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BEGIN:VEVENT
DTSTART;VALUE=DATE:20200917
DTEND;VALUE=DATE:20200918
DTSTAMP:20260416T035412
CREATED:20200916T182758Z
LAST-MODIFIED:20200916T182758Z
UID:595-1600300800-1600387199@xrayabsorption.org
SUMMARY:Santiago Figueroa: Spectroscopy and New Scientific Opportunities at SIRIUS\, part II
DESCRIPTION:Thursday September 17: 9 am Seattle\, 12 noon NY\, 5 pm London\, 7 pm Moscow\nlink: https://washington.zoom.us/j/91967881684 \n \n\n\nSirius is one of the first fourth-generation Synchrotron Light Sources to be built in the world and will have the highest brightness among the light sources in the energy range that goes from soft x-rays to hard X-rays with energies up to 20 keV.  The choice and design of the first Sirius beamlines were defined considering three general guidelines\, discussed in the first lecture of this sequence: access to new science\, Improvement to current science\, innovation in strategic areas.\n\n   \nThe second two x-ray absorption beamlines intended for Sirius are in the assembled phase. These two beamlines will enable unprecedented studies to be made in Brazil\, in practically all areas of knowledge\, whether of academic or industrial interest:\n     ** QUATI (QUick X-Ray Absorption Spectroscopy for TIme-Resolved experiments) is a beamline dedicated to high quality X-ray absorption spectroscopy experiments\, in XANES (X-Ray Absorption Near Edge Structure)  and EXAFS (Extended X-ray Absorption Fine Structure) modes\, allowing measurements in the time scale of milliseconds. Multitechnique approach will be performed: XRD\, Raman and IR coupled with XAFS experiments. X-ray Emission Spectroscopy (XES) will be accessible by a Von Hamos spectrometer to enable fast scan acquisition.\n     ** IPÊ (Inelastic and Photo-Electron spectroscopy) is a beamline that will have two experimental stations to allow complementary techniques probing the electronic structure of materials X-Ray Photoelectron Spectroscopy (AP-XPS) and Resonant Inelastic X-Ray Scattering (RIXS).
URL:https://xrayabsorption.org/events/figueroa-sirius2/
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200910
DTEND;VALUE=DATE:20200911
DTSTAMP:20260416T035412
CREATED:20200903T152554Z
LAST-MODIFIED:20200903T152759Z
UID:591-1599696000-1599782399@xrayabsorption.org
SUMMARY:Wolfgang Malzer: Principles and applications of laboratory XAS with graphite crystal von Hamos spectrometers
DESCRIPTION:The presentation will be at 9 am Seattle (Los Angeles) time (UTC-7). To join this meeting\, use the Zoom links as sent by Jerry Seidler
URL:https://xrayabsorption.org/events/journalclub_w_malzer/
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200903
DTEND;VALUE=DATE:20200904
DTSTAMP:20260416T035412
CREATED:20200902T115147Z
LAST-MODIFIED:20200903T143853Z
UID:584-1599091200-1599177599@xrayabsorption.org
SUMMARY:Helio Tolentino and Others: Spectroscopy and New Scientific Opportunities at SIRIUS\, part I
DESCRIPTION:The presentation will be at 9 am Seattle (Los Angeles) time (UTC-7). To join this meeting\, use the link: https://washington.zoom.us/j/99543082366   \nSirius is one of the first fourth-generation Synchrotron Light Sources to be built in the world and will have the highest brightness among the light sources in the energy range that goes from soft x-rays to hard X-rays with energies up to 20 keV. \n\nThe choice and design of the first Sirius beamlines were defined considering three general guidelines:\n–Access to New Science: to make the most out of the high brightness of a fourth-generation Synchrotron Light Source to explore techniques such as coherent scattering\, nanofocus and inelastic scattering spectroscopy;\n–Improvement to Current Science: to provide access to enhanced versions of experimental techniques currently available through the high brightness and wide spectrum provided by the Source;\n–Innovation in Strategic Areas: to provide high-tech tools to solve problems in strategic areas for the Country. \n\nThe first 2 x-ray absorption beamlines intended for Sirius are in the assembled phase. These two beamlines will enable unprecedented studies to be made in Brazil\, in practically all areas of knowledge\, whether of academic or industrial interest: \n– Carnauba (Coherent X-rAy NAnoprobe BeAmline) is a beamline for multiple advanced techniques using X-ray absorption\, scattering and emission\, and combining coherent light with nano-focusing. It is the longest of Sirius beamlines\, with 145 meters distance between the light source and the sample environment. This length is required to produce a high optical demagnification and attain a focus size of about 30 nm. \n– EMA (Extreme condition Methods of Analysis) beamline will be dedicated to study samples under extreme thermodynamical conditions by coupling both microfocus (1×1 µm2) and nanofocus (100×100 nm2) beamsizes to x-ray magnetic spectroscopy\, x-ray diffraction and x-ray coherent imaging in multiple experimental instruments\, placed along the beam path for optimization. \n\n 
