Extended X-ray absorption fine-structure (EXAFS) is a powerful tool for the analysis of atomic-scale structure around specific atoms. In addition to the determination of the atomic distance for the nearest neighboring atoms, it can give some information on the local dynamical properties of crystals. Recently, Dr. A. Sanson (Universita degli Studi di Verona , Italy
Recently in Spectroscopy Category
Professor M. A. Castro (Instituto de Ciencia de los Materiales de Sevilla, CSIC-Universidad de Sevilla, Spain
Argentinian scientists have recently published a paper on the emission of X-rays in the Kβ region of Mg, Al, Si, Sc, Ti, Cr, Fe, Ni, and Zn induced by electron bombardment. The research includes the KβIII and KβIV spectator hole transitions, the 1s→3s quadrupole decay, the Kβ2 and Kβ5 diagram transitions, the structures related to radiative Auger processes, and the Kβ' and Kβ" lines. For more information, see the paper, "Kβ satellite and forbidden transitions in elements with 12<Z<30 induced by electron impact", S. P. Limandri et al., Phys. Rev. A81, 012504 (2010).
X-ray Photon Correlation Spectroscopy (XPCS) is a novel technique which reveals the slow dynamics of equilibrium and non-equilibrium processes in condensed matter systems. A group led by Professor N. P. Balsara (
Dr. G. J. Havrilla (Los Alamos National Lab.,
Dr. I. Han (Ağrı İbrahim Çeçen University , Turkey
One of the most important applications of X-ray spectroscopy is chemical state analysis. A research group led by Dr. M. Jaksic (Rudjer Boskovic Institute, Croatia
Professor D. Sparks (University of Delaware , USA
It is known that sulfide sometimes play a significant role in the geochemistry of arsenic under reducing conditions. So far, it has been assumed that sulfide primarily reduced the solubility and mobility of arsenic by precipitation of arsenic-sulfide minerals, As2S3, but recent studies indicate that under certain conditions, significant concentrations of soluble As-S compounds can exist in sulfidic waters. Thus, the question is whether they are As(III)-S species ("thioarsenites") or As(V)-S species ("thioarsenates"). A research group led by Dr. B. Planer-Friedrich (
Dr. C. T. Chanter and his colleagues have published a paper on the unresolved quantitative discrepancies between experimental and theoretical Cu Kα spectra. For more information, see the paper, "Theoretical Determination of Characteristic X-Ray Lines and the Copper Kα Spectrum", C. T. Chantler et al., Phys. Rev. Lett. 103, 123002 (2009).
In the film Star Trek IV (1986), transparent aluminum is used for the exterior portals and windows of spacecraft. Now transparent aluminum has become a hot topic for real, rather than in science fiction. An international team, led by Oxford University scientists, has recently reported that a short pulse from the FLASH laser (wavelength 13.5 nm) knocks out a core L-shell electron from every aluminium atom in a 50 nm Al thin film without destroying the metal's crystalline structure. This rendered the aluminium almost invisible for this wavelength. This phenomenon is called saturable absorption. The transient state of aluminium produced in this way is as dense as ordinary matter but can only exist for an extremely short period of time of 40 femtoseconds. For more information, see the paper, "Turning solid aluminium transparent by intense soft X-ray photoionization", B. Nagler et al., Nature Physics 5, 693 (2009).
So far, diffusion in solids has been investigated by profiling the depth dependence of tracer atoms diffused into the sample. Although one can obtain the diffusion constant from this, the question is how diffusion takes place on the atomic scale, rather than on the micron scale. Sometimes quasielastic neutron scattering as well as Mobauer spectroscopy can be used in a very limited number of fortunate cases. A research group led by Professor G. Vogl (
When a strong laser beam hits the surface of a material, plasma is produced there, subsequently leading to the emission of a short burst of X-rays. It is believed that the electrons in the surface plasma are accelerated by the strong electric field of the laser and then penetrate the solid behind. There, they knock out electrons from inner electronic shells, which subsequently undergo inner-shell recombination, leading to characteristic line emissions such as Kα and Kβ spectra. A research group led by Professor U. Teubner (
Since 1984, laboratory-scale X-ray lasers have been extensively studied. The shortest wavelength achieved so far is 3.6 nm, with a weak intensity. On the other hand, X-ray free-electron lasers (XFEL) based on self-amplified spontaneous emission (SASE) from a long undulator in the linear electron accelerator will be available in near future. The next idea is the use of XFEL to pump a photoionization inner-shell X-ray laser in an atomic gas. Dr. R. London (Lawrence Livermore National Lab) and a colleague have recently published their theoretical calculations. For more information, see the paper, "Atomic inner-shell X-ray laser pumped by an x-ray free-electron laser", N. Rohringer et al., Phys. Rev. A 80, 013809 (2009).
