H. J. BEYER AND H. KLEINPOPPEN We are pleased to present Part D of Progress in Atomic Spectroscopy to the scientific community active in this field of research. When we invited authors to contribute articles to Part C to be dedicated to Wilhelm Hanle, we received a sufficiently enthusiastic response that we could embark on two further volumes and thus approach the initial goal (set when Parts A and B were in the planning stage) of an almost comprehensive survey of the current state of atomic spectroscopy. As mentioned in the introduction to Parts A and B, new experimental methods have enriched and advanced the field of atomic spectroscopy to such a degree that it serves not only as a source of atomic structure data but also as a test ground for fundamental atomic theories based upon the framework of quantum mechanics and quantum electrodynamics. However, modern laser and photon correlation techniques have also been applied successfully to probe beyond the "traditional" quantum mechanical and quantum electrodynamical theories into nuclear structure theories, electro- weak theories, and the growing field of local realistic theories versus quan- tum theories. It is obvious from the contents of this volume and by no means surprising that applications of laser radiation again played a decisive role in the development of new and high-precision spectroscopic techniques.

Table of Contents:
of Part D.- 1 Laser-Microwave Spectroscopy.- 1. Introduction.- 1.1. Classical Experiments with Radiofrequency Transitions.- 1.2. Lasers versus Classical Light Sources in rf Spectroscopy Experiments.- 2. Classification of Laser-Microwave Spectroscopy.- 2.1. General Considerations.- 2.2. Classification.- 2.3. Resume.- 3. Measurements Based on Optical Pumping.- 3.1. Experiments with Resonance Cells.- 3.2. Particle-Beam Techniques.- 3.3. Spectroscopy of Trapped Ions.- 3.4. Experiments in Solids.- 4. Measurements Based on Double Resonance.- 4.1. Low-Lying (Short-Lived) Excited States.- 4.2. Rydberg States.- 5. Measurements Based on Nonlinear Phenomena.- 5.1. General Considerations.- 5.2. Experiments with Resonance Vessels.- 5.3. Particle Beam Experiments.- 6. Other Schemes.- 7. Laser-Microwave Heterodyne Techniques for Spectroscopic Purposes.- 7.1. Frequency-Offset Locking.- 7.2. Laser Light Modulation and Side Band Tuning.- 7.3. Various Other Schemes.- 8. Concluding Remarks.- References.- 2 Collinear Fast-Beam Laser Spectroscopy.- 1. Introduction.- 2. Basic Concept and Experimental Realization.- 3. Experiments Based on the Doppler Effect.- 3.1. Beam Velocity Analysis.- 3.2. High-Voltage Measurement and Calibration.- 3.3. Relativistic Doppler Shift.- 4. Spectroscopic Studies.- 4.1. Experimental Details.- 4.2. Laser-rf and Related Techniques.- 4.3. Nonlinear Spectroscopy.- 4.4. Transient Phenomena.- 4.5. Spectroscopic Results.- 5. Spectroscopy on Unstable Isotopes.- 5.1. Hyperfine Structure and Isotope Shifts.- 5.2. Review of Experiments.- 5.3. Experimental Setup and Procedure.- 5.4. Results in Nuclear Physics.- 5.5. Higher Sensitivity by Ionization.- 5.6. Implantation of Polarized Atoms.- 6. Conclusion.- References.- 3 Radiofrequency Spectroscopy of Rydberg Atoms.- 1. Introduction.- 2. Rydberg Atoms.