URL:https://xrayabsorption.org/events/sirius-xas/
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200827
DTEND;VALUE=DATE:20200828
DTSTAMP:20260416T035412
CREATED:20200827T134704Z
LAST-MODIFIED:20200902T114910Z
UID:569-1598486400-1598572799@xrayabsorption.org
SUMMARY:Kristjan Kunnus: Probing of coherent nuclear wavepacket dynamics with X-ray emission and scattering in solvated Fe photosensitizers
DESCRIPTION:Spin and oxidation state sensitivity of 3d metal K-edge X-ray Emission Spectroscopy (XES) has been utilized in recent years to successfully probe the ultrafast spin transition and electron transfer processes in femtosecond time-resolved experiments [1\,2]. In this talk I will present the results from a combined time-resolved Fe Kα and Kβ XES and X-ray Solution Scattering (XSS) experiment at the LCLS where we investigated photoinduced dynamics in a molecular Fe photosensitizer [Fe(bmip)2]2+ (bmip = 2\,6-bis(3-methyl-imidazole-1-ylidine)-pyridine) [3]. Simultaneous tracking of electronic and nuclear structure allowed us to determine branching of electronic relaxation pathways and observe coherent nuclear dynamics. In particular\, I will discuss the origin of vibronic effects in time-resolved XES experiments and explain how these lead to the sensitivity of XES from nuclear wavepacket dynamics [4]. \nReferences: \n\nZhang et al.\, Nature 7\, 629 (2014). \nK. S. Kjær et al.\, Chem. Sci. 10\, 5749-5760 (2019). \nK. Kunnus et al.\, Nat. Commun. 11\, 634 (2020). https://doi.org/10.1038/s41467-020-14468-w \n M. Vacher et al.\, Struct. Dyn. 7\, 044102 (2020). https://doi.org/10.1063/4.0000022\n\n\n  \n\n 
URL:https://xrayabsorption.org/events/journalclub_kunnus/
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200820
DTEND;VALUE=DATE:20200821
DTSTAMP:20260416T035412
CREATED:20200827T134214Z
LAST-MODIFIED:20200827T134251Z
UID:567-1597881600-1597967999@xrayabsorption.org
SUMMARY:M. Darby Dyar: Application of Multivariate Analysis Techniques to Quantitative Interpretation of Valence States in XAS
DESCRIPTION:The study of extraterrestrial samples returned from the Moon\, asteroids\, and via meteorites has the potential to inform problems relating to the oxidation states of multivalent cations and the distribution of oxygen in our Solar System. For more than 25 years\, our group has worked to develop XAS methods for analyzing the partial pressure of oxygen in formation environments of tiny returned samples. This problem has application to all materials in which quantitative measurement of valence states is needed. This talk will provide a brief history of measurements of oxidation state in minerals\, and discuss the particular challenges of undertaking calibration data needed for anisotropic materials using a polarized synchrotron beam. We will show how multivariate analysis techniques such as partial least squares can be used to predict valence state and oxygen partial pressure at one-micron scales\, and enable mapping of small grains by selective choice of specific channels. These new methods enable understanding of processes as diverse as lunar volcanic eruptions and lightning strikes in terrestrial deserts. \nReferences: \n\nDyar et al. (2016) Accurate predictions of iron redox state in silicate glasses: A multivariate approach using x-ray absorption spectroscopy. Amer. Mineral.\, 101\, 744-748. https://doi.org/10.2138/am-2016-5555\nDyar et al. (2016) Use of multivariate analysis for synchrotron micro-XANES analysis of iron valence state in amphiboles. Amer. Mineral.\, 101\, 1171-1189. https://doi.org/10.2138/am-2016-5556\nMcCanta et al. (2017) In situ measurement of ferric iron in lunar glass beads using Fe-XAS. Icarus\, 285\, 95-102\, 10.1016/j.icarus.2016.12.029. https://doi.org/10.2138/am-2016-5556\nLanzirotti et al. (2018) Accurate predictions of microscale oxygen barometry in basaltic glasses using vanadium K-edge x-ray absorption spectroscopy: A multivariate approach. Amer. Mineral.\, 103\, 1282-1297.https://doi.org/10.2138/am-2018-6319\nRoberts et al. (2019) Oxidation state of iron in fulgurites and trinitite: Implications for redox changes during abrupt high-temperature and pressure events. Geochim. Cosmochim. Acta\, 266\, 332-350. https://doi.org/10.1016/j.gca.2019.08.021\n\n 
