XANES Investigation of Stage 1 and Stage 2 Donor GIC with K and Cs at the Carbon K Edge

Blocker, Jane; Werner, Harald; Herein, Daniel; Schlögl, Robert; Schedel‐Niedrig, Th.; Keil, Matthias; Bradshaw, Alexander M.

doi:10.4028/www.scientific.net/msf.91-93.337

Cited by 6 publications

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“…Graphite crystal.-The PT of graphite crystal near the K absorption edge have been calculated earlier [6,9]. It has been found that our calculation of the PT is in good agreement with the experimental absorption spectra [3].…”

Section: Sh Machavarianisupporting

confidence: 77%

“…It is shown that the method developed gives a simple way to construct an effective x-ray quarter-wave plate. [S0031-9007(98)05347-2] PACS numbers: 78.70.Ck, 07.85.Fv, 78.20.Ci, 78.70.DmExperiments on polarization dependence of x-ray reflectivity fine structure (XRFS) in hexagonal boron nitride (h-BN) crystal [1,2] and on orientational dependence of x-ray absorption near edge structure (XANES) in graphite crystal [3] prove that an appreciable anisotropy of permittivity tensor (PT) in soft x-ray region exists in lowsymmetry crystals when the photon energy is close to the absorption edge. In this case PT depends appreciably on the chemical state and environment of the scattering atoms.…”

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confidence: 99%

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Quarter-Wave Plate in Near-Edge Soft X-Ray Region Based on the Total External Reflection Principle

Machavariani

1998

Phys. Rev. Lett.

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A new way for the development of an x-ray quarter-wave plate is suggested. The idea is based on an effect of total external reflection from an anisotropic crystal in an anomalous dispersion region. It is found that in the case of reflection of plane polarized synchrotron radiation from a uniaxial crystal near the total external reflection angle the reflected radiation can be circularly polarized (right or left handed). The reflected beam polarization is calculated for a hexagonal BN crystal near the boron K absorption edge and for a graphite crystal near carbon K absorption edge. It is shown that the method developed gives a simple way to construct an effective x-ray quarter-wave plate. [S0031-9007(98)05347-2] PACS numbers: 78.70.Ck, 07.85.Fv, 78.20.Ci, 78.70.DmExperiments on polarization dependence of x-ray reflectivity fine structure (XRFS) in hexagonal boron nitride (h-BN) crystal [1,2] and on orientational dependence of x-ray absorption near edge structure (XANES) in graphite crystal [3] prove that an appreciable anisotropy of permittivity tensor (PT) in soft x-ray region exists in lowsymmetry crystals when the photon energy is close to the absorption edge. In this case PT depends appreciably on the chemical state and environment of the scattering atoms. Earlier we have shown [4,5] that this is caused by scattering of the photo or virtual electrons from the neighboring atoms (in the case of the x-ray elastic scattering process photo electrons do not appear in the final state, but the virtual electrons exist in the intermediate state). Because of photo and virtual electron interactions with surrounding atoms the PT becomes anisotropic. This anisotropy has a sharp photon energy dependence in the anomalous dispersion region. Our previous calculations of both and XANES in graphite crystal [6] appear to be in reasonable agreement with experimental spectra.Such an anisotropy of the PT leads not only to polarization and orientation dependencies of x-ray spectra but also to differences in fine structures of left and right-hand circularly polarized radiation in both reflectivity [5] and absorption [7] x-ray spectra. Moreover, this anisotropy in combination with the total external reflection gives an opportunity to create an x-ray polaroid device [8,9].In this paper we suggest to use the effect of total external reflection of x-ray radiation for development of the efficient x-ray quarter-wave plate. The idea of the quarter-wave plate is based, first, on the difference between the critical angles of total external reflection for two different polarizations of the incident radiation in low-symmetry crystals in the anomalous dispersion region and, second, on the sharp dependence of the phase difference between reflected and incident beam from the glancing angle near the total external reflection region.

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Section: Sh Machavarianisupporting

confidence: 77%

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confidence: 99%

Quarter-Wave Plate in Near-Edge Soft X-Ray Region Based on the Total External Reflection Principle

Machavariani

1998

Phys. Rev. Lett.

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“…The spectra of the two samples have two main features, around 285 and 291 eV, which are assigned to π* antibonding and σ* antibonding orbitals at the sp 2 (CC band in the ring) site from the C 1s level, respectively. 25,26 It can be observed that the intensity of the π* feature at around 285 eV of modified OLC is higher than that of T-OLC. This points to an increased π−π stacking between PQ and OLC.…”

Section: ■ Introductionmentioning

confidence: 98%

Electrocatalytic Water Oxidation at Quinone-on-Carbon: A Model System Study

Lin

Lü

et al. 2018

J. Am. Chem. Soc.

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Nanocarbon can promote robust and efficient electrocatalytic water oxidation through active surface oxygen moieties. The recent mechanistic understandings (e.g., active sites) of metal-free carbon catalysts in oxygen evolution reaction (OER), however, are still rife with controversies. In this work, we describe a facile protocol in which eight kinds of aromatic molecules with designated single oxygen species were used as model structures to investigate the explicit roles of each common oxygen group in OER at a molecular level. These model structures were decorated onto typical nanocarbon surfaces like onion-like carbons (OLC) or multiwalled carbon nanotubes (MWCNT) to build aromatic molecule-modified carbon systems. We show that edge (including zigzag and armchair) quinones in a conjugated π network are the true active centers, and the roles of ether and carboxyl groups are excluded in the OER process. The plausible rate-determining step could be singled out by H/D kinetic isotope effects. The turnover frequency per CO (∼0.323 s–1 at η = 340 mV) in 0.1 M KOH and the optimized current density (10 mA/cm2 at 1.58 V vs RHE) of quinone-modified carbon systems are comparable to those of promising metal-based catalysts.

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“…Similar information is accessible with much higher spatial resolution by means of electron energy loss spectroscopy (EELS) in the transmission electron microscope [113,114].…”

Section: Graphiticitymentioning

confidence: 99%

Carbonaceous Deposits

Albers¹,

Weitkamp

2008

Handbook of Heterogeneous Catalysis

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The sections in this article are Introduction Formation and Chemical Nature of Carbonaceous Deposits Educt Molecules and Alkaline Elements Coke Distribution, Porosity and Pore Blocking Graphiticity Hydrogen Content and Hydrogen Analysis Hydrogasification Conclusions

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XANES Investigation of Stage 1 and Stage 2 Donor GIC with K and Cs at the Carbon K Edge

Cited by 6 publications

References 0 publications

Quarter-Wave Plate in Near-Edge Soft X-Ray Region Based on the Total External Reflection Principle

Quarter-Wave Plate in Near-Edge Soft X-Ray Region Based on the Total External Reflection Principle

Electrocatalytic Water Oxidation at Quinone-on-Carbon: A Model System Study

Carbonaceous Deposits

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