X-ray resonant Raman scattering on Ni employing polarized and unpolarized exciting radiation

The X-ray resonant Raman scattering effect on nickel was studied by means of monochromatic polarized and unpolarized exciting radiation, respectively. Experiments involving polarized exciting radiation were carried out at the four crystal monochromator beamline of the Physikalisch-Technische Bundesanstalt for synchrotron radiation from 4 to 10 keV at the electron storage ring BESSY II. Resonant Raman spectra of thin Ni foils were recorded at the Cu-K_α (8041 eV) exciting beam energy. In the Institute of Nuclear Physics of the N.C.S.R. Demokritos, the resonant Raman spectrum of a thick nickel target was also recorded for an unpolarized Cu-K_α (8041 eV) exciting beam produced after the ionization of a thick Cu target by 1.7 MeV protons in a triaxial, orthogonal geometry.In the present work, the individual spectral characteristics and the methodological approaches adopted for the extraction of the Ni-RRS cross sections, with respect to each mode of excitation, are presented, compared and discussed. An excellent agreement was found between the Ni KL-RRS cross sections determined for polarized and unpolarized exciting radiation confirming the theoretical predictions within the experimental uncertainties achieved.     

Profile changes in barium Lα X-ray emission spectra due to excitation photon energies

New X-ray fluorescence satellites which are inside the natural width of the parent lines are observed in barium Lα_1,2 X-ray spectra. The measurements were performed with a double-crystal X-ray fluorescence spectrometer. Three X-ray tube anodes (Cr, W, Rh) were used in order to vary the excitation photon energy. As the photon energy of chromium Kα is between the L_III and the L_II threshold energies of barium, only an L_II electron of barium can be excited by the chromium anode tube. The narrowest profile was observed for Cr Kα excitation. Tungsten Lα and rhodium Kα photon energies are high enough to excite any L_I ,L_II or L_III electron of barium atom. Profile analysis shows that the satellite lines were produced by the excitation of W Lα or Rh Kα. It is concluded that the appearances of X-ray line-width satellites depend on primary photon energies, and that these satellites cause to smear the profiles of parent lines.     

Depth profiles of Al impurities implanted in Si wafers determined by means of the high-resolution grazing emission X-ray fluorescence technique

The synchrotron radiation based high-resolution grazing emission X-ray fluorescence (GEXRF) technique was used to extract the distribution of Al ions implanted with a dose of 10¹⁶ atoms/cm² in Si wafers with energies ranging between 1 and 100 keV. The depth distributions of the implanted ions were deduced from the measured angular profiles of the Al-Kα X-ray fluorescence line with nanometer-scale precision. The experimental results were compared to theoretical predictions of the depth distributions resulting from ion implantation. A good agreement between experiment and theory was found which proved that the presented high-resolution grazing emission X-ray fluorescence technique is well suited to perform depth profiling measurements of impurities located within the extinction depth, provided the overall shape of the distribution can be assumed a priori.     

Energy dispersion of X-ray continua in the energy range 8 keV to 16 keV by refraction on Si wafers

Total reflection of X-rays in matter at given grazing incidence angle is characterized by an energy cut-off. Photons with energies greater than the cut-off energy penetrate into matter and are refracted corresponding to a transition from the optically more dense to the optically less dense medium. Since the refractive index depends on photon energy, an energy dispersion of continuous X-radiation is observed. The present investigation is dedicated to the energy dispersion of continuous X-radiation from an X-ray tube with Mo target (operated at 45 kV) by Si wafers. Theory and experimental results are in excellent agreement. Measurement of the cut-off and refracted beam is a very good tool for angular calibration of experimental setups in total reflection X-ray fluorescence analysis (TXRF). A further interesting detail of this concept is its application to monochromators, which can be tuned over a wide range of photon energies. A refractive monochromator does not suffer from the occurrence of harmonics and a systematic variation of the photon flux and the spectral width of monochromatic radiation can be performed by a variation of slit widths in the collimator system.     

Lι, Lα, Lβ and Lγ X-ray fluorescence cross-sections of heavy elements for the exciting photons energy 38.18, 43.95, 50.21 and 59.5 keV

The cross-sections for the production of L_ι, L_α, L_β and L_γ X-ray fluorescence (XRF) in Er, Ta, W, Au, Hg, Tl, Pb and Bi by photons with energies in the range 38–59.5 keV have been measured, using a standard doublereflection experimental set-up. Measurements have been performed using an annular 241 Am primary source and X-ray emitting secondary-exciter system. Experimental cross-sections have been compared with the theoretically calculated values of L X-ray cross-sections and fairly good agreement is observed between the experimental and theoretical values.     

