C. H. Townes, winner of the Nobel Prize, and the distinguished scientist A. L. Schawlow have written a fundamental text on microwave spectroscopy. Microwave spectroscopy is the term for spectroscopic techniques based upon the absorption of radiation in the 1 to 1,000mm range. In the decades following World War II these techniques developed into a powerful research tool for the investigation of molecules and atoms. Microwave spectroscopy is now used in such diverse fields as nuclear physics, molecular structure, chemical kinetics, quantum electrodynamics, and astronomy. This systematic and comprehensive account of theory, techniques, experimental data and their interpretation is an important reference of lasting value to students, teachers, scientists, and researchers in any of the above fields or those specifically interested in microwave spectroscopy. The material in this volume is discussed critically, systematically, and in the simplest way. The simplicity of wording and mathematics (no group theory, as such, is used) will allow most of the discussion to be profitably read by those with a very elementary knowledge of quantum mechanics and atomic physics. Although the treatment is a continuously developed one, the authors have made each chapter — 18 in all — and each section as independent of the others as is practical so that the book can be used in as many fields as possible. The appendixes give most of the tables and information needed in doing research and in interpreting microwave spectra. They also contain extensive data on nuclear and molecular constants, including essentially all those determined by microwave techniques. "With each of its eighteen chapters essentially self-contained, this book is equally suitable for use as fundamental reference or advanced textbook." — U.S. Quarterly Book Review.