These proceedings report the lectures and seminars presented at the NATO Advanced Study Institute on "Optical Properties of Ions in Solids," held at Erice, Italy, June 6-21, 1974. The Institute was the first activity of the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Centre for Scientific Culture. The Institute consisted of a series of lectures on optical properties of ions in solids that, starting at a fundamental level, finally reached the current level of research. The sequence of lectures and the organization of the material taught were in keeping with a didactical presentation. In essence the Institute had the two-fold purpose of organizing what was known on the subject, and updating the knowledge in the field. Fif'teen series of lectures for a total of 44 hours were given. Five one-hour seminars and five twenty-minute seminars were presented. A total of 57 participants came from 40 laboratories in the following countries: Belgium, Canada, France, Germany, Ireland, Israel, Italy, Netherlands; Polatid, Romania, Switzerland, the United Ki~gdom, and the United States. The secretaries of the Institute were: D. Pacheco for the scientific aspects and A. La Francesca for the administrative aspects of the meeting. These proceedings report the lectures, the one-hour seminars (abstracts only) and the twenty-minute- seminars (titles only). The proceedings report also the contributions sent by Prof. K. Rebane and Dr. L. A. Rebane who, unfortunately, were not able to come.

Inhalt

Historical Survey of Studies of the Optical Properties of Ions in solids.- Abstract.- I. Introduction.- II. Early Investigations of Optical Transitions.- III. Quantum Mechanical Considerations.- IV. Crystal and Ligand Field Theory.- V. Energy Transfer.- VI. Ion Pairs.- VII. Multiphoton Transitions.- VIII. Concluding Remarks.- References.- Magnetic Ions in Solids.- Abstract.- I. Introduction.- II. Symmetry Concepts.- II.A Properties of a Group.- II.B Example.- II.C Classes.- II.D Representations.- II.E Characters.- II.F Group Theory and Quantum Mechanics.- III. Energy Levels of Atoms.- III. A Some Groups of Interest.- 1. Full Rotational Group.- 2. The Group C?h.- III.B Complete Set of Commuting Operators.- III.C Atomic States.- 1. The Hamiltonian.- 2. The Unperturbed Hamiltonian.- 3. The Electron-Electron Interaction.- 4. The Spin-Orbit Interaction.- 5. The Zeeman Interaction.- IV. Magnetic Ions in Crystals.- IV. A Magnetic Ions.- 1. Transition Metal Ions of the First Series (Iron Group).- 2. Transition Metal Ions of the Second Series (Palladium Group).- 3. Transition Metal Ions of the Third Series (Platinum Group).- 4. Rare Earth Ions (Group of the Lanthanides).- 5. Actinide Ions.- IV. B The Crystalline Field.- IV. C The Weak Field Scheme.- 1. The Hamiltonian of the Free Ion.- 2. The Crystalline Field Perturbation.- 3. Examples.- IV. D The Intermediate Field Scheme.- 1. The Hamiltonian of the Free Ion.- 2. The Crystalline Field Perturbation.- 3. The Spin-Orbit Interaction.- 4. Example.- IV. E The Strong Field Scheme.- 1. The Unperturbed Hamiltonian.- 2. The Crystalline Field Perturbation.- 3. The Electron-Electron Interaction.- 4. The Spin-Orbit Interaction.- 5. Example.- IV. F Kramers' Theorem.- V. Effect of Covalent Bonding.- V.A Why Covalent Bonding ?.- V.B Molecular Orbitals.- V.C Examples.- 1. N2 Molecule.- 2. HF Molecule.- 3. H2O Molecule.- 4. NH3 Molecule.- 5. CH4 Molecule ; Hybridization.- V.D Octahedral Complexes.- V.E Charge Transfer Spectra.- 1. Ligand to Metal Transfer Spectra.- 2. Metal. Oxidation Spectra.- 3. Rydberg Spectra.- 4. Intraligand Spectra.- References.- Fundamentals of Radiative Transitions of Ions and of Ion Pairs in Solids.- Abstract.- I. Introduction.- II. Transitions Induced by Perturbations Periodic in Time.- III. Transitions Induced by the Electromagnetic Radiation Field.- IV. Spontaneous Radiative Transitions.- V. Applications of the Theory to Radiative Transitions of Ions in Solids.- References.