URL:https://xrayabsorption.org/events/journalclub_dyar/
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200813
DTEND;VALUE=DATE:20200814
DTSTAMP:20260416T035412
CREATED:20200827T135248Z
LAST-MODIFIED:20200827T140155Z
UID:572-1597276800-1597363199@xrayabsorption.org
SUMMARY:Juanjuan Huang: Energy Dispersive X-ray Absorption Spectroscopy at the Munich Compact Light Source
DESCRIPTION:X-ray absorption spectroscopy (XAS) is an important characterization method but has been carried out mostly at large facilities\, limiting the power as a routine characterization for scientific purposes. Therefore\, a lot of effort has been put in developing laboratory XAS using x-ray tubes and other sources. Novel compact x-ray sources based on inverse Compton scattering can generate brilliant hard x-rays in a laboratory setting\, e.g. with a footprint of 7 × 3 m for the one installed at the Munich Compact Light Source (MuCLS). Their low-divergence intense beams with tunable well-defined x-ray energies make them well suited for XAS techniques\, especially for hard x-rays >10 keV. In this talk\, I will briefly introduce the MuCLS facility and a specific XAS setup for such a source. The XAS spectra can be obtained in a short time with great spectral quality. This approach shows great potential to be an efficient and less costly substitute for routine XAS measurements at large facilities. \nReferences: \n\n Huang\, J. et al. Energy-Dispersive X-ray Absorption Spectroscopy with an Inverse Compton Source. Sci. Rep.\, 10\, 8772 (2020). https://doi.org/10.1038/s41598-020-65225-4\n Eggl\, E.\, et al. The Munich Compact Light Source: initial performance measures. J. Synchrotron Rad.\, 23\, 1137-1142 (2016). https://doi.org/10.1107/S160057751600967X\nGünther\, B.\, et al. X-ray beamline of the Munich Compact Light Source. J. Synchrotron Rad.\, 27 (2020). https://doi.org/10.1107/S1600577520008309\n\n 
URL:https://xrayabsorption.org/events/journalclub_huang/
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200810
DTEND;VALUE=DATE:20200811
DTSTAMP:20260416T035412
CREATED:20200808T213818Z
LAST-MODIFIED:20200827T134919Z
UID:555-1597017600-1597103999@xrayabsorption.org
SUMMARY:Susan Cumberland: Determining uranium geochemistry within natural organic-matter rich environments using XAS and XFM techniques
DESCRIPTION: \nAnalysing metals within environmental samples using wet chemistry can pose analytical problems\, particularly with carbon-based and solid samples. X-ray absorbance spectroscopy (XAS) analysis is one alternative approach\, able to target elements of interest whilst avoiding matrix interference from low mass elements (e.g. carbon). One element that is particularly suited to XAS is uranium (U)\, which is commonly investigated at the L3 edge. Understanding behaviour of U within the environment has been the focus of researchers for many decades\, whether in exploration\, mining\, contamination\, remediation or nuclear. Uranium geochemistry is the same regardless of whether its source is natural\, depleted or as spent fuel\, and the study of U is therefore multifaceted. In general terms\, of the two main oxidation states\, U(IV) and U(VI)\, U(IV) minerals have extremely low solubility\, while U(VI) can be more soluble and therefore potentially mobilised.\n   In my work I have explored the nature of U within ore deposits\, in particular the relationship between U and natural organic matter (OM) using XAS and X-ray fluorescence microscopy (XFM). OM may influence U mobility whether facilitating its pathway through the environment or acting as a sink for U. In the case of the latter\, OM may accumulate U over millennia within sediments or wetlands. Combining techniques from two beamlines at the Australian Synchrotron\, XAS (XANES\, EXAFS) and XFM (element mapping\, µXANES)\, together with laboratory µXRD\, spatial and chemical information were acquired on organically hosted U sediments taken from Mulga Rock Deposit\, Western Australia.