News Article
At a Glance
Section titled âAt a Glanceâ| Metadata | Details |
|---|---|
| Publication Date | 2015-08-18 |
| Journal | X-Ray Spectrometry |
| Authors | Kenji Sakurai |
Abstract
Section titled âAbstractâDr. 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 ps. 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 do not 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 tabletop laser (Ti: Sapphire, 800 nm, 150 mJ, 10 Hz) 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 Ă 106 photons/eV/pulse. For more information, see the paper âExperimental Station for Laser-based Picosecond Time-resolved X-ray Absorption Near-edge Spectroscopyâ, F. Dorchies et al., Rev. Sci. Instrum. 86, 073106 (2015). Since the development of electron probe micro analysis by Castaingâs 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 MÎČ 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 âStandardless Quantification of Heavy Elements by Electron Probe Microanalysisâ, 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 Linac Coherent Light Source, Stanford, USA allowed them to do ultra fast snapshots of X-ray scattering in several tens of femtosecond (fs) 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 ÎŒJ, 100-”m size) and X-ray probe pulse (8.3 keV, around 30 fs, 1012 photons/pulse, 30-”m 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 âImaging Molecular Motion: Femtosecond X-Ray Scattering of an Electrocyclic Chemical Reactionâ, M. P. Minitti et al., Phys. Rev. Lett. 114, 255501 (2015). 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, polyÎČ-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 carried out with 5-keV X-ray photons at BL29XU, SPring-8, Japan. For more information, see the paper âQuantitative Imaging of Single Unstained Magnetotactic Bacteria by Coherent X.ray Diffraction Microscopyâ, 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/s 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 10â4 of the speed of the light. For more information, see the paper âTunable Subluminal Propagation of Narrow-band X-ray Pulsesâ, K. P. Heeg et al., Phys. Rev. Lett. 114, 203601 (2015). A Slovenian group has recently reported the Kα and KÎČ 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 âChemical State Analysis of Phosphorus Performed by X.ray Emission Spectroscopyâ, M. Petric et al., Anal. Chem. 87, 5632 (2015). Readers may remember that electrochemical X-ray fluorescence developed by Prof. Julie V. Macphersonâs group at Warwick University, UK, 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-ÎŒM concentration), time evolution analysis of electrodeposition can be a very promising application of this unique method. For more information, see the paper âDirect Identification and Analysis of Heavy Metals in Solution (Hg, Cu, Pb, Zn, Ni) by Use of in Situ Electrochemical X.ray Fluorescenceâ, G. D. OâNeil 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 âOxidation and Hydration of U3O8 Materials Following Controlled Exposure to Temperature and Humidityâ, 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 millisecond width and few microsecond 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 âHard Disk Drive Based Microsecond X-ray Chopper for Characterization of Ionization Chambers and Photodiodesâ, O. Muller et al., Rev. Sci. Instrum. 86, 035105 (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 Spectroscopyâs celebration of 30 years. It is a summary of her interviews with experts. For more information, see the article âAnalysis of the State of the Art: XRFâ, 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. 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, that can be used for classifying the type of disorder. For more information, see the paper âThe Crystallography of Correlated Disorderâ, D. A. Keen and A. L. Goodwin, Nature, 521, 303 (2015). The National Synchrotron Light Source II of Brookhaven National Laboratory will officially start user runs from the third 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 worldâs 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: https://www.youtube.com/watch?v=AzP8EGHw4BA Lecture date: Tuesday, 14 July 2015. Jerry LaRue of SLAC, delivered the SLAC public lecture, âCaught in the Act! Chemical Reactions Exposedâ. (https://www.youtube.com/watch?v=RiASAbniQYw) Professor Yi Cuiâs lecture, âBatteries for the Future: Whatâs Possibleâ? (https://www.youtube.com/watch?v=ISEzvNevyck) DECTRIS has introduced a new performance class of microstrip detectors, the Mythen2 X series. The frame rate is 1 kHz, and the dynamic range is 24 bit. For further information, visit the web page http://www.dectris.com/ Brukerâs new SkyScan-1294 is based on phase-contrast imaging with polychromatic X-rays patented by the Paul Scherrer Institute at the Swiss Light Source (Zurich, Switzerland) and licensed to Bruker for commercialization. For further information, visit the web page, https://www.bruker.com/ Shimadzu Corporation has established the Innovation Center at Shimadzu Scientific Instruments, Inc. (SSI), its wholly owned US subsidiary based in Columbia, Maryland, USA. For further information, visit the web page, http://www.shimadzu.com/ Rigaku Corporation has announced the completion of the acquisition of the X-ray diffraction business from Agilent Technologies Inc. (NYSE: A). Formerly known as Oxford Diffraction within Varian when that company was acquired by Agilent in 2010, the X-ray diffraction group develops single-crystal X-ray instruments for chemical crystallography. For further information, visit the web page http://www.rigaku.com/ For additional news about X-ray analysis and other spectroscopy sciences, please browse the Wiley website. http://www.SpectroscopyNow.com.