NIMS X-RAY LABORATORY directed by Kenji Sakurai

On Friday 2 December 2011, an unknown painting by Rembrandt was presented in the Rembrandt House Museum (Amsterdam).  The small panel, Old Man with a Beard, was painted by Rembrandt around 1630, at the end of his time in Leiden.  A research group led by Professor K. Janssens (University of Antwerp) and Professor J. Dik (Delft University of Technology) has performed experimental studies on this painting with a synchrotron beam at the European Synchrotron Radiation Facility (ESRF) and the Brookhaven National Laboratory (BNL), and has unveiled a hidden, unfinished self-portrait below the painting.  For further information, visit the web page, http://webh01.ua.ac.be/mitac4/rembrandt/index_301111.html

Recently, a very stimulating paper has been published discussing experimentally the fundamental processes of photo-absorption and excitation of electrons by using extremely high-fluence, ultra-short X-ray pulses.  The research was done for the electron system in inert Ne gas at LCLS (Linac Coherent Light Source), Stanford, USA, which is the world's first hard X-ray free-electron laser facility.  The scheme is as follows: an intense single X-ray pulse of sub-10-fs duration at 848 eV first strips a 2p electron from Ne and, at this stage, since the X-ray energy is below the binding energy of a 1s electron in neutral neon, 870 eV, a 1s hole cannot be produced, but because of the above 2p hole, the next pulse can excite the 1s electron, leading to 1s-2p resonance in the Ne⁺ ion and, finally, stimulated emission (2p-1s) competes with Auger decay to refill the 1s hole.  The results have indicated that intense X-ray pulses of sub-10-fs duration can modify and even control the Auger decay process.  For more information, see the paper, "Unveiling and Driving Hidden Resonances with High-Fluence, High-Intensity X-Ray Pulses", E. P. Kanter et al., Phys. Rev. Lett. 107, 233001 (2011).

BaTiO₃ is a promising candidate ferroelectric material for magnetoelectric composites and layered film structures.  Recently, some interesting soft X-ray absorption spectra at Ti-L_{II, III} , O-K, and Ba-M_{IV, V} edges have been discussed mainly from a theoretical point of view by a German group.  For more information, see the paper, "High-resolution x-ray absorption spectroscopy of BaTiO₃: Experiment and first-principles calculations", A. Chassֺé et al., Phys. Rev. B84, 195135 (2011).

Multi-wavelength anomalous diffraction (MAD) has been widely employed to determine phase information in X-ray crystallography.  The method uses the contrast of the scattering power of heavy atoms at the absorption edges.  However, when the X-ray source becomes extremely brilliant, the sample encounters severe electronic radiation damage, especially to heavy atoms, which makes the interpretation of MAD rather difficult.  Recently, a theoretical paper discussing this problem has been published.  The theory uses a Karle-Hendrickson-type equation in the high-intensity regime, and demonstrates the calculation of relevant coefficients with detailed electronic damage dynamics of heavy atoms.  For more information, see the paper, "Multiwavelength Anomalous Diffraction at High X-Ray Intensity", S-K.Son et al., Phys. Rev. Lett. 107, 218102 (2011).

The recipient of the 6th Asada Award, which is presented by the Discussion Group of X-ray Analysis, Japan, in memory of the late Professor Ei-ichi Asada (1924-2005) to promising young scientists in X-ray analysis fields in Japan, is Dr. Takashi Yamamoto (Tokushima Univ., "Studies on pre-edge peak in XANES spectra of transition metals for empirical chemical state analysis").  The ceremony was held during the 47th Annual Conference on X-Ray Chemical Analysis, Japan, at Kyushu University, Fukuoka.

Professor J. Kawai (Kyoto University, Japan; Associate editor of X-ray Spectrometry) and his colleagues recently developed a novel tiny X-ray instrument equipped with a pyroelectric LiTaO₃ crystal as an electron source, a sample stage and an X-ray detector.  The research group found that adequate X-ray fluorescence spectra can be measured for 0.03 mm² titanium, iron, and nickel wires.  For more information, see the paper, "Development of Miniaturized Electron Probe X-ray Microanalyzer", S. Imashuku et al., Anal. Chem., 83, 8363 (2011).

