"A Century of Crystallography: the Braggs Legacy"
https://www.youtube.com/watch?v=a-jE7BM902Q
"The humble Braggs and X-ray crystallography: Solving the patterns of matter"
https://www.youtube.com/watch?v=z-ZnLtFgGwY
"Seeing Things in a Different Light: How X-ray crystallography revealed the structure of everything"
https://www.youtube.com/watch?v=gBxZVF3s4cU
"Mars Diffracts! X-ray Crystallography and Space Exploration"
During the plenary session of the 65th Annual Denver X-Ray Conference, the following awards were presented. The 2016 Birks Award was presented to Alan C. Huber, Amptek, Inc., and Jacob (Nate) Sherman (awarded posthumously). The 2016 Robert L. Snyder Student Travel Awards were given to the following nine students; Valentina Aguilar, Quan Kuang, Yifeng Ling, Lara Maldanis, Scott McCormack, Adelita Mendoza, Sixberth Mlowe, Jing Zhang, He Zhang. The 2016 Hanawalt Award was presented to Matteo Leoni and Paolo Scardi, University di Trento, Trento, Italy. Dr. Leoni was present to receive the award. Dr. Scardi accepted his award and presented his Hanawalt Award Lecture at the XTOP2016 Conference, Brno, Czech Republic, 4-8 September 2016. The 2016 Jerome B. Cohen Student Award did not have a recipient. For further information, visit the Web page, http://www.dxcicdd.com/
The three free XRF posters offered by Professor James P Willis (James Willis Consultants cc, South Africa) have become one of the most popular, high-impact topics in the XRF-L mailing list. His posters are as follows: (i) The WDXRF spectrometer, illustrated with appropriate wavelength scans and pulse height distributions, (ii) Some factors affecting XRF sensitivity (Kα lines Sn to Na), and (iii) Theoretical intensities for Sn, Cu, Ti, K and S K lines excited by an end-window Rh tube operating at 60, 50, 40, 30 and 25 kV and 4kW. Information for downloading the PDF files is available at the Web site, http://xrfguidelines.co.za/
The recipient of the 10th 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. Shigetomo Shiki (National Institute of Advanced Industrial Science and Technology, Tsukuba), "Advances in X-ray absorption fine structure apparatus utilizing superconducting tunnel junction detector"). The ceremony was held during the 51th Annual Conference on X-Ray Chemical Analysis, at Jibasan Building , Himeji.
Reaching the milestone of X-ray lasers is something that X-ray physicists have dreamed of for many years. Recently developed X-ray free-electron lasers (XFEL) based on self-amplified spontaneous emission (SASE) constitute a very promising tool for future X-ray laser technologies. A team led by Professor H. Yoneda (University of Electro-Communications, Tokyo, Japan) has recently carried out very impressive experiments at Japanese XFEL facility, SACLA, on the same campus as SPring-8. Similar to an X-ray tube, the researchers employed a solid copper target to generate X-rays. However, their experiment is very unique in that two colors were employed by tuning undulator gaps; one energy is around 9 keV, i.e., above the Cu-K absorption edge, and the other energy is almost the same energy as Cu Kα1 or Kα2. While 9 keV photons ionize copper atoms and generate Cu K X-ray fluorescence spectra, the lower energy photons can amplify the X-ray fluorescence because of their temporal coherence. Their Cu Kα spectra are impressive, because Kα1/Kα2 can be controlled by tuning the second energy of XFEL pulses. The reason for the limited amplification is probably due to the energy band width of incoming temporary coherent X-ray photons. The researchers did not use any monochromators, but controlled only the undulator gaps. They have two different X-ray energies, but unfortunately monochromaticy has some limits and the band width is still quite wide. The present work could be a very important step toward achieving X-ray lasers by using atomic energy levels. For more information, see the paper, "Atomic inner-shell laser at 1.5-angstrom wavelength pumped by an X-ray free-electron laser", H. Yoneda et al., Nature 524, 446 (2015).
During the plenary session of the 64th Annual Denver X-Ray Conference, three awards were presented. The 2015 Barrett Award was presented to Brian Toby, Advanced Photon Source, Argonne National Laboratory, Argonne, IL, USA; the 2015 Jenkins Award was presented to Cev Noyan, Columbia University, New York, NY; and the 2015 Jerome B. Cohen Student Award was presented to Peter Metz, Alfred University, Alfred, NY for his manuscript, "X-ray and Neutron Total Scattering Analysis of Hy (Bi0.2Ca0.55Sr0.25)(Ag0.25Na0.75)Nb3O10 xH2O Perovskite Nanosheet Booklets with Stacking Disorder". For further information, visit the Web page, http://www.dxcicdd.com/
Dr. F. Dorchies (Universite Bordeaux, CNRS-CELIA, France) and his colleagues have recently developed a laser-base X-ray absorption spectrometer covering 0.5-4.0 keV with a time resolution of around 3.3 pico second. The spectrometer uses bremsstrahlung caused by the extremely high impact of laser pulses on the metallic target. To perform time-resolved X-ray spectroscopic studies, there have been quite a few challenges. For most research, it is crucial to avoid damaging/destroying samples, and the measuring time should not be very long. In addition, scientists don't like to compromise the signal-to-background ratio of spectral data taken at each time point, even though the quality is not the same as that of ordinary X-ray absorption spectra. The authors seem to believe that they are getting some breakthroughs. Their setup is a combination of a table-top laser (Ti: Sapphire, 800nm, 150mJ, 10Hz) and a Johan spectrometer equipped with a CCD camera. A set of polycapillary optics were employed as a beamline transport between the X-ray source and the sample (1 m distance) to maintain a clean, independent and flexible environment for the sample. The X-ray intensity near the Al K edge and Cu L edges is 1.3 × 106 photons/eV/pulse. For more information, see the paper, "Experimental station for laser-based picosecond time-resolved x-ray absorption near-edge spectroscopy", F. Dorchies et al., Rev. Sci. Instrum. 86, 073106 (2015).
