Spectroscopy of the anomalous scattering and transport of the X-ray fluorescence inside hollow microcapillaries

The reflection X-ray spectra have been studied experimentally and theoretically in the case of the grazing incidence of radiation on the plane surface and walls of the channels of microchannel plates. The fine structure of the X-ray spectra, as well as the angular distribution of the field passed through microchannels, has been analyzed for the energy corresponding to the anomalous dispersion region of the Si L _{2, 3} absorption edge. The theoretical calculations have been performed within the model including the transition layer on the surface of the sample.     

Anomalous X-ray scattering studies on semiconducting and metallic glasses

In order to explore local- and intermediate-range atomic structures of several semiconducting and metallic glasses, anomalous X-ray scattering (AXS) experiments were performed using an improved detecting system suitable for third-generation synchrotron radiation facilities, and the obtained data were analyzed using reverse Monte Carlo (RMC) modelling to obtain partial structure factors and to construct three-dimensional atomic configurations of these glasses. Examples of GeSe₂ semiconducting and Pd₄₀Ni₄₀P₂₀ metallic glasses are demonstrated to exhibit the feasibility of the combination of AXS and RMC techniques. Importance of an additional combination with neutron scattering is also described for alloys containing light elements.     

Anomalous small-angle X-ray scattering from charged soft matter

A review of recent applications of Anomalous Small-Angle X-ray Scattering (ASAXS) to charged soft matter systems is presented. Although the potential of ASAXS was realized in the eighties [1], applications to soft matter systems became feasible in recent years thanks to the technical developments at the synchrotron sources. Examples include both stiff chain and flexible polyelectrolytes, colloidal brush-like polyelectrolytes, DNA, RNA, and polysaccharides where the counterion profile could be determined with high precision and compared with theoretical models. In addition, ASAXS has also been found useful for microstructure characterization in soft materials. Finally, the present capability for ASAXS studies is illustrated by an example involving a surfactant micellar system.     

Anomalous scattering,transport, and spatial distribution of X-ray fluorescence at the exit of polycapillary structures

The angular distribution of the X-ray intensity at the exit of microchannel plates at grazing incidence of monochromatic radiation on the walls of microcapillaries has been investigated. The angles and energies of the primary radiation quanta at which the synchrotron beam excites X-ray fluorescence propagating inside polycapillary structures have been determined. The angular dependences of the intensity distribution of X-rays transmitted through the microcapillaries have been studied theoretically and experimentally for energies corresponding to the region of anomalous dispersion near the L _2,3 absorption edges of silicon. The propagation of waves in hollow polycapillary waveguides, the excitation of X-ray fluorescence, and the X-ray diffraction at the exit of microchannel plates have been modeled mathematically. The mathematical model takes into account the presence of a transition layer on the microchannel surface.     

X-ray diffuse scattering from incommensurable structures

X-Ray diffuse scattering from a series of examples where the reason for the existence of incommensurable features is fairly well understood, is described. They include in particular non stoichiometric compounds such as [DIPS Φ₄(l₃)0.76] and such as intercalated graphite RbC₂₄. and quasi one dimensional conductors. A particular emphasis is given on various 1 - D conductors and to the relation of the incommensurability to the characteristics of the electron conduction bands.     

Modeling of radar scattering conditions inside a circular hollow dielectric waveguide

A new ray representation of electromagnetic field inside a quasi — optical structure in the form of a circular hollow dielectric waveguide is suggested and confirms the possibility for the unusual application of such a waveguide as an off-beat microanechoic chamber for electromagnetic modeling in the near millimeter and submillimeter wave regions.     

Anomalous elastic scattering of X-ray photons by the molybdenum atom

The differential cross section for elastic scattering of an X-ray photon by the molybdenum atom is calculated in the region of the ionization threshold of the 1s shell. The calculation is performed in the nonrelativistic approximation taking into account the rearrangement of electron shells of the atomic core in the field of the virtual 1 s vacancy and processes of one-photon virtual excitation (ionization) of the ground state. Good agreement with experimental results is obtained     

X-ray scattering in multilayer structures with quantum dots

The scattering of X-rays on multilayer semiconductor structures with quantum dots was studied. Equations describing coherent and diffuse scattering in superlattices with an arbitrary number of layers in the period were obtained. Numerical simulation of coherent and diffuse scattering of X-rays from laser superlattices with different number of periods was performed to analyze the experimental data. A physical interpretation of the angular displacement of the coherent peaks from the maxima of diffuse scattering observed in the experiment is given.     

Anomalous elastic scattering of X-ray emission by an atom with open shells

In the nonrelativistic approximation for one-electron wave functions, the differential cross section for anomalous scattering of linearly polarized X-ray emission by a sodium atom near the ionization threshold of the 1s ² shell is studied. The analysis takes into account the many-body effects of relaxation of atomic shells in the field of a deep vacancy, multiplet splitting, and the double excitation/ionization processes. The theoretical results obtained for the anomalous-dispersion scattering region are predictive.     

