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X-WR-CALNAME:IXAS: The International X-ray Absorption Society
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DTSTART:20190101T000000
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BEGIN:VEVENT
DTSTART;VALUE=DATE:20200716
DTEND;VALUE=DATE:20200717
DTSTAMP:20260416T050928
CREATED:20200621T134547Z
LAST-MODIFIED:20200720T012215Z
UID:486-1594857600-1594943999@xrayabsorption.org
SUMMARY:Hao Yuan:  Ptychography and 4D imaging by spectro-ptycho-tomography
DESCRIPTION:Coherent X-ray scattering (diffraction) methods will be key to exploiting the high coherent flux of 4th generation synchrotron sources. Ptychography is a coherent diffraction technique that allows rapid\, reliable inversion of arrays of diffraction images into real space images by using overlapping spatial areas to constrain the reconstruction [1]. While ptychography is quite well developed in the hard X-ray regime and in electron and optical microscopy\, the implementation of soft X-ray ptychography is in its infancy. Soft X-ray ptychography is a coherent diffraction imaging technique readily implemented in Scanning Transmission X-ray Microscopy (STXM) [2]. 4D imaging by soft X-ray ptychography – chemically specific\, quantitative 3D mapping of nanostructures can provide insight into the physical and chemical properties. By measuring spectro-ptycho-tomography – 2D ptychographic images at multiple photon energies and multiple tilt angles – 3D chemical distribution can be derived [3]. \nReferences: \n\nPfeiffer F. X-ray ptychography. Nature Photonics\, 2018\, 12(1): 9-17. https://doi.org/10.1038/s41566-017-0072-5\n\nShapiro D A\, Yu Y S\, Tyliszczak T\, et al. Chemical composition mapping with nanometre resolution by soft X-ray microscopy. Nature Photonics\, 2014\, 8(10): 765-769. \nWu J\, Zhu X\, Shapiro D A\, et al. Four-dimensional imaging of ZnO-coated alumina aerogels by scanning transmission X-ray microscopy and ptychographic tomography. The Journal of Physical Chemistry C\, 2018\, 122(44): 25374-25385. https://pubs.acs.org/doi/abs/10.1021/acs.jpcc.8b07363\n\n\n 
URL:https://xrayabsorption.org/events/journalclub-hao-yuan/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200713
DTEND;VALUE=DATE:20200715
DTSTAMP:20260416T050928
CREATED:20200522T144512Z
LAST-MODIFIED:20200720T012040Z
UID:430-1594598400-1594771199@xrayabsorption.org
SUMMARY:Wantana Klysubun: XAS capability and science at the Thailand synchrotron
DESCRIPTION:
URL:https://xrayabsorption.org/events/journalclub-wantana-klysubun/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200709
DTEND;VALUE=DATE:20200710
DTSTAMP:20260416T050928
CREATED:20200522T144257Z
LAST-MODIFIED:20200714T010724Z
UID:427-1594252800-1594339199@xrayabsorption.org
SUMMARY:Dooshaye Moonshiram: Electronic and Structural Configurations of Earth-Abundant Water Splitting Catalysts and Spin Crossover Complexes
DESCRIPTION:The solar light-driven splitting of water for hydrogen fuel production is a promising alternative to fossil fuels due to their rapid depletion and concomitant environmental pollution. The design of light-driven devices composed of organic\, inorganic or hybrid materials that can mimic natural photosynthetic processes is extremely desirable. An essential component of such systems is the light-harvesting chromophore\, analogous to the photosynthetic pigments\, which can absorb the energy of the incident photons. Consequently\, the light energy is converted into an electronically excited state for the creation of a charge-separated state that helps to generate the required thermodynamic driving force for subsequent catalytic reactions. \nCommonly used molecular photosensitizers traditionally contain precious and scarce 4d or 5d transition metals such as Platinum\, Ruthenium\, Rhenium or Iridium. However\, over the past decades\, a range of noble metal-free photosensitizers based on earth-abundant metals such as Copper\, Chromium\, and Zinc appeared\, with the aim to bring these light-harvesting molecules into more practical applications. A systematic series novel homo- and heteroleptic Cu(I) photosensitizers based on tetradentate 1\,10-phenanthroline ligands of the type X^N^N^X containing two additional donor moieties in the 2\,9-position (X = SMe or OMe) were designed. Time-resolved X-ray absorption spectroscopy in the picosecond time scale\, coupled with time-dependent density functional theory calculations\, provided in-depth information on the excited state electron configurations. For the first time\, a significant shortening of the Cu-X distance and a change in the coordination mode to a pentacoordinated geometry is shown in the excited states of the two homoleptic complexes. These findings are important with respect to a precise understanding of the excited state structures and a further stabilization of this type of photosensitizers. This talk will further demonstate the reaction pathways of several cobalt and nickel-based hydrogen evolving complexes\, examined in unprecedented detail with picosecond time resolution when coupled with copper and ruthenium-based photosensitizers. Results shown will enable the rational design of molecular hydrogen-evolving photocatalysts that can perform beyond the current microsecond time scale\, and suggest ways in which the ligand structures can be adjusted to facilitate protonation and catalytic efficiency.\n \nReferences: \n\nIglesias et al\, Tracking Light-Induced Excited-State Dynamics…. Chem Eur J 2020 https://doi.org/10.1002/chem.202001393\nMoonshiram et al Tracking Structural and Electronic Configurations… JACS 2016 https://doi.org/10.1021/jacs.6b05680\nGotica et al Spectroscopic Characterization of a Bio-inspired … Chem Eur J 2019 https://doi.org/10.1002/chem.201904934\nRentschler Coordination Behavior of Cu(I) Photosensitizers… Chem Eur J 2019 https://doi.org/10.1002/chem.201905601\n\n 
URL:https://xrayabsorption.org/events/journalclub-dooshaye-moonshiram/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200706
DTEND;VALUE=DATE:20200708
DTSTAMP:20260416T050928
CREATED:20200522T144124Z
LAST-MODIFIED:20200714T011003Z
UID:425-1593993600-1594166399@xrayabsorption.org
SUMMARY:Chris Glover: Australian XAFS: Past\, present\, and a Br-ght future
DESCRIPTION:The Australian XAFS community started from small beginnings and currently\, XAFS is one of the most oversubscribed techniques at the Australian Synchrotron. The community has been fostered by access to facilities; initially the Australian National Beamline Facility (ANBF) at the Photon Factory\, to more recently the XAS beamline at the Australian Synchrotron. The ANBF was a simple and versatile\, non focussed bend magnet beamline\, which was retired in ~ 2010. The XAS beamline is a Wiggler based\, focussed beamline\, with much greater flux and high photon energies\, and has been operational since 2007. User demand has resulted in two new beamlines\, currently under construction at the Australian Synchrotron – the Medium Energy X-Ray Absorption Spectroscopy Beamlines (MEX 1 and 2). These beamlines share a bend magnet\, and are aimed to cover the Tender and medium energy range with differing beamsizes – from microns’s to mm’s. MEX will be equipped with 4 endstations in total\, including a microprobe\, a 5 crystal Rowland circle spectrometer and a custom low energy X-Ray spectrometer. \n\nI this talk\, I will briefly describe the past\, present and the bright future of XAFS in the Australian context. I will briefly summarise the ANBF\, the capabilities and performance of the XAS beamline and highlight the scientific opportunities and complementary nature of the new MEX beamlines.\n \nReferences: \n\nhttps://www.nature.com/articles/srep20350\nhttps://pubs.acs.org/doi/10.1021/cn200097s\nhttps://pubs.acs.org/doi/10.1021/acs.biochem.5b01136\nhttps://www.ansto.gov.au/user-access/instruments/australian-synchrotron-beamlines/x-ray-absorption-spectroscopy\nhttps://www.ansto.gov.au/research/facilities/australian-synchrotron/project-br-ght\n\n 
URL:https://xrayabsorption.org/events/journalclub-chris-glover/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200702
DTEND;VALUE=DATE:20200703
DTSTAMP:20260416T050928
CREATED:20200522T143805Z
LAST-MODIFIED:20200705T154542Z
UID:423-1593648000-1593734399@xrayabsorption.org
SUMMARY:Yuanyuan Li: Multimodal approach for determining the electronic and atomic structure of ceria supported Pt single atoms catalyst