Since the development of EPMA (electron probe micro analysis) by Castaing's PhD thesis in 1951, great efforts have been made to improve the technique. It was believed that the use of standard samples is absolutely indispensable to the determination of the concentration of each element. This can be a limit for some fields, such as nuclear materials application, where the quantification of minor actinides in fresh or spent fuel is demanded with no availability of any standard samples. In France, Dr. A Moy (Universite de Montpellier) and his colleague have recently reported successful standardless analysis of Pb and U in PbS, PbTe, PbCl2, Pb5(VO4)3Cl (vanadinite), and UO2, by measuring absolute Mα and Mβ X-ray intensity by a wavelength dispersive spectrometer. Experimentally obtained X-ray intensity was converted into absolute X-ray yields by evaluating the detector efficiency and then compared with calculated background X-ray intensity based on Monte Carlo simulations. For more information, see the paper, "Standardless quantification of heavy elements by electron probe microanalysis", A. Moy et al., Anal. Chem. 114, 255501 (2015).
A team led by Dr. M. Minitti (SLAC National Accelerator Laboratory, USA) has recently succeeded in recording the time evolution of a structural change of ring-type 1,3-cyclohexadiene gas molecule to linear 1,3,5-hexatriene. The employment of the X-ray free-electron laser at LCLS (Linac coherent light source), Stanford allowed them to do ultra fast snapshots of X-ray scattering in several tens of fs (femtosecond) scale. The study is based on pump-and-probe measurement; i.e., X-ray data were collected as a function of the controlled delay time between the UV pump pulse (267 nm, 65 fs, 4-8 μJ, 100 μm size) and X-ray probe pulse (8.3 keV, around 30 fs, 1012 photons/pulse, 30 μm square size). The team established that some signals caused by structural change are found as early as 30 fs, and the reaction finishes at 200 fs. For more information, see the paper, "Imaging Molecular Motion: Femtosecond X-Ray Scattering of an Electrocyclic Chemical Reaction", M. P. Minitti et al., Phys. Rev. Lett. 114, 255501 (2015).
Ms. Laura Bush, who is an editorial director of Spectroscopy, has recently published an article on the present and future of X-ray fluorescence on the occasion of Spectroscopy's celebration of 30 years. It is a summary of her interviews with experts. For more information, see the article, "Analysis of the State of the Art: XRF", Laura Bush, Spectroscopy, 30 (6) 86-94 (2015), which can be found online at http://www.spectroscopyonline.com/analysis-state-art-xrf A PDF file can also be downloaded from iTunes.
Coherent X-ray diffraction imaging is one of a number of recently developed lens-less microscopic techniques giving 2D real space structure when combined with phase retrieval data processing. A team in Shandong University in China has recently published an interesting observation of intact unstained magnetotactic bacteria. It was confirmed that the reconstructed images give some intercellular structures, such as nucleoid, polyβ-hydroxybutyrate granules, and magnetosomes, which have been identified by electron microscopy. The team was also successful in quantification of the density, i.e., it was found that the average density of magnetotactic bacteria is 1.19 g/cm3 from their data. The experiment was done with 5 keV X-ray photons at BL29XU, SPring-8, Japan. For more information, see the paper, "Quantitative Imaging of Single Unstained Magnetotactic Bacteria by Coherent X.ray Diffraction Microscopy", Jiadong Fan et al., Anal. Chem. 87, 5849 (2015).
A research group led by Professor Jorg Evers (Max Planck Institute for Nuclear Physics, Heidelberg, Germany) has recently reported a method for narrowing the spectral width of X-ray pulses by the use of subluminal light propagation. So far, in visible light, slow group velocity such as 17 m/sec has been observed in low temperature sodium gas at 435 nK (see, L. V. Hau et al., Nature, 397, 594 (1999)). The authors intend a similar effect in X-ray wavelength photons by manipulating the optical response of the 14.4 keV Mössbauer resonance of 57Fe nuclei. The method combines coherent control, as well as cooperative and cavity enhancements of light-matter interaction in a single setup. It was found that the reduced group velocity of the obtained X-ray pulses is lower than 10-4 of the speed of the light. For more information, see the paper, "Tunable Subluminal Propagation of Narrow-band X-Ray Pulses", K. P. Heeg et al., Phys. Rev. Lett. 114, 203601 (2015).