Total-reflection X-ray fluorescence analysis of Austrian wine

The concentration of major, minor and trace elements in Austrian wine was determined by total-reflection X-ray fluorescence using gallium as internal standard. A multi-elemental analysis was possible by pipetting 6 μl of wine directly on the reflector and drying. Total-reflection X-ray fluorescence analysis was performed with Atomika EXTRA II A (Cameca) X-rays from a Mo tube with a high-energy cut-off at 20 keV in total-reflection geometry. The results showed that it was possible to identify only by the elemental analysis as fingerprint the vineyards and year of vintage among 11 different wines.     

Variation of K X-ray fluorescence cross-sections of Fe in F compounds at an energy interval of 7.6–14.4 keV

The photon-induced K X-ray fluorescence cross-sections (σ_Kα, σ_Kβ) for Fe in F compounds were investigated. Measurements were carried out at 10 different energies in the interval of 7.6–14.4 keV by using a secondary excitation method. K X-rays emitted by samples were counted by a Si(Li) detector with a resolution of 160 eV at 5.9 keV. Obtained values were compared with the theoretical values of pure elements.     

Measurements of Coster–Kronig enhancement factors for Yb,Lu, Os and Pt elements

In this work X-ray production cross-sections’ measurements, L_ι, L_α, L_β and L_γ, of Yb, Lu, Os and Pt elements have been studied at energies in the range 9.572–14.384 keV and the effect of Coster–Kronig transitions on fluorescence cross-sections for L X-ray line has been obtained. From these studies absolute values of L X-ray cross-sections have been calculated with incorporation of the enhancement due to the Coster–Kronig effect. The experimental enhancement factors tend to be smaller than those predicted by theory.     

Phytoecdysteroids of plants of the genusSilene XIV. Brahuisterone fromSilene brahuica

A new ecdysteroid with the composition C₂₇H₄₄O₆ which has been called brahuisterone has been isolated from the epigeal part of the plantSilene brahuica Boiss. Its chemical and complete spatial structures have been established by spectral studies and the x-ray structural method (diffractometer, Cu-K_α radiations, 996 reflections, direct method, R=0.119).     

Grazing incidence X-ray absorption spectra of (Si/W) 100/Si multilayer

Tungsten (W) M_III X-ray absorption spectra of a periodic multilayer, (Si/W)₁₀₀/Si, were measured with the change of X-ray grazing angle using sample current method. Under not total reflection condition, the absorbance changed little except at W M_III absorption edge. While under the total reflection condition, the absorbance increased with the increase of the X-ray energy and the increment changed from low to high at the W M_III absorption edge. This result reflected the variation of the X-ray evanescent wavelength caused by the absorption effect of W.     

Effect of energy dependence of primary beam divergence on the X-ray standing wave characterization of layered materials.

Incident primary beam divergence is a source of systematic error in X-ray standing wave (XSW) characterization of single and multilayer thin films. Primary beam divergence significantly alters the XSW profile of a layered material and can lead to large errors when used with higher excitation energies. The present study suggests that when one uses Mo-Kalpha excitation, the primary beam divergence should be in range of 0.005(0). On the other hand, in the case of Cu-Kalpha excitation, primary beam divergence can be relaxed up to 0.01(0).     

The molecular and crystal structure of (+)-mianserin hydrobromide

X-ray analysis of crystals of (+)-mianserin hydrobromide (1,2,3,4,10,14b-hexahydro-2-methyl-dibenzol[c,f]pyrazino[1,2-a]azepine) has established the stereochemistry and absolute configuration of this compound (S at 14b).The crystals are orthorhombic with unit-cell dimensions: a = 1299(1)pm, b = 1420(1)pm, c = 1002(1)pm; Z = 4. The space group is P2₁2₁2₁. Intensity data for about 1000 reflections were measured on a single-crystal diflractometer with Cu-K_α radiation. The crystal structure was solved by the heavy-atom method and refined by least-squares procedures. Final R-factor 9·4%. The absolute configuration was determined by Bijvoet's technique.     