Dr. P. Glatzel (European Synchrotron Radiation Facility (ESRF),
In January 2006, NASA's Stardust spacecraft brought comet coma particles and interstellar grains from Comet 81P/Wild2. Synchrotron facilities all over the world have been used for extensive analysis of the chemical composition and crystal structures of the matter. Recently, Professor L. Vincze (X-ray Microspectroscopy and Imaging Group,
Confocal X-ray micro fluorescence is a method of 3D analysis, and uses the formation of confocal volume (probing microvolume) defined through the intersection of a focused excitation beam and the sensitive volume of a polycapillary lens placed in front of the detector. Because of increasing demands, the technique has been widely used at both synchrotron and laboratory sources. However, some essential problems in quantitative analysis have remained so far. Dr. A-G. Karydas (
Spider silk is a tough yet light material, but recently it has been found that it becomes three times stronger by adding small amounts of metal such as Zn, Ti and Al. The idea was inspired by research which established that trace metals are frequently found in the toughest parts of some insect bodies. Bio-materials scientists think that such metals could be incorporated in the protein structures and lead to unusual mechanical properties. Dr. M. Knez (Max Planck Institute of Microstructure Physics, Halle , Germany
Professor K. Tsuji (Osaka City University , Japan
At the Photon Factory, KEK, Japan , Dr. T. Okuda (University of Tokyo
Dr. A. von Bohlen (Institute for Analytical Sciences, Germany
Eu is one of the most interesting lanthanides, compounds of which often exhibit remarkable optical, electrical, and magnetic properties. Therefore, it is extremely important to develop a technique for chemical state analysis. The X-ray emission spectra of Eu had not been thought to exhibit significant chemical effects. A research group led by Professor H. Hayashi (Japan Women's Univ) firstly found a large chemical shift (~5 eV) in Eu Lγ4 emission line, depending on the valence state. They discussed the feasibility of using this as a probe for spin- and valence-selective X-ray absorption fine structure spectroscopy. For more information, see the paper, "Probe for spin- and valence-selective X-ray absorption fine structure spectroscopy: EuLγ4 emission", H. Hayashi et al., Anal. Chem., 81, 1522 (2009).
X-ray absorption spectroscopy is one of the most powerful probes of molecular structures. So far, applications have been limited to the steady state and/or quite slowly changing systems. Recently, Professor M. Chergui (Ecole Polytechnique Federale de Lausanne, (EPFL),
Professor T. Rayment (
Neuromeranin (NM) is a dark colored pigment synthesized within specific catecholamine-producing neurons in the human brain. It is of uncertain origin and exists as amorphous granules with a heterogeneous structure called NM granules. At the European Synchrotron Radiation Facility (ESRF) in Grenoble, the microchemical environment of NM in whole neurons from formalin-fixed and paraffin-embedded human substantia nigra sections was recently analyzed. It was found that concentrations of NM-associated elements increase in the developing brain, and that iron-rich microdomains colocalized with other elements within the pigment. Furthermore, intracellular speciation of sulfur in NM has revealed the presence of reduced sulfur compounds and various forms of oxidized sulfur compounds which have not previously been reported. For more information, see the paper, "Intracellular Chemical Imaging of the Developmental Phases of Human Neuromelanin Using Synchrotron X-ray Microspectroscopy", S. Bohic et al., Anal. Chem., Article ASAP, DOI: 10.1021/ac801817k
Recent progress in synchrotron X-ray microscopy has opened up extremely attractive applications. A group led by Professor B. M. Weckhuysen (Utrecht University, The Netherlands) recently watched heterogeneous catalysts in action at high temperature. Solid catalysts have been widely used in the chemical industry, and accelerate the production of many important compounds. They are typically composed of nanometre-sized metal or metal oxide particles attached to a solid support with a high surface area. As complex structural and chemical changes take place during catalytic reactions, direct observation of the reacting catalyst is extremely important. The team employed X-ray microscopy at the Advanced Light Source, Berkeley, United States, to study the catalytic Fischer-Tropsch reaction where a solid catalyst of iron oxide particles mounted on silica is used to convert carbon monoxide and hydrogen into liquid hydrocarbons that can be used as fuels. By the use of Fe LII, III and C K absorption edges, scanning transmission X-ray imaging has revealed that during the reaction the iron oxide underwent several transformations; the initial iron oxide (Fe2O3) is converted into another oxide (Fe3O4), before iron silicates (Fe2SiO4) and metallic iron begin to form. Iron carbides (FexCy) appear in the final stage. For more information, see the paper, "Nanoscale chemical imaging of a working catalyst by scanning transmission X-ray microscopy", E. de Smit et al., Nature 456, 222-225 (2008).
Professor L. Natarajan (University of Mumbai, India) recently published a paper calculating the energies and electric dipole rates of X-rays from the empty K shells of atoms in the range of Z=12 to 56. For more information, see the paper, "Relativistic fluorescence yields for hollow atoms in the range 12<Z<56", L. Natarajan, Phys. Rev. A78, 052505 (2008).
Dr. R. Fernandez-Ruiz (Universidad Autonoma de Madrid, Spain) recently published a theoretical paper on the expanded uncertainty associated with TXRF measurements. For more information, see the paper, "Uncertainty in the Multielemental Quantification by Total-Reflection X-ray Fluorescence: Theoretical and Empirical Approximation", R. Fernandez-Ruiz, Anal. Chem., 80, 8372-8381 (2008).
X-ray fluorescence (XRF) spectra for a number of rock samples from Mars, the Moon, and Mercury have been measured at the Physikalisch-Technische Bundesanstalt (PTB) beamline in the BESSY II electron storage ring. In the future, both ESA and NASA will send spacecraft to Mercury. Remote X-ray sensing is planned to obtain chemical composition mapping on the planetary surface. The present synchrotron XRF spectra will be used as valuable reference for the analysis. For more information, see the paper, "Measuring and Interpreting X-ray Fluorescence from Planetary Surfaces", A. Owens et al., Anal. Chem., 80, 8398-8405 (2008).
