Multiple-order reflections from monochromating crystals for the collection of X-ray absorption spectra at extremely high energies

A simple method to collect X-ray absorption spectra at extremely high energies (greater than or equal to 50 keV) is presented. The method is based on the use of the third harmonic signal from a conventional double-crystal monochromator. Strengths and limitations of the method are shown, together with a few experimental examples on metallic foils and oxide powders in transmission and fluorescence mode

EXAFS Study of Rutile and Anatase

Two crystallographic forms of TiO2 (rutile and anatase) were subject to an extended x-ray absorption fine structure study at the K threshold of titanium. Data analysis was carried out by Fourier methods and curve fitting techniques. Using the theoretical phases, Ti-O bond distances of 1.93(1) Å were derived both for rutile and anatase, as compared to the crystallographic values of 1.948 - 1.980(1) Å (rutile) and 1.934-1.980(1) Å (anatase). The ratio of the cation coordination numbers Nr/Na = 1.07 is close to the theoretical value

Response to W. K. Warburton's Comments on Treatment of EXAFS data taken in the fluorescence mode in non-linear conditions by G. Ciatto et al. (2004). J. Synchrotron Rad. 11, 278–283

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Laboratory EXAFS in a dispersive mode

A laboratory dispersive mode spectrometer, capable of operating in either the analysing crystal transmission mode or a reflection mode, is described. Extended X-ray absorption fine structure (EXAFS) spectra of Re and ReO2, obtained in the transmission mode, compare favourably with those from a scanning spectrometer at a synchrotron source. Factors affecting resolution, intensity and background in this transmission mode are discussed. Experiments with asymmetric reflection geometries, which have shown both improved resolution for X-ray absorption near edge structure (XANES) and reduced collection times, are reported. Methods of reducing backgrounds due to multiple Bragg reflections and Compton scattering are proposed

Anomalous wide-angle X-ray scattering apparatus on the GILDA beamline at the ESRF.

The experimental apparatus for anomalous wide-angle X-ray scattering (AWAXS) on the GILDA beamline at the ESRF is described. The main features are the high beam stability and reproducibility which allow anomalous scattering effects to be resolved also on dilute elements, the large spectral range which allows AWAXS experiments at the K edges of heavy elements, and the use of a high-efficiency detection system. The apparatus has been tested in extreme conditions by performing AWAXS experiments at the Eu K edge in Eu-doped Sr metaphosphate glasses