X-ray scattering by water molecules studied by using synchrotron radiation

The energy spectra of free water molecules were measured at scattering angles 2θ ranging from 10.5° to 75.7°, using an angle-dispersive-type diffractometer and synchrotron radiation as an X-ray source. A silicon (111) monochrometer was used to obtain incident X-rays with the wavelengths of (1.543/n) Å (n = 1,3,4,5). Observed inelastic scattering peaks are clearly separated from eleastic ones at s values [s = (4π/λ) sin Å] larger than 8 Å^?1. The increase of the separation with an increasing s value was consistent with the classical theory of the Compton shift. The total (elastic plus inelastic) intensities were obtained over a range of s = 0.74–5.0 Å^?1. Experimental difference intensities Δσ_ee and Δσ_ne were obtained separately by combining the X-ray and high-energy electron scattering data. The experimental results are in reasonable agreement with the theoretical intensities calculated from SCF and CI molecular wave functions with a basis set of double-zeta plus polarization functions. © 1994 John Wiley & Sons, Inc.     

Diamond detectors for synchrotron radiation X-ray applications

Due to its unique physical properties, diamond is a very appealing material for the development of electronic devices and sensors. Its wide band gap (5.5 eV) endows diamond based devices with low thermal noise, low dark current levels and, in the case of radiation detectors, high visible-to-X-ray signal discrimination (visible blindness) as well as high sensitivity to energies greater than the band gap. Furthermore, due to its radiation hardness diamond is very interesting for applications in extreme environments, or as monitor of high fluency radiation beams. In this work the use of diamond based detectors for X-ray sensing is discussed. On purpose, some photo-conductors based on different diamond types have been tested at the DAFNE-L synchrotron radiation laboratory at Frascati. X-ray sensitivity spectra, linearity and stability of the response of these diamond devices have been measured in order to evidence the promising performance of such devices.     

Photoresists comparative analysis using soft X-ray synchrotron radiation and time-of-flight mass spectrometry

Positive photoresists are widely used in lithographic process for the fabrication of relief components. When exposed to UV radiation they suffer chemical reactions modifying their chemical and physical properties. Aiming to follow molecular modifications among two different photoresists unexposed and previously exposed to ultraviolet light we have employed spectroscopic techniques coupled with mass spectrometry in the study of the AZ-1518 and AZ-4620 photoresists. The photon stimulated ion desorption (PSID) technique following the S K-edge NEXAFS spectrum was employed at the brazilian synchrotron light source (LNLS), during single-bunch operation and using time-of-flight mass spectrometry (TOF-MS) for ion analysis. NEXAFS and PSID mass spectra on both AZ-1518 and AZ-4620 photoresists (unexposed and exposed) were obtained and relative desorption ion yield curves determined for the main fragments as a function of the photon energy. They present marked different PSID spectra. Fragments related to the photochemical decomposition of the AZ-1518 photoresist could be clearly identified differently from the AZ-4620. Studies on the hardness of both photoresists were performed using O₂ plasma reactive ion etching (RIE) technique, analyzed by scanning electron microscopy (SEM) and used to explain different desorption yields in the PSID spectra. These results show that the PSID technique is adequate to investigate structural changes in molecular level in different unexposed and exposed photoresists, which is crucial for improving our knowledge about the breakup process.     

Multi-elemental analysis of produced water by synchrotron radiation total reflection X-ray fluorescence

The synchrotron radiation total reflection X-ray fluorescence (SRTXRF) technique was used for the analysis of heavy metals in produced water samples from oil field in Rio Grande do Norte, in order to determine potential sources of pollution. Since the inorganic components in produced water generally resembling sea water, pre-concentration procedures have been applied to increase the concentration of the analyte of interest and to minimize the salt matrix effects. This technique allows us to determine the contents of V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Hg and Pb in 20 produced water samples. The great majority of the sampling points presented low elemental concentration value. However, in some sample, the Fe, Ni, Cu, Zn and Hg concentration were higher than the established limits by the Brazilian legislation.     