- Absorption and Emission Spectra.- Abstract.- I. The One-Dimensional Configurational Coordinate Model.- I. A Introduction.- I.B The Emission and Absorption Peaks.- I.C The Shape of Emission and Absorption Spectra.- I.D A Study of Some Particular Cases.- 1. The Case of Linear Coupling.- 2. The Case of Quadratic Coupling.- I.E Simple Improvement of the Semi-Classical Approximation: H. Payen de la Garanderie's Law of the Rectilinear Diameter.- II. The Huang and Rhys Model.- II.A The Emission Spectrum.- II.B The Absorption Spectrum.- II.C A Remark.- II.D Shape and Asymmetry of Huang's and Rhys' and Pekarian Curves.- 1. The Moments.- 2. A More Detailed Study of the Pekarian Curve.- III. A Deeper Insight into the Shape of the Spectra.- III.A Weak Coupling and Strong Coupling.- III.B The Case of a Distribution of Phonons Interacting with the Emitting Center.- 1. Selection Rules.- 2. The Coupling Parameter S.- 3. The Moments of the Shape Function.- IV. A Study of Some Experimental Cases.- IV.A Large Band Spectra of II-VI Compounds.- 1. ZnS:Cu.- 2. ZnSe:Cu.- 3. CdS:Ag.- 4. ZnS:Ag, Cl.- 5. Self-Activated Materials.- IV. B ZnS:Mn.- IV.C The R-Lines of Ruby.- IV.D Edge Emissions in II-VI Compounds.- IV.E Stokes versus Anti-Stokes Emission.- References.- Quantum Theory of Lattice Vibrations.- Abstract.- I. Lattice Vibrations.- I.A Linear Diatomic Chain.- 1. Equations of Motion.- 2. One Dimensional Zone Scheme.- 3. Density of States.- I.B Three Dimensional Lattice. Classical Theory.- 1. Potential Energy.- 2. Equations of Motion.- 3. Eigenvalue Spectrum and Eigenvectors.- 4. Boundary Conditions and the Reciprocal Lattice.- 5. Brillouin Zones.- 6. Energy Surface Theorem.- I.C Three Dimensional Lattice. Quantum Theory.- 1. Introduction Coordinates.- 2. Commutation Relations.- 3. Energy Matrix.- 4. Eigenvalue Spectrum.- II. Thermodynamic Properties of Lattice Vibrations.- II.A Construction and Use of the Partition Function.- 1. Distribution Function.- 2. Summation of Terms.- 3. Internal Energy.- 4. Free Energy.- 5. Entropy.- 6. Specific Heat.- II. B Density of States.- 1. Enumeration of States.- 2. Critical Points, Small Wave Vector Limit. Debye Approximation.- 3. Critical Points. Minima.- 4. Critical Points. Maxima.- 5. Critical Points. Saddle Points.- 6. Conditions on Number and Types of Critical Points.- II.C Equation of State.- 1. Gruneisen Constant.- 2. Lattice Vibrational Equation of State.- 3. Relation between Gruneisen Constant and Compressibility.- II.D Effect of the Boundary Conditions on the Frequency Distribution.- References.- Theory of Vibronic Spectra.- Abstract.- I. Introduction.- II. Infrared Absorption.- II.A Characteristics of Infrared Absorption in Crystals.- II.B Quantum Mechanical Treatment of Infrared Processes.- III. Raman Scattering.- III.A Characteristics of Raman Scattering in Crystals.- III.B Theoretical Treatment of Raman Scattering.- IV. Neutron Scattering.- IV.A Characteristics of Neutron Scattering from Crystals.- IV.B Theory of Neutron Scattering.- V. Vibronic Spectra.- V.A Magnetic Ions in Host Lattices.- V.B Characteristics of Vibronic Spectra.- V.C Theory of Vibronic Transitions.- V.D Vibronic Selection Rules from Group-Theoretical Analysis.- V.E. Vibronic Theory: Alternate Approaches and Numerical Calculations.- VI. Example: Analysis of 2Eg ? 4A2g Sideband of MgO:V2+.- References.- Luminescence and Spectroscopy of Small Molecular Ions in Crystals.- Abstract.- I. Introduction.- II. General Description of the Spectra of Molecular Centres in Crystals.- II.A Structure of Luminescence and Absorption Spectra. Parameters of Potential Curves.- II.B Electron-Phonon Interaction. Structure of Phonon Wings.- II.C Electron-Phonon Interaction. Anharmonicity Effects. No-Phonon Lines.- II.D Radiationless Transitions and Vibrational Relaxation in Molecular Centres.- III. Rotation and Libration of the NO2- Ion in Potassium Halide Crystals.- III.A Hindered Rotation of the Impurity Molecule in Crystals.-…