Vibrational Spectroscopy of Adsorbates

Over the past few years, there has been a growing awareness of the vibratio­ nal properties of solid surfaces and adsorbates due to a steady growth in the number of experimental techniques which have evolved with sufficient resolution and surface sensitivity. An understanding of the surface vibratio­ nal modes is of fundamental importance in many areas of the physics and chemistry of surfaces, most notably in the field of heterogeneous catalysis on metals and alloys. The present volume derives from a one day meeting of invited lectures, held under the auspices of the Thin Films and Surfaces Section of the Insti­ tute of Physics in the Cavendish Laboratory, University of Cambridge, 13 December 1979. The object was to bring together specialists from various diverse fields who would examine the wide variety of methods currently avail­ able for studying surface adsorbate vibrations. Since these methods cover several scientific disciplines, it was subsequently felt that it would be useful to provide a permanent record of the talks as a source lor future reference by workers in what is rapidly becoming an expanding field of',inter­ est in an increasing number of laboratories. The contributions, however, are not in any way meant to constitute exhaustive reviews.

Inhalt

1. Introduction.- 1.1 Vibrational Spectroscopy in Relation to Surface Science.- 1.2 Techniques in Surface Vibrational Spectroscopy.- 1.3 Vibrational Coupling and Surface Phonon Modes.- References.- 2. Theory of Dipole Electron Scattering from Adsorbates.- References.- 3. Angle and Energy Dependent Electron Impact Vibrational Excitation of Adsorbates.- 3.1 Background.- 3.2 Inelastic Electron Scattering from Oriented Molecules.- 3.3 Surface Dipole Scattering.- 3.3.1 Modes Perpendicular to the Surface.- 3.3.2 Surface Trapping in Bound State Surface Resonances.- 3.3.3 Modes Parallel to the Surface.- 3.4 Dipole Theory of One-Phonon Excitation.- 3.5 Multiple Scattering Theory of One-Phonon Excitation.- 3.6 Hydrogen Modes on W(100).- 3.6.1 Angle Dependence.- 3.6.2 Phonon Sidebands Linewidth.- 3.6.3 Impact Energy Dependence.- 3.7 Concluding Remarks.- References.- 4. Adsorbate Induced Optical Phonons.- 4.1 Background.- 4.2 A Short Review.- 4.3 Some Physical Effects.- 4.4 Hydrogen on (001) Surface of Tungsten.- 4.5 Oxygen on the (111) Surface of Nickel.- 4.6 Conclusion.- References.- 5. Inelastic Electron Tunnelling Spectroscopy.- 5.1 Background.- 5.2 IETS.- 5.2.1 Principle of IETS.- 5.2.2 Nature of Interaction.- 5.2.3 Linewidths.- 5.2.4 Sensitivity and Surface Coverage.- 5.3 Oxides.- 5.3.1 Clean Aluminium Oxide.- 5.3.2 Formic Acid on Aluminium Oxide.- 5.3.3 Clean Magnesium Oxide.- 5.3.4 Formic Acid on Magnesium Oxide.- 5.4 Comparison.- 5.4.1 Comparison with Electron Energy Loss Spectroscopy(EELS).- 5.4.2 Comparison with Surface Infrared and Raman Spectroscopies.- 5.5 Adsorbate Orientation.- 5.6 Conclusion.- References.- 6. Inelastic Molecular Beam Scattering from Surfaces.- 6.1 Background.- 6.2 Atom Scattering from Surfaces.- 6.3 Experimental Considerations.- 6.3.1 Beam Sources.- 6.3.2 Detectors.- 6.3.3 Systems.- 6.4 Data Interpretation.- 6.4.1 Selection of Scattering Conditions.- 6.4.2 Selection Rules.- 6.4.3 Scattering Kinematics.- 6.5 Experimental Results.- 6.5.1 Inelastic Studies Without Energy Resolution.- 6.5.2 Velocity Resolved Studies.- 6.5.3 Dispersion Relations.- 6.6 Conclusions and Outlook.- References.- 7. Neutron Scattering Studies.- 7.1 Theoretical Background.- Experimental Considerations.- 7.2 Applications.- 7.2.1 Sulphide Catalysts.- 7.2.2 Butane Adsorption Upon Graphite.- 7.2.3 C6H6 Adsorbed on Raney-Nickel.- 7.2.4 Collective Excitations.- 7.3 Future Considerations.- References.- 8. Reflection Absorption Infrared Spectroscopy: Application to Carbon Monoxide on Copper.- 8.1 Background.- 8.2 Physical Factors in Infrared Reflection at Metal Surfaces.- 8.3 Experimental Aspects.- 8.4 Some Applications of RAIRS.- 8.5 Spectra of CO on Copper.- 8.6 Coupling Effects in Vibrational Spectra.- 8.7 Modified Dipole Coupling Theories.- 8.8 Dipole Coupling in Islands.- References.- 9. Raman Spectroscopy of Adsorbates at Metal Surfaces.- 9.1 Background.- 9.2 Experimental Features.- 9.3 Enhanced Raman Spectra of Adsorbates on Silver Surfaces.- 9.4 Enhanced Raman Spectra of Adsorbates at Metal Other Than Silver.- 9.5 The SERS Selection Rule.- 9.6 Some Observations on the Mechanism of the Surface Raman Enhancement.- References.- 10. Vibrations of Monatomic and Diatomic Ligands in Metal Clusters and Complexes - Analogies with Vibrations of Adsorbed Species on Metals.- 10.1 Background.- 10.2 Hydrogen as Adsorbed Species or as a Ligand on Metals.- 10.3 Carbon Monoxide as Adsorbed Species and Ligands.- 10.4 Nitrogen as Adsorbed Species and as Ligands.- 10.5 Oxygen as Adsorbed Species and as Ligands.- 10.6 Nitric Oxide, NO, as Adsorbed Species and as Ligands.- 10.7 General Conclusions.- References.- 11. Coupling Induced Vibrational Frequency Shifts and Island Size Determination: CO on Pt{001} and Pt{111}.- 11.1 Background.- 11.2 CO on Pt{001}: Island Growth.- 11.3 CO on Pt{001}: "Gaseous" and Island Species.- 11.4 Conclusion.- References.