An introduction to cavity ring-down spectroscopy

Spectroscopy, the study of the interaction of light (electromagnetic radiation) and matter, is the most ubiquitous and precise method available to the physical scientist. Especially for isolated atoms, molecules, and small clusters, it has no peer. It is used to elucidate the structure and dynamics of quantum systems from atomic nuclei to natural proteins. Essentially everything we know about the universe beyond the domain that humans and their instruments can physically touch, comes from spectroscopy. Without it, astronomy would be no more than stamp collecting. While a mature field, spectroscopy is periodically reborn by the development of new tools that open up new vistas, such as under-explored regions of the spectrum, dramatic improvements in resolution, or in sensitivity. Almost always, these are initially unexpected and have been developed to address some specific problem. However, truly seminal work inspires and leads to an explosion of new applica tions and with it advancement of methods. Nuclear magnetic resonance spectroscopy is the epitome of this experience. This book is devoted to Cavity Ring-Down Spectroscopy (CRDS). Like most new methods in science, CRDS grew out of an advance in technology, in this case the dramatic improvement in the reflectivity of the best dielectric mirrors, which in turn was made possible by the development of the ion sputtering method for forming thin films.