DESCRIPTION:Single atoms catalysts (SACs) have been heavily investigated in the recent years because of their good catalytic properties (especially activity and selectivity) for many chemical reactions [1]. In addition to that\, in SACs\, the supported metals are used with extremely high efficiency compared to their nano counterparts. That is very important for noble metals\, which are naturally scare yet widely used in industry for a vast number of important chemical reactions. Despite of the progress that has been made\, there are fundamental questions remained unaddressed: what is the structure (electronic and atomic) that responsible for the improved catalytic properties? How does the structure respond to the reaction environment? Only by addressing these questions\, are we able to improve synthesis processes to get desired catalysts. \nThe key to address the above-mentioned questions is the capability of characterizing the structure of single atoms catalysts. The challenge originates from: 1) for SACs\, the weight loading of single atoms on the support is usually low\, 2) the heterogeneity of the single atom sites owing to the surface heterogeneity of most solid supports\, and 3) the complex structure of the single atoms system resulted from the strong correlation between the single atoms and the support. This work aimed to address those issues by developing synthesis methods for obtaining homogeneously distributed single atoms with high weight loadings and combining multiple experimental techniques (STEM\, DRIFTS\, XPS\, RIXS\, XAS) with calculation methods to study the electronic and atomic structure of single atoms with the presence of strong metal-support interactions. For demonstration\, the specific system studied here is ceria supported Pt single atoms [2]. \nReferences: \n\nA. Wang\, J. Li\, T. Zhang\, Heterogeneous single-atom catalysis. Nature Reviews Chemistry 2\, 65–81 (2018). https://doi.org/10.1038/s41570-018-0010-1\n\nM. Kottwitz\, Y. Li\, R. M. Palomino\, Z. Liu\, Q. Wu\, G. Wang\, J. Huang\, J. Timoshenko\, S. D. Senanayake\, M. Balasubramanian\, D. Lu\, R. G. Nuzzo\, A. I. Frenkel\, Local structure and electronic state of atomically dispersed Pt on nanosized CeO2 support\, ACS Catalysis 9\, 8738-8748 (2019). https://doi.org/10.1021/acscatal.9b02083\n\n\n 
URL:https://xrayabsorption.org/events/journalclub-yuanyuan-li/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200629
DTEND;VALUE=DATE:20200630
DTSTAMP:20260416T050928
CREATED:20200522T143648Z
LAST-MODIFIED:20200630T151555Z
UID:421-1593388800-1593475199@xrayabsorption.org
SUMMARY:Feng Lin: Ion Reactions to Modulate Solid-State Electrochemistry for Batteries and Electrocatalysis
DESCRIPTION:Ion reactions offer a huge playground for tuning the electronic and crystal properties of inorganic solids for energy applications. Our research focuses on resolving a longstanding question in materials electrochemistry regarding redox active solids: how does the mesoscale chemical distribution influence ion reactions at different length scales? Through manipulating the thermodynamics and kinetics of the ion intercalation chemistry\, our goal is to develop experimental methodologies and establish novel design principles to enhance the electrochemical properties of ion-intercalating solids for batteries and electrocatalysis. Our studies are largely facilitated by synchrotron X-ray spectroscopic and imaging techniques that provide fundamental insights into intercalation chemistries. In this presentation\, we will first highlight our recent progress in understanding and improving electrode materials for lithium and sodium batteries. We design novel synthetic approaches to overcome the surface challenges of oxide cathode materials for high energy density\, high power density and long cycle life. Then\, we will discuss how we make use of interfacial ion reactions to modulate the electronic properties of water splitting electrocatalysts. We will highlight that tailoring the phase segregation at the catalyst-electrolyte interface constitutes a large space for stabilizing catalytic activity. \n 
URL:https://xrayabsorption.org/events/journalclub-feng-lin/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200625
DTEND;VALUE=DATE:20200626
DTSTAMP:20260416T050928
CREATED:20200522T143526Z
LAST-MODIFIED:20200630T151432Z
UID:419-1593043200-1593129599@xrayabsorption.org
SUMMARY:Sara Lafuerza:	 The chemical sensitivity of core-to-core XES in 3d transition metals
DESCRIPTION:K-fluorescence X-ray emission spectroscopy (XES) is receiving a growing interest in all branches of natural sciences to investigate the local spin in 3d transition metal complexes. Unlike the valence-to-core emission lines\, the core-to-core transitions in Kβ (3p to 1s) and Kα (2p to 1s) do not probe the valence shell directly and the chemical sensitivity is thus indirect. In Kβ and Kα emission\, the local spin sensitivity stems from the exchange interaction between the 3p (Kβ) or 2p (Kα) core-hole and the 3d valence shell spin of the transition metal ion\, which is larger for Kβ than Kα [1]. The magnitude of the exchange interaction depends for a given element on the valence shell spin\, which is defined by the metal atom oxidation and spin state within an ionic picture. This is a very crude description of the electronic structure and the influence of covalence in Kβ has been pointed out by several authors [1\,2].\nIn this talk\, the results of a systematic investigation of Kβ and Kα XES spectra measured on a wide range of iron compounds will be presented. More than 30 samples with different oxidation state (+2\, +3\, +4 and mixed-valence)\, spin (high-spin\, low-spin and mixed-spin)\, ligands (fluorides\, oxides\, sulfides\, etc.) or local coordination (octahedral\, tetrahedral) were measured at beamline ID26 of the ESRF synchrotron. We analysed the experimental spectra in terms of commonly used quantitative parameters (Kβ1\,3-first moment\, Kα1-full width half maximum\, and integrated absolute difference –IAD– [3]) and we carefully examined the difference spectra. We also performed multiplet calculations to elucidate the underlying mechanisms that lead to the chemical sensitivity.\nOur results confirm a strong influence of covalency on both Kβ and Kα lines. We establish a reliable spin sensitivity of Kβ XES as it is dominated by the exchange interaction whose variations can be quantified by either Kβ1\,3-first moment or Kβ-IAD and result in a systematic difference signal lineshape. We find an exception in the Kβ XES of Fe3+ and Fe2+ in aqueous solution\, where a new difference spectrum is identified that cannot be explained by scaling the exchange integrals. We explain this with strong differences in orbital mixing between the valence orbitals. This result calls for caution in the interpretation of Kβ XES spectral changes as due to spin variations without careful analysis of the lineshape. For Kα XES\, the smaller exchange interaction together with the influence of other electron-electron interactions make it difficult to extract a quantity that directly relates to the spin. \nReferences: \n\n P. Glatzel and U. Bergmann\, Coord. Chem. Rev. 249\, 65 (2005); https://doi.org/10.1016/j.ccr.2004.04.011 \nC. J. Pollock\, M. U. Delgado-Jaime\, M. Atanasov\, F. Neese and S. De Beer\, J. Am. Chem. Soc. 136\, 9453 (2014); https://doi.org/10.1021/ja504182n\n G. Vankó\, T. Neisius\, G. Molnár\, F. Renz\, S. Kárpáti\, A. Shukla\, and F. M. F. de Groot\, J. Phys. Chem. B 110\, 11647 (2006); https://doi.org/10.1021/jp0615961 \n\n 
URL:https://xrayabsorption.org/events/journalclub-sara-lafuerza-2/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200622
DTEND;VALUE=DATE:20200623
DTSTAMP:20260416T050928
CREATED:20200522T143357Z
LAST-MODIFIED:20200714T011226Z
UID:417-1592784000-1592870399@xrayabsorption.org
SUMMARY:Lijia Liu:	XEOL studies of Light-Emitting Materials