A research group at Lawrence Livermore National Laboratory recently reported an interesting application of ultrafast X-ray spectrometry to studies on the compression and heating of shocked matter. Here, the sample is 300 μm thick LiH, which is heated by a 450 J nsec laser, and the X-ray used is Ti Kα X-ray fluorescence (4.51 keV) from Ti foil heated by another pulse laser of 5 psec. X-ray photons produced at the Ti foil are estimated as a 2 × 1013/pulse. The energy spectra of X-ray scattering by the LiH sample during compression were taken by a spectrometer consisting of a large curved graphite (HOPG) crystal in van Hamos geometry and an Imaging Plate (IP) detector. It was found that the X-ray scattering spectrum from shocked LiH shows elastic Rayleigh scattering and inelastic plasmon scattering features. Whereas earlier in time only elastic scattering was observed, at 7 nsec, a plasmon energy shift of 24 eV was detected. This indicates the transition to metallic free electron plasma in the solid phase. For more information, see the paper, "Ultrafast X-ray Thomson Scattering of Shock-Compressed Matter", A. L. Kritcher et al., Science, 322, 69 -71 (2008).
A French research group has reported the application of X-ray fluorescence microscopy to the analysis of macrophages exposed to unpurified and purified single-walled (SW) and multiwalled (MW) carbon nanotubes (CNT). During this research, elemental mapping at cell level was performed for P, Cl, K, Ca and Fe. For more information, see the paper, "Carbon Nanotubes in Macrophages: Imaging and Chemical Analysis by X-ray Fluorescence Microscopy", C. Bussy et al., Nano Lett., 8, 2659-2663 (2008).
It is well-known that Vincent van Gogh (1853-1890) often reused canvases and painted over his older works. Specialists estimate that about one third of his early paintings conceal other compositions under them. Recently, an international team led by Professor K. Janssens (University of Antwerp, Belgium) and Dr J. Dik (Delft University of Technology, The Netherlands) successfully applied synchrotron radiation induced X-ray fluorescence spectroscopy to the painting entitled Patch of Grass (painted by Van Gogh in Paris in 1887 and owned by the Kroller-Muller Museum). The research group recorded X-ray fluorescence intensity maps of several tens of square cm and, in particular, the distribution of Hg and Sb, which corresponds to red and light tones, respectively. In this way, it could analyze an approximate color reconstruction of the flesh tones. Accordingly, a portrait of a woman was discovered behind the painting. The measurement was done at DESY in Hamburg, Germany. For more information, visit the Website, http://www.vangogh.ua.ac.be/, and see the paper, "Visualization of a Lost Painting by Vincent van Gogh Using Synchrotron Radiation Based X-ray Fluorescence Elemental Mapping", J. Dik et al., Anal. Chem., ASAP Article, 10.1021/ac800965g (2008).
When X-rays satisfy Bragg's law for a perfect crystal, a significant transparency to X-ray beams is observed. This is the so-called Bormann effect, and is caused because the X-ray electric field approaches zero amplitude at the crystal planes, corresponding to almost no scattering by atoms. Recently, Dr. S. P. Collins (Diamond Light Source, United Kingdom) and his colleagues attempted several very interesting experiments - X-ray spectroscopy under the Bormann transmission condition. The main idea is that the electric quadrupole absorption transitions could be effectively enhanced under conditions of absorption suppression. The measured sample is gadolinium gallium garnet (Gd3Ga5012) cut parallel to the (100) planes, and some new spectral features were observed in the LI (8,376 eV), LII (7,930 eV) and LIII (7,243 eV) edges for gadolinium, at different temperatures. They are basically additional peaks on the low energy side, and correspond to an electric quadrupole transition from 2s, 2p1/2 and 2p2/3 to the narrow, half-filled 4f states, respectively. For more information, see the paper, "Quadrupole transitions revealed by Borrmann spectroscopy", R. F. Pettifer et al., Nature, 454, 196-199 (2008).
Scientists at Argonne National Laboratory and Ames Laboratory, Iowa State University, have recently performed X-ray magnetic circular dichroism (XMCD) measurements of giant magnetocaloric material, Gd5(Ge1-xSix)4. It was found that germanium becomes magnetic by spin-dependent hybridization between Ge 4p and Gd 5d. This hybridization can change at the germanium-silicon bond-breaking transition, causing the destruction of magnetic ordering and leading to the giant magnetocaloric effect. By combining the experimental results with calculations based on density functional theory, it was concluded that the magnetized germanium orbitals act as "magnetic bridges" in mediating the magnetic interactions across the distant gadolinium ions. For more information, see the paper, "Role of Ge in Bridging Ferromagnetism in the Giant Magnetocaloric Gd5(Ge1-xSix)4 Alloys", D. Haskel et al., Phys. Rev. Lett., 98, 247205 (2007).
