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The electron-density distribution and the contribution to anomalous scattering factors for Fe ions in magnetite have been analyzed by X-ray resonant scattering at the pre-edge of Fe K absorption. Synchrotron X-ray experiments were carried out using a conventional four-circle diffractometer in the right-handed circular polarization. Difference-Fourier synthesis was applied with a difference in structure factors measured on and off the pre-edge ( Eon = 7.1082 keV, Eoff = 7.1051 keV). Electron-density peaks due to X-ray resonant scattering were clearly observed for both A and B sites. The real part of the anomalous scattering factor f′ has been determined site-independently, based on the crystal-structure refinements, to minimize the squared residuals at the Fe K pre-edge. The f′ values obtained at Eon and Eoff are −7.063 and −6.682 for the A site and −6.971 and −6.709 for the B site, which are significantly smaller than the values of −6.206 and −5.844, respectively, estimated from the Kramers-Kronig transform. The f′ values at Eon are reasonably smaller than those at Eoff. Our results using a symmetry-based consideration suggest that the origin of the pre-edge peak is Fe ions occupying both A and B sites, where p- d mixing is needed with hybridized electrons of Fe in both sites overlapping the neighbouring O atoms. [ABSTRACT FROM AUTHOR]

Spatial distribution of bromobenzene (BrBz) and 4-bromophenol (BrPh) as hydrophobic aromatic compounds incorporated in polymer micelles with vesicular structure consisting of poly(ethylene glycol)-b-poly(tert-butyl methacrylate) (PEG-b-PtBMA) in aqueous solution is investigated by anomalous small-angle X-ray scattering (ASAXS) analyses near Br K edge. Small-angle X-ray scattering (SAXS) intensities from PEG-b-PtBMA micelles containing BrBz and BrPh were decreased as the energy of incident X-ray approached to Br K edge corresponding to the energy dependence of anomalous scattering factor of Br. The analysis for the energy dependence of SAXS profiles from the PEG-b-PtBMA micelles containing BrBz revealed that BrBz molecules were located in hydrophobic layer of PEG-b-PtBMA micelles. On the contrary, it was found by ASAXS that BrPh existed not only in the hydrophobic layer but also in the shell layer. Since ASAXS analysis successfully accomplished to visualize the spatial distribution of hydrophobic molecules in polymer micelles, it should be expected to be a powerful tool for characterization of drug delivery vehicles. [ABSTRACT FROM AUTHOR]

The polarization dependence of the cross sections of two-photon transitions including X-ray scattering was analyzed. We developed the regular approach to the derivation of the polarization parameters of photoprocesses. Our approach is based on the tensor representation of the photon density matrix, which is written in terms of the unit vectors directed along the major axis of the polarization ellipse ( ϵ ˆ ) and the photon propagation ( k ˆ ). Explicit expressions for the product of two photon density matrices were derived. As an example, the parametrization of the polarization dependence of the X-ray scattering by closed-shell atoms is given both in terms of (i) scalar products of photon vectors ϵ ˆ 1 , 2 , k ˆ 1 , 2 and (ii) X-ray Stokes parameters. We discuss the applicability of the atomic scattering for the measurement of the polarization of X-rays. [ABSTRACT FROM AUTHOR]

We review our recent studies on the occurrence of atomic charge localization in magnetite and halfdoped manganites. X-ray resonant scattering experiments at the iron K-edge of magnetite and X-ray absorption spectroscopy at the Mn K-edge of Ca-doped manganites show the lack of charge localization on the transition metal atom, either temporal or spatial. The evolution of the intensity of (002) and (006) forbidden reflections in magnetite across the Verwey transition, as a function of the incoming X-ray beam energy, the azimuthal angle and the polarization of the scattering process, indicates that the atomic anomalous scattering factors for the octahedral iron ions are identical to each other, i.e. all of them show an identical electronic state. High resolution XANES spectra of RE[sub 1-χ]Ca[sub χ]MnO[sub 3] series cannot be reproduced by a linear combination of REMnO[sub 3] and CaMnO[sub 3] spectra. Accordingly, the electronic state of the Mn atom in these intermediate compounds cannot be described as a bimodal distribution of Mn[sup 3+] and Mn[sup 4+] pure ionic states. The claimed experimental evidence of charge ordering in Mn[sup 3+]/Mn[sup 4+] = 1 manganites proposed from X-ray resonant scattering experiments has also been critically re-examined. We show that although these experiments prove the existence of two kinds of Mn atoms, they cannot be identified as Mn[sup 3+] and Mn[sup 4+] ions. Moreover, the so-called chargeordering (CO) and orbital-ordering (OO) resonant scattering reflections are naturally explained due to the presence of local distortions without including any ordering of the Mn d-orbitals. [ABSTRACT FROM AUTHOR]