Professors D. A. Keen (Rutherford Appleton Laboratory) and A. L. Goodwin (University of Oxford) have recently published an interesting review paper on disordered structures. For many years, crystallographers have determined the structures of many complicated crystals with atomic or even sub-atomic resolution. On the other hand, the structures of disordered systems, which lack the crystalline periodic order, are still not well understood because of the limits of the analytical technique. Correlated disorder is a disorder, but maintains crystallographic signatures, which can be used for classifying the type of disorder. For more information, see the paper, "The crystallography of correlated disorder", D. A. Keen and A. L. Goodwin, Nature, 521, 303 (2015).
A Slovenian group has recently reported the Kα and Kβ emission spectra of phosphorus, measured by monochromatic synchrotron X-rays (3 keV, at ID26, ESRF) and a 2 MeV proton beam. They also compared them with a Density Functional Theory calculation using StoBe-deMon code (Stockholm-Berlin version of demon). For more information, see the paper, "Chemical State Analysis of Phosphorus Performed by X.ray Emission Spectroscopy", M. Petric et al., Anal. Chem. 87, 5632 (2015).
Readers may remember that electrochemical X-ray fluorescence developed by Prof. Julie V. Macpherson's group at Warwick University, England can analyze sub-ppb level heavy elements in solution (See, News in No.5, Vol.43 (2014)). Recently the research team published their successful extension of the technique to in situ time-evolution analysis. Their electrode is a freestanding film of boron-doped diamond, and it can work also as an X-ray window. Primary X-rays pass through the back side of the electrode and excite the heavy elements in the electrodeposit on the electrode. In addition to quantitative analysis of a mixed solution of Hg2+, Pb2+, Cu2+, Ni2+, Zn2+, and Fe3+(all at 10 μM concentration), time-evolution analysis of electrodeposition can be a very promising application of this unique method. For more information, see the paper, "Direct Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X.ray Fluorescence", G. D. O'Neil et al., Anal. Chem. 87, 4933 (2015).
Scientists at Los Alamos National Laboratory have recently reported the X-ray analysis of uranium oxideα-U3O8 samples under controlled temperatures and humidities. They found that the combined use of powder X-ray diffraction and U L-III EXAFS can help in identifying temporal changes of uranium oxide stored for a number of years. For more information, see the paper, "Oxidation and Hydration of U3O8 Materials Following Controlled Exposure to Temperature and Humidity", A. L. Tamasi et al., Anal. Chem. 87, 4210 (2015).
A very interesting idea that proposes the use of a motor in a hard disk drive as an X-ray chopper has been recently published. It can produce X-ray pulses of ms width and few μs rise time. In the research, the system was used to test the response of X-ray detectors such as ionization chambers and photo diodes. For more information, see the paper, "Hard disk drive based microsecond x-ray chopper for characterization of ionization chambers and photodiodes", O. Muller et al., Rev. Sci. Instrum. 86, 035105 (2015).
National Synchrotron Light Source II of Brookhaven National Laboratory will officially start user runs from the 3rd cycle in 2015. Seven beamlines will be commissioned in September, 2015, and a further 21 beamlines will be designed and constructed in the coming years. The facility provides the world's smallest electron beam emittance, resulting in the brightest X-ray source. For more information, visit the Web page, http://www0.bnl.gov/ps/nsls2/about-NSLS-II.php
The following YouTube video also gives useful information.
At the soft X-ray free-electron laser (XFEL) facility, FLASH, in Hamburg, Germany, all-optical synchronization has finally been achieved. Scientists are reporting that the timing is better than 30 fs rms for 90 fs X-ray photon pulses. As one of the most promising experiments using XFEL is time-resolved analysis based on the pump & probe scheme, it is crucial to synchronize all independent components, including all accelerator modules and all external optical lasers, to better than the delivered free-electron laser pulse duration such as shorter than 100 fs. For more information, see the paper, "Femtosecond all-optical synchronization of an X-ray free-electron laser", S. Schulz et al., Nature Communications, 6, 5895 (2015).
