Inelastic X-Ray Scattering from Electrons in Matter

Abstract

Scattering experiments have given a great deal of important information about the microscopic behavior of an enormous variety of physically interesting systems. Neutrons, [1], electron beams [2] and a range of electromagnetic radiation [3,4] have all been successfully utilized by several groups to elucidate many of the interesting phenomena in condensed matter. The exact information which can be extracted from a given scattering experiment ultimately depends on the characteristics of the probe (typically its energy and momentum) and on the nature of its coupling to the medium. Neutrons have energy in the millivolt range with DeBroglie wave vectors approximating 10 cm⁻¹. They couple primarily to mass (phonons) and magnetic moments (magnons, etc). X-rays are in a real sense the high-frequency limit of visible light. They extend manyfold the range of frequencies and wavelength one can hope to examine. They have energies in the 10 kilovolt range with wavevectors in the 10⁸ cm⁻¹ range. They couple primarily to charge and to light masses (i.e. electrons).