Refracted X-rays propagating near the surface under grazing incidence condition

X-ray refractions through a silicon wafer and an organic thin film, n-C₃₃H₆₈/Si, were measured using white incident X-rays under a grazing incidence condition. The energy variation of a refracted X-ray beam by a silicon wafer was well explained by the simple Snell's law when the position of the detector (solid-state detector) was changed. On the other hand, two refracted X-ray beams were observed from the organic thin film. The energy variation of one beam which propagated through the silicon substrate followed Snell's law, while that of another beam did not and changed little when the detector position was varied.     

Recent results of synchrotron radiation induced total reflection X-ray fluorescence analysis at HASYLAB,beamline L

At the Hamburger Synchrotronstrahlungslabor (HASYLAB), Beamline L, a vacuum chamber for synchrotron radiation-induced total reflection X-ray fluorescence analysis, is now available which can easily be installed using the adjustment components for microanalysis present at this beamline. The detector is now in the final version of a Vortex silicon drift detector with 50-mm² active area from Radiant Detector Technologies. With the Ni/C multilayer monochromator set to 17 keV extrapolated detection limits of 8 fg were obtained using the 50-mm² silicon drift detector with 1000 s live time on a sample containing 100 pg of Ni.Various applications are presented, especially of samples which are available in very small amounts: As synchrotron radiation-induced total reflection X-ray fluorescence analysis is much more sensitive than tube-excited total reflection X-ray fluorescence analysis, the sampling time of aerosol samples can be diminished, resulting in a more precise time resolution of atmospheric events. Aerosols, directly sampled on Si reflectors in an impactor were investigated. A further application was the determination of contamination elements in a slurry of high-purity Al₂O₃. No digestion is required; the sample is pipetted and dried before analysis. A comparison with laboratory total reflection X-ray fluorescence analysis showed the higher sensitivity of synchrotron radiation-induced total reflection X-ray fluorescence analysis, more contamination elements could be detected. Using the Si-111 crystal monochromator also available at beamline L, XANES measurements to determine the chemical state were performed. This is only possible with lower sensitivity as the flux transmitted by the crystal monochromator is about a factor of 100 lower than that transmitted by the multilayer monochromator. Preliminary results of X-ray absorption near-edge structure measurements for As in xylem sap from cucumber plants fed with As(III) and As(V) are reported. Detection limits of 170 ng/l of As in xylem sap were achieved.     

Depth profiling of Irganox‐3114 nanoscale delta layers in a matrix of Irganox‐1010 using conventional Cs+ and O2+ ion beams

Depth profiling of an organic reference sample consisting of Irganox 3114 layers of 3 nm thickness at depths of 51.5, 104.5, 207.6 and 310.7 nm inside a 412 nm thick Irganox 1010 matrix evaporated on a Si substrate has been studied using the conventional Cs⁺ and O₂⁺ as sputter ion beams and Bi⁺ as the primary ion for analysis in a dual beam time‐of‐flight secondary ion mass spectrometer. The work is an extension of the Versailles Project on Advanced Materials and Standards project on depth profiling of organic multilayer materials. Cs⁺ ions were used at energies of 500 eV, 1.0 keV and 2.0 keV and the O₂⁺ ions were used at energies of 500 eV and 1.0 keV. All four Irganox 3114 layers were identified clearly in the depth profile using low mass secondary ions. The depth profile data were fitted to the empirical expression of Dowsett function and these fits are reported along with the full width at half maxima to represent the useful resolution for all the four delta layers detected. The data show that, of the conditions used in these experiments, an energy of 500 eV for both Cs⁺ beam and O₂⁺ beam provides the most useful depth profiles. The sputter yield volume per ion calculated from the slope of depth versus ion dose matches well with earlier reported data. Copyright © 2013 John Wiley & Sons, Ltd.     

Multilayer characterization by energy dispersive X-ray reflectivity technique

An experimental setup was developed to verify the feasibility of silicon drift detector to be used for the multilayer characterization by means of multilayer energy dispersive X-ray reflectivity. Such a detector allows high count rates up to 3 × 10⁵ cps and can be used in principle for the direct beam intensity measurement, which is to be done for the X-ray multilayer reflectivity patterns obtaining. A series of measurements were performed for Mo/B₄C multilayer sample. A quality of the experimentally obtained data turns out to be enough to perform a sample structure exploration using a numerical procedure of experimental data fitting. Due to low cost and short time, required for the measurements, an experimental technique proposed has a good perspective to be used for some practical applications in industry.     

