Niels Bohr (1885-1962) was a Danish physicist who played a key role in the development of atomic theory and quantum mechanics, he was awarded the Nobel Prize for Physics in 1922. Originally written for various journals during the 1920s, these articles investigate the epistemological significance of discoveries in quantum physics.

Introduction to the Theory of Atomic Spectra is a systematic presentation of the theory of atomic spectra based on the modern system of the theory of angular momentum. Many questions which are of interest from the point of view of using spectroscopic methods for investigating various physical phenomena, including continuous spectrum radiation, excitation of atoms, and spectral line broadening, are discussed. This volume consists of 11 chapters organized into three sections. After a summary of elementary information on atomic spectra, including the hydrogen spectrum and the spectra of multi-electron atoms, the reader is methodically introduced to angular momentum, systematics of the levels of multi-electron atoms, and hyperfine structure of spectral lines. Relativistic corrections are also given consideration, with particular reference to the use of the Dirac equation to determine the stationary states of an electron in an arbitrary electromagnetic field. In addition, the book explores the Stark effect and the Zeeman effect, the interaction between atoms and an electromagnetic field, and broadening of spectral lines. The final chapter is devoted to the problem of atomic excitation by collisions. This book is intended for advanced-course university students, postgraduate students and scientists working on spectroscopy and spectral analysis, and also in the field of theoretical physics.

A knowledge of atomic theory should be an essential part of every physicist's and chemist's toolkit. This book provides an introduction to the basic ideas that govern our understanding of microscopic matter, and the essential features of atomic structure and spectra are presented in a direct and easily accessible manner. Semi-classical ideas are reviewed and an introduction to the quantum mechanics of one and two electron systems and their interaction with external electromagnetic fields is featured. Multielectron atoms are also introduced, and the key methods for calculating their properties reviewed.

This book provides a hands-on experience with atomic structure calculations. Material covered includes angular momentum methods, the central field Schrödinger and Dirac equations, Hartree-Fock and Dirac-Hartree-Fock equations, multiplet structure, hyperfine structure, the isotope shift, dipole and multipole transitions, basic many-body perturbation theory, configuration interaction, and correlation corrections to matrix elements. The book also contains numerical methods for solving the Schrödinger and Dirac eigenvalue problems and the (Dirac)-Hartree-Fock equations.