\n   Results from XAS on bulk samples revealed how U at Mulga Rock is predominantly U(VI) within the OM sediments. However\, from using µXANES transects across U on pyrite rims\, we observe U(IV) outwardly transitioning to U(VI). Analysis of other features suggest that U has immortalised bacteria as coffinite (USiO4) ellipsoids. Furthermore\, I show from laboratory experiments how OM may immobilise U(VI) rapidly without change in oxidation state. Thus\, challenging traditional views that reduction of U(VI) to U(IV) has to occur for U to be immobilised within OM sediments.  \n\n \nReferences:\n\nCumberland\, S.A.\, Douglas\, G.\, Grice\, K. and Moreau\, J.W.\, 2016. Uranium mobility in organic matter-rich sediments: A review of geological and geochemical processes. Earth-Science Reviews\, 159: 160-185. https://doi.org/10.1016/j.earscirev.2016.05.010\nCumberland\, S.A.\, Etschmann\, B.\, Brugger\, J.\, Douglas\, G.\, Evans\, K.\, Fisher\, L.\, Kappen\, P. and Moreau\, J.W.\, 2018a. Characterization of uranium redox state in organic-rich Eocene sediments. Chemosphere\, 194: 602-613. https://doi.org/10.1016/j.chemosphere.2017.12.012\nCumberland\, S.A.\, Wilson\, S.A.\, Etschmann\, B.\, Kappen\, P.\, Howard\, D.\, Paterson\, D. and Brugger\, J.\, 2018b. Rapid immobilisation of U(VI) by Eucalyptus bark: Adsorption without reduction. Applied Geochemistry\, 96: 1-10. https://doi.org/10.1016/j.apgeochem.2018.05.023.\nCumberland\, SA.\, Evans\, K.\, Douglas\, G.\, de Jonge\, M.\, Fisher\, L.\, Howard\, D.\, Moreau.\, J. Characterisation of uranium-pyrite associations within organic-rich Eocene sediments using EM\, XFM-μXANES and μXRD.  (submitted\, Ore Geology Reviews)
URL:https://xrayabsorption.org/events/journalcub_susan_cumberland/
END:VEVENT
BEGIN:VEVENT
DTSTART;TZID=UTC:20200805T080000
DTEND;TZID=UTC:20200805T170000
DTSTAMP:20260416T035412
CREATED:20200805T221626Z
LAST-MODIFIED:20200805T221643Z
UID:549-1596614400-1596646800@xrayabsorption.org
SUMMARY:Liang Zhang: In situ/operando XAS for energy storage materials
DESCRIPTION:Rechargeable batteries (Li-ion batteries and beyond) have received extensive attention as powerful boosters for the development of human society. However\, the application of rechargeable batteries is still hindered by low energy density\, serious voltage hysteresis\, and long-term degradation. Therefore\, it is of great importance for understanding the underlying redox reaction and capacity fading mechanisms to circumvent these problems and improve the overall battery performance. In this talk\, I will mainly talk about the application in-situ/operando X-ray absorption spectroscopy for understanding the electrochemical reaction mechanism of electrode materials of various rechargeable batteries under real operation conditions\, which is an imperative prerequisite for the further optimization of the battery performance.   \n\nReferences:\n\nYan et al.\, Deciphering the Reaction Mechanism of Lithium–Sulfur Batteries by In Situ/Operando Synchrotron-Based Characterization Techniques\, Adv. Energy Mater.\, 2019\, 1900148\, https://doi.org/10.1002/aenm.201900148\nLin et al.\, Synchrotron X‑ray Analytical Techniques for Studying Materials Electrochemistry in Rechargeable Batteries\, Chem. Rev.\, 2017\, 117\, 13123\, https://doi.org/10.1021/acs.chemrev.7b00007\nZhu et al.\, In Situ Probing Multiple-Scale Structures of Energy Materials for Li-Ion Batteries\, Small Methods\, 2019\, 1900223\, https://doi.org/10.1002/smtd.201900223\n\n  \n\n 
URL:https://xrayabsorption.org/events/journalclub_liangzhang/
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200730
DTEND;VALUE=DATE:20200731
DTSTAMP:20260416T035412
CREATED:20200621T135910Z
LAST-MODIFIED:20200805T221341Z
UID:494-1596067200-1596153599@xrayabsorption.org
SUMMARY:Thomas Penfold: Towards the Rapid Analysis of XANES for Complex Systems using Deep Neural Networks