Resonant inelastic X-ray scattering of tantalum double perovskite structures

In this paper, we investigated the electronic structures and defect states of SrLaMgTaO₆ (SLMTO) double perovskite structures by using resonant inelastic x-ray scattering. Recently, Eu³⁺ doped SLMTO red phosphors have been vigorously investigated due to their higher red emission efficiency compared to commercial white light emitting diodes (W-LED). However, a comprehensive understanding on the electronic structures and defect states of host SLMTO compounds, which are specifically related to the W-LED and photoluminescence (PL), is far from complete. Here, we found that the PL spectra of SLMTO powder compounds sintered at a higher temperature, 1400 °C, were weaker in the blue emission regions (at around 400 nm) and became enhanced in near infrared (NIR) regions compared to those sintered at 1200 °C. To elucidate the difference of the PL spectra, we performed resonant inelastic x-ray spectroscopy (RIXS) at Ta L-edge. Our RIXS result implies that the microscopic origin of different PL spectra is not relevant to the Ta-related defects and oxygen vacancies.     

Polar smectic subphases: Phase diagrams, structures and X-ray scattering

We analyze a discrete phenomenological model accounting for phase transitions and structures of polar Smectic-C* liquid-crystalline phases. The model predicts a sequence of phases observed in experiment: antiferroelectric SmC _A ^* –ferrielectric SmC _FI1 ^* –antiferroelectric SmC _FI2 ^* (three-and four-layer periodic, respectively)–incommensurate SmC _α ^* –SmA. We find that, in the three-layer SmC _FI1 ^* structure, both the phase and the module of the order parameter (tilt angle) differ in smectic layers. This modulation of the tilt angle (and therefore of the layer spacing d) must lead to X-ray diffraction at the wave vectors Q _s =2πs/d(s=n±1/3) even for the nonresonant scattering.     

The analysis of forward scattering channeling data

The use of large angle forward scattering offers the advantage of performing dechanneling measurements at low beam fluences in comparison to the backscattering technique. Here, we present the method for the analysis of forward scattering channeling data and discuss the advantages of the technique.     

Depositing nanoparticles inside millimeter-size hollow tubing

The inner and the outer walls of hollow tubing with an inner diameter of 0.4-0.9 cm and an outer diameter of 0.6-1.3 cm were coated with silver nanoparticles (NPs) by a one-step process using ultrasound irradiation. The structure and morphology of the nanoparticles (NPs) inside the hollow tubing and on the outer surface were characterized using methods such as XRD, TEM, HR-TEM, and HRSEM. The inner surface of the tubing was found to be coated with more silver than the outer surface. The coating was done on tubing made of rubber, PVC, Teflon and polyethylene. Sonochemistry is demonstrated as a method for depositing nanoparticles on the inner wall of a tube.     

Anomalous large angle alpha scattering

Forα-nucleus potentials which contain a pocket, the scattering matrix may be split into ‘barrier’ and ‘internal’ components. Using simple parametrizations for these components, analytic expressions are derived for the corresponding ‘barrier’ and ‘internal’ cross sections. The oscillations present in these cross sections are interpreted as arising from interference between various terms in the Poisson summation formula for the scattering amplitudes. At backward angles the ‘internal’ cross section and the cross sections resulting from various Regge pole models are shown to have the same angular dependence. A method is given to locate roughly the position of the dominant Regge pole of the scattering matrix. At more foreward angles the ‘internal’ cross section, unlike those from the Regge pole models, describes the nuclear refraction undergone byα-particles that are transmitted through the target. Such refraction effects have previously been invoked to explain intermediate energyα-nucleus scattering.     

Diffuse X-ray scattering from crystalline structures with quantum dots of pyramidal shape

Diffuse scattering from crystalline structures with quantum dots (QDs) in the shape of a regular truncated pyramid with a square base is investigated. The elastic strains around QDs are calculated using the Green function method. The fields of the QD atomic displacements and the angular distribution of scattering intensity in the reciprocal space as functions of the QD concentration are simulated numerically. The influence of a pyramidal QD cross section by the diffraction plane on the diffuse X-ray scattering is demonstrated.     

Anomalous neutron scattering and ferroelectric soft modes

It is suggested that anomalous neutron scattering could prove a powerful experimental tool in studying ferroelectric phase transition, the sublattice displacements of the soft modes as well as their symmetry characteristics.     

Anomalous light scattering by small particles

Light scattering by a small spherical particle with a low dissipation rate is discussed based upon the Mie theory. It is shown that if close to the plasmon (polariton) resonance frequencies the radiative damping prevails over dissipative losses, sharp giant resonances with very unusual properties may be observed. In particular, the resonance extinction cross section increases with an increase in the order of the resonance (dipole, quadrupole, etc.); the characteristic values of electric and magnetic near fields for the scattered light are singular in the particle size, while energy circulation in the near field is rather complicated, so that the Poynting vector field includes singular points whose number, types, and positions are very sensitive to fine changes in the incident light frequency. The results may provide new opportunities for a giant, controlled, highly frequency-sensitive enhancement and variation of electromagnetic field at nanoscales.