159 elements only between states which differ in one of the single-electron wave functions, in short, HeR induces only one-electron transitions. The matrix elements 1mn and Pmn reduce to matrix elements between the single-electron wave functions. We are interested primarily in crystalline solids for which the band model is a good approximation. The Bloch single-electron wave function in this model has the form: N'I ili-';; U. r.;;) ( (1.14) ""nk r, =e nh\r , where n is the band index and U (r) has the periodicity of the lattice. The form of the Bloch function follows from the translational symmetry of the crystal, and the matrix elements between Bloch states are subject to the condition of wave-vector conservation: k'=k, for

Inhalt
Optical Constants and their Measurement.- A. Introduction.- B. Optical properties of an absorbing medium.- C. Optical properties of simple classical systems.- D. Determining optical constants from experimental data.- Acknowledgements.- References.- Phonons in Perfect Crystals.- A. Elementary lattice dynamics.- B. Experimental methods.- C. Interpretation of phonon dispersion curves.- D. Calculation of phonon dispersion curves, and comparison with experiment.- E. The frequency distribution of the normal modes.- F. Anharmonic interactions.- G. Lattice dynamics of ferroelectric crystals.- H. Thermodynamic properties.- Appendix: Many-body techniques for anharmonic crystals.- References.- Photon-Electron Interaction, Crystals Without Fields.- A. General theory.- B. Experimental observations.- References.- Magneto-Optics in Crystals.- I. Introduction.- II. Macroscopic theory.- III. Quantum mechanical theory.- IV. Free carrier magneto-optical effects.- V. Interband effects.- VI. Impurities and magnetic materials.- VII. Experimental techniques.- VIII. Summary.- Sachverzeichnis (Deutsch-Englisch).- Subject Index (English-German).