This book presents an account of the course "Advances in Nonradiative Processes in Solids" held in Erice, Italy, from June 15 to 29, 1989. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Centre for Scientific Culture. An area of solid state research that continues to attract the attention of experimental and theoretical physicists is that of nonradiative relaxation processes of excited solids. The interest in these processes stems from their technological relevance, and from the difficulty in the quantitative characterization and differentiation of their various pathways. The decay channels leading to the ground state include the conversion of electronic excitation energy into phonon energy, nonradiative transfer of excitation energy, upconversion processes, etc. Considerable advances have been achieved in understanding and modeling the radiative process that follow the electronic excitations of solids; the progress in this field has been instrumental in the development of new solid-state devices and laser materials. On the other hand, these advances have underscored the inadequacy in the understanding of the nonradiative relaxation processes. This course dealt with the advances in physical modeling, mathematical formalisms and experimental techniques relevant to the quantitative characterization of the various pathways of nonradiative relaxation of solids in excited electronic states.

Nonradiative Relaxation of Solids: Different Pathways to the Ground State.- The Role of Nonradiative Processes in the Spectroscopy of Optically Active Centers in Solids.- Radiative and Nonradiative Rates in Luminescence Centers.- Advances in Non-Radiative Processes in Solid State Laser Materials.- Model Calculations of Nonradiative Multiphonon Processes in INORGANIC Insulating Solids.- Advances in Nonradiative Processes in Semiconductors.- Radiative and Nonradiative Processes in Color Centers.- Nonradiative Transitions Between Electronic Levels of Opticallyactive Ions in Glass.- Nonradiative Processes in Luminescent Materials: A Materials Scientists View.- Techniques for the Investigation of Nonradiative Processes.- New Applications of Efficient Phosphors.- Long Seminars.- Energy Transfer in Cr, Tm: Yag.- Luminescence and Nonradiative Processes in Porous Glasses.- Laser Spectroscopy Techniques Applied to Cr3+ -Doped Materials.- How to Play with Springs and Pulses in a Classical Harmonic Crystal.- Thermal Response and Decoupling of Excitations at Low Temperatures.- New Laser Crystals (Abstract only).- Degenerate Four-Wave Mixing Technique for Studying Very Fast Radiationless Processes in Very Short Time Scale.- Photothermal Optical Nonlinearities, Optical Bistability and Possible Applications.- Crystals: Growth Methods and Characterization.- 4He and 3He Calorimetric Absorption Spectroscopy: Principles and Results on Ingaas/Alinas Quantum Wells and Fe in InP and GaAs.- Special Topics (Abstracts).- Particles and Elementary Excitations.- Short Seminars (Abstracts).- Excited State Absorption in Tb Activated Phosphor Powders.- Picture of the Participants.- Participants.