Continuous Cauchy Wavelet Transform of XAFS Spectra

Muñoz, Manuel; Farges, François; Argoul, Pierre

doi:10.1238/physica.topical.115a00221

Cited by 36 publications

(40 citation statements)

References 4 publications

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“…Independent X-ray diffraction measurements affirm a bcc structure with a lattice constant of 286.68±0.03 pm for this sample. Peaks from multiple rescattering paths can be difficult to distinguish in general, and we use continuous Cauchy wavelet transform (CCWT) to decompose the EXAFS amplitude terms in real and reciprocal space (Figure 2A) [39]. Such a 2D plot can provide information for the k and R range of each nearest neighbor shell contribution and discriminate the shell distances for complex systems ( Figure 2C).…”

mentioning

confidence: 99%

Near- and Extended-Edge X-Ray-Absorption Fine-Structure Spectroscopy Using Ultrafast Coherent High-Order Harmonic Supercontinua

et al. 2018

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Recent advances in high-order harmonic generation have made it possible to use a tabletop-scale setup to produce spatially and temporally coherent beams of light with bandwidth spanning 12 octaves, from the ultraviolet up to x-ray photon energies >1.6 keV. Here we demonstrate the use of this light for x-ray-absorption spectroscopy at the K- and L-absorption edges of solids at photon energies near 1 keV. We also report x-ray-absorption spectroscopy in the water window spectral region (284-543 eV) using a high flux high-order harmonic generation x-ray supercontinuum with 10^{9} photons/s in 1% bandwidth, 3 orders of magnitude larger than has previously been possible using tabletop sources. Since this x-ray radiation emerges as a single attosecond-to-femtosecond pulse with peak brightness exceeding 10^{26} photons/s/mrad^{2}/mm^{2}/1% bandwidth, these novel coherent x-ray sources are ideal for probing the fastest molecular and materials processes on femtosecond-to-attosecond time scales and picometer length scales.

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confidence: 99%

Near- and Extended-Edge X-Ray-Absorption Fine-Structure Spectroscopy Using Ultrafast Coherent High-Order Harmonic Supercontinua

et al. 2018

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“…The used k weight for the first shell was 3. CCWT was performed following Muñoz et al [30,36]. FEFF paths were simulated with ARTHEMIS code.…”

Section: Methodsmentioning

confidence: 99%

“…In our case, we applied the Continuous Cauchy Wavelet Analysis (CCWT) to the EXAFS spectra which allows determining the identity of the atoms in noisy signals [30,36].…”

Section: Introductionmentioning

confidence: 99%

Structural characterization and EXAFS wavelet analysis of Yb doped ZnO by wet chemistry route

Otal

Sileo

Aguirre

et al. 2015

Journal of Alloys and Compounds

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a b s t r a c tLanthanide doped ZnO are interesting materials for optical and electrical applications. The wide band gap of this semiconductor makes it transparent in the visible range (E gap = 3.2 eV), allowing a sharp emission from intra shell transition from the lanthanides. From the electrical side, ZnO is a widely used material in varistors and its electrical properties can be tailored by the inclusion of lanthanides. Both applications are influenced by the location of the lanthanides, grain boundaries or lattice inclusion. Yb doped ZnO samples obtained by wet chemistry route were annealed at different temperatures and characterized by Transmission Electron Microscopy (TEM), X-ray Diffraction (XRD), Rietveld refinement of XRD data, and X-ray Absorption Fine Structure (XAFS). These techniques allowed to follow the changes occurred in the matrix and the Yb environment. The use of the Cauchy continuous wavelet transform allowed identifying a second coordination shell composed of Zn atoms, supporting the observations from XRD Rietveld refinement and XAFS fittings. The information obtained confirmed the incorporation of Yb in O h sites of the wurtzite structure without Yb 2 O 3 clustering in the lattice.

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“…For some samples, the third cumulant expansion term, C 3 , was varied to account for anharmonicity in the EXAFS spectra [4]. The presence of multiple scattering was identified using continuous Cauchy wavelet transform analysis (CCWT) [5]. Figure 1 shows that more Zn sorbs on hematite microparticles than on the nanoparticles after normalization for differences in surface area.…”

Section: Methodsmentioning

confidence: 99%

Adsorption and Precipitation of Aqueous Zn(II) on Hematite Nano- and Microparticles

Ha¹,

Farges²,

Brown³

2007

AIP Conference Proceedings

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Abstract. As part of a study of the effect of particle size on reactivity of hematite to aqueous metal ions, the sorption of Zn(II) on hematite nanoparticles and microparticles was examined over a wide range of Zn(II) concentrations using Zn K-edge EXAFS. When reacted with nanoparticles at pH 5.5 and low Zn(II) sorption densities (0.04 < Γ < 2.76 μmol/m 2 ), Zn(II) formed five-coordinated or a mixture of four-and six-coordinated surface complexes with an average Zn-O distance of 2.04(±0.02)Å. At pH 5.5 and high Zn(II) sorption densities (2.76 < Γ < 3.70 μmol/m 2 ), formation of surface precipitates is suggested based on the presence of second-shell Zn and multiple scattering features in the Fourier transform (FT) of the EXAFS spectra. EXAFS fitting of these high Γ samples yielded an average first-shell Zn-O distance of 2.10(±0.02)Å, with second-shell Zn-Fe and Zn-Zn distances of 3.23(±0.03)Å and 3.31(±0.03)Å, respectively. Qualitative comparison between the EXAFS spectra of these sorption samples and that of amorphous zinc hydroxide and Zn-bearing hydrotalcite indicates the development of surface precipitates with increasing Γ. EXAFS spectra of Zn(II) sorbed on hematite microparticles under similar experimental conditions showed no evidence for surface precipitates even at the highest Zn surface coverage (Γ = 4 μmol/m 2 ). These results indicate that reactivities of hematite nanoparticles and macroparticles differ with respect to Zn(II)aq, depending on Zn(II) sorption density. We suggest that the degree of hematite crystallinity affects the reactivity of hematite surfaces toward Zn(II)aq and the formation of the Zn(II) surface complexes.

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Continuous Cauchy Wavelet Transform of XAFS Spectra

Cited by 36 publications

References 4 publications

Near- and Extended-Edge X-Ray-Absorption Fine-Structure Spectroscopy Using Ultrafast Coherent High-Order Harmonic Supercontinua

Near- and Extended-Edge X-Ray-Absorption Fine-Structure Spectroscopy Using Ultrafast Coherent High-Order Harmonic Supercontinua

Structural characterization and EXAFS wavelet analysis of Yb doped ZnO by wet chemistry route

Adsorption and Precipitation of Aqueous Zn(II) on Hematite Nano- and Microparticles

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