DESCRIPTION:X-ray spectroscopy delivers strong impact across the physical and biological sciences by providing end users with highly detailed information about the electronic and geometric structure of matter. To decode this information in challenging cases\, e.g.\, in operando catalysts\, batteries\, and temporally evolving systems [1]\, advanced theoretical calculations are necessary. The complexity and resource requirements often render these out of reach for end users\, and therefore\, the data are often not interpreted exhaustively\, leaving a wealth of valuable information unexploited. In this talk\, I will discuss our recently developed method based upon supervised machine learning of X-ray absorption spectra through the development of a deep neural network (DNN) [2]. This DNN is able to estimate Fe K-edge X-ray absorption near-edge structure spectra in less than a second with no input beyond geometric information about the local environment of the absorption site. We predict peak positions with sub-eV accuracy and peak intensities with errors over an order of magnitude smaller than the spectral variations that the model is engineered to capture. I will also discuss its extension to other absorption edges\, the properties of the network and also highlights areas on which future developments should focus. \nReferences: \n\n C. J. Milne\, T. J. Penfold and M. Chergui Coord. Chem. Rev. 277\, 44-68 (2014).\nC. D. Rankine\, M. M. M. Madkhali\, and T. J. Penfold J. Phys. Chem. A 2020\, 124\, 21\, 4263?4270
URL:https://xrayabsorption.org/events/journalclub-thomas-penfold/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200727
DTEND;VALUE=DATE:20200729
DTSTAMP:20260416T035412
CREATED:20200621T135456Z
LAST-MODIFIED:20200727T030303Z
UID:492-1595808000-1595980799@xrayabsorption.org
SUMMARY:Andy Aquila: The Tender X-ray Imaging (TXI) instrument at the LCLS
DESCRIPTION:This presentation will take place at 6 pm Monday\, Seattle (Los Angeles) time / 9 am Tuesday\, Beijing time using Zoom. For the Zoom link and password\, visit  https://tinyurl.com/XAFStalks  within 30 minutes of the beginning of the presentation. \nThe Linac Coherent Light Source (LCLS) upgrade to a high repetition source offers new avenues to pump/probe X-ray spectroscopies. Here I will briefly introduce the new capabilities of the LCLS focusing on the Tender X-ray Instrument (TXI). The TXI instrument is a dual-beam instrument\, fed by both the soft X-ray and hard X-ray undulators of LCLS; a feature currently unique among XFEL instruments. The tender x-ray instrument will enable x-ray pump/x-ray probe techniques especially in the emerging field of nonlinear x-ray science\, support tender X-ray spectroscopy measurements\, and provide a coherent scattering/ forward diffraction instrument for sub-micron samples. It is designed to accommodate a variety of additional techniques\, such as absorption and photoemission spectroscopy\, as well as an array of samples from fixed targets to gases\, aerosols\, and liquid jet targets. \n\nAbbamonte\, et al.\, New Science Opportunities Enables by LCLS-II X-ray Lasers https://portal.slac.stanford.edu/sites/lcls_public/Documents/LCLS-IIScienceOpportunities_final.pdf\nhttps://lcls.slac.stanford.edu/instruments/neh-1-2
URL:https://xrayabsorption.org/events/journalclub-andy-aquila/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200723
DTEND;VALUE=DATE:20200724
DTSTAMP:20260416T035412
CREATED:20200621T135236Z
LAST-MODIFIED:20200727T030438Z
UID:490-1595462400-1595548799@xrayabsorption.org
SUMMARY:Matthew Marcus: Soft x-ray spectromicroscopy in extraterrestrial materials
DESCRIPTION:Extraterrestrial materials such as meteorites and interplanetary dust particles are often very complex and non-uniform\, with diverse species within a small sample. In some cases\, especially for the products of sample-return missions\, the available samples are small and precious. X-ray micro- and nano-spectroscopy are ideal complements to other methods such as TEM and nano-SIMS. In this talk\, I will review several examples from the literature showing how X-ray spectromicroscopy has been used to study extraterrestrial materials and infer their histories of formation and alteration. I will also review some experimental techniques\, especially STXM. \nReferences: \n\nSandford\, Scott A.\, et al. “Organics captured from comet 81P/Wild 2 by the Stardust spacecraft.” Science 314\, no. 5806 (2006): 1720-1724.\nLo\, Yuan Hung\, et al. “Multimodal x-ray and electron microscopy of the Allende meteorite.” Science advances 5\, no. 9 (2019): eaax3009.\nVan Aken\, P. A.\, and B. Liebscher. “Quantification of ferrous/ferric ratios in minerals: new evaluation schemes of Fe L 23 electron energy-loss near-edge spectra.” Physics and Chemistry of Minerals 29\, no. 3 (2002): 188-200.
