The current understanding is summarized from a unified point of view, which Bethe initiated four decades ago and which enables one to put a variety of theoretical and experimental data into a coherent picture. Properties of the generalized oscillator strength, which plays the central role in the theory, are treated in detail. The integrated cross section for inelastic scattering and related quantities at the high-velocity limit also are discussed. The theory provides a series of criteria for testing the compatibility of cross-section data and atomic (or molecular) properties that may be obtained from theory or independent experiments.
© 1971 The American Physical Society