Atoms become ions when exposed to extremely intense light. The process is predicted to occur via tunnelling through the binding potential that is suppressed by the light field near the peaks of its oscillations. Professor F. Krausz (Max Planck Institute of Quantum Optics in Garching, Germany) and his collaborators recently reported the real-time observation of this most elementary step in strong-field interactions, i.e., light-induced electron tunnelling. The team used 250-attosecond pulses of UV radiation, and confirmed theoretical predictions about the tunneling process. It was also found that the process lasted for several hundred attoseconds, depleting atomic-bound states. This would suggest that the use of tunneling itself is feasible for probing short-lived, transient states of atoms or molecules, e.g., multi-electron excitation (shake-up) and relaxation (cascaded Auger decay) processes etc. For more information, see the paper, "Attosecond real-time observation of electron tunnelling in atoms", M. Uiberacker et al., Nature, 446, 627 (2007).
It has long been believed that birds can in some way use the natural magnetism of the earth to navigate. Recently, scientists from the University of Frankfurt employed micro X-ray fluorescence as well as micro XAFS spectroscopy to analyze the skin of the upper beak of homing pigeons. Within the skin lining, they established the existence of tiny maghemite (g-Fe2O3) and magnetite (Fe3O4) particles (with a ratio of around 9:1) in the dendritic nerve branches that were arranged in a 3D pattern. According to the research team, this strongly supports the theory that the upper beak of pigeons houses a highly sensitive magneto-receptor that can be used for navigation. The experiments were done with synchrotron X-rays at HASYLAB in Hamburg, Germany. For more information, see the paper, "A novel concept of Fe-mineral-based magnetoreception: histological and physicochemical data from the upper beak of homing pigeons", G. Fleissner et al., Naturwissenschaften, published online in mid-March, 2007.
Platinum is the most efficient electrocatalyst for accelerating chemical reactions in fuel cells for electric vehicles. However, the reactions that take place during the stop-and-go driving of an electric car cause the platinum to dissolve, which reduces its efficiency as a catalyst. Recently, a Brookhaven National Lab group led by Dr. R. Adzic found that adding gold clusters to the platinum electrocatalyst is effective in stabilizing and prolonging the life of the electrocatalyst. The group tested the performance under the oxidizing conditions of the O2 reduction reaction and potential cycling between 0.6 and 1.1 V in over 30,000 cycles, and obtained successful results. X-ray absorption spectra measured at the Pt LIII edge clearly showed that the Au clusters contribute to protecting the platinum from being oxidized. The next step of the research is to duplicate the results in real fuel cells. For more information, see the paper, "Stabilization of Platinum Oxygen-Reduction Electrocatalysts Using Gold Clusters", J. Zhang et al., Science, 315, 220 (2007).
In January 2006, the Stardust spacecraft brought back a number of tiny particles from comet Wild 2, which is believed to have originated within a cloud of comets just beyond the orbit of Neptune called the Kuiper Belt. The particles have been analyzed by X-rays at six synchrotron radiation facilities around the world, ESRF (France), APS (Argonne, USA), SSRL(Stanford, USA), ALS (Berkeley, USA), NSLS (Brookhaven, USA) and SPring-8 (Japan). The particles from this comet are important because they are believed to be close to the starting material of the solar system, which is now about 4.5 billion years old. The particles were found to contain a wide variety of minerals and organic materials that look similar to those seen in primitive meteorites found on earth, but the samples also revealed the presence of new materials not previously found in meteorites. It was also discovered that the samples contained minerals similar to Calcium Aluminum-rich inclusions (CAIs), which can be formed at high temperatures, i.e., in the innermost part of the solar nebula, well inside the orbit of Mercury. For more information on the Stardust mission, visit http://stardust.jpl.nasa.gov/home/index.html. Some interesting results have been published as part of a special series of papers in the Dec. 15, 2006, edition of the journal Science.
Professor Weckhuysen (Utrecht University, Netherlands) and his colleagues have recently solved the molecular mechanism for the organic-base-mediated synthesis of zeolites. AlPO4-5 is a typical zeolite, which can be constructed from aluminium-based tetrahedra (AlO4) and phosphorus-based tetrahedra (PO4). The research group compared the formation of the chargeless AlPO4-5 framework with the negatively charged framework (known as ZnAPO-34) that is formed by replacing Al3+ in AlPO4-5 with Zn2+. The former contains one-dimensional channels, but the latter spherical cavities rather than channels. By employing not only small and wide angle X-ray scattering (SAXS and WAXS), but also X-ray absorption spectroscopy, it was possible to observe in real time both the structural changes in the aluminophosphate gel and the conformational features of the organic base (tetraethylammonium hydroxide) used as a template for the crystallization of zeolite. The tetraethylammonium ion was found to form a complex with developing zeolite subunits in the gel, adopting a molecular structure close to that found in the final crystal. This molecular recognition process determines which type of crystal lattice is formed. The principal point here is that molecular organization takes place before crystallization. The experiments were done at BM26A, ESRF (Grenoble, France). For more information, see the paper, "A Combined SAXS/WAXS/XAFS Setup Capable of Observing Concurrent Changes Across the Nano-to-Micrometer Size Range in Inorganic Solid Crystallization Processes", A. M. Beale et al., J. Am. Chem. Soc., 128, 12386 (2006). Another interesting account can also be found in "Physical chemistry: Porous solids get organized", R. A. van Santen1, Nature, 444, 46 (2006).