Analysis of mineral water from Brazil using total reflection X-ray fluorescence by synchrotron radiation

The total reflection X-ray fluorescence using synchrotron radiation (SRTXRF) has become a competitive technique for the determination of trace elements in samples that the concentrations are lower than 100 ng ml⁻¹. In this work, thirty-seven mineral waters commonly available in supermarkets of Rio de Janeiro, Brazil, were analyzed by SRTXRF. The measurements were performed at the X-Ray Fluorescence Beamline at Brazilian National Synchrotron Light Laboratory (LNLS), in Campinas, São Paulo, using a polychromatic beam with maximum energy of 20 keV for the excitation. Standard solutions with gallium as internal standard were prepared for calibration of the system. Mineral water samples of 10 μl were added to Perspex sample carrier, dried under infrared lamp and analyzed for 200 s measuring time. It was possible to determine the concentrations of the following elements: Si, S, K, Ca, Ti, Cr, Mn, Ni, Cu, Zn, Ge, Rb, Sr, Ba and Pb. The elemental concentration values were compared with the limits established by the Brazilian legislation.     

X-ray scattering of non-crystalline biological systems using synchrotron radiation

This tutorial review gives an overview of the progress in the study of non-crystalline systems by X-ray scattering and closely related imaging techniques, made possible by advances in synchrotron radiation sources and instrumentation. A brief introduction to the techniques is followed by the presentation of a variety of recent applications to problems in fundamental and applied research in biochemistry and biophysics and food and pharmaceutical technology.     

Photoreduction kinetics of sodium tetrachloroaurate under synchrotron soft X-ray exposure

We report on the time evolution of the sodium tetrachloroaurate (NaAuCl(4)) chemical properties as a function of soft X-ray exposure in a dried sample on a silicon surface using X-ray photoelectron spectroscopy (XPS). Our investigations provide mechanistic insight into the photoreduction kinetics from Au(III) to Au(I) and then Au(I) to Au(0). We unambiguously show that XPS photoreduction occurs in stepwise fashion via the Au(I) state. Both photoreduction steps undergo first-order kinetics.     

X-ray fluorescent analysis using synchrotron radiation: Subjects of research

The brief review has been presented about the application of X-ray fluorescent analysis using synchrotron radiation (storage ring VEPP-3, BINP SB RAS) for determination of elemental composition of the samples of different nature–biological and geological samples, objects of environment, archeological objects, and new materials. The feature of the presented research is the employment of the unique properties of synchrotron radiation, which allow analyzing samples of small mass (of the order of several milligrams), and also scanning core of bottom sediments with high resolution (less than 1 mm) that is not practical to realize by traditional analysis methods.     

Time-resolved synchrotron X-ray scattering of the crystallization of a soft hexagonal columnar crystal

We have recently shown (Langmuir 2000, 16, 5846) that a soft surfactant hexagonal phase exhibits, above a critical shear rate, a shear-melting transition, where a two-dimensional polycrystalline texture is converted into a liquid of rods aligned along the flow. Moreover, after abrupt cessation of high shear, a monocrystal-like structure is obtained. In this paper, we investigate the kinetics of crystallization from the shear-melted phase by means of time-resolved synchrotron X-ray scattering experiments. After a latency time, the sample is found to continuously evolve from a liquid of rods to a monocrystal of rods. We show that the crystallization results from a coupling between bulk crystallization and interfacial crystallization, due to a specific anchoring of the liquid crystal at the walls of the shear cell. A detailed analysis of the experimental data allows the evaluation of the propagation of the interfacial front and the time evolution of the size of the crystallites. We find that the size scales as t(v) with v approximately equal to 0.3, in fair agreement with recent theories and simulations on grain rotation-induced grain growth of columnar polycrystalline structures.     

Atomic level characterization by synchrotron radiation for the design of high performance catalysts

SPring-8 is the largest third-generation synchrotron radiation facility in the world. Synchrotron radiation is the most powerful light source currently available, especially in the EUV and X-ray regions, and in the research area of catalysis synchrotron radiation offers a very useful analysis method, i.e. XAFS. This spectroscopic investigative technique enables the determination of the chemical states and local structure of the atoms in the specific elements of a sample. Here, we introduce the SPring-8 facility and report how synchrotron radiation XAFS spectroscopy is utilized for the characterization and analysis of catalysts.     

