What is XANES spectra?
What is XANES spectra?
X-ray Absorption Near Edge Strucure (XANES) is a type of X-ray Absorption Spectroscopy (XAS). It refers to the absorption fine structure close to an absorption edge, about the 10 eV below the absorption edge and 20 eV above the edge. XANES is also called Near Edge X-Ray Absorption Fine Structure (NEXAFS).
How does XANES spectroscopy work?
The fundamental processes which contribute to XANES spectra: 1) photoabsorption of an x-ray into a core level followed by photoelectron emission, followed by either 2) (left) filling of the core hole by an electron in another level, accompanied by fluorescence; or (right) filling of the core hole by an electron in …
What does XANES measure?
2.3. XAS measures the X-ray absorption coefficient of a material as a function of energy. Each element has a set of characteristic absorption edges corresponding to the different binding energies of its electrons, giving XAS element selectivity.
What is the difference between XANES and EXAFS?
EXAFS (Extended X-ray Absorption Fine Structure) yields information about the interatomic distances, near neighbor coordination numbers, and lattice dynamics. XANES (X-ray Absorption Near Edge Structure), on the other hand, gives information about the valence state, energy bandwidth and bond angles.
What is K-edge Xanes?
K-edge. L-edges. An edge results when a core electron absorbs energy equal to or greater than its binding energy. Edges are labeled according to the shell the core electron originates from. XAS is an element specific technique.
Is Xanes surface sensitive?
This method is only sensitive to the first ~10s of nm of the sample surface due to electron scattering, and only works for solid samples.
What is EXAFS analysis?
Analysis of the extended x-ray-absorption fine-structure (EXAFS) provides fine details of the partial pair distribution functions of atoms surrounding the absorber, including distances, mean square deviations in distance, coordination numbers, and coordinating species.
What is the difference between XAS and XPS?
In XPS one is analyzing the kinetic energy of the photoelectrons that are emitted due to the excitation by X-rays of well-defined energy. XAS or XAFS provides unique information on the structure as well as on the electronic structure of a system [1, 2, 3].
What determines Xray absorption?
the X-ray absorption near edge structures (XANES), and. The resolution in the X-ray spectra, determined by the optical setup (monochromators or mirrors) should be high for the XANES (Δ ≤ 0.2 eV) and can be low for the EXAFS (Δ ≈ 6 eV) (Bianconi, 1980).
Why is AES surface sensitive?
Surface sensitivity in AES arises from the fact that emitted electrons usually have energies ranging from 50 eV to 3 keV and at these values, electrons have a short mean free path in a solid. Because of the low energy of Auger electrons, most AES setups are run under ultra-high vacuum (UHV) conditions.
What is the function of retarding voltage in Nexafs?
The surface sensitivity can be further enhanced by applying a retarding voltage. By suppressing lower kinetic energy electrons, only those electrons that emerge from the outermost surface region (3nm) are detected.
What are the application of EXAFS?
Frequent use of EXAFS occurs in environmental chemistry, where scientists try to understand the propagation of pollutants through an ecosystem. EXAFS can be used along with accelerator mass spectrometry in forensic examinations, particularly in nuclear non-proliferation applications.