Artists in ancient Pompeii painted the town red 2,000 years ago with a brilliant crimson pigment made of cinnabar (HgS) that dominated many of the doomed city's wall paintings. The eruption of the volcano Vesuvius showered the neighbouring towns in pumice and ash, and the Villa Sora, in Torre del Greco, remained buried until just 20 years ago, which is when excavation work started. In the remains of the house, the distinctive red colour of the wall frescoes has turned black in many places. The origins of this darkening degradation have not been clearly identified yet and remain a major issue for curators. At ESRF, by aid of micro X-ray fluorescence and absorption spectroscopy, scientists analyzed red cinnabar paintings coated on a sparry calcite (CaCO3) mortar exhibiting different levels of degradation. The results indicate two possible degradation mechanisms; formation of HgCl2 and CaSO4 through reaction with NaCl and SO2 from the environment, respectively. For more information, see the paper, "Blackening of Pompeian Cinnabar Paintings: X-ray Microspectroscopy Analysis", M. Cotte et al., Anal. Chem., 78, 7484-7492, (2006).
Scientists at North Carolina State University, USA recently published an interesting report on the significance of the anomalously high concentration of local Ge-Ge bonds in amorphous Ge2Sb2Te5, which is commonly used in data storage technologies such as DVD, DVD-RAM etc. The ability to change phases from a crystalline to a non-crystalline state is what allows the DVD to take and hold data. While the basic properties of this alloy are well known, there are still a lot of unsolved problems: we do not know how the process works on a microscopic level. The paper indicates that the amorphous phase is an ideal network structure in which the average number of constraints per atom equals the network dimensionality. For more information, see the paper, ""Application of Bond Constrain Theory to the Switchable Optical Memory Material Ge2Sb2Te5", D. A. Baker et al., Phys. Rev. Lett. 96, 255501 (2006).
A series of very interesting experiments has been performed at beamline ID26 at the European Synchrotron Radiation facility (ESRF), Grenoble, to see how gold nanoparticles catalyze carbon monoxide (CO) with oxygen (O2) into carbon dioxide (CO2). High-energy resolution X-ray absorption spectroscopy reveals how the oxygen becomes chemically active when bound to the particles. The reaction took place when the scientists switched from a flow of O2 to one of CO - the O2 bound to the gold reacts with the CO to form CO2. The technique can be applied to a variety of reactions. For more information, see the paper, "Activation of Oxygen on Gold/Alumina Catalysts: In Situ High-Energy-Resolution Fluorescence and Time-Resolved X-ray Spectroscopy", Jeroen A. van Bokhoven et al., Angewandte Chemie, published online June 21, 2006.
The sketch for View on the Stour near Dedham, painted by Constable in 1822, has been analyzed by X-rays prior to Tate Britain's exhibition, Constable: the Great Landscapes, which opens on 1 June 2006. The sketch is the 4th of the 6 large River Stour paintings that Constable exhibited at the Royal Academy during 1819-1825. As with the other River Stour scenes, Constable made a preliminary full-scale compositional sketch in oils when planning the exhibition picture. The X-ray investigation clearly shows that the sketch originally included two boys fishing by the water's edge and a little girl close to one of the wooden beams marking the edge of a boat-building yard in the foreground. These figures were then painted out of the sketch by Constable and replaced by two young boys sitting on the edge of the river bank. In the finished exhibition painting, View on the Stour near Dedham, Constable altered the composition again and did not include the two boys from the sketch. X-ray analysis has successfully revealed a number of such alterations that are not visible on the surface of the work. For more information, contact Helen Beeckmans/Patricia O'Connor, Tate Press Office, Millbank, London SW1P 4RG, Phone: +44-20-7887-8730/32, Fax: +44-20-7887-8729, pressoffice@tate.org.uk
Professor E. Ma (Johns Hopkins University, USA) and his colleagues recently succeeded in explaining the atomic packing of metallic glasses, which are of great importance due to their distinctive mechanical and magnetic properties. The structure is known as 'amorphous' (non-crystalline) and shows no sharp Bragg peaks in the X-ray diffraction pattern. The research group adopted quite a unique strategy; first, they aimed at obtaining 3D pictures in the short-to-medium range, unlike conventional atomic-level analysis, which looks only at short-range order, and secondly, they did not resort to a predetermined structural model but used reverse Monte Carlo simulations based on experimental X-ray diffraction and absorption data. One of their key findings was that metallic glass atoms do not arrange themselves in a completely random way. Instead, groups of 7-15 atoms tend to arrange themselves around a central atom, forming 3D shapes called Kasper polyhedra, which join together in unique ways as small nanometer-scale clusters. For more information, see the paper, "Atomic packing and short-to-medium-range order in metallic glasses", H. W. Sheng et al., Nature, 439, 419-425 (2006).
At the Advanced Photon Source (APS) at Argonne, USA, massive amounts of lead have been detected in bone fragments of 19th Century composer Ludwig von Beethoven (1770-1827), indicating the cause of his years of chronic illness. The bone fragments, checked by DNA testing to have come from Beethoven's body, were analyzed by micro X-ray florescence. The findings confirm earlier work done on hair samples. Furthermore, neither cadmium nor mercury was found within detectable levels this time. The half life of lead in the human body is about 22 years, and almost 95 percent is captured in the skeletal structure. For more information, contact Catherine Foster, Phone: +1-630-252-5580, cfoster@anl.gov, http://www.anl.gov
Scientists at the U.S. Department of Energy's Argonne National Laboratory have recently unearthed new clues to making magnets longer lasting and more powerful through element-specific X-ray magnetic circular dichroism (XMCD) measurements. They have analyzed magnetic moment reversal at each of two inequivalent Nd sites (g and f sites) in a tetragonal single crystal of Nd2Fe14B, which is currently known to be the strongest permanent magnet. The results provide clear evidence that intrinsic magnetic stability has its atomic origins predominantly at Nd g sites, which exhibit a strong preference for c-axis alignment at ambient temperature and dictate the macroscopic easy-axis direction. Chemical substitution at Nd f sites, which undermines stability by favoring the xy plane, could enhance intrinsic coercivity. For more information, contact Catherine Foster (+1-630-252-5580, cfoster@anl.gov) at Argonne, and also see the paper, "Atomic Origin of Magnetocrystalline Anisotropy in Nd2Fe14B", D. Haskel et al., Phys. Rev. Lett., 95, 217207 (2005).
