This volume contains the lectures and seminars presented at the NATO Advanced Study Institute on "Coherence in Spectroscopy and Modern Physics," the seventh course of the International School of Quantum Electronics, affiliated with the "Ettore Majorana" Centre for Scientific Culture, Erice, Sicily. The Institute was held at Villa LePianore (Lucca), Versilia, Italy, July 17-30, 1977. The International School of Quantum Electronics was started in 1970 with the aim of providing instruction for young researchers and advanced students already engaged in the area of quantum electronics or wishing to switch to this area from a different background. From the outset the School has been under the direction of Prof. F. T. Arecchi, then at the University of Pavia, now at the University of Florence, and Dr. D. Roess of Siemens, Munich. Each year the Directors choose a subject of particular interest, alternating fundamental topics with technological ones, and ask colleagues specifically competent in a given area to take the scientific responsibility for that course.

Inhalt
A - Basic Tools.- Coherence in Spectroscopy.- Coherence in Synergetics.- B - Coherence in Spin-like Systems.- Coherent Optical Transients.- Mean Field Theory of Optical Bistability and Resonance Fluorescence.- Optical Bistability and Differential Gain.- Superfluorescence Experiments.- Coherent Two-Photon Amplication in an Inverted Medium.- C - Coherence in Atomic Spectroscopy.- High Resolution Spectroscopy in Atomic Rydberg States.- The Method of Separated Fields in Optics.- Coherence in Beam-Foil Spectroscopy.- Magnetic Resonances in Sodium Vapours Oriented by a C. W. Dye Laser.- D - Applications of Coherence to Physical Systems.- Superconductivity and Quantum Optics.- Surface Plasmon Effects on Molecular Decay Processes near Metallic Interfaces.- to Picosecond Spectroscopy.- Picosecond Spectroscopy and Solid State Physics.- Coherent Effects in Picosecond Spectroscopy.- Nonthermal Microwave Resonances in Living Cells.- E - New Laser Sources.- The Free Electron Laser: A Single Particle Classical Model.- Frequency Tunability and High Speed Modulation of Far Infrared Optically Pumped Lasers by Stark Effect.