DESCRIPTION:X-ray excited optical luminescence (XEOL) is a photon-in-photon-out process which monitors the visible luminescence emitted from materials upon X-ray excitation. Unlike using low energy excitation source such as UV\, during X-ray excitation\, core electrons are excited and the production of luminescence is a much more complicated process. Because of this\, X-ray excited luminescence can be correlated with the decay process of a specific core electron. In this talk\, I will introduce the fundamental process of XEOL and the unique information it provides\, when combining with X-ray absorption near-edge structure (XANES)\, in revealing the origin of the luminescence. Two materials systems\, nanostructured TiO2 and metal-doped lead halide perovskite\, will be used as examples to demonstrate the XEOL-XANES analysis technique.  \nReferences: \n\nLi et al\, https://doi.org/10.1021/acs.chemmater.5b00363\nMa et al\, https://doi.org/10.1039/c9nr00143c\n\n 
URL:https://xrayabsorption.org/events/journalclub-lijia-liu/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200618
DTEND;VALUE=DATE:20200619
DTSTAMP:20260416T050928
CREATED:20200522T142943Z
LAST-MODIFIED:20200714T011612Z
UID:415-1592438400-1592524799@xrayabsorption.org
SUMMARY:Anatoly Frenkel:	Machine learning - assisted analysis of material’s structure using XANES and EXAFS spectra
DESCRIPTION:Tracking the structure of functional nanomaterials (e.g.\, metal catalysts) remains a challenge due to the paucity of experimental techniques that can provide atomic-level information for metal species in harsh conditions\, often required for studying chemical transformations. Here we report on the use of X-ray absorption spectroscopy (XANES and EXAFS) and supervised machine learning (SML) for determining the three-dimensional geometry of monometallic and alloy nanoparticles [1]. Artificial neural network (NN) is used to unravel the hidden relationship between the XANES features and material’s geometry [2]. In the case of EXAFS\, NN is used to obtained the partial radial distribution function (PRDF) directly from the spectra [3]. In other words\, we trained computer to learn how to ‘invert” the unknown spectrum and obtain the underlying structural descriptors. Training of the NN was performed by using theoretical spectroscopy codes. These applications are demonstrated by reconstructing the compositional distributions of nanocatalysts from the coordination numbers obtained by NN-XANES\, or from the PRDF obtained by NN-EXAFS. The first applications of these method to the determination of structure of nanocatalysts in reaction conditions will be demonstrated [4-6]. \nReferences: \n\nJ. Timoshenko\, A. I. Frenkel. “Inverting” X-ray Absorption Spectra of Catalysts by Machine Learning in Search of Activity Descriptors. ACS Catalysis (Perspective) 9\, 10192-10211 (2019).  https://pubs.acs.org/doi/10.1021/acscatal.9b03599\nJ. Timoshenko\, D. Lu\, Y. Lin\, A. I. Frenkel. Supervised machine learning-based determination of three-dimensional structure of metallic nanoparticles. J. Phys. Chem. Lett.\, 8\, 5091-5098 (2017). https://pubs.acs.org/doi/abs/10.1021/acs.jpclett.7b02364\nJ. Timoshenko\, et al. Artificial neural network approach for characterizing structural transformations by X-ray Absorption Fine Structure spectroscopy. Phys. Rev. Lett. 120\, 225502 (2018). https://journals.aps.org/prl/abstract/10.1103/PhysRevLett.120.225502\nN. Marcella\, Y. Liu\,et al Neural network assisted analysis of bimetallic nanocatalysts using X-ray absorption near edge structure spectroscopy. Phys. Chem. Chem. Phys. (2020) Early view. https://pubs.rsc.org/en/content/articlehtml/2020/cp/d0cp02098b\nJ. Timoshenko\, et al . Probing atomic distributions in mono- and bimetallic nanoparticles by supervised machine learning. Nano Letters 19\, 520-529 (2019). https://pubs.acs.org/doi/10.1021/acs.nanolett.8b04461\nY. Liu\,et al . Mapping XANES spectra on structural descriptors of copper oxide clusters using supervised machine learning. J. Chem. Phys. 151\, 164201 (2019).  https://aip.scitation.org/doi/full/10.1063/1.5126597\n\n\n 
URL:https://xrayabsorption.org/events/journalclub-anatoly-frenkel/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200615
DTEND;VALUE=DATE:20200616
DTSTAMP:20260416T050928
CREATED:20200522T142834Z
LAST-MODIFIED:20200617T021815Z
UID:413-1592179200-1592265599@xrayabsorption.org
SUMMARY:Anna Zymakova: Introduction to ELI-Beamlines
DESCRIPTION:Introduction to ELI-Beamlines – a new user facility in the heart of Europe. Status and prospective of ELI X-ray spectroscopy end-station \nImproved access to state-of-the-art facilities is a key element to groundbreaking advances in science. One such facility is the Extreme Light Infrastructure (ELI); a pan-European project of which one pillar (ELI-Beamlines) is located near Prague in Czech Republic. The new facility utilizes ultra-high power lasers in research projects aimed at studying intense light/matter interactions as well as making use of short pulsed lasers to drive secondary X-ray and XUV sources (such as Plasma X-ray sources\, Betatron\, High-order Harmonic generation etc.) and particle accelerators (electrons and ions) for applications in material science\, biomedicine\, laboratory astrophysics etc. The E1 experimental hall at ELI Beamlines houses a few secondary sources that generate beams in wide\, complementary\, energy ranges\, as well as end-stations that will be used for correlative ultrafast experiments. Particularly\, the station for time-resolved experiments with X-rays (TREX) includes diffractometry and spectroscopy setup for pump-probe X-ray experiments. These will use plasma X-ray sources driven by the in-house developed L1-ALLEGRA laser (1kHz\, 100mJ\, <20fs laser pulses @830nm)\, as well as conventional support lasers. The presentation will give a short overview of the ELI project and ELI-Beamlines structure. I will focus on the status and outlook of the x-ray spectroscopy station currently under development for an improved user availability for high demand ultrafast x-ray techniques. \nReferences: \n\nF. Batysta et al.\, Opt. Express 24\, 17843 (2016) https://doi.org/10.1364/OE.24.017843\n\n 
URL:https://xrayabsorption.org/events/journalclub-anna-zymakova/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200611
DTEND;VALUE=DATE:20200612
DTSTAMP:20260416T050928
CREATED:20200514T015818Z
LAST-MODIFIED:20200617T021645Z
UID:384-1591833600-1591919999@xrayabsorption.org
SUMMARY:Alessandra Leri: XANES Spectroscopy to Illuminate Biogeochemical Cycling of Halogens in Environmental Systems
DESCRIPTION:The halogens chlorine and bromine have high electron affinities and exist in seawater mainly as chloride and bromide anions\, which have generally been considered unreactive in the environment. Using Cl and Br K-edge XANES spectroscopy\, we have measured high concentrations of organo-chlorine and -bromine in naturally degraded particulate organic matter (POM) from oceanic sediment traps. While organobromine speciation in marine POM is exclusively aromatic\, organochlorine is fractionated into aliphatic and aromatic particles that appear in a heterogeneous distribution. The major precursor of sediment trap material is phytoplankton biomass\, the detritus of which under-goes oxidative breakdown as part of the marine carbon cycle. We hypothesized that unsaturated lipid and protein moieties in phytoplankton detritus would be susceptible to halogenation through oxidative degradation mechanisms. Using model experiments\, we showed that algal particulates are readily chlorinated and brominated through various abiotic pathways\, including photochemical and Fenton-like reactions. These processes produce organohalogens in particulate algal detritus at levels exceeding 0.1% by mass. In contrast with the exclusively aromatic organobromine observed in natural marine POM\, the lab-based experiments generate aliphatic organobromine in algal particulates; however\, the aliphatic organobromine produced appears to be labile and susceptible to debromination on relatively short (3-week) timescales under highly oxidizing conditions. These findings have implications for the transformation and stabilization of marine organic carbon prior to sedimentary burial.\nWe have also measured high concentrations of non-volatile organochlorine and -bromine in several varieties of edible kelps. Such compounds are likely to contribute to organohalogen body burden in humans and other organisms.\n \nReferences: \n\nA. Leri\, M. Dunigan\, R. Wenrich\, and B. Ravel (2019). Particulate organohalogens in edible brown seaweeds. Food Chemistry 272\, 126. https://doi.org/10.1016/j.foodchem.2018.08.050\nA. Leri\, L. Mayer\, K. Thornton\, P. Northrup\, M. Dunigan\, K. Ness\, and A. Gellis (2015). A marine sink for chlorine in natural organic matter. Nature Geoscience 8\, 620. https://www.nature.com/articles/ngeo2481\nA. Leri\, L. Mayer\, K. Thornton\, and B. Ravel (2014). Bromination of marine particulate organic matter through oxidative mechanisms. Geochimica et Cosmochimica Acta 142\, 53. https://doi.org/10.1016/j.gca.2014.08.012\nA. Leri and B. Ravel (2014). Sample thickness and quantitative concentration measurements in Br K-edge XANES spectroscopy of organic materials. Journal of Synchrotron Radiation 21\, 623. https://doi.org/10.1107/S1600577514001283\n\n\n 
