IAU Symposium 135 on Interstellar Dust was hosted and co-sponsored by NASA's Ames Research Center from July 26-30, 1988. The symposium was held at the lovely campus of Santa Clara University situated around the historic Santa Clara Mission in California. The meeting was made possible by generous grants from the Astron omy and Relativity Branch of the National Aeronautics and Space Administration and the Galactic Astronomy Program of the National Science Foundation. The International Astronomical Union provided travel grants to a few participants from countries with limited travel funds. We are particularly grateful for the support and services rendered by the dedicated staff at NASA's Ames Research Center and to the" SET! Institute for professionally and expeditiously administering the U.S. grants. This symposium brought together 199 scientists representing 19 different coun tries. The wide range of interest and expertise of the participants - all in some way related to interstellar dust - is reflected in the great variety of topics that were discussed during the symposium ranging from UV, visible and IR observations of interstellar extinction to quantum-statistical calculations of the IR emission from highly vibrationally excited molecules. During the course of the meeting, 41 invited review papers and 140 contributed papers were presented. This book is a collection of the invited review papers. The contributed papers have been published in a companion volume, NASA CP-3036, available from National Technical Information Service, Springfield, Virginia 22161, USA.

The mystery of the diffuse interstellar bands has been variously a curiosity, a co nundrum, and a nuisance for astronomers in the seven decades since the features were first noticed, but recently they have become a forefront issue in astrophysics. Ever since Paul Merrill, in a series of papers starting in 1934, pointed out the interstellar and unidentified nature of the bands, a Who's Who of twentieth century astronomers have tried their hands at solving the problem of identifying the carriers. Henry Norris Russell, Pol Swings, Otto Struve, Paul Ledoux, W. W. Morgan, Walter Adams, Jesse Greenstein, Lawrence Aller, and Gerhard Herzberg all briefly entered the stage, only to move on quickly to other problems where the chances for progress appeared more realistic. In more recent times a number of equally prominent scientists have pursued the bands, but generally only as a sideline to their real astronomical research. But in the past decade, and particularly in the past three years, the view of the search for the diffuse band absorbers as an interesting but perhaps quixotic quest has changed. Today there are several astronomers, as well as laboratory chemists, who are devoting substantial research time and resources to the problem and, as perhaps the most reliable indicator of the newly elevated status of research in this field, some research grants have now been awarded for the study of the bands."

The mystery of the diffuse interstellar bands has been variously a curiosity, a co nundrum, and a nuisance for astronomers in the seven decades since the features were first noticed, but recently they have become a forefront issue in astrophysics. Ever since Paul Merrill, in a series of papers starting in 1934, pointed out the interstellar and unidentified nature of the bands, a Who's Who of twentieth century astronomers have tried their hands at solving the problem of identifying the carriers. Henry Norris Russell, Pol Swings, Otto Struve, Paul Ledoux, W. W. Morgan, Walter Adams, Jesse Greenstein, Lawrence Aller, and Gerhard Herzberg all briefly entered the stage, only to move on quickly to other problems where the chances for progress appeared more realistic. In more recent times a number of equally prominent scientists have pursued the bands, but generally only as a sideline to their real astronomical research. But in the past decade, and particularly in the past three years, the view of the search for the diffuse band absorbers as an interesting but perhaps quixotic quest has changed. Today there are several astronomers, as well as laboratory chemists, who are devoting substantial research time and resources to the problem and, as perhaps the most reliable indicator of the newly elevated status of research in this field, some research grants have now been awarded for the study of the bands.

IAU Symposium 135 on Interstellar Dust was hosted and co-sponsored by NASA's Ames Research Center from July 26-30, 1988. The symposium was held at the lovely campus of Santa Clara University situated around the historic Santa Clara Mission in California. The meeting was made possible by generous grants from the Astron omy and Relativity Branch of the National Aeronautics and Space Administration and the Galactic Astronomy Program of the National Science Foundation. The International Astronomical Union provided travel grants to a few participants from countries with limited travel funds. We are particularly grateful for the support and services rendered by the dedicated staff at NASA's Ames Research Center and to the" SET Institute for professionally and expeditiously administering the U.S. grants. This symposium brought together 199 scientists representing 19 different coun tries. The wide range of interest and expertise of the participants - all in some way related to interstellar dust - is reflected in the great variety of topics that were discussed during the symposium ranging from UV, visible and IR observations of interstellar extinction to quantum-statistical calculations of the IR emission from highly vibrationally excited molecules. During the course of the meeting, 41 invited review papers and 140 contributed papers were presented. This book is a collection of the invited review papers. The contributed papers have been published in a companion volume, NASA CP-3036, available from National Technical Information Service, Springfield, Virginia 22161, USA."

Focusing on the organic inventory of regions of star and planet formation in the interstellar medium of galaxies, this comprehensive overview of the molecular universe is an invaluable reference source for advanced undergraduates through to entry-level researchers. It includes an extensive discussion of microscopic physical and chemical processes in the universe; these play a role in the excitation, spectral characteristics, formation, and evolution of molecules in the gas phase and on grain surfaces. In addition, the latest developments in this area of molecular astrophysics provide a firm foundation for an in-depth understanding of the molecular phases of the interstellar medium. The physical and chemical properties of gaseous molecules, mixed molecular ices, and large polycyclic aromatic hydrocarbon molecules and fullerenes and their role in the interstellar medium are highlighted. For those with an interest in the molecular universe, this advanced textbook bridges the gap between molecular physics, astronomy, and physical chemistry.

This work provides a comprehensive overview of our theoretical and observational understanding of the interstellar medium of galaxies. With emphasis on the microscopic physical and chemical processes in space, and their influence on the macroscopic structure of the interstellar medium of galaxies, the book includes developments in this area of molecular astrophysics. The various heating, cooling, and chemical processes relevant for the rarefied gas and submicron-sized dust grains that constitute the interstellar medium are discussed in detail. This provides a firm foundation for an in-depth understanding of the ionized, neutral atomic, and molecular phases of the interstellar medium. The physical and chemical properties of large polycyclic aromatic hydrocarbon molecules and their role in the interstellar medium are highlighted, and the physics and chemistry of warm and dense photodissociation regions are discussed. This is an invaluable reference source for advanced undergraduate and graduate students, and research scientists.

This work provides a comprehensive overview of our theoretical and observational understanding of the interstellar medium of galaxies. With emphasis on the microscopic physical and chemical processes in space, and their influence on the macroscopic structure of the interstellar medium of galaxies, the book includes developments in this area of molecular astrophysics. The various heating, cooling, and chemical processes relevant for the rarefied gas and submicron-sized dust grains that constitute the interstellar medium are discussed in detail. This provides a firm foundation for an in-depth understanding of the ionized, neutral atomic, and molecular phases of the interstellar medium. The physical and chemical properties of large polycyclic aromatic hydrocarbon molecules and their role in the interstellar medium are highlighted, and the physics and chemistry of warm and dense photodissociation regions are discussed. This is an invaluable reference source for advanced undergraduate and graduate students, and research scientists.