This book presents an account of the NATO Advanced Study Institute on "Radiationless Processes," held in Erice, Italy, from November 18 to December 1, 1979. This meeting was organized by the International School of Atomic and Molecular Spectroscopy of the "Ettore Majorana" Centre for Scientific Culture. The objective of the Institute was to formulate a comprehensive treatment of the various processes by which molecules and crystals in excited electronic levels relax nonradiatively to the ground level. A total of 83 participants came from 62 laboratories and 22 nations (Australia, Belgium,...