Understanding by-product spectra that accompany XAS data

Dielectric response of materials is a classical phenomenon with quantum mechanical underpinnings. Atomic shell structure gives rise to x-ray absorption near edge spectra (XANES or XAS), which can be computed near edges using many approaches (e.g., self-consistent or time-dependent density functional theory or by the Bethe-Salpeter equation). Results along this line will be presented. Most simply, an absorption event can be considered as the joint product of a photoelectron and core hole that interact. Beyond this, however, there are signatures of other effects within XAS spectra and their by-products. These include features with resonant Auger and resonant inelastic x-ray scattering, as well as signatures because of Debye-Waller factors. We shall survey various aspects of XAS in solid C60, perovskites, simple metals and semiconductors, as well as resonant Auger and related spectra in MoS2 and noble metals.