Application of X-ray fluorescence holography to the analysis of the interior and surface of an yttrium oxide thin film

We report on the characterization of a thin film of yttrium oxide by X-ray fluorescence holography. The sample has a layered structure with an YO base layer and an oxidized Y₂O₃ surface. Both layers are clearly observed in the atomic image reconstructions, and their local structure is analyzed. We show that by using incident energies close to the absorption edge of the fluorescing atom, it becomes possible to observe the thin surface layer clearly, even next to a base layer containing the same fluorescing element.     

Standardless energy-dispersive X-ray fluorescence analysis using primary radiation monochromatized with LiF(200) crystal

Energy-dispersive X-ray fluorescence spectrometer (EDXRF) with primary radiation monochromatized by LiF(200) crystal was developed. In the constructed spectrometer, the radiation from the Ag target X-ray tube operated at 50 kV and 40 mA excites the secondary target (Cu, Se, Zr or Mo). The characteristic radiation (Cu K_α, Se K_α, Zr K_α or Mo K_α) of the target is monochromatized with LiF(200) crystal and excites elements in the analyzed sample. The X-ray spectra are collected by thermoelectrically cooled Si-PIN detector with resolution of 145 eV at 5.9 keV. The pinhole collimator placed in front of the X-ray detector allows reducing size of the analyzed area. Quantitative analysis is performed using standardless fundamental parameters (FP) method. Because sample is excited using highly monochromatized radiation, the calculations are much simpler and analysis error resulting from uncertainty of X-ray tube spectral distribution is completely eliminated. Moreover, EDXRF system allows obtaining very low background and appropriate secondary target can be selected for the best excitation of the determined elements and to avoid overlapping of the analyte peaks with characteristic radiation originating from the secondary target. The FP calculations were verified using several certified reference materials of stainless steel. The spectrometer was used for nondestructive analysis of mono- and polycrystals of selenide spinels of general formula M_xN_yCr_zSe₄ (where M, N are Cu²⁺, Zn²⁺, Cd²⁺, Mn²⁺, Ge²⁺, Ni²⁺, V³⁺, Sb³⁺, Ga³⁺). The results from EDXRF were compared with those obtained by means of the wavelength-dispersive X-ray fluorescence spectrometry (WDXRF).     

Focused beam total reflection X-ray fluorescence with low power sources coupled to doubly curved crystal optics

A focused beam total X-ray fluorescence technique was developed based on doubly curved crystal optics. This technique provides good detection sensitivity and spatial resolution for localized detection of surface deposits. Compact low power X-ray sources were used to demonstrate the benefit of the X-ray optics for focusing Cr Kα, Cu Kα and Mo Kα radiation. The detection capability of the focused beam Total reflection X-ray fluorescence system was investigated with dried droplets of calibrated low concentration solutions. Detection limits at the femtogram level were demonstrated.     

Analysis of exponent values of Gaussian‐type functions on quantum protons and deuterons in charged or polarized systems

The optimal exponent α values (α_opt) in s‐type Gaussian‐type functions (GTFs) for quantum protons and deuterons, which are used for multicomponent molecular orbital calculations including nuclear quantum nature of protons and deuterons, are analyzed for several charged or polarized systems and their deuterated species. Ishimoto and coworkers (Ishimoto, Int. J. Quantum Chem. 2006 , 106, 1465) have already proposed the average exponent values for five neutral molecules (α_ave), and demonstrated that their α_ave enables us to evaluate the H/D isotope effect on energies and geometries of various neutral species. The differences between total energies of several charged or polarized systems with previous α_ave and our α_opt correspond to only less than 0.004% of the total energy (0.47 kcal·mol^?1) except for HeH⁺ and HeD⁺ molecules, while the difference between interaction energies of H₂OH^+…OH₂ and H₂OD^+…OH₂ systems with previous α_ave is 19% (0.22 kcal·mol^?1) smaller than that with our α_opt. Meanwhile, the difference between O? H bond lengths in H₂OH^+…OH₂ system with α_ave and α_opt values is 0.027 Å. We also found that the interaction energies with α_opt value at the geometry optimized with previous α_ave value (α_sp) well reproduce those at the geometry optimized with α_opt value. We have demonstrated that the nuclear basis functions based on s‐type GTFs with previous α_ave values enable us to evaluate the H/D isotope effect on energies and geometries of charged or polarized systems. © 2016 Wiley Periodicals, Inc.