URL:https://xrayabsorption.org/events/journalclub-alessandra-leri/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200608
DTEND;VALUE=DATE:20200609
DTSTAMP:20260416T050928
CREATED:20200514T015707Z
LAST-MODIFIED:20200609T025341Z
UID:382-1591574400-1591660799@xrayabsorption.org
SUMMARY:Jerry Seidler:  Overview of lab XAFS/XES
DESCRIPTION:After decades of relative silence\, lab-based spectroscopy has made a comeback in recent years. Modern spectrometers have energy resolution comparable to synchrotron XAS beamlines and have performances demonstrated in dozens of recent publications. Here\, I will briefly summarize the various technical approaches before focusing on examples for XAFS and XES in the hard and tender regime. A unifying theme of much of this work can be termed “analytical XAS”\, where many applications require very high access for iterative measurement of material properties — a use model that fits poorly with synchrotron scheduling. I will conclude with a discussion of several schemes for the interplay between synchrotron and lab-based XAS\, with an emphasis on the already clear fact that these two approaches are generally complemnetary rather than competitive. \n  \nReferences: \n\nhttp://dx.doi.org/10.1063/1.5049383 \nhttp://dx.doi.org/10.1021/acs.analchem.8b00302 \nhttp://dx.doi.org/10.1063/1.4901599 \nhttp://dx.doi.org/10.1063/1.4994739\n\n 
URL:https://xrayabsorption.org/events/journalclub-jerry-seidler_june2020/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200604
DTEND;VALUE=DATE:20200605
DTSTAMP:20260416T050928
CREATED:20200512T160713Z
LAST-MODIFIED:20200606T233732Z
UID:367-1591228800-1591315199@xrayabsorption.org
SUMMARY:Maryjo Brounce: The oxidation state of sulfur in Apollo-era lunar rocks and curation best practices for future sample return missions
DESCRIPTION:Lunar apatites contain hundreds to thousands of parts per million of sulfur. This is puzzling because lunar basalts are thought to form in low oxygen fugacity (fO2) conditions where sulfur can only exist in its reduced form (S2–)\, a substitution not previously observed in natural apatite. We present measurements of the oxidation state of S in lunar apatites and associated mesostasis glass that show that lunar apatites and glass contain dominantly S2–\, whereas natural apatites from Earth are only known to contain S6+. It is likely that many terrestrial and martian igneous rocks contain apatites with mixed sulfur oxidation states. The S6+/S2– ratios of such apatites could be used to quantify the fO2 values at which they crystallized\, given information on the portioning of S6+ and S2– between apatite and melt and on the S6+/S2– ratios of melts as functions of fO2 and melt composition. Such a well-calibrated oxybarometer based on this the oxidation state of S in apatite would have wide application. \nReferences: \n\nBrounce\, M.\, Boyce\, J.\, McCubbin\, F.M.\, Humphreys\, J*.\, Reppart\, J.\, Stolper\, E.\, and Eiler\, J. (2019) The oxidation state of sulfur in lunar apatite. American Mineralogist\, 104\, 307-312. doi: https://doi.org/10.2138/am-2019-680\n\n 
URL:https://xrayabsorption.org/events/journalclub-maryjo-brounce/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200601
DTEND;VALUE=DATE:20200602
DTSTAMP:20260416T050928
CREATED:20200512T153844Z
LAST-MODIFIED:20200604T042831Z
UID:365-1590969600-1591055999@xrayabsorption.org
SUMMARY:Anne Marie March:  Capturing photochemical reaction intermediates with time-resolved synchrotron x-ray spectroscopy
DESCRIPTION:The pump-probe technique allows for measurement of timescales that are shorter than a detector’s response time. Using a MHz-repetition-rate laser to pump a sample\, the full x-ray flux of synchrotrons such as the Advanced Photon Source (APS) can be used to probe the ensuing photoinduced reaction(s). The obtained time-resolved XAS and XES spectra can be used to capture the electronic and geometric structure of short lived intermediate species. In this presentation\, I will give a brief introduction to the pump-probe measurement technique as implemented at Sector 7 of the APS and present recent studies of the photoinduced aquation reaction of [FeII(CN)6]4-\, where we were able to detect an intermediate species with a lifetime 4x shorter than the x-ray probe pulse duration.  \nReferences: \n\nhttps://doi.org/10.1063/1.5117318\nhttps://doi.org/10.1107/S1600577519012268\n\n 
URL:https://xrayabsorption.org/events/journlclub-anne-marie-march/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200528
DTEND;VALUE=DATE:20200529
DTSTAMP:20260416T050928
CREATED:20200512T030817Z
LAST-MODIFIED:20200604T042648Z
UID:310-1590624000-1590710399@xrayabsorption.org
SUMMARY:Megan Holycross:	Probing the deep Earth oxygen cycle with XANES
DESCRIPTION:The oxidation state of the solid Earth influences\, to a first order\, the structure of the planet and the chemistry of rocks\, ores and volcanic gases; mass transfer of oxygen between terrestrial reservoirs enables a habitable world. Fe K-edge XANES spectroscopy shows magmas erupted from continental crust\, formed at subduction zones\, are more oxidized than magmas erupted from oceanic crust\, formed at mid-ocean ridges (e.g.\, Kelley and Cottrell 2009; Science). However\, there is long-standing debate over the timing and mechanism of the processes that produce oxidized continental crust. The high-pressure mineral phase garnet is a key reservoir of iron in the crust and garnet Fe3+/ƩFe ratios record the transfer of oxygen throughout the subduction process. Here\, I’ll use garnet Fe-XANES to quantify the oxidation state of two suites of subduction-related rocks to examine changes in the deep Earth oxygen cycle over space (scale of ~100 km) and time (scale of ~2.5 billion years). \nReferences: \n\n\n\nK. A.  Kelley and E. Cottrell\, Water and the Oxidation State of Subduction Zone Magmas Science  325\, pp 605  (2009)   https://doi.org/10.1126/science.1174156 \n\n\nM. D. Dyar\, et al\,  Accurate determination of ferric iron in garnets by bulk Mössbauer spectroscopy and synchrotron micro-XAS American Mineralogist 97 pp 1726–1740 (2012) https://doi.org/10.2138/am.2012.4107\n\n  \n  \n 
URL:https://xrayabsorption.org/events/journalclub-megan-holycross/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200525
DTEND;VALUE=DATE:20200526
DTSTAMP:20260416T050928
CREATED:20200512T031248Z
LAST-MODIFIED:20200526T032812Z
UID:312-1590364800-1590451199@xrayabsorption.org
SUMMARY:Joshua Kas: Corvus: A Workflow Tool for X-ray and Related Spectroscopies
DESCRIPTION:Great strides have been made over the past decade in the theory and calculation of X-ray and related spectra. Some advances involve predictions of material properties such as structure or dynamics in order to make a prediction more complete\, thus requiring less input\, or otherwise reducing the number of free parameters required to fit to experimental data. Other advances\, e.g.