Natural photosynthesis can convert solar energy into chemical energy with almost 100% efficiency. During photosynthesis, O2 is evolved at a tetra manganese-calcium complex bound to the proteins of photosystem II. As the details of the mechanism have not been fully understood, artificial solar systems still capture only a minute amount of energy. Very recently, a German research group has succeeded in providing new insights into the mechanism by means of time-resolved X-ray absorption spectroscopy, which measures Mn K X-ray fluorescence after laser-flash illumination with a time resolution of 10 μs. The model of the so-called S-cycle treats the manganese complex cycles through five oxidation states, but only four intermediates have been identified experimentally (S0 through S3). Dioxygen is formed during the transition from S3 to S0, but the expected S4 intermediate in this transition has been elusive. Real-time X-ray monitoring of photosynthetic O2 production has identified the S4 intermediate and, in contrast to previous proposals, the research group concluded that it is formed by a deprotonation process rather than by electron transfer. The experiments were done at beamline ID26, European Synchrotron Radiation Facility (ESRF), Grenoble, France. For more information, see the paper, "Photosynthetic O2 Formation Tracked by Time-Resolved X-ray Experiments", M. Haumann et al., Science, 310, 1019-1021 (2005).
Japanese scientists at Kyoto University have recently found that copper plays a significant role in the formation of toxic dioxin during the incineration of urban waste. They measured copper K X-ray absorption spectra for fly ash, and investigated the changes in oxidation number when the temperature was controlled near 300 C, where dioxin is sometimes formed. The data suggest some clear correlation between the existence of cuprous chloride (CuCl) and the formation of dioxin. The experiments were done at beamline BL01B1, SPring-8, Harima, Japan. The scientists presented the results at the 41st Annual Conference on X-Ray Chemical Analysis, Japan held at Fukui Institute for Fundamental Chemistry, Kyoto University. For more information, contact Professor Masaki Takaoka, Kyoto University, phone: +81-75-753-5162, fax: +81-75-753-5170, takaoka@epsehost.env.kyoto-u.ac.jp
An international team led by Professor M. Sandström (University of Stockholm) has analyzed the sulfur and iron composition of the wooden timbers of the Mary Rose, a warship of King Henry VIII of England that was wrecked in 1545 and salvaged two decades ago. Synchrotron X-rays from the Stanford Synchrotron Radiation Laboratory (USA) and the European Synchrotron Radiation Facility (France) were employed. The experimental results indicate the surviving wood contains two tons of sulfur in different forms, uniformly distributed within the 280-ton hull. In addition, the Mary Rose contains a great deal of iron from corroded iron bolts, nails and other objects from the ship. Exposed to oxygen in air, the iron catalyzes the oxidation of sulfur into sulfuric acid. For more information, see the paper, "Sulfur accumulation in the timbers of King Henry VIII's warship Mary Rose: a pathway in the sulfur cycle of conservation concern", M. Sandström et al., Proceedings of the National Academy of Sciences of USA, 102, 14165-14170 (2005).
Professor E. Weber's team at Berkeley, California, US has recently succeeded in finding a new technique to handle metal defects in low-grade silicon, which could dramatically reduce the cost of solar cells. At present, around 90 % of solar cells in the world are made from a refined, highly purified form of silicon. This is because solar cells made from cheaper forms of silicon do not perform well and also because removing impurities is expensive. The new idea is to manipulate the impurities in a way that reduces their detrimental impact on the solar cell, instead of purifying the material. The team analyzed how metal contaminants in silicon respond to different types of processing using a synchrotron X-ray microprobe capable of detecting metal clusters as small as 30 nanometers. In addition to micro-XRF and micro-XAFS, they employed a new method based on a spectrally resolved X-ray-beam-induced current, which generates a map of the minority-carrier diffusion length, revealing the precise impacts of metal impurity clusters on local material performance. They found that they were able to manipulate the distribution of the metal impurities by varying the cooling rate of the silicon. When the material is cooled quickly, the metal defects are quickly locked in a scattered distribution. For more information, see the paper, "Engineering metal-impurity nanodefects for low-cost solar cells", T. Buonassisi et al., Nature Materials, 4, 676-679 (2005).
X-ray analysis is a strong tool for speculating on the chemical and physical weathering processes on Mars. The elemental compositions of the bright dust, dark soil and other soil components collected at different sites on Mars, such as the Gusev crater and Meridiani Planum, have been determined by X-ray fluorescence spectrometers fitted to the Mars Explorer Rovers. A comparison between the results obtained at both sites generally shows that the bright dust is global in nature and not dominated by the composition of local rocks, and also that the dark soil has the same origin, while other soil components are fairly different. For more information, see the paper, "An integrated view of the chemistry and mineralogy of martian soils", A. S. Yen et al., Nature, 436, 49-54 (2005).