Comparison of different excitation methods for X-ray spectral analysis: the case of synchrotron radiation

Different excitation means, protons, photons and electrons (PIXE, XRFA, and EPMA, respectively) have previously been compared with regard to the figures of merit, i.e. detection power, precision and accuracy. The aim in this article is to compare synchrotron radiation SR as another excitation method with the methods mentioned above. From this point of view the evaluation of (SR) was missing as an again independently optimized excitation method and was based as previously on practical problems of trace analysis, in this case on the determinations of traces in lead. The experiment has been performed with thick homogeneous samples of lead, the same samples already used in the former work, so that a direct comparison is possible. The calculation of the figures of merit is based on the measurements of the blank values and their relative standard deviation for the detection limit and on the random errors for the precision. Regarding the thick homogeneous target of lead XRFA still turns out to be the best method, whereas Synchrotron X-Ray Fluorescence SY-XRF compares favorably, at least for larger atomic numbers Z. Even PIXE is inferior to (SY-XRF) in the case of larger Z; when information on the lateral distribution of the elements is of interest, PIXE is indispensable.     

Comparison of different excitation methods for X-ray spectral analysis: the case of synchrotron radiation

Different excitation means, protons, photons and electrons (PIXE, XRFA, and EPMA, respectively) have previously been compared with regard to the figures of merit, i.e. detection power, precision and accuracy. The aim in this article is to compare synchrotron radiation SR as another excitation method with the methods mentioned above. From this point of view the evaluation of (SR) was missing as an again independently optimized excitation method and was based as previously on practical problems of trace analysis, in this case on the determinations of traces in lead. The experiment has been performed with thick homogeneous samples of lead, the same samples already used in the former work, so that a direct comparison is possible. The calculation of the figures of merit is based on the measurements of the blank values and their relative standard deviation for the detection limit and on the random errors for the precision. Regarding the thick homogeneous target of lead XRFA still turns out to be the best method, whereas Synchrotron X-Ray Fluorescence SY-XRF compares favorably, at least for larger atomic numbers Z. Even PIXE is inferior to (SY-XRF) in the case of larger Z; when information on the lateral distribution of the elements is of interest, PIXE is indispensable. Received: 13 June 2000 / Revised: 2 August 2000 / Accepted: 5 August 2000     

High precision X-ray diffraction studies of polycrystalline materials on synchrotron radiation

The review is devoted to application of synchrotron radiation (SR) for studying the structure of polycrystalline materials. The main emphasis is made on the equipment and techniques for acquiring high precision structural information — high angular resolution powder diffractometry and the use of anomalous scattering effect in structural studies. Various schemes of recording the high resolution X-ray patterns are presented, diffractometers operating in the world’s leading synchrotron radiation centers are described, and examples of particular applications are reported.     

Investigation of supported nickel catalysts by X-ray absorption spectrometry and X-ray diffraction using synchrotron radiation

In a previous paper a study of the supported nickel catalysts based on extended X-ray absorption fine structure spectroscopy was presented for analysis of the first coordination shell. The present study evidenced a strong deformation of the local structure of the metal due to its interaction with oxide support. The average particle size, microstrains and probability of faults, the particle size distribution function of supported Ni catalysts were determined by X-ray diffraction method. The method is based on Fourier analysis of experimental X-ray line profile (1 1 1), (2 0 0) and (2 2 0). The global structure is obtained with a fitting method based on the generalized Fermi function facilities for approximation. A chemisorption model was elaborated by correlation of the local and global structure connected with the specific surface areas. The results obtained on supported Ni catalysts which are used in H/D isotopic exchange reactions are reported. Both types of measurements were performed on the Beijing synchrotron radiation facilities.     

