X-ray emission spectroscopy
X-ray emission spectroscopy (XES) is a form of X-ray spectroscopy in which a core electron is excited by an incident x-ray photon and then this excited state decays by emitting an x-ray photon to fill the core hole. The energy of the emitted photon is the energy difference between the involved electronic levels. The analysis of the energy dependence of the emitted photons is the aim of the X-ray emission spectroscopy. There are several types of XES and can be categorized as non-resonant XES (XES), which includes -measurements, valence-to-core (VtC/V2C)-measurements, and ()-measurements, or as resonant XES (RXES or RIXS), which includes XXAS+XES 2D-measurement, high-resolution XAS, 2p3d RIXS, and Mössbauer-XES-combined measurements. In addition, Soft X-ray emission spectroscopy (SXES) is used in determining the electronic structure of materials. History The first XES experiments were published by Lindh and Lundquist in 1924 In these early studies, the authors utilized the electron beam of an X-ray tube to excite core electrons and obtain the -line spectra of sulfur and other elements. Three years later, Coster and Druyvesteyn performed the first experiments using photon excitation. Their work demonstrated that the electron beams produce artifacts, thus motivating the use of X-ray photons for creating the core