Empirical and semiempirical K-shell fluorescence yields (ωK) and Kβ/Kα intensity ratios for ZnCo alloy with various chemical compositions, leading to differences in pH, have recently been published.  The samples were excited by 59.5-keV γ rays from a ²⁴¹Am annular radioactive source, and X ray fluorescence spectra were measured by an Ultra-LEGe detector.  For more information, see the paper, "Effect of pH treatment on K-shell x-ray intensity ratios and K-shell x-ray-production cross sections in ZnCo alloys", N. Kup Aylikci et al., Phys. Rev. A84, 042509 (2011).

European XFEL and the Spanish Center for Ultrashort Ultraintense Pulsed Lasers (CLPU) in Salamanca will pool their efforts to promote research into high-energy density science and to develop new ultrafast lasers to analyze physical and chemical processes in conjunction with the X-ray beams of the European XFEL.  Both research institutions signed a memorandum of understanding at the European XFEL headquarters in Hamburg.  In the framework of this cooperation, an optical laser expert from CLPU has now joined the European XFEL Optical Lasers Group for an initial period of six months.  For further information, visit the web page,  http://www.xfel.eu/

A German group led by Dr. B. Beckhoff (Physikalisch-Technische Bundesanstalt (PTB), Berlin) recently analyzed quantitatively the buried B₄C nanolayer on a silicon substrate by using synchrotron radiation at BESSY II.  The thickness and elemental composition were successfully determined by reference-free X-ray fluorescence spectrometry under conventional and grazing-incidence conditions.  For more information, see the paper, "Complementary Characterization of Buried Nanolayers by Quantitative X-ray Fluorescence Spectrometry under Conventional and Grazing Incidence Conditions", R. Unterumsberger et al., Anal. Chem., 83, 8623 (2011).

A Korean group led by Professor J. H. Je (Pohang University of Science and Technology) has recently reported some interesting experiments on water vaporization by X-ray photons.  The experiments were done at the undulator beamline, XSD 32-ID, Advanced Photon Source in Argonne, USA.  It was found that water is vaporized at a rate of 5.5 pL/sec at a 100 msec exposure of 1-Å-wavelength (~13 keV) X-ray irradiation of around 10⁷ photons/μm² (0.1 photons/Ų), which corresponds to a dose rate of ~50 kGy/sec.  They also confirmed that water vapor is reversibly condensed during pauses in irradiation.  This result suggests that photoionization induces vaporization through the reduction of the surface tension of water.  For more information, see the paper, "X-ray-induced water vaporization", B. M. Weon et al., Phys. Rev. E84, 032601 (2011).

The European Molecular Biology Laboratory (EMBL) and the European XFEL have signed a Memorandum of Understanding, thereby laying the foundation for close future collaboration in deciphering the structure and dynamics of biomolecules.  For further information, visit the Web page, http://www.xfel.eu/

Most living vertebrates are jawed vertebrates (gnathostomes), and only scarce information on the evolutionary origin of jaws is available from living jawless vertebrates (cyclostomes), hagfishes and lampreys.  The extinct bony jawless vertebrates, or 'ostracoderms', have been regarded as precursors of jawed vertebrates and provide an insight into this formative episode in vertebrate evolution. Very recently, Chinese scientists employed synchrotron radiation X-ray tomography in an effort to analyze the cranial anatomy of galeaspids, a 370-435-million-year-old 'ostracoderm' group from China and Vietnam.  For more information, see the paper, "Fossil jawless fish from China foreshadows early jawed vertebrate anatomy", Z. Gai et al., Nature 476, 324 (2011).