At the European Synchrotron Radiation Facility (ESRF) in Grenoble, France, scientists from Italy, Germany and France have succeeded in 'reading' letters inside a papyrus roll found in the ancient library, discovered in Herculaneum. The experiments were done at the beamline ID17, and the X-ray phase contrast tomography technique was employed. The team was successful in extracting words under several papyrus layers in a fragment, and finally found that they are the complete Greek alphabet. For more information, see the paper, "Revealing letters in rolled Herculaneum papyri by X-ray phase-contrast imaging", V. Mocella et al., Nature Communications, 6, 5895 (2015). An interesting movie has also been uploaded to Youtube, https://www.youtube.com/watch?v=d3aWBgNYOCU
X-ray ptychography is known as a promising lensless imaging method. Compared with other similar techniques, it can give a rather wide viewing area with the same high-spatial-resolution in nano scale, by combining multiple coherent diffraction measurements from the illumination of several overlapping regions on the sample. However, this apparently has to assume a highly sophisticated scanning/positioning instrumentation. The method may suffer also from partial-coherence effects and fluctuations. Dr. A. Menzel (Paul Scherrer Institut, Switzerland) and his colleagues have recently published an interesting report on fast measurement. The authors discussed ptychographic on-the-fly scans, i.e., collecting diffraction patterns while the sample is scanned with constant velocity. It was found that such a scan can be used as a model for a state mixture of the probing radiation and helps to achieve reliable image recovery. The feasibility of on-the-fly measurements in traditional scanning transmission X-ray microscopy is already known. This time, the research team was successful in applying these to X-ray ptychography, which usually uses reconstruction algorithms assuming diffraction data from a static sample. Such problems were discussed in detail. For more information, see the paper, "On-the-fly scans for X-ray ptychography", P. M. Pelz et al., Appl. Phys. Lett., 105, 251101 (2014).
A team led by Professor Harald Ade (North Carolina State University, USA) has reported that grazing resonant soft X-ray scattering (GRSoXS), a technique measuring diffusely scattered soft X-rays from grazing incidence, can reveal the statistical topography of buried thin-film interfaces. So far, in wide variety of material systems, the internal structures of layered systems, particularly interfaces between different materials, have been critical to their functions. However, the analysis of buried interfaces has always presented some difficulties. It is known that X-ray electric field intensity distribution along the depth can be controlled by a change of either the incidence angle or the X-ray energy. The research team was able to manipulate it by scanning the X-ray energy, and succeeded in identifying the microstructure at different interfaces of a model polymer bilayer system such as PMMA/PEG. The authors attempted to gauge the feasibility of the technique for further practical systems like an organic thin-film transistor, PS[100nm]/PBTTT[50nm]/Si. For more information, see the paper, "Topographic measurement of buried thin-film interfaces using a grazing resonant soft x-ray scattering technique", E. Gann et al., Phys. Rev. B90, 245421 (2014).
Professor P. S. Pershan (Harvard University, USA) has recently published an interesting review paper on X-ray studies of the interface between liquid metals and their coexisting vapor. For more information, see the paper, "Review of the highlights of X-ray studies of liquid metal surfaces", P. S. Pershan, J. Appl. Phys., 116, 222201 (2014).
In addition to large-scale X-ray facilities such as synchrotrons and X-ray FELs, there have been increasing demands for much more compact X-ray sources with high brilliance, ultra short pulse properties and coherence. Dr. W. S. Graves (Massachusetts Institute of Technology, USA) and his colleagues have proposed a design for a compact X-ray source based on inverse Compton scattering. The source consists of a 1m linuc and an ultra short pulse laser. The whole size of the source including X-ray experiment space is nearly 4m. The colliding laser is a Yb:YAG solid-state amplifier producing 1030 nm, 100 mJ pulses at 1 kHz repetition rate. The calculation shows that X-ray intensity at 12.4 keV is 5×1011 photons/second in a 5% bandwidth. For more information, see the paper, "Compact x-ray source based on burst-mode inverse Compton scattering at 100 kHz", W. S. Graves et al., Phys. Rev. STAB, 17, 120701 (2014).
A team led by Dr. T. Jach (NIST, USA) and Dr. W. T. Elam (University of Washington, USA) has recently published an interesting theoretical paper discussing the broadening of N K absorption and emission spectra of NH4NO3 and NH4Cl. The authors studied many-body lifetime effects in valence-band X-ray emission. For more information, see the paper, "Origins of extreme broadening mechanisms in near-edge x-ray spectra of nitrogen compounds", J. Vinson et al., Phys. Rev. B90, 205207 (2014).
A German and Austrian group has recently developed a table-top X-ray source based on ultra-short laser pulses. Generation of X-ray pulses by lasers may not be a big surprise for readers (See, for example, "Ultrafast X-ray Pulses from Laser-Produced Plasmas" by M. M. Murnane, Science, 251, 531 (1991), "Microfocus Cu Kα source for femtosecond x-ray science" by N. Zhavoronkov, Opt. Letter, 30, 1737 (2005)). However, so far, the X-ray intensity has not been sufficient for use in practical measurements such as pump-and-probe time resolved X-ray analysis. This time, scientists employed a mid infrared wavelength (3.9 micron) to accelerate electrons from the copper tape target to very high kinetic energy by making use of its comparably long optical period. The pulse width of the laser employed is 80 femto second. It was found that the system gives 109 copper Kα photons per pulse generated with pulses of a peak intensity of 6×1016 W/cm2. This is about 25 times higher than that generated by 800 nm wavelength laser pulses. For more information, see the paper, "High-brightness table-top hard X-ray source driven by sub-100-femtosecond mid-infrared pulses", J. Weisshaupt et al., Nature Photonics, 8, 927 (2014).
