Extended X-ray absorption fine structure

About: Extended X-ray absorption fine structure is a research topic. Over the lifetime, 10452 publications have been published within this topic receiving 276744 citations.

Structure of bimetallic clusters. Extended x-ray absorption fine structure (EXAFS) studies of Ru--Cu clusters

Abstract: A study was made of the extended x‐ray absorption fine structure (EXAFS) associated with the K absorption edges of ruthenium and copper in a silica supported ruthenium–copper catalyst containing 1.0 wt.% ruthenium and 0.63 wt.% copper (1:1 atomic ratio of ruthenium to copper). Previous chemisorption and catalysis studies indicated a strong interaction between the ruthenium and copper in the catalyst, and led to the suggestion that the catalyst consisted of bimetallic clusters of ruthenium and copper dispersed on the silica. The EXAFS data of this investigation provide information on the structure of the ruthenium–copper clusters. The ruthenium in the bimetallic clusters appears to be very similar to the ruthenium in a silica supported ruthenium reference catalyst, in that the ruthenium atoms are coordinated predominantly to other ruthenium atoms and only to a minor extent to copper atoms. By contrast, the copper atoms in the clusters have nearest neighbors which are more nearly equally distributed among c...

Optical absorption edge of semi-insulating GaAs and InP at high temperatures

Abstract: The temperature dependences of the optical absorption edges of semi-insulating GaAs and InP have been measured from room temperature to 905 °C and 748 °C, respectively, with accuracies of ±1 °C at room temperature and ±5 °C at 900 °C. The temperature dependence of the optical absorption edge is adequately reproduced by an Einstein model although the Varshni model gives an improved fit to the band gap. Finally, the widths of the absorption edges are correlated with ionicity.

Optical Absorption of Pure Silver Halides

Abstract: The absorption spectra of pure silver bromide and silver chloride crystals grown from the melt have been measured in and near the so-called "absorption edge," where the absorption coefficient increases very rapidly with frequency. The temperature-dependence of the absorption edge has also been investigated. More limited data have been collected on the absorption spectra of mixed AgBr---AgCl and AgBr---AgI crystals.

Nucleation and Growth Mechanisms of Fe Oxyhydroxide in the Presence of PO4 Ions. 2. P K-Edge EXAFS Study

Abstract: P K-edge EXAFS spectroscopy has been used to determine the local environment of phosphorus during the hydrolysis of FeCl3 in the presence of phosphate. Measurements were performed on liquid samples and in the fluorescence mode. With the detection geometry adopted during experiments, the self absorption of fluorescence has been quantified and does not appear to be an important phenomenon. Thus no correction was made. In order to clearly identify the neighboring atoms around P, a multiple scattering approach has been used. Multiple scattering seems to be an important phenomenon in PO4/FeCl3 clusters. P K-edge EXAFS data show that even for very acidic solutions, pH < 1, all the phosphate ions are complexed to Fe. For a P/Fe molar ratio of 0.2 one phosphate progressively bonds one, two, and three irons when n (=[OH]/[Fe]) increases from 0 to 2.0. At n = 2, one phosphate bridges three iron dimers and two kinds of PO4−Fe linkages are detected. For P/Fe = 0.5, the number of irons linked to PO4 increases when n i...