This book has developed through a series of lectures on atomic theory
given these last eight years at Chalmers University of Technology and
several oth- er research centers. These courses were intended to make
the basic elements of atomic theory available to experimentalists
working with the hyperfine structure and the optical properties of atoms
and to provide some insight into recent developments in the theory. The
original intention of this book has gradually extended to include a wide
range of topics. We have tried to provide a complete description of
atomic theory, bridging the gap between introductory books on quantum
mechanics - such as the book by Merzbacher, for instance - and present-
day research in the field. Our presentation is limited to static atomic
prop- erties, such as the effective electron-electron interaction, but
the formalism can be extended without major difficulties to include
dynamic properties, such as transition probabilities and dynamic
polarizabilities.