Professor A. Adriaens (Ghent University, Belgium) and her colleagues have recently reported on an X-ray-excited optical luminescence microscope using synchrotron light and its applications. The experiments were done at beamlines BM28 and BM26A at the ESRF in Grenoble, France. A broad X-ray beam is used to illuminate large areas of ~4 mm2 of the sample, and the resulting optical emission is observed by a specifically designed optical microscope equipped with a CCD camera. By scanning the X-ray energy near the absorption edge, the image can obtain the sensitivity of chemical states. The authors studied copper surfaces with well-defined patterns of different corrosion products (cuprite Cu2O and nantokite CuCl). For more information, see the paper, "Evaluation of an X-ray Excited Optical Microscope for Chemical Imaging of Metal and Other Surfaces", P-J. Sabbe et al., Anal. Chem., 86, 11789 (2014).
The recipient of the 9th 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. Susumu Imashuku (Kyoto Univ.), "Portable electron probe microanalyzer using pyroelectric crystal". The ceremony was held during the 50th Annual Conference on X-Ray Chemical Analysis, at Tohoku University, Sendai.
So far, monochromatic X-rays have been used for 3D micro X-ray fluorescence analysis based on confocal geometry. Dr. P. Wrobel (AGH University of Science and Technology, Poland) and his colleagues have recently discussed the feasibility of polychromatic excitation. The research group described the full theoretical expression of matrix effects and geometrical effects for polychromatic X-ray photons in confocal arrangement. It was demonstrated that the introduction of effective energy approximation works well. For more information, see the paper, "Depth Profiling of Element Concentrations in Stratified Materials by Confocal Microbeam X-ray Fluorescence Spectrometry with Polychromatic Excitation", P. Wrobel et al., Anal. Chem., 86, 11275 (2014).
Dr. F. P. Romano and his colleagues have reported full-field X-ray fluorescence imaging based on the principle of the pin-hole camera. The instrument consists of a low power X-ray source (W anode, 50kV-2mA), a pinhole (50 micron dia) and a CCD camera (back illuminated type, 1024 × 1024 pixels, pixel size 13 micron square). To obtain good energy resolution (133 eV at 5.9 keV), the research team took a number of images in single photon counting mode. The team also obtained a reasonable spatial resolution down to 30 microns. The system can change the magnification ratio from 0.35 to 6, depending on the viewing area of interest and the required spatial resolution. For more information, see the paper, "Macro and Micro Full Field X-Ray Fluorescence with an X-Ray Pinhole Camera Presenting High Energy and High Spatial Resolution", F. P. Romano et al, Anal. Chem., 86, 10892 (2014).
So far, high-resolution microscopic analysis of individual atmospheric particles has been fairly difficult because of problems with the filters used for capturing particles. The research group in the National Institute for Standards and Technologies, United States, is proposing a multiplatform approach for microscopically assessing chemical and optical properties of individual heterogeneous urban dust particles. The procedures described in the paper could also be useful for similar analysis. The method uses 5 steps; (i) particles embedded in fibrous filters are transferred to polished silicon/germanium wafers with electrostatically-assisted high-speed centrifugation, (ii) particles with light absorbing/scattering behavior are identified from bright/dark field light-microscopy, (iii) particles identified from light microscopy are compositionally mapped at high-definition with field-emission scanning electron microscopy and energy-dispersive X-ray spectroscopy, (iv) compositionally-mapped particles are further analyzed with focused ion-beam (FIB) tomography whereby a series of thin slices from a particle are imaged, and the resulting image stack is used to construct a 3-dimensional model of the particle, and (v) particle chemistry is assessed over two distinct regions of a thin FIB slice of a particle with energy-filtered transmission electron microscopy (TEM) and electron energy-loss spectroscopy associated with scanning TEM. For more information, see the paper, "Qualitative Multiplatform Microanalysis of Individual Heterogeneous Atmospheric Particles From High-Volume Air Samples", J. M. Conny et al., Anal. Chem., Just Accepted (DOI: 10.1021/ac5022612 Publication Date (Web): September 14).
Professor L. Vincze (Ghent University, Belgium) and his colleagues have reported on the latest fluorescence mode XANES imaging using the SLcam, which is an energy dispersive pnCCD detector. At BM26A, ESRF, the measurements were done for iron foil with some oxides and geological standard samples. The typical detection limit and measuring time were 0.5 wt% and 15 h, respectively. Readers might think that energy-resolution can be sacrificed near the absorption edges of interest in order to shorten the measuring time in the same way as ordinary XANES measurement by means of X-ray fluorescence. Although the use of ordinary X-ray CCD in accumulation mode for a very similar experiment was published 10 years ago (for example, M. Mizusawa et al, J. Synchrotron Rad. 11, 209 (2004)), the present system has the advantage of being able to reduce the background from the major light elements contained in the sample. For more information, see the paper, "Full-Field Fluorescence Mode Micro-XANES Imaging Using a Unique Energy Dispersive CCD Detector", P. Tack et al, Anal. Chem., 86, 8791(2014).