Elemental distributions of Fe, Mn, and Co in ultrathin FeMn/Co multilayers have been profiled by the x-ray anomalous scattering technique. Chemical intermixing is observed at the FeMn/Co interfaces with intermixing regions up to 14 Å. The chemical compositions in the intermixing regions are found to vary gradually from FeMn to FeMnCo[sub 2] and from FeMnCo[sub 2] to Co., respectively, but not from FeMn to Co. This result suggests that a reaction may occur and FeMnCo[sub 2] appears at the interface during the deposition. © 2002 American Institute of Physics. [ABSTRACT FROM AUTHOR]

Overlapping absorption edges will occur when an element is present in multiple oxidation states within a material. DetOx is a program for partitioning overlapping X-ray absorption spectra into contributions from individual atomic species and computing the dependence of the anomalous scattering factors on X-ray energy. It is demonstrated how these results can be used in combination with X-ray diffraction data to determine the oxidation state of ions at specific sites in a mixed-valance material, GaCl2. [ABSTRACT FROM AUTHOR]

The pattern of charge modulations and local anisotropies below the Verwey transition has been determined and quantified in high-quality Fe3O4 single crystals and thin films grown on MgO by using resonant X-ray scattering at the Fe K-edge. The energy, polarization and azimuthal angle dependencies of an extensive set of reflections with potential sensitivity to charge or local anisotropy orderings have been analyzed to explore their origins. A charge disproportion on octahedral B sites of 0.20 ± 0.05 e− with [0 0 1] and cubic periodicities has been confirmed, while no significant charge disproportion has been obtained with [0 0 1/2] cubic periodicity. Additional charge modulations in the monoclinic a-b plane are also present. In addition, the occurrence of new forbidden (1, 1, 0) and (0, 0, 2 n + 1/2) cubic reflections that arise from the anisotropy of the local structure around different tetrahedral and octahedral Fe atoms is shown. This complex pattern of weak charge modulations and local anisotropies is fully compatible with the low-temperature crystal structure refined in the non-polar C2/ c space group and disproves any bimodal charge disproportion of the octahedral Fe atoms. [ABSTRACT FROM AUTHOR]

Abstract: We have performed resonant X-ray scattering study on at the Pr and edges. Below the metal–insulator transition temperature , resonant signal appears in the superlattice reflections in addition to the lattice distortion, which demonstrates that different electronic states of the Pr atoms are alternatingly ordered in the BCC unit cell. Polarization analysis of the scattered X-ray shows that the intensity changing the polarization from to is absent or very weak. This means that the difference of the anomalous scattering factor between two Pr atoms in the BCC unit cell, which reflects the character of the intermediate 5d states of the resonant process, is almost isotropic. [Copyright &y& Elsevier]

The characteristic in-plane length scales of ultrathin films of regenerated cellulose are measured using noncontact atomic force microscopy (NC-AFM) and grazing incidence small-angle x-ray scattering (GISAXS) in ambient atmosphere and under various humidity conditions. The aim is to elucidate the structural basis for the excellent compatibility of cellulose supports to planar lipid membranes. Films are deposited on silicon wafers by Langmuir-Blodgett (LB) transfer and spin coating. NC-AFM height profiles and the resulting calculated power spectral density functions indicate that both kinds of cellulose films have almost identical root-mean-square roughness values (0.7–0.8 nm) and very similar characteristic length scales (32 nm), respectively. GISAXS measurements, both above and below the critical angle of total external reflection, show that the dominant length scales in the bulk and near the surface of the films are comparable (∼50 nm). The origin of these length scales can be attributed to the bundle of rodlike molecules of cellulose that result during the regeneration process (i.e., as a consequence of the cleavage of the silyl side chains of trimethylsilylcellulose). Exposure of the cellulose samples to various humidities shows that above a relative humidity of 97% a significant swelling of the films occurs, which is consistent with our previous findings. The swelling of films with more than 30 LB monolayers of cellulose induces a remarkable out-of-plane rearrangement of the cellulose bundles, due to a reduced influence of the solid substrate compared to thinner films with only eight to ten LB monolayers. [ABSTRACT FROM AUTHOR]

The article introduces the resonant X-ray scattering (RXS) as a technique to detect the orbital ordering of electrons. Magnetic ions in a highly symmetrical crystalline field may have an orbital degeneracy in the ground state. When the electrons partially occupy the degenerate states, it is defined as a system having orbital degrees of freedom. Further, the RXS can be applied to the detection of the orbital ordering in f-electron systems, that is, quadrupolar ordering. The much weaker coupling between the orbital degree of freedom and the lattice in 4f-electron systems makes them an ideal platform to study orbital interactions originating from electronic mechanisms.

