NEXAFS and SEXAFS Studies of Chemisorbed Molecules: Bonding, Structure and Chemical Transformations

Abstract

We discuss the application of the surface extended X-ray absorption fine structure (SEXAFS) and near edge X-ray absorption fine structure (NEXAFS) techniques to study the intramolecular and chemisorption bonds of carbon-, nitrogen-, oxygen-, and sulfur-containing molecules and their reaction intermediates on metal surfaces. NEXAFS is dominated by intramolecular multiple scattering resonances and is, therefore, preferentially sensitive to the intramolecular bonding and structure. It provides the intramolecular bond length, the hybridization of the molecular bond and the molecular orientation on the surface. SEXAFS mainly arises from single scattering processes off the atomic cores of substrate neighbor atoms and determines the chemisorption site and the chemisorption bond lengths. An example is given of a complete structure determination for formate (HCO2) on Cu(100). The power of NEXAFS is pointed out to monitor surface-induced molecular bond length variations, e.g., C2H2 on Pt(lll), CO/Na/Pt(111) as well as chemical transformations of complex molecules, e.g., C4H4S/Pt(lll).KeywordsAntibonding OrbitalAtomic CoreChemisorption BondChemisorb MoleculeFree Polyatomic MoleculeThese keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.