Advances in Quantum Electronics, Volume 3 covers articles on the theoretical and experimental work undertaken in the field of optical pumping and on gaseous ion lasers. The book presents an overview of the optical-pumping field and a review of the use and properties of the density matrix as applied to the statistical behavior of assemblages of atoms or ions. The text discusses the application of the density matrix approach to the theory of optical-pumping r.f. spectroscopy and spin-exchange optical pumping. Optical-pumping experiments are also considered. The book further provides a comprehensive survey of all the important aspects of laser action in gaseous ions, dealing in particular with the spectroscopy of the ion lasers the important and interesting physical processes which occur in them, their properties, technology and applications. People engaged in theoretical and experimental studies in the field of quantum electronics and physicists will find the book invaluable.