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.

Hydrogen and higher shell contributions in Zn2+, Ni2+, and Co2+ aqueous solutions: an X-ray absorption fine structure and molecular dynamics study.

Abstract: A detailed investigation of the hydration structure of Zn2+, Ni2+, and Co2+ in water solutions has been carried out combining X-ray absorption fine structure (EXAFS) spectroscopy and Molecular Dynamics (MD) simulations. The first quantitative analysis of EXAFS from hydrogen atoms in 3d transition metal ions in aqueous solutions has been carried out and the ion−hydrogen interactions have been found to provide a detectable contribution to the EXAFS spectra. An accurate determination of the structural parameters associated with the first hydration shell has been performed and compared with previous experimental results. No evidence of significant contributions from the second hydration shell to the EXAFS signal has been found for these solutions, while the inclusion of the hydrogen signal has been found to be important in performing a quantitative analysis of the experimental data. The high-frequency contribution present in the EXAFS spectra has been found to be due to multiple scattering (MS) effects inside...

Local structures, excited states, and photocatalytic reactivities of highly dispersed catalysts constructed within zeolites

Abstract: Transition metal oxides (Ti, V, Mo, Cr) incorporated within the framework of zeolites as well as transition metal ions (Cu+, Ag+, Pr3+) exchanged within the zeolite cavities were found to exhibit high and unique photocatalytic activities for various reactions such as the decomposition of NOx (NO, N2O) into N2 and O2 or the reduction of CO2 with H2O to produce CH4 and CH3OH. Various in situ spectroscopic investigations of these catalytic systems using photoluminescence, X-ray absorption fine structure (XAFS) (X-ray absorption near edge structure (XANES) and Fourier transform of EXAFS (FT-EXAFS)), electron spin resonance (ESR), FT-IR, etc. revealed that the photo-excited states of these transition metal oxides or ions play a vital role in these photocatalytic reactions. The photocatalytic reactivity of these oxides and ions in their efficiency and selectivity were found to depend strongly on their local structures, which are controlled by the unique and restricted framework structures of zeolites.

l2,3 absorption-spectra of the lighter 3d transition-metals

Abstract: A theory is presented for the x-ray absorption spectra of materials characterized by bandwidths which are somewhat larger than the (quasiatomic) electron correlation energies. Assuming that an empty-band approximation is appropriate for nearly empty bands we show that the problem is much akin to the well-known Coulomb localization problem in Auger spectroscopy, with an enhanced sensitivity for exchange and multipole effects because of the dipole selection rules. Using first-principles band structure and atomic data as input for the theory, we calculate the spectra of Ca, Ti, and V and obtain good agreement with high-resolution experimental spectra.

Some optical properties of the AlxGa1−xAs alloys system

Abstract: Optical transmission data covering the Γ15V–Γ1C absorption edge are presented, together with photoluminescence (PL) results, for AlxGa1−xAs crystals of high purity [n (293 K) <1017 cm−3] for 0