Analysis of metal-containing proteins by gel electrophoresis and synchrotron radiation X-ray fluorescence

For the analysis of metal-containing proteins, sodium dodecylsulfate polyacrylamide gel electrophoresis (SDS-PAGE) has been combined with synchrotron radiation X-ray fluorescence (SRXRF). In a pilot study the applicability of this combined method was tested in the analysis of metalloaded apoazurin and of the selenoproteins in rat testis homogenate. It was shown that it can be applied in the determination of the major stable binding forms of trace elements. After further improvement of the limits of detection the method will allow the analysis of trace element-containing proteins present in the samples at low concentrations. This revised version was published online in August 2006 with corrections to the Cover Date.     

High-speed X-ray microscopy by use of high-resolution zone plates and synchrotron radiation

X-ray microscopy based on synchrotron radiation has become a fundamental tool in biology and life sciences to visualize the morphology of a specimen. These studies have particular requirements in terms of radiation damage and the image exposure time, which directly determines the total acquisition speed. To monitor and improve these key parameters, we present a novel X-ray microscopy method using a high-resolution zone plate as the objective and the matching condenser. Numerical simulations based on the scalar wave field theory validate the feasibility of the method and also indicate the performance of X-ray microscopy is optimized most with sub-10-nm-resolution zone plates. The proposed method is compatible with conventional X-ray microscopy techniques, such as computed tomography, and will find wide applications in time-resolved and/or dose-sensitive studies such as living cell imaging.     

Analysis of beers from Brazil with synchrotron radiation total reflection X-ray fluorescence

Summary In this study the concentrations of P, S, Cl, K, Ca, Mn, Fe, Zn and Br in twenty-nine brands of national and international beers were determined by synchrotron radiation total reflection X-ray fluorescence analysis (SR-TXRF). The results were compared with the limits established by the Brazilian legislation and the nutritional values established by National Agricultural Library (NAL, USA). The measurements were performed at the X-Ray Fluorescence Beamline at Brazilian National Synchrotron Light Laboratory, in Campinas, S?o Paulo, Brazil, using a polychromatic beam for excitation. A small volume of 5 ml of beers containing an internal standard used to correct geometry effects was analyzed without pretreatment. The measuring time was 100 seconds and the detection limits obtained varied from 1 mg ^. l^-1 for Mn and Fe to 15 mg ^. l^-1 for P.     

High-resolution soft X-ray photoelectron spectroscopy of liquid water

High-resolution soft X-ray photoelectron spectra of liquid water (H(2)O and D(2)O) were measured using a liquid beam photoelectron spectrometer. The 1a(1) (O1s) band and the lowest valence 1b(1) band had single peaks, which is not consistent with the split 1b(1)→ 1a(1) of the X-ray emission band of liquid water if the splitting is assumed to originate from level shifts in two different hydrogen bonding structures. The second valence 3a(1) band of liquid water exhibited a flat top implying that two bands exist underneath a broad feature, which is similar to the case of the 3a(1) band of amorphous ice. The energy splitting between the two 3a(1) bands is estimated to be 1.38 eV (H(2)O) and 1.39 eV (D(2)O). Ab initio calculations suggest that the large splitting of the 3a(1) band is characteristic of water molecules that function as both proton donor and acceptor. The overall result is consistent with the conventional model of a tetrahedral hydrogen-bonding network in liquid water.     

A wavelength-dispersive arrangement for wafer analysis with total reflection X-ray fluorescence spectrometry using synchrotron radiation

Currently, the only apparent means to enhance the detection power of the TXRF technique would be to increase the intensity of the primary beam. Using synchrotron radiation, the most powerful X-ray source available, unfortunately, not only the fluorescence signal of the contaminant elements is increased, but also in equal measure, the intensities of the Si–K radiation from the wafer together with the scattered radiation. This results in an overloading of the energy-dispersive Si (Li) detector systems used hitherto, with the effect that the available primary intensity cannot be fully exploited. Wavelength-dispersive systems are free of such problems; they generate less detector background and can withstand higher count rates. Due to their small angle of acceptance, however, their detection efficiency is quite low. In this contribution we propose a wavelength-dispersive TXRF solution, which is optimized with regard to higher efficiency on the basis of large area multilayer mirrors in combination with a position-sensitive detector. The count rates in relation to energy-dispersive instruments and the energy resolution of the new system have been calculated using ray-tracing techniques.