Most X-ray experiments can be done at high quality with ease in an ordinary laboratory. Some experiments, however, have to be done in the field. It is hard to imagine a more extreme definition of "in the field" than the planet of Mars, which is why exciting times have come about since NASA's Mars rover "Curiosity" landed on Mars in August 2012. It has since recorded and sent back a large number of datasets including X-ray fluorescence (XRF) and X-ray diffraction (XRD) data. Naturally, the scientists involved with the projects have been speaking globally since. During EXRS 2014 (June, Bologna, Italy), Professor J. L. Campbell (University of Guelph, Canada) gave a keynote lecture entitled "XRF and PIXE on the Mars Science LAB Curiosity Rover". At the Denver X-ray conference (July, Big Sky, Montana), the Plenary Session was "X-rays on Mars", and 3 scientists gave lectures. Professor D. L. Bish (Indiana University) gave a talk entitled "The First X-ray Diffraction Results From Mars". Professor J. L. Campbell's talk on "XRF Combines with PIXE in Curiosity's Alpha Particle X-ray Spectrometer" was the extension on his talk at EXRS 2014, and further detailed and specific discussion was done there. Professor S.M. Clegg talked about "Exploring Mars with ChemCam on the Curiosity Rover" (ChemCam enables quick element determination by the laser-induced plasma emission spectroscopy). In August, at Montreal, during the International Union of Crystallography's congress, Professor D. L. Bish gave a talk entitled "The First X-ray Powder Diffraction Measurements on Mars". These talks highlighted many interesting technological aspects of the measurements: XRF analysis is done first by the same CCD camera, which works as an energy-dispersive 2D X-ray detector, even when the main aim of the measurement is obtaining the XRD pattern. In the analysis of unknown samples, generally both chemical composition and the crystal structure are indispensable. Another reason is that XRF helps the systematic use of single photon counting mode of the CCD camera to get a good quality XRD pattern. Secondly, the samples are vibrated all the time to ensure a smooth and continuous Debye ring. The rover furthermore contains a series of standard samples to check the reliability and reproducibility of the measurements. The readers might be interested in such a compact X-ray analyzer, which combined both XRD and XRF machine. Very similar system is now commercially available. For further information on the scientific activity on Mars, visit the Web page, http://mars.jpl.nasa.gov/msl/
Professor J. Wang (University of California San Diego, USA) and his colleagues have applied X-ray fluorescence to the analysis of gunshot residue, which has been usually detected based on the analysis trace amounts of metallic and organic species deposited on the hands, face, hair, and clothing of the shooter. The researchers tried to couple square-wave stripping voltammetry (SWSV) and scanning electron microscopy (SEM) plus energy dispersive X-ray spectroscopy (EDX). The former method can be used as a rapid screening tool, while the latter contributes to confirmation of the presence of the characteristic morphology and metal composition of gunshot residue particles. For more information, see the paper, "Orthogonal Identification of Gunshot Residue with Complementary Detection Principles of Voltammetry, Scanning Electron Microscopy, and Energy-Dispersive X-ray Spectroscopy: Sample, Screen, and Confirm", A. M. O'Mahony et al., Anal. Chem., 86, 8031 (2014).
A research team led by Professor I. Nakai (Tokyo University of Science, Japan) has recently clarified the detailed chemical nature of radioactive aerosol microparticles emitted during the Fukushima Daiichi Nuclear Power Plant accident. They collected three fine particles of 2 microns in dia, containing radioactive cesium, on March 14th and 15th, 2011, in Tsukuba, 172 km away from the power plant. In addition to Fe, Zn, Rb, Zr, Mo, Sn, Sb, Te, Cs, and Ba, U was detected in two particles. The oxidation states of the heavy elements were also studied by X-ray absorption spectra. The experiments were done at BL37XU, SPring-8, Japan. For more information, see the paper, "Detection of Uranium and Chemical State Analysis of Individual Radioactive Microparticles Emitted from the Fukushima Nuclear Accident Using Multiple Synchrotron Radiation X-ray Analyses", Y. Abe et al., Anal. Chem., 86, 8521 (2014).
During the plenary session of the 65th Annual Denver X-Ray Conference, two awards were presented. The 2014 Birks Award was presented to George Havrilla, Los Alamos National Laboratory for his many contributions to microXRF, especially the development of the confocal XRF microscope. Dr. Havrilla has been a leader in the field of analytical XRF; including 19 years on the Denver X-ray Conference Organizing Committee; nine years as North American Editor of X-ray Spectrometry; and six years as Co-Editor-in-Chief for Advances in X-ray Analysis. The ICDD Fellow Award was presented to John Getty, Instructor in Geophysical Engineering and Principal Investigator in the Proppant Research Group at Montana Tech. John has played a key role in the planning and execution of the Denver X-ray Conference for more than 30 years. For further information, visit the Web page, http://www.dxcicdd.com/
It is now known that X-ray free-electron lasers can produce ultrafast X-ray pulses as short as 3 fs in FWHM. Scientists at the Linac Coherent Light Source (LCLS), Stanford are trying to reduce delay time errors in optical-pump & X-ray probe measurements to the 1 fs level, by 2D spectrogram measurement of the relative X-ray/optical delay. For more information, see the paper, "Sub-femtosecond precision measurement of relative X-ray arrival time for free-electron lasers", N. Hartmann et al., Nature Photonics, 8, 706 (2014).
