X-ray absorption spectroscopy

Physical Biosciences Division, Lawrence Berkeley National Laboratory, University of California, Berkeley, CA 94720, USA.
Photosynthesis Research (Impact Factor: 3.5). 09/2009; 102(2-3):241-54. DOI: 10.1007/s11120-009-9473-8
Source: PubMed


This review gives a brief description of the theory and application of X-ray absorption spectroscopy, both X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS), especially, pertaining to photosynthesis. The advantages and limitations of the methods are discussed. Recent advances in extended EXAFS and polarized EXAFS using oriented membranes and single crystals are explained. Developments in theory in understanding the XANES spectra are described. The application of X-ray absorption spectroscopy to the study of the Mn(4)Ca cluster in Photosystem II is presented.

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    • "Scattering (RIXS) are routine methods in surface and solid-state investigations at third generation synchrotron radiation sources [1] [2] [3] [4]. The development of forth generation free-electron-laser (FEL) sources such as FERMI, FLASH, LCLS and XFEL opens new perspectives for single-shot XES and RIXS measurements of low-density, liquid and condensed matter [5] [6] [7] [8] [9]. "
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    ABSTRACT: We present the design and characterization of a compact and portable spectrometer realized for photon in-photon out experiments (in particular X-Ray Emission Spectroscopy, XES), in particular tailored to be used at the FERMI freeelectron- laser (FEL) at ELETTRA (Italy). The spectrometer can be installed on different end stations at variable distances from the target area both at synchrotron and FEL beamlines. Different input sections can be accommodated in order to fit the experimental requests, with/without an entrance slit and with/without an additional relay mirror. The design is compact in order to realize a portable instrument within a total footprint of less than one square meter. The instrument is based on the use of two flat-field grazing-incidence gratings and an EUV-enhanced CCD detector to cover the 25-800 eV spectral range, with spectral resolution better than 0.2%. The absolute response of the spectrometer, has been measured in the whole spectral region of operation, allowing calibrated measurements of the photon flux. The characterization on the Gas Phase beamline at ELETTRA Synchrotron as instrument for XES and some experimental data of the FEL emission taken at EIS-TIMEX beamline at FERMI, where the instrument has been used for photon beam diagnostics, are presented.
    SPIE Optical Engineering + Applications; 09/2014
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    • "XAS of arsenic in environmental samples generally uses the principles of x-ray fluorescence ; that is, incoming X-rays with energy at or higher than the binding energy of a core electron of the arsenic compound (E O ) are absorbed, ejecting a core electron and allowing another electron from the outer shells to fill the hole, emitting florescence [55]. X-ray absorption spectra are characterized by a sharp increase in absorption at specific X-ray photon energies giving rise to an absorption edge that is characteristic of the absorbing element [56]. The absorption edge corresponds to the energy required to eject a core electron; when a 1 s electron is ejected this is called a K-edge. "
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    ABSTRACT: The toxicity of arsenic greatly depends on its chemical form and oxidation state (speciation) and therefore accurate determination of arsenic speciation is a crucial step in understanding its chemistry and potential risk. High performance liquid chromatography with inductively coupled mass spectrometry (HPLC-ICP-MS) is the most common analysis used for arsenic speciation but it has two major limitations: it relies on an extraction step (usually from a solid sample) that can be incomplete or alter the arsenic compounds; and it provides no structural information, relying on matching sample peaks to standard peaks. The use of additional analytical methods in a complementary manner introduces the ability to address these disadvantages. The use of X-ray absorption spectroscopy (XAS) with HPLC-ICP-MS can be used to identify compounds not extracted for HPLC-ICP-MS and provide minimal processing steps for solid state analysis that may help preserve labile compounds such as those containing arsenic-sulfur bonds, which can degrade under chromatographic conditions. On the other hand, HPLC-ICP-MS is essential in confirming organoarsenic compounds with similar white line energies seen by using XAS, and identifying trace arsenic compounds that are too low to be detected by XAS. The complementary use of electrospray mass spectrometry (ESI-MS) with HPLC-ICP-MS provides confirmation of arsenic compounds identified during the HPLC-ICP-MS analysis, identification of unknown compounds observed during the HPLC-ICP-MS analysis and further resolves HPLC-ICP-MS by identifying co-eluting compounds. In the complementary use of HPLC-ICP-MS and ESI-MS, HPLC-ICP-MS helps to focus the ESI-MS selection of ions. Numerous studies have shown that the information obtained from HPLC-ICP-MS analysis can be greatly enhanced by complementary approaches.
    Spectrochimica Acta Part B Atomic Spectroscopy 09/2014; 99. DOI:10.1016/j.sab.2014.07.001 · 3.18 Impact Factor
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    Chemical Reviews 12/2007; 107(11):5004-64. DOI:10.1021/cr0500030 · 46.57 Impact Factor
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