- 3. Core Polarization and Penetration.- 3.1. Fine Structure.- 3.2. The Stark Effect in Alkali Atoms.- 4. Experimental Techniques.- 4.1. Quantum Beats.- 4.2. Optical Spectroscopy.- 4.3. Radiofrequency Resonance.- 4.4. Optical Detection.- 4.5. Selective Field Ionization.- 4.6. Delayed Field Ionization.- 4.7. Selective Resonance Ionization.- 4.8. Applicability.- 5. Overview of the Results Obtained.- 5.1. Quantum Defects-Core Polarization.- 5.2. The Nonadiabatic Effects in Alkaline Earth Atoms.- 5.3. Fine Structure Intervals of Alkali Atoms.- 5.4. Applications.- References.- 4 Rydberg Series of Two-Electron Systems Studied by Hyperfine Interactions.- 1. Introduction.- 2. Experimental Techniques.- 2.1. Atomic Beam Experiments.- 2.2. Experiments Using Vapor Cells.- 3. Even-Parity Rydberg Series of Alkaline-Earth Elements.- 3.1. msns1,3S Rydberg Series of Ca (m = 4), Sr (m = 5), and Ba (m = 6).- 3.2. msnd1,3D Rydberg Series of Ca, Sr, and Ba.- 4. Odd-Parity Rydberg Series of Alkaline-Earth Elements.- 4.1. Hyperfine Structure and Singlet-Triplet Mixing of 6snp1P1 Ba Rydberg States.- 4.2. Hyperfine Structure of 6snf3F Rydberg Series of 137Ba.- 4.3. Hyperfine-Induced Singlet-Triplet Mixing of 3snf1,3F Rydberg States of 25Mg.- 5. Hyperfine Structure and Isotope Shifts of Rydberg States of Other Two-Electron Systems.- 5.1. 6snl Rydberg Series of Yb.- 5.2. 1sns and 1snd Rydberg States of 3He.- 6. Conclusion.- References.- 5 Parity Nonconservation in Atoms.- 1. Introduction.- 1.1. The Weak Interaction-Charged Currents and Neutral Currents.- 1.2. Atomic Structure and Parity Nonconservation.- 1.3. Optical Rotation and Circular Dichroism.- 2. Theory.- 2.1. A Simple Calculation.- 2.2. Effect in Heavy Atoms.- 2.3. Transitions of Interest.- 3. Circular Dichroism and Optical Rotation-Rigorous Discussion.- 3.1. PNC-Stark Interference.- 4. Optical Rotation Experiments.- 4.1. Angle Resolution.- 4.2. Faraday Rotation.- 4.3. The Seattle Optical Rotation Experiments.- 4.4. Results of the Seattle Bismuth Experiment.- 4.5. Measurements on the 1.28-?m Line of Atomic Lead.- 5. Stark-PNC Experiments; Cesium and Thallium.- 6. Discussion of Results; Conclusions.- 6.1. Future Prospects.- References.- 6 Energy Structure of Highly Ionized Atoms.- 1. Introduction.- 2. General Energy Relations in Isoelectronic Ions.- 3. Survey of the Low Configurations in Isoelectronic Sequences.- 4. The n = 2 Configurations.- 5. The Neon Sequence (N = 10).- 6. Ions with Ground Configurations of 3s and 3p Electrons.- 7. The Configurations 3dk.- 7.1. The Potassium Sequence (N = 19).- 7.2. The Iron Sequence (N = 26).- 7.3. The Cobalt Sequence (N = 27).- 7.4. The Nickel Sequence (N = 28).- 8. The Copper Sequence (N = 29).- 9. The Silver Sequence (N = 47).- References.- 7 Inner-Shell Spectroscopy with Hard Synchrotron Radiation.- 1. Introduction.- 2. Instrumental Details.- 2.1. Characteristics of Synchrotron Radiation.- 2.2. X-Ray Monochromators.- 2.3. X-Ray Detectors.- 3. X-Ray Absorption by Free Atoms.- 3.1. X-Ray Attenuation.- 3.2. Energies and Widths of Inner-Shell Levels.- 3.3. Correlation Effects in X-Ray Absorption.- 4. X-Ray Absorption by Bound Atoms.- 4.1. X-Ray Absorption near Edge Structure (XANES).- 4.2. Extended X-Ray Absorption Fine Structure (EXAFS).