Professor T. M. Cahill (Arizona State University) and his colleagues have recently compared the performance of the different excitation modes of synchrotron radiation X-ray fluorescence. The research team evaluated four different beamline configurations for the analysis of three representative environmental samples; a thin aerosol sample, an intermediate thickness biological sample, and a thick rare earth mineral specimen. They found that white beam excitation is optimal for the analysis of thin samples with little mass, and that filtered white beam excitation (removing lower energy X-rays by absorber) gives better sensitivity for elements emitting more energetic X-rays. In their study, monochromatic excitation, which tends to be the standard mode of operation, did not give good results in terms of sensitivity. For more information, see the paper, "Evaluation of Different Synchrotron Beamline Configurations for X.ray Fluorescence Analysis of Environmental Samples", S. R. Barberie et al., Anal. Chem., 86, 8253 (2014).
A Spanish group has recently published a very interesting application of total-reflection X-ray fluorescence (TXRF). The research team has evaluated the bioaccumulation kinetics of gold nanorods (GNRs) in various tissues upon intravenous administration in mice. It was found that the main achievement was clearly differentiating two kinds of behaviors; gold nano rods were quickly bioaccumulated by highly vascular filtration organs such as the liver and spleen, while they do not show bioaccumulation rates in the brain and lung for the period of time investigated. For more information, see the paper, "Evaluation of Bioaccumulation Kinetics of Gold Nanorods in Vital Mammalian Organs by Means of Total Reflection X-Ray Fluorescence Spectrometry", R. Fernandez-Ruiz et al., Anal. Chem., 86, 7383 (2014).
Dr. V-D. Hodoroaba (BAM, Berlin, Germany) and his colleague have published a report on the feasibility of quantitative X-ray fluorescence (XRF) analysis using coherent (Rayleigh) and incoherent (Compton) X-ray scattering. They have evaluated the ratio of the Compton-to-Rayleigh intensity observed in XRF spectra and also have discussed its relation to the average atomic number. In so-called reference-free XRF analysis, which uses only fundamental parameters and a theoretical formula and does not rely on the calibration curve, there still exist many difficulties, particularly for matrices of lower mean atomic numbers. The analysis presented in this research has sufficiently high sensitivity to distinguish the average atomic number of specimens even within the 0.1 difference. For more information, see the paper, "Gaining Improved Chemical Composition by Exploitation of Compton-to-Rayleigh Intensity Ratio in XRF Analysis", V-D. Hodoroaba et al., Anal. Chem., 86, 6858 (2014).
The Ultrafast X-ray Summer Seminar (UXSS) 2014 took place from June 15 to 19 at SLAC National Accelerator Laboratory, California, United States. The program is organized specifically to train students and post-docs on new opportunities in ultrafast science, particularly using X-ray Free Electron Lasers. Almost all the lectures presented by expert scientists are now available as videos on YouTube. The lecture by Dr. Pieter Glatzel (ESRF) on "Hard X-ray Spectroscopy" (https://www.youtube.com/watch?v=0sMD8lZzuTE) is surely useful for young X-ray spectroscopists. Other exciting lectures are available from Dr. Oleg Shpyrko (UCSD) on "Coherent X-ray Scattering at Ultrafast Timescales" (https://www.youtube.com/watch?v=OIR_ltSOl2U), Dr. Michael Odelius (Stockholm University) on "Electronic Structure & Ultrafast Solution Dynamics in Xray vision w/ theoretical spectacles" (https://www.youtube.com/watch?v=ITIzAmYuyWA), Dr. Alexander Fohlisch (Helmholtz Zentrum Berlin) on "Soft X-ray General and Solid State Aspects" (https://www.youtube.com/watch?v=xTz1oCV5cWI), Dr. Philippe Wernet (Helmholtz Zentrum Berlin) on "Ultrafast Molecular Spectroscopy with X-rays: Experiment", and Prof. Claudio Pellegrini (UCLA) on "X-ray Free Electron Lasers" (https://www.youtube.com/watch?v=5v68nuOTwns). For more information on this summer seminar, visit the following Web site, https://conf-slac.stanford.edu/uxss-2014/
Dr. B. Kanngießer (Technische Universität Berlin, Germany) and her colleagues have recently reported an interesting archaeological application of 3D chemical analysis based on confocal X-ray absorption near edge spectroscopy. This is highly significant for clarifying the technological background of the decorated black- and red-figured Athenian vases (6th and 5th century BC) and the plain black glaze. The research team discussed the correlation of the iron oxidation state in the black glaze layer with the manufacturing process. The 3-stage firing process, which was used in the modern reproduction, was retraced by correlating selected attic black glazed (BG) specimens from different periods (Archaic, Classical, Hellenistic). For more information, see the paper, "Confocal XANES and the Attic Black Glaze: The Three Stage Firing Process through Modern Reproduction", L. Luhl et al., Anal. Chem., Article ASAP (DOI: 10.1021/ac500990k).
