Plasma Spectroscopy systematically develops the foundations of spectroscopy for plasmas subjected to quasi-monochromatic electric fields in the microwave or visible range. Such fields may be due to longitudinal Langmuir waves or low hybrid oscillations, which are excited in pulsed discharged or by high-current beams of charged particles. Even more important are the transverse fields present in the plasmas of tokamaks, laser fusion, and technological microwave discharges. This book is intended for researchers dealing with plasma spectroscopy, plasma diagnostics, high frequency and microwave discharges, laser induced discharges, particle and laser-beam interactions with plasmas, controlled fusion, and ionospheric and astrophysical plasmas. It describes methods for measuring the field and plasma parameters and discusses their practical application. It also presents new results on nonpertubative analysis of the interaction of quantum systems with a strong radiation field.