equivalent core approxima tion is found to be highly accurate and electronic and geometric equil ibrium properties of the core-ionized adsorbate are extracted. [S0031- 9007(98)06752-0].