- 5. Induced X-Ray Fluorescence and Auger-Electron Emission.- 5.1. Application for Chemical Analysis.- 5.2. Decay Channels of Inner-Shell Vacancies.- 5.3. Resonant Raman Auger (RRA) Process.- 6. Scattering of X-Rays.- 6.1. Rayleigh and Compton Scattering.- 6.2. Resonant Raman Scattering (RRS).- References.- 8 Analysis and Spectroscopy of Collisionally Induced Autoionization Processes.- 1. Introduction.- 2. Description of Autoionizing States.- 2.1. The Independent Particle Model.- 2.2. Correlated Electron Motion.- 3. Experimental Methods.- 3.1. Kinematical Effects.- 3.2. Coincidence Experiments.- 4. Line Shapes and Interference Effects in Autoionization Spectroscopy.- 4.1. Direct Ionization and Autoionization.- 4.2. Postcollision Interaction (PCI) in Ion-Atom Collisions.- 4.3. PCI in Electron-Atom Collisions.- 4.4. PCI-Influenced Auger Electron Spectra.- 4.5. PCI-Induced Exchange of Angular Momentum.- 5. Spectroscopic Data for Various Atoms.- 5.1. H" and He.- 5.2. Rare Gases Ne***Xe.- 5.3. Alkali Atoms.- 5.4. Alkaline Earth Atoms.- 6. Correlated and Uncorrelated Angular Distributions of Autoionization Electrons.- 6.1. Excitation Amplitudes and Density Matrix of Excited Atoms.- 6.2. Theoretical Shapes of Angular Electron Distributions.- 6.3. Coincidence Measurements to Determine Angular Correlations between Ejected Electrons and Scattered Projectiles.- 6.4. Noncoincident Measurements of Angular Electron Distributions.- 6.5. Electron Beats.- 7. Electron Emission from Quasimolecules.- 7.1. Coherent Electron Emission from Two Separated Collision Partners.- 7.2. Quasimolecular Autoionization at Small Internuclear Distances.- References.- 9 Near Resonant Vacancy Exchange between Inner Shells of Colliding Heavy Particles.- 1. Introduction.- 2. Theoretical Methods.- 2.1. Vacancy Exchange Mechanisms.- 2.2. Basic Formalism.- 2.3. Model Matrix Elements.- 3. Two-State Systems.- 3.1. Two-State Formalism.- 3.2. MO Energies and Radial Coupling Matrix Elements.- 3.3. Highly Ionized Collision Systems.- 3.4. Vacancy Sharing.- 3.5. Impact Parameter Dependence.- 3.6. Double Passage Process.- 3.7. Total Cross Sections.- 4. Multistate Systems.- 4.1. General Considerations.- 4.2. KL- and LK-Vacancy Sharing.- 4.3. L-Vacancy Sharing.- 5. Conclusions.- References.- 10 Polarization Correlation in the Two-Photon Decay of Atoms.- 1. Introduction.- 2. Theoretical Considerations.- 2.1. Polarization Correlation.- 2.2. The Two-Photon State Vector.- 2.3. Bell's Inequalities for the Ideal Case.- 2.4. The BCHSH Inequality in Experimental Situations.- 2.5. Quantum Mechanical Predictions.- 2.6. The No-Enhancement Hypothesis.- 2.7. The Schrodinger-Furry Hypothesis.- 3. Experimental Work.- 3.1. Experiment of Kocher and Commins (1967).- 3.2. Experiment of Freedman and Clauser (1972).- 3.3. Experiment of Holt and Pipkin (1973).- 3.4. Experiments of Clauser (1976).- 3.5. Experiment of Fry and Thompson (1976).- 3.6. Experiment of Aspect, Grangier, and Roger (1981).- 3.7. Experiment of Aspect, Grangier, and Roger (1982).- 3.8. Experiment of Aspect, Dalibard, Grangier, and Roger (1984).- 3.9. Experiment of Aspect, Dalibard, and Roger (1982).- 3.10. Experiments of Perrie, Duncan, Beyer, and Kleinpoppen (1985).- 4. Discussion.- References.