\, GW/BSE approaches\, improve common approximations for electron correlation or electron-phonon interactions. However\, many of these advanced methods require a combination of approaches to obtain complete calculations. Thus users must be proficient in a variety of codes\, with multiple input and output formats. Moreover\, users must usually manually link codes by translating the output of one to a format consistent with the input of the next. These aspects of state-of-the-art approaches create barriers to their widespread use and hence reduce the overall quality of theory and analysis methods for X-ray spectra. To address this situation we present Corvus [1\,2]\, a property driven workflow tool designed to combine and execute multiple codes. Corvus interfaces electronic structure\, molecular or crystal structure\, and molecular dynamics or phonon effects\, with end-product codes for calculating spectroscopic quantities such as XAS. Thus Corvus serves to: (1) simplify and unify input and output formats; and (2) automatically create workflows based on target properties and input supplied by a user. The simplification of input/output works through a set of code-specific translation routines to eliminate the need for users to learn a multitude of formats\, while automating the translation of output to be used in the next step in the workflow chain. The automatic generation of workflows sets up a dependency tree for target properties\, which can be filled by user input\, online database search\, or calculations. This allows users to focus on physical properties of interest\, rather than on details of any one calculation step. At present\, translation tools exist for several DFT and MD codes as well as spectroscopy codes. More capabilities will be added as implementation of new code interfaces is relatively easy. We have applied Corvus to a variety of workflows\, for example: structural optimization with ORCA [4]\, followed by calculations of XES and RXES using FEFF [3]; DFT/MD averaged XANES using NWCHEM [5] and FEFF; and FEFF calculations of XAS using ab initio Debye-Waller factors obtained from dynamical matrices provided by ABINIT [6]. Examples of Corvus simplified input\, and automatically generated workflows are presented\, together with results that yield improved agreement in comparison to experiment. \nReferences \n\nS. Story\, Thesis\, http://hdl.handle.net/1773/34136 (2015). \nStory\, S. M.\, Vila\, F. D.\, Kas\, J. J.\, Raniga\, K. B.\, Pemmaraju\, C. D. & Rehr\, J. J. (2019). J. Synchrotron Rad. 26\, 1694-1704. https://doi.org/10.1107/S1600577519007495\nJ.J. Rehr et al.\, Phys. Chem. Chem. Phys.\, 12\, 5503-5513 (2010). https://doi.org/10.1039/b926434e\nF. Neese\, Wiley Interdiscip. Rev. Comput. Mol. Sci. 2\, 73-78 (2012). https://doi.org/10.1002/wcms.81\nM. Valiev et al.\, Comput. Phys. Commun. 181\, 1477 (2010)\,  https://doi.org/10.1016/j.cpc.2010.04.018\nX. Gonze et al.\, Comput. Phys. Commun. 180\, 2582-2615 (2009) https://doi.org/10.1016/j.cpc.2009.07.007
URL:https://xrayabsorption.org/events/journalclub-joshua-kas/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200521T090000
DTEND;TZID=America/Los_Angeles:20200521T100000
DTSTAMP:20260416T050928
CREATED:20200512T021354Z
LAST-MODIFIED:20200527T123615Z
UID:305-1590051600-1590055200@xrayabsorption.org
SUMMARY:Jason Shearer:	Structural Determination of Small Molecular Systems Using a Wavelet Analysis
DESCRIPTION:Presented will be a discussion of efforts to employ a wavelet transform (WT) analysis towards the quantitative structural determination of discrete molecular systems using an EXAFS analysis. Unlike a transition Fourier transform (FT) analysis\, a WT analysis yields a 2D plot in both k- and R-space. Thus\, information contained in k-space that can be lost in a FT analysis is retained. In theory\, this can allow for the unambiguous assignment of different scattering pathways at similar distances\, distinguishing multiple scatterer pathways from single scattering pathways and noise\, and an increase in the resolution between shells. A WT EXAFS analysis has shown utility in the analysis of solid-state periodic samples\, but there has been a paucity of examples of a WT analysis applied to small molecular species in solution. In this talk I will present our initial efforts towards determining the utility of a WT analysis applied towards such systems. Different data analysis strategies will be presented with examples of where we have found both success and “failure” in obtaining structural information using a WT analysis. \nReferences: \n\nPenfold et. al. J. Chem. Phys. 138\, 014104 (2013); https://doi.org/10.1063/1.4772766 \n\n 
URL:https://xrayabsorption.org/events/journaclub-jason-shearer/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200518T090000
DTEND;TZID=America/Los_Angeles:20200518T100000
DTSTAMP:20260416T050928
CREATED:20200512T020337Z
LAST-MODIFIED:20200518T203853Z
UID:298-1589792400-1589796000@xrayabsorption.org
SUMMARY:Jennifer Mass:	MicroXANES studies of pigment degradation in works by Henri Matisse and a Dutch golden age still life
DESCRIPTION:The new painting materials used by the Impressionists\, Fauvists\, and Expressionists were critical components of their break with traditional modes of representation. These artists heavily exploited the synthetic organic and inorganic pigments that were newly available as a result of the industrial revolution. However\, the bright and novel hues that made their way onto these artists’ palettes (and in many cases defined the movements listed above) were not always synthesized properly. Pigments in some of the greatest masterpieces of these movements have been found to be highly fugitive or rapidly discolored. These unstable materials can react with adjacent or admixed pigments\, agents of degradation in the environment\, and even the paint binding media surrounding them. The urgent need for preservation of these works calls for intensive materials engineering approaches to identify their mechanisms of degradation and ensure their longevity for future generations. As complex multilayered mesoscale inorganic-organic composites\, these paintings present a wealth of analytical challenges.\nArtists working in this period of the 1880s to the 1920s were aware of the limitations of the materials available to them\, and they attempted to make choices based upon the most stable options at hand. Paint manufacturers were also aware that not all of their offerings were equally stable\, and they would note the stability of the pigments offered for sale. Within this context\, however\, we still have monumental works from this period changing so substantially that they no longer represent the artists’ original vision. Pigments from this period that have been found to alter over time include chrome yellow (PbCrO4.PbSO4)\, zinc yellow (4ZnO.4CrO3\,K2O.3H2O)\, cadmium yellow (CdS)\, emerald green (Cu(C2H3O2)2.3Cu(AsO2)2\, eosin red (C20H8O5Br4\, germanium lake)\, and purpurin (1\,2\,4-trihydroxyantrhaquinone).\nNoninvasive methods for identifying these pigments (both before and after their alteration) including x-ray fluorescence\, hyperspectral imaging\, and ultraviolet-induced infrared fluorescence. To understand their mechanisms of degradation\, however\, requires microscale x-ray diffraction methods (XRD)\, x-ray absorption near edge spectroscopy (XANES) and mapping\, and scanning transmission electron microscopy (STEM) based methodologies such as electron energy loss spectroscopy (EELS). Henri Matisse’s Le Bonheur de vivre (1905-1906) will be used as a case studies to identify highly degraded pigments\, their technologies of manufacture\, and their mechanisms of degradation. Adriaen de Coorte’s Still Life with Five Apricots (1704) will be discussed to probe degradation mechanisms in more traditional artists’ materials.  \nReferences: \n\nMass\, J.L.\, Opila\, R.\, Buckley\, B. et al. The photodegradation of cadmium yellow paints in Henri Matisse’s Le Bonheur de vivre (1905–1906). Appl. Phys. A 111\, 59–68 (2013). https://doi.org/10.1007/s00339-012-7418-0\nCotte\, M.\, Susini\, J.\, Dik\, J.\, and Janssens\, K. Synchrotron-Based X-ray Absorption Spectroscopy for Art Conservation: Looking Back and Looking Forward\, Accounts of Chemical Research 43 705-714 (2010). https://doi.org/10.1021/ar900199m\nKeune\, K. et. al  Tracking the transformation and transport of arsenic sulfide pigments in paints: synchrotron-based X-ray micro-analyses J. Anal. At. Spectrom.\, 30\, 813-827 (2015) https://doi.org/10.1039/c4ja00424h\n\n 
URL:https://xrayabsorption.org/events/journalclub-jennifer-mass/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200514T090000
DTEND;TZID=America/Los_Angeles:20200514T100000
DTSTAMP:20260416T050928
CREATED:20200512T014422Z
LAST-MODIFIED:20200516T162413Z
UID:294-1589446800-1589450400@xrayabsorption.org
SUMMARY:Pieter Glatzel: Reflections on hard X-ray photon-in/photon-out spectroscopy