Total X-ray scattering intensities σ[sub ee]([sup q]) for N[sub 2] and CO have been measured as a function of momentum transfer using the energy dispersive method. Novel procedures to extract accurate σ[sub ee]([sup q]), which eliminate effects of polarization, inelastic scattering, anomalous dispersion, and molecular vibration, have been proposed. A simplified theoretical treatment based on configuration interaction singles and doubles (CISD) calculations has been suggested. This procedure makes it possible to apply combined theoretical and experimental X-ray scattering studies to larger molecules. The inclusion of f and g functions is crucial, and the σ[sub ee]([sup q]) calculated with the cc-pVQZ[5s4p3d2f1g] basis set almost reproduces the data based on more elaborate MR-CISD calculations within the experimentally most relevant region of up to [sup q] ≈ 3au. In contrast to experimental electron scattering data, the X-ray scattering intensities agree well with the computed results. [ABSTRACT FROM AUTHOR]

The miscibility of Ag with FePt composited films was investigated with anomalous x-ray scattering (AXS) and extended x-ray absorption fine structure (EXAFS) at Ag K edge. In the AXS spectra for FePt Bragg peaks, the cusp near Ag K edge was observed, indicating alloying between Ag and FePt in the FePt-Ag thin films. Semiquantitative analysis showed 4.2 at. % and 5.9 at. % Ag were in FePt lattice for the samples with 20 vol % and 30 vol % Ag, respectively. EXAFS studies indicated in the alloyed FePt-Ag phase, Ag replaced the Fe sites in FePt lattice. Most of Ag segregated from FePt and formed fcc phase. This segregated Ag phase only had short range order, which may be due to that segregated Ag had small grain size and/or some disordered Ag phase existed in FePt grain boundaries. [ABSTRACT FROM AUTHOR]

Scattering techniques represent non-invasive experimental approaches and powerful tools for the investigation of structure and conformation of biomaterial systems in a wide range of distances, ranging from the nanometric to micrometric scale. More specifically, small-angle X-rays and neutron scattering and light scattering techniques represent well-established experimental techniques for the investigation of the structural properties of biomaterials and, through the use of suitable models, they allow to study and mimic various biological systems under physiologically relevant conditions. They provide the ensemble averaged (and then statistically relevant) information under in situ and operando conditions, and represent useful tools complementary to the various traditional imaging techniques that, on the contrary, reveal more local structural information. Together with the classical structure characterization approaches, we introduce the basic concepts that make it possible to examine inter-particles interactions, and to study the growth processes and conformational changes in nanostructures, which have become increasingly relevant for an accurate understanding and prediction of various mechanisms in the fields of biotechnology and nanotechnology. The upgrade of the various scattering techniques, such as the contrast variation or time resolved experiments, offers unique opportunities to study the nano- and mesoscopic structure and their evolution with time in a way not accessible by other techniques. For this reason, highly performant instruments are installed at most of the facility research centers worldwide. These new insights allow to largely ameliorate the control of (chemico-physical and biologic) processes of complex (bio-)materials at the molecular length scales, and open a full potential for the development and engineering of a variety of nano-scale biomaterials for advanced applications. [ABSTRACT FROM AUTHOR]

The phase miscibility of Co, Cr and Pt in oriented nanostructured CoCrPt magnetic thin films was investigated using anomalous x-ray scattering (AXS) from the (002) reflection and extended x-ray absorption fine structure (EXAFS) at Co K, Cr K and Pt LIII edges. The AXS measurements at Co K edge clearly showed the presence of Co in the crystalline region. However, Cr was not detected in the lattice. The EXAFS at Co K edge indicated that the nearest neighboring atoms of Co were mixed with 80% Co and 20% Pt, consistent with the results of EXAFS at Pt LIII edge. Our observations suggested that only Pt and Co were at the Co (002) lattice of the nanotextured CoCrPt thin films. This indicated that the AXS alone may not be reliable to determine the phase miscibility in textured thin films. Complementary information from the EXAFS was useful to understand the phase miscibility of nanoscale materials. [ABSTRACT FROM AUTHOR]

We have determined the absolute indium content incorporated in the crystalline lattice of InGaN films and InGaN/GaN multiple quantum wells using anomalous x-ray scattering (AXS). AXS spectra were obtained near the In K absorption edge at the InGaN (0006) Bragg peak where the InGaN Bragg reflection is well-resolved from the GaN reflections. By comparing the indium composition obtained by AXS to regular x-ray scattering results, which are also sensitive to the lattice strain, we determine the Poisson ratio of InGaN to be ν≈0.23. The AXS method can be effective in determining absolute chemical composition of InGaN independent of the lattice strain, which is especially valuable for InGaN multiple quantum wells. [ABSTRACT FROM AUTHOR]

Reports on the structure determination of nanostructured nickel-cobalt films by anomalous x-ray scattering. Structural characterization of solid solutions by conventional x-ray diffraction; Components of the atomic scattering factor; Fabrication of nanostructured metastable alloy from immiscible elements using nanoequilibrium processing.

Anomalous small-angle X-ray scattering measurements of Zr–Cu–Al–Ni quaternary alloys have been made at the Zr K absorption edge. In melt-quenched samples, small cluster components without crystallization were found. The contrast change at the edge suggested that compositional fluctuation of Al is incorporated. [ABSTRACT FROM AUTHOR]