This volume contains review articles written by the invited speakers at the eighth International Summer Institute in Surface Science (ISISS 1987), held at the University of Wisconsin-Milwaukee in August of 1987. During the course of ISISS, invited speakers, all internationally recognized experts in the various fields of surface science, present tutorial review lectures. In addition, these experts are asked to write review articles on their lecture topic. Former ISISS speakers serve as advisors concerning the selection of speakers and lecture topics. Em­ phasis is given to those areas which have not been covered in depth by recent Summer Institutes, as well as to areas which have recently gained in significance and in which important progress has been made. Because of space limitations, no individual volume of Chemistry and Physics of Solid Surfaces can possibly cover the whole area of modem surface science, or even give a complete survey of recent pro­ gress in the field. However, an attempt is made to present a balanced overview in the series as a whole. With its comprehensive literature references and extensive subject indices, this series has become a valu­ able resource for experts and students alike. The collected articles, which stress particularly the gas-solid interface, have been published under the following titles: Surface Science: Recent Progress and Perspectives, Crit. Rev. Solid State Sci. 4, 125-559 (1974) Chemistry and Physics of Solid Surfaces, Vols. I, II, and III (CRC Press Boca Raton, FL 1976, 1979, and 1982); Vols.

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1. Activated Chemisorption.- 1.1 A Brief History.- 1.2 Classification of Activated Chemisorption.- 1.2.1 Molecular Structure.- 1.2.2 Electronic Structure of the Gas.- 1.2.3 Electronic Structure of the Solid.- 1.2.4 Atomic Arrangement of the Solid.- 1.2.5 Strength of Chemisorption Bonding.- 1.2.6 Surprises.- 1.3 Formal Kinetics.- 1.3.1 Concentration Dependence of Chemisorption Rates.- 1.3.2 Temperature Dependencies.- 1.3.3 Angular and Mass Dependence.- 1.4 Case Studies in Activated Adsorption.- 1.4.1 Methane and Other Alkanes on Metal Surfaces.- 1.4.2 Hydrogen on Copper.- 1.4.3 Hydrogen on Elemental Semiconductors.- 1.4.4 Activated Adsorption on Densely Packed Planes.- a) Hydrogen and Nitrogen on W{110}, Re{0001}, and Ru{0001}.- b) Hydrogen on Platinum {111}.- c) Hydrogen on Nickel {111} and {110}.- 1.4.5 Slow Chemisorption of Nitrogen.- a) Nitrogen on Platinum Group Metals.- b) Chemisorption of Nitrogen on Iron.- 1.4.6 A Surprise: Oxygen on W{110}.- 1.5 Summary.- References.- 2. Physisorbed Rare Gas Adlayers.- 2.1 Experimental Techniques.- 2.1.1 General Remarks.- 2.1.2 Probe Particles.- a) Electrons.- b) Neutrons.- c) X-Ray Photons.- d) Helium Atoms.- 2.2 Solid-Solid Transitions in Two Dimensions.- 2.2.1 Commensurability.- 2.2.2 Fundamentals of the Theory Describing the Commensurate-Incommensurate Transition in 2D.- 2.2.3 The C-I Transition of Monolayer Xe on Pt{111}.- 2.2.4 Can High Order Commensurate Adlayers be Distinguished from Incommensurate Ones?.- i) Thermal expansion.- ii) Commensurate buckling.- iii) Lattice dynamical criterion.- iv) Bragg peak singularities.- 2.2.5 The I-HOC Phase Transition of Monolayer Kr on Pt{111}.- 2.2.6 Rotational Epitaxy of Monolayers.- 2.3 Multilayer Growth of Rare Gases.- 2.3.1 Dynamical Coupling Between Adlayer and Substrate.- 2.3.2 Layer-by-Layer Evolution of the Lattice Dynamics.- 2.3.3 Growth Mode and the Scale of Substrate Strength.- 2.3.4 Epitaxial Layer Growth of Xe on Pt{111}.- 2.4 Conclusion.- References.- 3. Infrared Spectroscopy of Semiconductor Surfaces.- 3.1 Theoretical Framework.- 3.1.1 Macroscopic Theory (Three-Layer Model).- 3.1.2 Microscopic Model of the Active Layer.- 3.1.3 Model for Electronic Absorption.- 3.1.4 Discussion of the Assumption of Sharp Boundaries.- 3.1.5 First-Principle Calculations.- 3.2. Experimental Geometries and Techniques.- 3.2.1 Vibrational Modes in Substrate Optical Gap.