Recently, a very old copy of Archimedes' writings, which had been erased, written over and even painted over during the past 1,000 years, has been analyzed by X-ray fluorescence with a sub-micron X-ray beam at Stanford Synchrotron Radiation Laboratory, California, United States. The palimpsest, which is preserved at Walters Art Museum in Baltimore, is a goatskin parchment on which a 10th-century scribe copied some of Archimedes' manuscripts originally written around 220 B. C. Later, the ink was erased by being scraped off with a pumice stone. Further damage was done when forgers painted Byzantine religious images on four pages. Archaeologists have successfully analyzed much of the 174-page palimpsest by conventional methods using visible and ultraviolet light, but several pages, including those under the paintings, remained obscured. The main idea behind the work at Stanford is that the ink contains iron pigment, and therefore the analysis is basically the mapping of iron K X-ray fluorescence. As the ink is only 1-2 microns thick, the use of a sub-micron beam was crucial. The analysis revealed that the hidden text on two of the pages is about floating bodies and the equilibrium of planes. Surprisingly, the third page is a previously unknown introduction to Archimedes' Method of Mechanical Theorems. The main source of the news is an article by Heather Rock Woods, Stanford University,http://news-service.stanford.edu/news/2005/may25/archimedes-052505.html
For further details, contact Neil Calder, Stanford Linear Accelerator Center, Phone +1-650-926-8707, or Uwe Bergmann, Stanford Synchrotron Radiation Laboratory, Phone +1-650-926-3048, bergmann@SLAC.Stanford.EDU
For further details, contact Neil Calder, Stanford Linear Accelerator Center, Phone +1-650-926-8707, or Uwe Bergmann, Stanford Synchrotron Radiation Laboratory, Phone +1-650-926-3048, bergmann@SLAC.Stanford.EDU
A joint research group from the Universities of Sheffield and Warwick (both in the United Kingdom) and the European Synchrotron Radiation Facility (ESRF) in Grenoble, France have recently reported an interesting application of a dispersive XAFS (X-ray absorption fine structure) spectrometer, which has no moving parts and is thus inherently more stable than a conventional step-scanning instrument, thereby permitting comparative measurements to be taken rapidly. The measurements were performed on a FeCo alloy thin film located between the poles of a magnet, which induces a saturating field in the sample. The magnets were rotated via a stepping motor such that the induced magnetization, causing the strain, lies either along or perpendicular to the X-ray polarization vector. Transmitted X-ray intensity measurements were made repeatedly at every 90 degree angle between the magnetization vector and the polarization vector. An entire four-quadrant measurement took about 1s, with repeated measurements accumulated over a 2h period. The differential absorption spectra obtained in this way can give atomic displacements due to magnetostriction. The research group demonstrated that it is possible to observe the movement of atoms with a resolution of 0.01 Å i.e., an improvement of 100 times on the previous level. For further details, see the paper, "Measurement of femtometre-scale atomic displacements by X-ray absorption spectroscopy", R. F. Pettifer et al., Nature, 435, 78-81 (2005).
At beamline ID18, ESRF, scientists studied pieces of hair and skin of Agnès Sorel, who was the beautiful mistress of 15th century French king, Charles VII. Very recently, from X-ray fluorescence spectra, they found that Sorel's remains contained abnormal levels of mercury. The manner of her death was previously unknown, but incredibly high levels of mercury have been found in her remains. This finding will give fresh impetus to the search to reveal the the truth behind this historical event. The source of this news is the web page of ESRF, http://www.esrf.fr/NewsAndEvents/PressReleases/sorel/
X-ray analysis has been applied to a 230-year-old painting by William Hodges, the artist who accompanied Captain James Cook on his second voyage to the Pacific (1772-75). Recently, it was noticed that the canvas was thicker in some places than in others. An X-ray subsequently revealed that two icebergs had been painted over and replaced with the lush green foliage of New Zealand, thus proving that Hodges' work is the oldest painting of Antarctica. The discovery ignited much discussion as to why Hodges erased the icebergs after having survived an extremely hard voyage around the frozen continent. The main news source is an article by Matt Apuzzo, Associated Press (http://hosted.ap.org/dynamic/fronts/HOME). For more information about William Hodges's painting, see for example, http://www.nmm.ac.uk/upload/package/30/home.php
A Japanese group is using a brilliant synchrotron microbeam at the SPring-8, Harima, Japan to study the marine pollution problem caused by organic tin compounds, which are known as environmental hormones because of their harmful influence on the endocrine system. The scientists attempted to determine Sn distribution in the testes of rats exposed to tributyltin chloride, which was orally administered to rats at a dose of 45 x 10-6 mol/kg per day for 3 days. They employed a 37.5 keV X-ray beam of 3 x 3 micron2 to detect Sn K X-ray fluorescence from the sperm of a seminiferous tubulem, the key point being that measurement can be performed for single cells, thus enabling cell-selective analysis. For more information, see the paper, "Tin accumulation in spermatozoa of rats exposed to tributyltin chloride by synchrotron radiation X-ray fluorescence (SR-XRF) analysis with microprobe", S. Homma-Takeda et al., Nucl. Instrum. & Methods, B231, 333-337 (2005).