DESCRIPTION:The presentation will be a collection of thoughts that I find interesting for the experimentalist employing hard X-ray photon-in/photon-out spectroscopy with a wavelength dispersive instrument. I would like to draw the attention to some experimental aspects and will give hopefully useful advice that may be considered for the experimental protocol. Furthermore\, I will present the two instruments for X-ray emission spectroscopy at ESRF ID26 and discuss the challenges of a multi-crystal spectrometer. \nReferences:\n[1] Glatzel\, P\, et al. . “Reflections on Hard X-Ray Photon-in/Photon-out Spectroscopy for Electronic Structure Studies” J. Electron Spectros. Relat. Phenomena 2013\, 188\, 17–25; https://doi.org/10.1016/j.elspec.2012.09.004\n[2] Rovezzi\, M\, et al.\,. “High Energy-Resolution x-Ray Spectroscopy at Ultra-High Dilution with Spherically Bent Crystal Analyzers of 0.5 m Radius” Rev. Sci. Instrum. 2017\, 88 (1) 013108 https://doi.org/10.1063/1.4974100;\n[3] M. Rovezzi\, et al.\, “TEXS: in-vacuum tender x-ray emission spectrometer with eleven Johansson crystal analysers.” Journal of Synchrotron Radiation 2020\, 27\, 813. https://doi.org/10.1107/S160057752000243X \n 
URL:https://xrayabsorption.org/events/journalclub-pieter-glatzel/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200511T090000
DTEND;TZID=America/Los_Angeles:20200511T100000
DTSTAMP:20260416T050928
CREATED:20200512T021026Z
LAST-MODIFIED:20200514T015444Z
UID:303-1589187600-1589191200@xrayabsorption.org
SUMMARY:John Rehr: Fast throughput calculations and the XAFS data base in the Materials Project
DESCRIPTION:Modern electronic structure theory and computational methods now permit efficient calculations of ground state properties\, as exemplified by the tabulation of many-thousands of structures in the Materials Project [1]. Complementary advances in the theory of excited states have led to efficient methods for calculations of x-ray and electron spectroscopies\, e.g.\, using the real-space Green’s multiple scattering theory in the FEFF9 code [2]. Here we discuss these developments and how they have been applied to high throughput calculations of x-ray absorption spectra in the Materials Project [3]. In particular\, the world’s largest x-ray database has been constructed\, which currently contains nearly 200\,000 computed K-edge spectra for over 40\,000 materials [4]. Recently this data base has been exploited using Machine-Learning techniques to accurately predict local coordination environments [5]. The database including the FEFF input and output files\, is freely available from the Materials Project [1]. Extensions to L-edge and XAFS spectra are in progress. \nReferences:\n[1] A. Jain et al.\, The Materials Project: A materials genome approach to accelerating materials innovation\, APL Materials 1\, 011002 (2013); https://www.materialsproject.org.\n[2] John J. Rehr et al.\, Parameter-free calculations of X-ray spectra with FEFF9\, Physical Chemistry Chemical Physics 12\, 5503 (2010).\n[3] K. Matthew\, et al.\, High-throughput computational X-ray absorption spectroscopy\, Scientific Data 5\, 180151 (2018).\n[4] Chen Zheng et al.\, Automated generation and ensemble-learned matching of X-ray absorption spectra\, npj Computational Materials 4\, 12 (2018).\n[5] Chen Zheng et al.\, Random Forest Models for Accurate Identification of Coordination Environments from X-Ray Absorption Near-Edge Structure\, Patterns 1\, 100013 (2020). \n 
URL:https://xrayabsorption.org/events/journalclub-john-rehr/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200507T090000
DTEND;TZID=America/Los_Angeles:20200507T100000
DTSTAMP:20260416T050928
CREATED:20200512T032236Z
LAST-MODIFIED:20200512T035931Z
UID:319-1588842000-1588845600@xrayabsorption.org
SUMMARY:Paul Northrup: The TES Beamline (8-BM) at NSLS-II:  tender-energy spatially-resolved X-ray absorption spectroscopy and X-ray fluorescence imaging
DESCRIPTION:I will present details of the TES Beamline at the National Synchrotron Light Source II\, covering its design\, commissioning\, and early results. Its scientific mission includes static and in-situ/operando XRF imaging and spatially resolved (microbeam) XAS — in the tender energy range — for characterization of complex heterogeneous\, structured and dynamic natural or engineered materials and systems. My approach for design of TES centered on two primary goals:\n1) optimize for the tender energy range\, which offers access to elements and edges not accessible (or not accessible with optimal performance) at either hard or soft X-ray beamlines.\n2) bring the essential capabilities of an XAS beamline down to the microscale\, so as to measure full EXAFS of a single particle or structure the same size as the probe beam.\nTES offers routine operations from 2.0 to 5.5 keV\, with capabilities to reach down to 1.2 keV with configuration change. It is also designed as an “EXAFS Microprobe” for applications of um-scale extended X-ray absorption spectroscopy fine structure to heterogeneous and small-particle samples. Beam size is user-tunable from ~2 um to 25 um. Energy may be scanned on-the-fly or in step scanning mode. Importantly\, the position of the microbeam at the sample location does not move significantly during energy scanning\, or when changing energy across the entire routine energy range. This enables full EXAFS of a particle or domain the same size as the probe beam\, and measurement of the same spot at different energies. In addition\, there is no measurable drift in energy calibration (repeatability) scan-to-scan and over >24 hours. This is critical in an energy range where simultaneous calibration measurements in transmission are generally not feasible\, and for speciation mapping where precise and stable control of incident energy is essential. The sample environment is helium atmosphere at room pressure\, with infrastructure for in-situ electrochemistry and catalysis in small sample cells or microreactors. \nReferences: \n1) P. Northrup\, 2019. The TES Beamline (8-BM) at NSLS-II\, J. Synch. Rad.\, 26\, 2064-2074 (2019) https://doi.org/10.1107/S1600577519012761 \n2) A Leri\, et al.\, A Marine Sink for Chlorine in Natural Organic Matter\, Nature Geosci.\, 8\, 620-624\, 2015. https://doi.org/10.1038/ngeo2481 \n3) E. Ingall\, et al\, J. Synch. Rad.\, 18\, 189-197. http://journals.iucr.org/s/issues/2011/02/00/hi5614/hi5614.pdf
URL:https://xrayabsorption.org/events/journalclub-paul-northrup/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200504T090000
DTEND;TZID=America/Los_Angeles:20200504T100000
DTSTAMP:20260416T050928
CREATED:20200512T032509Z
LAST-MODIFIED:20200512T035931Z
UID:321-1588582800-1588586400@xrayabsorption.org
SUMMARY:Faisal Alamgir: Soft and Hard X-ray Operando and In/Ex-situ XAFS: Towards a Unified View of Local Structure and Magnetic Properties in LiMO2 Delafossite Batteries
DESCRIPTION:We will look at how electrochemically active materials such as batteries can be studied in a concerted way by tuning to relevant resonant x-ray absorption at both the soft and the hard x-ray energy regimes. We will specifically examine the role of oxygen in the charge compensation of LiMO2 delafossite compounds\, that serve as cathodes for an important class of rechargeable batteries\, and the consequences of such for battery safety and for unprecedented changes to magnetic properties. As a case study of the reactions in LiCoO2\, the electronic and atomic structure local to oxygen was first examined indirectly using hard x-rays by operando resonant Co K-level measurements and was later complemented by operando measurements at the O K-level using soft x-rays. A charge compensation roadmap was established for the LiCoO2 cathodes where we find tandem charge compensation reactions\, first involving oxygen and later by cobalt. The generation of electron holes at oxygen sites explains the transitions in magnetic moment observed in LiCoO2 as a function of de-lithiation. A similar case was found in in the de-lithiation of Li[Ni1/3Co1/3Mn1/3]O2 cathodes. We hope to make the case that a detailed electrochemical roadmap for the reaction mechanisms in LiMO2 cathodes could only be revealed by a combination of soft and hard x-ray based experiments. \nReferences:\nF. M. Alamgir et al.\, LiCoO2 Thin-Film Batteries: Structural Changes and Charge Compensation\, Journal of The Electrochemical Society}\,152\, 5\, (2005) A845. doi: 10.1149/1.1872672 ;\nC. F. Petersburg\, et al\, Oxygen and transition metal involvement in the charge compensation mechanism of LiNi1/3Mn1/3Co1/3O2 cathodes\, J. Mater. Chem.\, 22\, 37\, (2012) 19993-20000;\nC. F. Petersburg\, et al\, Soft X-ray characterization technique for Li batteries under operating conditions\, J. Synchrotron Rad.\, 16\, (2009) 610-615.
