The volume deals with the infrared spectra of complexes of two, three, . . . molecules in collisional interaction. More than 800 original papers have been published in the field since the discovery of collision-induced absorption by H. L. Welsh and associates in 1949. This volume is the first attempt to present the theoretical and experimental foundations of this basic science of the interaction of radiation with supermolecular systems.

Following a brief introduction and recapitulation of background information (e.g., dipole radiation, molecular collisions and interactions, etc.), the measurements of supermolecular absorption of electromagnetic radiation are reviewed. The focus is on the non polar gases whose molecules are infrared inactive but the effects described are universal for nearly all fluids.

At high enough gas densities, corresponding roughly to atmospheric pressure or higher, absorption by complexes of two or more interacting molecules takes place. Supermolecular absorption in gases may be described in terms of a virial expansion in powers of the gas density, a fact that permits the separation of the 2-, 3-, . . . body spectral components for detailed studies. One chapter reviews in detail our knowledge of the interaction-induced dipole moments of dissimilar atomic and of molecular pairs, along with the knowledge of the dipoles of supermolecular systems consisting of three molecules.

In subsequent chapters the theory of interaction-induced absorption by rare-gas mixtures and molecular gases is reviewed. Ab initio calculations of the interaction-induced absorption, especially in the various rotovibrational bands of hydrogen, are reviewed and compared with the measurements. A final chapter discusses related phenomena and important applications, especially in the planetary sciences and astrophysics.

. Specialists and advanced graduate students concerned with the basic principles or applications of the infrared spectroscopy of dense fluids, or with the fundamental interactions of supermolecular complexes with electromagnetic radiation, will find this a valuable text and general reference.