Los Alamos National Laboratory scientists, C. Worley, S. S. Wiltshire, T. C. Miller, G. J. Havrilla and V. Majidi, have developed a novel method for detecting fingerprints on surfaces that typically render such prints invisible. The technique uses micro-X-ray fluorescence (MXRF) and can therefore determine the elements in a fingerprint and obtain a pattern at the same time. Salts such as sodium chloride and potassium chloride that are excreted in sweat are sometimes present in detectable quantities in human fingerprints. As the new method might also be able to tell if the person that left the fingerprints also handled something like bomb-making materials, it could potentially be used as a tool in forensic investigation. For more information, contact Todd Hanson, Phone +1-505-65-2085, tahanson@lanl.gov, http://www.lanl.gov/.
Researchers at the National Cancer Institute (NCI), part of the National Institutes of Health, have found that zinc deficiency in humans is associated with an increased risk of developing esophageal squamous cell carcinoma, an often-fatal form of esophageal cancer numbering about 7,000 cases a year. The research basically measures the zinc concentration contained in the tissue by means of X-ray fluorescence analysis using synchrotron radiation at Advanced Photon Source, Argonne, USA. For more details, see the paper, "Zinc concentration in esophageal biopsy specimens measured by X-ray fluorescence and esophageal cancer risk", C.C. Abnet, B. Lai, Y.-L. Qiao, S. Vogt, X.-M. Luo, P.R. Taylor, Z.-W. Dong, S.D. Mark, S.M. Dawsey, J. Nat. Cancer I. 97, 301 (2005). Information about cancer is available at http://www.cancer.gov or NCI's Cancer Information Service at +1-800-422-6237.
An Austrian research group recently succeeded in obtaining highly collimated, spatially coherent X-rays, at a wavelength of about 1 nm and at photon energies extending to 1.3 keV, from high-order harmonic generation in an atomic gas ionized by a 720-nm, 5-fs, 0.2-TW laser pulse. The beam divergence was evaluated as 0.2 mrad for the spectral range above 200 eV from a knife-edge scan, indicating perfect coherence of the atomic dipoles within a macroscopic volume of diameters of 13μm and 4μm at photon energies of 0.3 keV and 1 keV, respectively. The beam seems to be diffraction-limited to within a factor of five. The spectrum of the generated radiation was observed by an energy-dispersive X-ray spectrometer with some filters. The results are really exciting, because they could detect the copper L-edges (~950 eV)! One would notice that the energy of photons produced by laser technologies has been increasing every year - the main idea behind this progress is the creation of time-gradient in the driving pulse, which allows some 25% of the helium atoms to be ionized within half a cycle before the pulse peak. The electrons detached within this time are pushed in the most intense half-cycle back to the atomic core. For more information, see the paper, "Source of coherent kiloelectronvolt X-rays", J. Seres et al., Nature, 433, 596 (2005). C. Streli and P. Wobrauschek (Atominstitut der Osterreichischen Universtitaten, Technische Universitat Wien) were the co-authors of this paper.
One of the most exciting recent scientific discoveries is that Mars was possibly once wet and salty, suggesting an environment that could serve as a candidate for early life. The two Mars Rovers, Sprit and Opportunity, have been collecting large amounts of data on the soil, rock and atmosphere by utilizing state-of-the-art analytical instruments including an X-ray spectrometer, which recently determined the major and minor elements of soil and rock samples taken from Meridiani Planum. For more information, see the paper, "Chemistry of Rocks and Soils at Meridiani Planum from the Alpha Particle X-ray Spectrometer", R. Rieder et al., Science, 306, 1746-1749 (2004).
A whitish cream in a small canister, which was recently discovered during archaeological surveys of the remains of a Roman temple in London, has been found to contain SnO2. Archaeologists think the SnO2 was added intentionally, presumably for use as cosmetic. They believe the unguent was prepared using sophisticated technology: animal fat was heated, possibly with the aim of bleaching it, and the starch was separated by treatment of roots or grains with boiling water, and then white SnO2 , which is readily produced by heating refined tin metal in air, was added. The non-toxic properties of SnO2 would also have been desirable, because by the second century AD, the dangers of lead were becoming recognized. XRF and XRD analysis played an important role in the identification of the ancient cosmetic cream. For more information, see the paper, "Archaeology: Formulation of a Roman cosmetic", R. P. Evershed et al., Nature, 432, 35-36 (2004).
Argonne research group recently published details of their successful application of high-spatial-resolution XRF and XAFS measurements, which they performed in order to make elemental maps and qualitative chemical analyses of single free-floating, or planktonic, and surface-adhered, or biofilm, cells of Pseudomonas fluorescens. The results revealed differences between the planktonic and biofilm cells in terms of morphology, elemental composition and sensitivity to hexavalent chromium, a heavy-metal contaminant and a known carcinogen. The biofilm cells were more tolerant of the contaminant, which damaged or killed the planktonic cells. The experiments were performed with a 150 nm X-ray beam produced by phase zone plate at the beamline XOR 2-ID, at the Advanced Photon Source (APS), Argonne, USA. For more information, see the paper, "Elemental and Redox Analysis of Single Bacterial Cells by X-ray Microbeam Analysis", K. M. Kemner et al., Science, 306, 686-687 (2004).
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