Professor J. R. Engstrom (Cornell University) and his colleagues have recently published a detailed comparative study on surface morphology obtained from in-situ, time-resolved X-ray reflectivity, which is extremely feasible as a tool for investigating surface and interfaces during thin film growth, but requires some modeling of the growth process for the interpretation.  The research group prepared two sets of organic thin films, pentacene/SiO₂ and diindenoperylene SiO₂; for each system, giving a total of four films, grown to different thicknesses, under nominally identical conditions.  The X-ray reflectivity data were analyzed based on three different models, and the obtained parameters were directly compared with AFM data.  It was found that all models employed can give good agreement between the surface morphology obtained from fits with the actual morphology at early times.  On the other hand, this agreement deteriorates at later times, once the root-mean squared (rms) film roughness exceeds about 1 monolayer.  It was also found that the best fits to reflectivity data, corresponding to the lowest values of χ², do not necessarily yield the best agreement between simulated and measured surface morphologies, simply because the model reproduces all local extrema in the data.  For more information, see the paper, "Quantitative modeling of in situ x-ray reflectivity during organic molecule thin film growth", A. R. Woll et al., Phys. Rev. B84, 075479 (2011).

The following awards were presented during the plenary session of the 60th Annual Denver X-Ray Conference: The 2011 Barrett Award was presented to Dr. Juan Rodriques-Carvajal, Institute Laue-Langevin, Grenoble, France to honor his exceptional contributions to the field of X-ray diffraction, in particular for his work on characterization of the structural and magnetic properties of strongly correlated oxides using diffraction techniques and for writing and freely disseminating FULLPROF, the most widely used Rietveld refinement program for analysis of crystallographic and magnetic structures.  The 2011 Jenkins Award was given to Dr. Paul K. Predecki to honor his contributions to the development of X-ray methods for a wide variety of materials, and his generosity in teaching and inspiring others in X-ray materials analysis both at the University of Denver and through organization and management of the Denver X-ray Conference.  The 2011 Jerome B. Cohen Student Award was given to Vallerie Ann Innis-Samson, University of Tsukuba, Ibaraki, Japan, for her work, X-ray Reflection Tomography: A New Tool for Surface Imaging.  For further information, visit the Web page, http://www.dxcicdd.com/

X-ray spectroscopy is an extremely strong tool for metal speciation at the molecular level in biological and environmental samples, especially for metalloproteins.  When samples are quite easily influenced by photoreduction, however, analysis has not been straightforward.  Recently, a Chinese group has studied in detail soft X-ray induced photoreduction in organic Cu(II) compounds.  The research team measured XANES spectra at Cu-LIII, O-K, and C-K edges to see how the valence state of Cu changes.  A scanning transmission X-ray microscopy was also employed to look at specific radiation damages.  It was found that reducing the radiation dose to 0.1 MGy effectively prevented the photoreduction of organic Cu(II) compounds.  For more information, see the paper, "Soft X-ray Induced Photoreduction of Organic Cu(II) Compounds Probed by X-ray Absorption Near-Edge (XANES) Spectroscopy", J. Yang et al., Anal. Chem., Article ASAP (DOI: 10.1021/ac201622g  Publication Date (Web): August 1, 2011).

An innovative X-ray camera, designed to record bursts of images at an unprecedented speed of 4.5million frames per second, is being built with the help of the UK's Science and Technology Facilities Council (STFC) and will be delivered to the European XFEL (X-ray Free-Electron Laser) in 2012.  For further information, visit the Web page, http://www.stfc.ac.uk/About%20STFC/36221.aspx

Parametric down-conversion is a quantum-optical process in which a 'pump' photon splits spontaneously into two (the 'signal' and 'idler') in a nonlinear optical medium.  Recently, Professor T. Ishikawa (RIKEN, Harima, Japan) and his colleagues reported their experiments with X-ray photons.  They have visualized three-dimensionally the local optical response of diamond at wavelengths between 103 and 206 Å with a resolution as fine as 0.54 Å.  This corresponds to a resolution from λ/190 to λ/380, an order of magnitude that is the best ever achieved.  For more information, see the paper, "Visualizing the local optical response to extreme-ultraviolet radiation with a resolution of λ/380", K. Tamasaku et al., Nature Physics 7, 705 (2011).