URL:https://xrayabsorption.org/events/journalclub-faisal-alamgir/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200430T090000
DTEND;TZID=America/Los_Angeles:20200430T100000
DTSTAMP:20260416T050928
CREATED:20200512T032821Z
LAST-MODIFIED:20200512T035931Z
UID:323-1588237200-1588240800@xrayabsorption.org
SUMMARY:Frank deGroot: Transition metal K edge spectral shapes: The influence of core hole screening
DESCRIPTION:Using High-Energy-Resolution-Fluorescence-Detection (HERFD)\, one can sharpen the pre-edge structures revealing their multiplet nature. In ionic systems\, they can be calculated from the transition from the 3dN ground state to the 1s13dN+1 final state\, where covalent systems need the inclusion of charge transfer effects.[1] The main edge is usually interpreted from the calculation of the transitions to empty states\, using DFT theory\, for example multiple scattering (FEFF). The 1s XPS spectra of transition metal oxides show multiple peaks\, implying that one photon energy gives rise to electrons with multiple kinetic energies. This implies that the 1s XAS spectral shape must be described as the convolution of the empty states with the 1s XPS spectral shape [2]. Isolated transition metal ions only show a pre-edge and an edge\, but bulk oxides show additional intensity between the pre-edge and edge. One can show that this intensity is related to dipole transitions of metal p-character that is part of the 3d-states of a near-neighbour metal ion [3]. X-MCD measurements of CrO2 reveal that the pre-edge is invisible in normal XAS [4]. In systems with two different metal ions one can observe the metal-metal charge transfer in the non-local peaks. [5] \nReferences:\n[1] J. Phys. Cond. Matt. 21\, 104207 (2009).\n[2] Ghiasi et al.\, Phys. Rev. B. 100\, 075146 (2019).\n[3] Juhin et al.\, Phys. Rev. B. 81\, 115115 (2010).\n[4] Zimmermann et al.\, J. Elec. Spec. 222\, 74 (2018).\n[5] Juhin et al. Inorg. Chem. 56\, 10882 (2017).
URL:https://xrayabsorption.org/events/journalclub-frank-degroot/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200427T090000
DTEND;TZID=America/Los_Angeles:20200427T100000
DTSTAMP:20260416T050928
CREATED:20200512T033137Z
LAST-MODIFIED:20200512T035931Z
UID:325-1587978000-1587981600@xrayabsorption.org
SUMMARY:Eleanor Schofield:	X-ray Absorption Spectroscopy in the service of Henry VIII: Conserving a Tudor shipwreck
DESCRIPTION:The conservation of marine archaeological wood is complicated by the presence of iron and sulfur. The sulfur originates from sulfate ions in seawater being transformed by sulfur reducing bacteria\, and iron from dissolved fixture and artefacts. Incorporated in to the wood as reduced sulfur/iron compounds\, such as pyrite\, they can become problematic during the drying of the wood as rapid oxidation can result in acid formation which can promote degradation. The Mary Rose was a 16th century Tudor warship\, commissioned by Henry VIII. After 34 years sailing\, the ship sank off the coast of Portsmouth in 1545. Rediscovered in the late 1960s\, the remaining hull emerged from the Solent in 1982 and now resides in a purpose built museum in Portsmouth Historic. In 2013 the consolidation treatment of the wood\, to compensate for degradation\, was completed and an air drying process commenced. During this phase samples have been periodically taken to monitor the evolution of iron and sulfur as a function of drying time using X-ray Absorption Spectroscopy. Alongside this Fourier-Transform Infrared Spectroscopy has been used to correlate any observed changes to the degradation levels within the wood. This information is crucial in understanding the chemical state of the wood and designing future conservation strategies. \nReferences:\n1. Schofield\, E. J.\, “Illuminating the past: X-ray analysis of our cultural heritage” Nat. Rev. Mater. 3\, 285-287\, 2018\n2. Schofield\, E. J.\, Sarangi\, R.\, Mehta\, A.\, Jones\, A. M. and Chadwick\, A. V. “Nanotechnology and Synchrotron light in the service of Henry VIII: preserving the Mary Rose” Materials Today\, Vol 14 (7-8) Pages: 354-358 2011\n3. M. Sandström\, F. Jalilehvand\, I Persson\, U. Gelius\, P. Frank\, I. Hall-Roth\, Nature 2002\, 415\, 893–897.
URL:https://xrayabsorption.org/events/journalclub-eleanor-schofield/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200423T090000
DTEND;TZID=America/Los_Angeles:20200423T100000
DTSTAMP:20260416T050928
CREATED:20200512T033410Z
LAST-MODIFIED:20200512T035931Z
UID:327-1587632400-1587636000@xrayabsorption.org
SUMMARY:Joe Fowler: X-ray Fluorescence Line Metrology for the 21st Century
DESCRIPTION:Databases of x-ray fluorescence line energies such as those of Deslattes (2003) and Bearden (1967) are critical to the calibration of any analytical tools that identify elemental compositions by their x-ray “fingerprints.” To be useful\, such tables have to favor completeness over accuracy. Unfortunately\, a full 75% of the lines in the current NIST database (SRD-128) rely on measurements at least 50 years old\, coming from an age when the SI meter and the x-ray wavelength had never been tied together. Worse\, SRD-128 lacks all information about line shapes or any M lines whatsoever. At NIST\, we have begun a program to measure as many lines as possible with transition-edge sensor (TES) microcalorimeters\, starting with the hard x-ray L lines of certain lanthanide metals. As Kelsey Morgan described on March 30\, a TES combines advantages of solid-state detectors and diffractometers: it measures an enormous spectral region at once with resolving power of 1000 or higher. In tandem\, we have also rejuvenated the SI-traceable diffractometer of Deslattes’ team\, in order to expand the limited set of lines available for calibration of the TES spectrometer. \nhttps://arxiv.org/abs/1702.00507 and https://arxiv.org/abs/1511.03950
URL:https://xrayabsorption.org/events/journalclub-joe-fowler/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200420T090000
DTEND;TZID=America/Los_Angeles:20200420T100000
DTSTAMP:20260416T050928
CREATED:20200512T033612Z
LAST-MODIFIED:20200512T035931Z
UID:329-1587373200-1587376800@xrayabsorption.org
SUMMARY:Rene Bes: Nuclear fuel study using XAS: benefits of HERFD for U valence states evaluation
DESCRIPTION:The safe use and disposal of UO2 based nuclear fuels relies on the stability of their material properties\, under extreme conditions of temperature and irradiation\, and with constantly evolving chemical composition. Among them\, the uranium valence state’s behavior is at the heart of safety assessment during the entire fuel lifecycle. First\, the oxidation from UO2 to UO3 induces for example considerable reorganization of the crystal structure and results in a volume expansion of about 36% when reaching the U3O8 intermediate state\, eventually leading to fuel cladding failure. Secondly\, the uranium valence state U6+ and to a lesser extent U5+ are known to have solubility several orders of magnitude higher than U4+\, which is a critical parameter during fuel final disposal\, the UO2 matrix very slow dissolution acting as the ultimate barrier of radioactivity release into the environment. X-ray absorption spectroscopy (XAS) is a key technique to assess U valence states in nuclear fuels thanks to its elemental sensitivity. However\, XAS applied to nuclear fuels suffers from the presence of almost all the periodic table in spent fuel\, from the high radioactive background limiting the number of available beamlines\, from the fact that transmission mode is often impossible to perform\, and from the large core-hole broadening effects. I will discuss how High Energy Resolution Fluorescence Detected XAS (HERFD-XAS) can help overcoming those drawbacks through a selection of a few recent examples\, and I will describe the main benefits of HERFD for U valence state evaluation. \nReferences:\nK. O. Kvashnina\, S. M. Butorin\, P. Martin\, and P. Glatzel\, Phys. Rev. Lett. 111 (2013) 253002 http://dx.doi.org/10.1103/PhysRevLett.111.253002 ;\nR. Bès\, M. Rivenet\, P.-L. Solari\, K. O. Kvashnina\, A. C. Scheinost\, and P. M. Martin\, Inorg. Chem. 55 (2016) 4260-4270 http://dx.doi.org/10.1021/acs.inorgchem.6b00014 ;\nG. Leinders\, R. Bès\, J. Pakarinen\, K. Kvashnina\, and M. Verwerft\, Inorg. Chem. 56 (2017) 6784−6787 http://dx.doi.org/10.1021/acs.inorgchem.7b01001;\nG. Leinders\, R. Bès\, K. Kvashnina\, and M. Verwerft\, Inorg. Chem. 59 (2020) 4576−4587 https://dx.doi.org/10.1021/acs.inorgchem.9b03702
URL:https://xrayabsorption.org/events/journalclub-rene-bes/
CATEGORIES:XAFS Journal Club
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BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200416T090000
DTEND;TZID=America/Los_Angeles:20200416T100000
DTSTAMP:20260416T050928
CREATED:20200512T033955Z
LAST-MODIFIED:20200512T035931Z
UID:332-1587027600-1587031200@xrayabsorption.org
SUMMARY:Yulia Pushkar:	X-ray Emission Spectroscopy at X-ray Free Electron Lasers: Limits to Observation of Unperturbed Electronic Structures
