Almost fifteen years have now elapsed since the first observations of per­ sistent spectral hole-burning in inhomogeneously broadened absorption lines in solids. The fact that the spectral shape of an inhomogeneously broadened line can be locally modified for long periods of time has led to a large number of investigations of low-temperature photophysics and photochemistry that would not have been possible otherwise. Using hole­ burning, important information has been obtained about a variety of in­ teractions, including excited-state dephasing processes, host-guest dynam­ ics, proton tunnelling, low-frequency excitation in amorphous hosts, relaxation mechanisms for vibrational modes, photochemical mechanisms at liquid helium temperatures, and external field perturbations. At the same time, the possibility that persistent spectral holes might be used to store digital information has led to the study of materials and configura­ tions for frequency-domain optical storage and related possible applica­ tions. This is the first full-length book on persistent spectral hole-burning. The goal is to provide a broadly based survey of the scientific principles and applications of persistent spectral hole-burning. Since the topic is quite interdisciplinary, the book is intended for researchers, graduate stu­ dents, and advanced undergraduates in the fields of chemical physics, solid-state physics, laser spectroscopy, solid-state photochemistry, and high-performance optical storage and optical processing.

1. Introduction.- 1.1 Fundamental Requirements for Persistent Spectral Hole-Burning.- 1.2 Significance for Science and Applications.- 1.3 Historical Overview and Survey of Mechanisms.- 1.4 Synopsis of the Book.- References.- 2. Basic Principles and Methods of Persistent Spectral Hole-Burning.- 2.1 Background.- 2.2 Homogeneous Spectrum of an Electron-Vibrational Transition.- 2.3 Inhomogeneous Broadening of the Vibronic Spectrum.- 2.4 Persistent Spectral Hole-Burning.- 2.5 Kinetics of Persistent Spectral Hole-Burning.- 2.6 Spectroscopic Applications.- 2.7 Special Methods of Hole-Burning and Detection.- 2.8 Hole-Burning Time-and-Space-Domain Holography.- 2.9 Concluding Remarks.- References.- 3. Photochemical Hole-Burning in Electronic Transitions.- 3.1 Photochemical, Photophysical, and Spin Hole-Burning.- 3.2 Spectroscopic Analysis of Hole-Burning Experiments.- 3.3 Field Effects in Hole-Burning Spectroscopy.- References.- 4. Persistent Spectral Hole-Burning in Inorganic Materials.- 4.1 Introduction.- 4.2 Hole-Burning Mechanisms.- 4.3 Color Centers.- 4.4 Rare Earth Compounds.- 4.5 Transition Metal Ions.- 4.6 Conclusion.- References.- 5. Two-Level-System Relaxation in Amorphous Solids as Probed by Nonphotochemical Hole-Burning in Electronic Transitions.- 5.1 Background.- 5.2 Survey of NPHB Systems.- 5.3 Optical Linewidths and Dephasing in Amorphous Solids.- 5.4 Density of States Functions for TLS.- 5.5 Laser-Induced Hole Filling.- 5.6 Recent Developments.- 5.7 Concluding Remarks.- References.- 6. Persistent Infrared Spectral Hole-Burning for Impurity Vibrational Modes in Solids.- 6.1 Introduction.- 6.2 Molecules in Van der Waals Matrices.- 6.3 ReO4? in Alkali Halide Crystals.- 6.4 Persistent Spectral Hole-Burning for CN? Molecules in Alkali Halide Crystals.- 6.5Conclusion.- References.- 7. Frequency Domain Optical Storage and Other Applications of Persistent Spectral Hole-Burning.- 7.1 Introduction.- 7.2 Systems Issues for Frequency Domain Optical Storage.- 7.3 Materials Research for Frequency Domain Optical Storage.- 7.4 Alternative Data-Storage Configurations.- 7.5 Other Applications of Persistent Spectral Hole-Burning.- 7.6 Summary and Future Prospects.- References.