This book consolidates and brings up to date the variational theory and methods currently used in many branches of theoretical physics and chemistry. The text surveys essential ideas and methods, concentrating on theory as used in applications rather than on fine points of rigorous mathematics. Essential concepts are developed in a common notation and from a uniform critical point of view. Examples of important applications are reviewed in sufficient detail to provide the reader with a critical understanding of context and methodology.

The investigation of scattering phenomena is a major theme of modern physics. A scattered particle provides a dynamical probe of the target system. The practical problem of interest here is the scattering of a low- energy electron by an N-electron atom. It has been difficult in this area of study to achieve theoretical results that are even qualitatively correct, yet quantitative accuracy is often needed as an adjunct to experiment. The present book describes a quantitative theoretical method, or class of methods, that has been applied effectively to this problem. Quantum mechanical theory...