- 3.2.2 Vibrational Modes in Substrate Absorption Region.- 3.2.3 Experimental Apparatus.- a) Surface Infrared Spectrometer.- b) Sample Geometry.- c) Other Techniques.- 3.3 Selected Examples.- 3.3.1 Structure of the Si{100}-(2x1)H System.- 3.3.2 H-saturated Si{100} and Ge{100} Surfaces.- 3.3.3 Dynamics of H on Si{100}.- 3.3.4 H2O on Si{100}.- 3.3.5 Electronic Absorption of Si{100} and Si{111}.- a) Si{100}.- b) Si{111}.- 3.3.6 Chemistry at Semiconductor Surfaces.- 3.4 Problems and Future Directions.- 3.5 Conclusions.- References.- 4. Surface Phonons - Theory.- 4.1 Discoveries and Advances.- 4.1.1 Advances in Experimental Studies of Surface Phonons.- 4.1.2 New Computational Methods.- A) Clean Surfaces.- a) Spectral Densities.- b) Surface Phonons and Resonances.- c) Anharmonic Effects.- d) First Principles Calculations of Surface Phonon Dispersion Curves.- B) Adsorbate Covered Surfaces.- a) A Single Adparticle.- b) A Periodic Array of Adatoms.- 4.2 Surface Phonons on Complex Crystals and Structures.- 4.2.1 Surface Phonon Anomalies Caused by the Electron-Phonon Interaction.- 4.2.2 Surface Phonon Kohn Anomalies.- 4.2.3 Molecular Crystals.- 4.2.4 Crystal Surfaces with High Miller Indices.- 4.2.5 Reconstructed Surfaces.- 4.2.6 Amorphous Media.- 4.2.7 An Incommensurate Array of Adatoms.- 4.3 Some Directions for Future Research.- References.- 5. Interpretation of the NEXAFS Spectra of Adsorbates Using Multiple Scattering Calculations.- 5.1 Multiple Scattering Calculations of Near Edge Spectra of Molecules.- 5.2 Atomic and Diatomic Adsorbates.- 5.3 Computational Method for Complex Molecules and Clusters.- 5.4 More Complex Adsorbates.- 5.4.1 Ethylene and Ethylidyne on Pt{111}.- 5.4.2 Benzene on Pt{111}.- 5.4.3 Saturated Cyclic Hydrocarbons.- 5.4.4 Thiophene and Platinum Metallacycle.- 5.5 Conclusions.- References.- 6. Near-Edge X-Ray Absorption Fine Structure Spectroscopy: A Probe of Local Bonding for Organic Gases, Solids, Adsorbates, and Polymers.- 6.1 Development of NEXAFS: An Overview.- 6.2 Experimental Details.- 6.3 Results and Analysis.- 6.3.1 The Signatures of Individual Bonds.- 6.3.2 Assembly of Diatomics to Functional Groups.- 6.3.3 The Fingerprints of Functional Groups.- 6.3.4 Assembly of Functional Groups to Macromolecules.- 6.3.5 Limitations of the Building Block Approach.- 6.4 Conclusions and Future Prospects.- References.- 7. Surface Kinetics with Near Edge X-Ray Absorption Fine Structure.- 7.1 An Overview of Methods for Characterizing Surface Reactions.- 7.2 Transient Near-Edge X-ray Absorption Fine Structure (NEXAFS) as a Probe of Surface Reactions.- 7.2.1 Soft X-ray Absorption Using Electron Detection.- 7.2.2 CO Desorption from the Pt{111} Surface.- 7.2.3 Pyridine Reorientation of the Ag{111} Surface.- 7.2.4 Ethylene Conversion to Ethylidyne on the Pt{111} Surface.- 7.2.5 Summary: Transient NEXAFS Using Electron Detection.- 7.3 Fluorescence Yield Near-Edge Structure (FYNES).- in the Soft X-ray Region.- 7.3.1 Apparatus.- 7.3.2 Summary: Soft X-ray Absorption Using Fluorescence Detection.- 7.4 Future Opportunities.- References.- 8. Overview of Electron Microscopy Studies of the So-Called "Strong Metal-Support Interaction" (SMSI).- 8.1 Experimental.- 8.2 Results and Discussion.- 8.3 Summary.- References.- 9. Theory of Desorption Kinetics.- 9.1 Nonequilibrium Thermodynamics of a Two-Phase Adsorbate.- 9.1.1 Preliminary Comments.- 9.1.2 General Formulation.- a) Adsorption.- b) Desorption.- c) Two-Dimensional Condensation and Evaporation.- d) Equilibration of the 2D Gas Phases.- e) Equilibrium Properties.- 9.1.3 Results.- 9.1.4 A Simplified Model.- 9.2 Microscopic Approaches.- 9.3. Outlook.- References.- 10. Fractals in Surface Science: Scattering and Thermodynamics of Adsorbed Films.- 10.1 Fundamentals of Fractal Geometry.- 10.1.1 Definition 1.- 10.1.2 Definition 2.- 10.2 Small-Angle Scattering from Fractal Surfaces.- 10.2.1 Theorem 1.- 10.2.2 Theorem 2.- 10.2.3 Theorem 3.- 10.3 Application: Small-Angle He Scattering from Adsorbate Islands on an Ordered …