So far, laser combs in visible light wavelength have been known as an extremely precise measure of dimensions. What would happen if they move into the X-ray region? The advent of an X-ray free electron laser (XFEL) may realize an X-ray frequency comb in the near future. Dr. S. M. Cavalettobe (Max-Planck-Institut fur Kernphysik, Heidelberg, Germany) is proposing such an ambitious experiment. The research could open up wide-ranging applications; ultraprecise X-ray atomic clocks, determination of many X-ray fundamental parameters, quantitative understanding of astrophysical models and quantum electrodynamics etc. For more information, see the paper, "Broadband high-resolution X-ray frequency combs", S. M. Cavaletto et al, Nature Photonics, June 2014 (DOI: 10.1038/nphoton.2014.113).
Lecture Date: Tuesday May 27, 2014. Dr. Johanna Nelson Weker, SLAC, delivered the SLAC public lecture, "X-rays Reveal Secret Life of Batteries" (https://www.youtube.com/watch?v=V8lSTLRkKEk)
At ESRF in Grenoble, France, several very interesting imaging experiments are going on. Some fossils of Archaeopteryx, which were believed to live 150 million years ago, are being imaged by using a pin-hole X-ray camera at synchrotron beamlines BM5 and ID19. The main question is about their wings - whether they could fly or not. So far, the research has encountered a number of challenges. The project is conducted by Germany's Burgermeister-Muller-Museum (the Solnhofen Museum). For more information, see the following Web site, http://www.solnhofen.de/index.php?id=0,49
The use of X-ray free-electrons has enabled plenty of fascinating science, such as watching non-equilibrium excited-state dynamics in complexes of 3d transition metals. Scientists at LCLS, Stanford have performed femtosecond resolution X-ray fluorescence spectroscopy, with its sensitivity to spin state, elucidating the spin crossover dynamics of [Fe(2, 2ˈ-bipyridine)3]2+ on photoinduced metal-to-ligand charge transfer excitation. For more information, see the paper, "Tracking excited-state charge and spin dynamics in iron coordination complexes", W. Zhang et al., Nature, 509, 345 (2014).
A group led by Prof. Julie V. Macpherson (Warwick University, England) has reported electrochemical X-ray fluorescence, which can quantitatively detect heavy metals in solution. In this technique, electrochemical preconcentration of a species of interest onto the target electrode is achieved by cathodic electro-deposition. X-ray fluorescence can then help unambiguous elemental identification and quantification of metal concentration. The key is that the electrochemical preconcentration step improves the detection limit by over 4 orders of magnitude, and it can reach the sub-ppb level. For more information, see the paper, "Electrochemical X-ray Fluorescence Spectroscopy for Trace Heavy Metal Analysis: Enhancing X-ray Fluorescence Detection Capabilities by Four Orders of Magnitude", L. A. Hutton et al., Anal. Chem., 86, 4566 (2014).
Prof. K. Binnemans (KU Leuven, Heverlee, Belgium) and his colleagues have published several papers on the application of TXRF to the determination and quantification of halide impurities in liquid. So far, the detection of halide ions in solution has been problematic because volatile hydrogen halide compounds are formed when the sample is mixed with the acidic metal standard solution. The loss of hydrogen halide during the drying step of the sample preparation procedure gives imprecise and inaccurate results. To avoid this, the research group is proposing to introduce an alkaline copper standard Cu(NH3)4(NO3)2. For more information, see the papers, "Determination of Halide Impurities in Ionic Liquids by Total Reflection X-ray Fluorescence Spectrometry", T. V. Hoogerstraete et al., Anal. Chem., 86, 3931 (2014), and "Determination of Halide Ions in Solution by Total Reflection X-ray Fluorescence (TXRF) Spectrometry", T. V. Hoogerstraete et al., Anal. Chem., 86, 1391 (2014).
An interesting and useful tutorial on X-ray analytical methods for newcomers is now available in the Materials Today Podcast. Dr. Ravi Yellepeddi (Thermo Fisher Scientific) explains the principle of X-ray fluorescence, recent progress in instruments, and the variety of applications in industry and research laboratories. The talk is around 30 min. Visit the following Web site,
http://www.materialstoday.com/characterization/podcasts/wavelength-dispersive-xray-fluorescence/
An interesting application of confocal micro-X-ray fluorescence has been reported by Dr. Tianxi Sun (Beijing Normal University, China) and his colleagues. The technique employs a polycapillary focusing X-ray lens and a polycapillary parallel X-ray lens, as well as the laboratory X-ray source (Mo tube). In the present research, the scan of the confocal point can give the Cu2+ ion distribution near the surface of the electrode in a steady-state diffusion in an electrolytic tank. The research group studied the effects of the concentration of the electrolyte and the bath voltage on the shape of the layer on the nonuniform distribution of the Cu2+ ions. For more information, see the paper, "Spatially Resolved In Situ Measurements of the Ion Distribution Near the Surface of Electrode in a Steady-State Diffusion in an Electrolytic Tank with Confocal Micro X-ray Fluorescence", S. Peng et al., Anal. Chem., 86, 362 (2014).
