In the early 1970s, researchers in Canada, the Soviet Union and the United States discovered that powerful infrared laser pulses are capable of dissociating mole­ cules such as SiF4 and SF6' This result, which was so unexpected that for some time the phenomenon of multiple-photon dissociation was not recognized in many cir­ cumstances in which we now know that it occurs, was first publicized at a time when the possibility of using lasers for the separation of isotopes had attracted much attention in the scientific community. From the mid-1970s to the early 1980s, hun­ dreds of experimental papers were published describing the multiple-photon absorp­ tion of C02 laser pulses in nearly every simple molecule with an absorption band in the 9 - 11 jJm region. Despite this impressive volume of experimental results, and despite the efforts of numerous theorists, there is no agreement among re­ searchers in the field on many fundamental aspects of the absorption of infrared laser light by polyatomic molecules. This book is devoted to reviells of the experimental and theoretical research that provides the foundations for our current understanding of molecular multiple­ photon exc itat i on, and to rev i ews of research that is pert i nent to the 1 aser sep­ aration of isotopes.

Molecular Multiphoton Excitation.- Single-Infrared-Frequency Studies of Multiple-Photon Excitation and Dissociation of Polyatomic Molecules.- Molecular-Beam Studies of Laser-Induced Multiphoton Dissociation.- Two-Frequency Technique for Multiple-Photon Dissociation and Laser Isotope Separation.- Excitation Spectrum of SF6 Irradiated by an Intense IR Laser Field.- Laser-Induced Decomposition of Polyatomic Molecules: A Comparison of Theory with Experiment.- A Method of Laser Isotope Separation Using Adiabatic Inversion.- Three-Level Superfluorescence.