Science

Shell fitting of extended X-ray absorption fine structure (EXAFS) is commonly done in Artemis, part of the Demeter package. Athena turns an experimental spectrum into a file Artemis can import. Artemis then lines the measured oscillation up with scattering paths from FEFF, and from that estimates the coordination number $N$, a distance correction, the disorder $\sigma^2$, and the energy-origin shift $\Delta E_0$. The interface, the order of operations, and three examples are kept apart below....

Battery-material characterisation usually falls into three layers. Diffraction and electron microscopy read structure and morphology. Raman spectroscopy and X-ray photoelectron spectroscopy (XPS) read chemical state. In-situ diffraction and absorption read the charge–discharge process. In an all-solid-state cell the interface reactions often sit inside the sample, so that part leans on synchrotron X-ray diffraction (SXRD) and X-ray absorption spectroscopy (XAS), which can penetrate the cell. ...

All-solid-state lithium-ion batteries (ASSLIBs) replace the liquid electrolyte with a solid electrolyte (SE). Both the electrodes and the electrolyte are solids, so the interfaces are buried. Side reactions, poor contact, and lithium dendrites are hard to see directly. Synchrotron X-rays can do diffraction, absorption spectroscopy, and imaging in the same facility, which is why they are used to watch bulk ion transport and how a solid–solid interface changes during cycling. The cases below ar...

The near-edge structure (XANES) of an X-ray absorption spectrum can be used to discuss the local chemical environment of the absorbing atom. The thirteen questions below are grouped as structure and speciation, quantitative analysis, and how a spectrum changes. The thirteen questions Approach What is observed Example or question Coordination edge and near-edge shape separate valence, coordination number, or geometry Crystallinity spectral shape crystalline versus amorphous $\mathrm{SiO...

Grazing-incidence wide-angle X-ray scattering (GIWAXS) is suited to molecular packing, crystal orientation, and crystallisation in thin films. This note keeps the composition ratios, spectral parameters, and times reported for D18/BTP-eC9-4F organic films, and lines them up with the other measurements in the same source. What GIWAXS measuresSynchrotron X-rays hit the film at a grazing angle of about 0.1°–1°. The source states that the evanescent wave from total reflection at the interfac...

Synchrotron radiation (SR) and X-ray absorption spectroscopy (XAS) are often mentioned together, but they are not the same object. A synchrotron is a light source. XAS is an experiment that uses X-rays interacting with matter to analyse a sample. The synchrotron: a source of tunable X-raysSynchrotron radiation is the electromagnetic radiation emitted along the tangent when a fast charged particle is deflected in a magnetic field. In 1947, researchers saw the intense radiation produced when hi...

The SXAS formulae are short. The time goes into beamtime, vacuum, and the sample. What follows is the shape of a typical synchrotron soft X-ray experiment. It is a process note, not a claim that a particular beamline has already been measured. 1. Write the proposal, then wait for timeA synchrotron station is not walk-up. Users submit a proposal: the scientific question, why this edge is required, the sample form, the polarisation, temperature, or in-situ environment, and how many edges will ...

An XAS scan from low energy to high energy looks like a flat line, then a step, then a wobble. The usual split is: XANES (X-ray absorption near-edge structure): the pre-edge, the edge, and roughly the first 50 eV above it. EXAFS (extended X-ray absorption fine structure): the decaying oscillations from about 50 eV above the edge out to several hundred electronvolts. In soft X-ray and surface-science papers, the near-edge region is often called NEXAFS (near-edge X-ray absorption fine structu...

SXAS stands for Soft X-ray Absorption Spectroscopy. It belongs to the wider family of XAS, with the photon energy kept between roughly 50 eV and 2 keV. That window happens to cover: the K-edges of carbon, nitrogen, oxygen and fluorine (a 1s electron is excited); the L-edges of 3d transition metals (2p → 3d); some alkali and alkaline-earth edges. In other words, it is good at light elements and 3d metals — exactly the actors in battery materials, catalysts, polymers and biomolecules. The ab...

“Synchrotron radiation” sounds like nuclear physics, but the everyday picture is simpler: push electrons to almost the speed of light, then make them turn. Turning costs the electrons energy, and that energy leaves as light. The light spans infrared, ultraviolet and hard X-rays, and it is several orders of magnitude brighter than a laboratory X-ray tube. So a synchrotron is not a bigger X-ray machine. It is a whole facility — accelerator, storage ring and experimental stations chained togethe...