DESCRIPTION:Modern free electron lasers provide intense X-ray pulses with 10^12 photons within ~10-100 femtoseconds. Such pulses enable new experimental techniques and provide unique opportunities for investigation of electronic and nuclear dynamics on their intrinsic time-scales. Interaction of ultra-bright\, ultra-short X-ray pulses with matter can induce a multitude of nonlinear excitation processes which must be carefully considered when planning spectroscopic measurements and interpreting data recorded at XFELs. In most cases correct interpretation of the spectroscopic response and analysis of the electronic structure hinges on the assumption of single photon excitations. Here we attempted to answer the fundamental question on the limits to probing the ground (or native) electronic structure of a 3d transition metal ion at XEFL sources. Ions of the 3d transition metal\, e.g.\, Mn(II)\, in a lighter element (O\, C\, H) environment were used as a model system. X-ray emission spectroscopy recorded from Mn2+ at different pulse conditions demonstrate spectral changes as a function of increased pulse intensity and pulse duration. To explain these changes\, we develop a rate equation based on sequential ionization and relaxation events forming multiply ionized states during a single pulse which agree with observed spectroscopic trends. The percentage of Mn Kbeta emission recorded after the 1st\, 2nd and 3rd 1s ionization events is calculated from the developed rate equation model and validated by experimental measurements. A method for estimating shifts in atomic X-ray emission lines from sequential ionization during a single XFEL pulse is given. From our data we infer that\, in addition to multiple ionization\, the impact of electron cascades is more significant for longer pulses. We note that while use of shorter X-ray pulses will help to counteract additional effects of electron cascades it will not help to overcome the spectral shifts due to sequential ionization. Presented data and associated analysis will help with experimental designs at current and upcoming XFELs where even higher intensities and shorter pulses are expected. 3d elements have a variety of important applications such as in bio-inorganic catalysis\, chemical catalysis and energy storage / conversion making robust protocols for their XFEL analysis of general importance. \nhttp://dx.doi.org/10.1021/acs.jpclett.8b03595
URL:https://xrayabsorption.org/events/journalclub-yulia-pushkar/
CATEGORIES:XAFS Journal Club
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BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200413T090000
DTEND;TZID=America/Los_Angeles:20200413T100000
DTSTAMP:20260416T050928
CREATED:20200512T034144Z
LAST-MODIFIED:20200512T035931Z
UID:334-1586768400-1586772000@xrayabsorption.org
SUMMARY:Jacinto Sa:	Solving chemical mechanisms with X-ray spectroscopy
DESCRIPTION:As a scientist have been always fascinated with how chemical systems react and interact with the natural world. Spectroscopy is a great tool to look at systems in real-time and operation conditions. Hard X-ray photon-in photon-out spectroscopy offers great possibilities due to its chemical sensitivity and speciation as well as high penetration. In this webinar\, I will talk about two chemical processes and the developments in X-ray spectroscopy that made the studies possible. My studies have been made possible with the development of the dispersive von Hamos-type spectrometer (1)\, which enabled us to perform high-resolution studies on real systems due to its simple and versatile geometry. The first case study is called atomic telemetry\, a method that enables us to follow chemotherapy drugs action mechanism under physiological conditions. The methodology was validated with a known drug (cisplatin) but in this webinar\, I will present the findings from a drug (Pt-103) with an unknown action mechanism (2). The second case relates to the understanding of plasmonic materials hot carrier formation\, and their importance to solar applications. Using synchrotron radiation and HR-XAS we were able to demonstrate for the first time the formation of hot electrons (3). However\, to address their dynamics one needed to develop a way to perform RIXS measurements at the XFEL with the shortest and most intense X-ray pulses. I will show how we can do that (4) and what we plan to do with this methodology. \nReferences: (1 ) J. Szlachetko et al. Rev. Scie. Instrum. 2012\, 83\, 103105 https://doi.org/10.1063/1.4756691  (2 ) J. Czapla-Masztafiak et al. J. Phys. Chem. Lett. 2017\, 8\, 805-811 https://doi.org/10.1021/acs.jpclett.7b00070 (3) J. Sá\, et al. Energy Scie. Technol. 2013\, 6\, 3584-3588 https://doi.org/10.1039/C3EE42731E (4) Y. Kayser et al. Nat. Commun. 2019\, 10\, 4761 https://doi.org/10.1038/s41467-019-12717-1
URL:https://xrayabsorption.org/events/jacinto-sasolving-chemical-mechanisms-with-x-ray-spectroscopy/
CATEGORIES:XAFS Journal Club
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BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200409T090000
DTEND;TZID=America/Los_Angeles:20200409T100000
DTSTAMP:20260416T050928
CREATED:20200512T034432Z
LAST-MODIFIED:20200512T035932Z
UID:337-1586422800-1586426400@xrayabsorption.org
SUMMARY:Neil Hyatt: Multimodal microfocus XAS to understand and remediate DU munitions contamination
DESCRIPTION:The talk will show how multimodal microfocus X-ray spectroscopy has been applied to characterize depleted uranium particles from munitions testing to predict and understand their environmental behavior. A combination of spatially resolved XRD\, XRF and XAS techniques\, combined with laboratory SEM observations\, is shown to effectively differentiate DU particulate contamination in near surface and burial sites\, and provide evidence of particulate alteration. This knowledge was used to design and understanding more effective remediation measures for depleted uranium contamination\, with multimodal characterisation supporting process optimisation. \nReferences:\nCrean et al.\, Environ. Sci. Tech.\, 2014\, 48\, 1467; https://doi.org/10.1021/es403938d \nCrean et al.\, J. Haz. Mat.\, 2013\, 263\, 382. https://doi.org/10.1016/j.jhazmat.2013.08.013
URL:https://xrayabsorption.org/events/journalclub-neil-hyatt/
CATEGORIES:XAFS Journal Club
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BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200406T090000
DTEND;TZID=America/Los_Angeles:20200406T100000
DTSTAMP:20260416T050928
CREATED:20200512T034629Z
LAST-MODIFIED:20200512T035932Z
UID:339-1586163600-1586167200@xrayabsorption.org
SUMMARY:Steve Heald: Sector 25 at the APS-U: Two new beamlines for advanced spectroscopy
DESCRIPTION:As part of the Advanced Photon Source (APS) Multibend Achromat lattice upgrade two new beamlines for spectroscopy will be constructed on a canted undulator source at Sector 25. The programs at the 20-ID beamline at the APS need to move to sector 25 to make room for a planned long beamline. These will be combined with some other APS spectroscopy programs at sector 25 to use two new beamlines on a canted undulator. These two beamlines will service existing and upgraded endstations covering a variety of spectroscopy applications. There will be a microprobe branch that will provide sub-micron beams for fluorescence imaging\, and micro-XAFS. These can be combined with confocal optics for micron level depth sensitivity. This branch will also have a station for XAFS experiments requiring a high-brilliance high-flux beam such as doped thin films or ultra-dilute samples. The second Advanced Spectroscopy branch will provide beam to two inline hutches. The first will have stations for both an enhanced LERIX spectrometer for non-resonant inelastic scattering (x-ray Raman)\, and spectrometers for high resolution emission spectroscopy. The second hutch will provide space for experiments requiring extensive setup\, such as time-resolved pump-probe experiments. Both hutches will have a variety of focusing options providing beam sizes down to a few microns. To provide greater beam separation\, both lines will have side deflecting mirrors for harmonic rejection\, and focusing/collimation. The planned energy ranges are 4-32 keV for the microprobe branch\, and 4-40 keV for the Advanced Spectroscopy branch. The horizontal deflection mirrors allow use of small offset monochromators equipped with liquid nitrogen cooled Si (111) crystals for monochromatic beam\, and wide-bandpass multilayers providing higher flux for experiments that do not need high resolution such as imaging and non-resonant emission spectroscopy. The Advanced Spectroscopy branch will also have a secondary monochromator for experiments needing better resolution than provided by Si (111).
URL:https://xrayabsorption.org/events/journalclub-steve-heald/
CATEGORIES:XAFS Journal Club
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