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.

Cobalt valence states and origins of ferromagnetism in Co doped TiO2 rutile thin films

Abstract: Co doped rutile thin films were fabricated on α-Al2O3 (10-12) substrates by laser molecular beam epitaxy. X-ray diffraction, scanning electron microscopy, and transmission electron microscopy indicated that the rutile thin films are (101) oriented and have smooth surfaces with no impurity phases. Co K-edge x-ray absorption near-edge structure, extended x-ray absorption fine structure, and x-ray photoelectron spectroscopy revealed the coexistence of different valence states of Co in the film. Magnetic circular dichroism studies suggest that the observed ferromagnetism is uniform and is related to the electron band structure of TiO2 rutile. Contribution of oxidized (Co2+) and metallic (Co0) cobalt to the ferromagnetism is discussed.

Structural analysis of ultrafast extended x-ray absorption fine structure with subpicometer spatial resolution: application to spin crossover complexes.

Abstract: We present a novel analysis of time-resolved extended x-ray absorption fine structure (EXAFS) spectra based on the fitting of the experimental transients obtained from optical pump/x-ray probe experiments. We apply it to the analysis of picosecond EXAFS data on aqueous [FeII(bpy)3]2+, which undergoes a light induced conversion from its low-spin (LS) ground state to the short-lived (τ≈650 ps) excited high-spin (HS) state. A series of EXAFS spectra were simulated for a collection of possible HS structures from which the ground state fit spectrum was subtracted to generate transient difference absorption (TA) spectra. These are then compared with the experimental TA spectrum using a least-squares statistical analysis to derive the structural change. This approach reduces the number of required parameters by cancellation in the differences. It also delivers a unique solution for both the fractional population and the extracted excited state structure. We thus obtain a value of the Fe–N bond elongation in the ...

Determination of the temperature dependence of the free carrier and interband absorption in silicon at 1.06μm

Abstract: Simultaneous determinations of the free-carrier absorption cross-section, the interband absorption coefficient, and the surface reflectivity, at the Nd:YAG laser wavelength 1.06 mu m and in the temperature interval 195-372K are reported, using a method developed previously. The influence of the free-carrier absorption is described by an analytical model which fits the experimental data very well. The values of the interband absorption coefficient measured with short high-intensity laser pulses agree with the literature values measured at low intensity. The free-carrier absorption cross-section sigma was found to be proportional to the absolute temperature, sigma = sigma n+ sigma p=1.7*10-20 T cm2.

Practical method for full curved-wave theory analysis of experimental extended x-ray-absorption fine structure

Abstract: Recent work has indicated that the single-scattering theory of x-ray absorption may be valid down to much closer to the edge than previously thought. It is in this region that the plane-wave approximation used in the standard extended x-ray-absorption fine structure analysis breaks down. Using a simple reformulation, we obtain modified backscattering amplitude and phase-shift functions which are similar to those of Teo and Lee but which use the full curved-wave theory for single scattering. These can then be used to analyze experimental data without any modification of those programs that presently use the functions of Teo and Lee. We also present results of using this method to compare experimental data with theoretical calculations for copper metal and NiO.