Spectra are fundamental characteristics of atoms and ions, and are the main source of information on their structure and properties. This monograph presents a complete guide to the theory of modern spectroscopy of atoms. The book describes the contemporary state of the theory of many-electron atoms and ions, the peculiarities of their structure and spectra, the processes of their interaction with radiation, and some of the applications of atomic spectroscopy. It contains a large number of new results, which have been mainly published in Russian and are therefore almost unknown to Western...