URL:https://xrayabsorption.org/events/journalclub-matthew-marcus/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200720
DTEND;VALUE=DATE:20200722
DTSTAMP:20260416T035412
CREATED:20200621T134914Z
LAST-MODIFIED:20200727T030541Z
UID:488-1595203200-1595375999@xrayabsorption.org
SUMMARY:Li Song: Soft X-ray endstaions at the Hefei Light Source and some applications of XAS
DESCRIPTION:Hefei Light Source (HLS) is the first dedicated synchrotron radiation facility in China with electron ring energy of 0.8 Gev\, which is located on the West Campus of the University of Science and Technology of China (USTC). With the completion of twice constructions and recent upgradation\, HLS become a fully upgraded soft X-ray synchrotron radiation facility\, now operating ten experimental stations (Infrared Spectroscopy and Microspectroscopy\, Combustion and Flame\, Mass Spectrometry\, Soft X-ray Microscopy\, Spectral Radiation Standard and Metrology\, Atomic & Molecular Physics\, Photoemission Spectroscopy\, Catalysis and Surface Science\, X-Ray Magnetic Circular Dichroism\, Angle-resolved Photoemission Spectroscopy) [1]. The well-designed beamlines and experimental stations at HLS\, together with the Shanghai synchrotron Radiation Facility and the Beijing Synchrotron Radiation Facility\, allow us to perform cutting edge scientific experiments. Here\, I will briefly introduce the soft X-ray endstations at HLS\, and present our recent studies based on X-ray absorption techniques. In particular\, two progress will be discussed: (1) adopt the rational atom-binding strategy and develop the method of precise nano-confined synthesis\, subsequently establish the structure-property relationships in several functional nanomaterials anchored with single atoms by combining synchrotron XAS and XPS [2-5]; (2) propose the controllable ion-intercalating and ion-exchanging strategies and develop the method of in-situ reconstructed synthesis\, eventually clarify the working mechanism of cation-/anion-modulated functional nanomaterials by the means of operando XAS with synchrotron-on-line devices[6-9]. \n  \nReferences: \n\nhttp://en.nsrl.ustc.edu.cn/main.htm\n\nAtomically dispersed platinum supported on curved carbon supports for efficient electrocatalytic hydrogen evolution\, Nature Energy\, 2019\, 4:512-518. https://doi.org/10.1038/s41560-019-0402-6\n\nAchieving Efficient Alkaline Hydrogen Evolution Reaction over a Ni5P4 Catalyst Incorporating Single-Atomic Ru Sites\, Advanced Materials\, 2020\, 32:1906972. https://doi.org/10.1002/adma.201906972\n\nElectrochemical Conversion of CO2 to Syngas with Controllable CO/H2 Ratios over Co and Ni Single-Atom Catalysts\, Angewandte Chemie International Edition\, 2020\, 59:3033-3037. https://doi.org/10.1002/anie.201912719\n\nSingle Nickel Atoms on Nitrogen-Doped Graphene Enabling Enhanced Kinetics of Lithium-Sulfur Batteries\, Advanced Materials\, 2019\, 31:1903955. https://doi.org/10.1002/adma.201903955\n\nStable Metallic 1T-WS2 Nanoribbons Intercalated with Ammonia Ions: The Correlation between Structure and Electrical/Optical Properties\, Advanced Materials\, 2015\, 27:4837-4844. https://doi.org/10.1002/adma.201502134\n\nAtomic Cobalt Covalently Engineered Interlayers for Superior Lithium-Ion Storage\, Advanced Materials\, 2018\, 30:1802 https://doi.org/10.1002/adma.201802525525.\n\nTracking Structural Self-Reconstruction and Identifying True Active Sites toward Cobalt Oxychloride Precatalyst of Oxygen Evolution Reaction\, Advanced Materials\, 2019\, 31:1805127. https://doi.org/10.1002/adma.201805127\n\nAtomic Sn4+ Decorated into Vanadium Carbide MXene Interlayers for Superior Lithium Storage\, Advanced Energy Materials\, 2018\, 9:1802977. https://doi.org/10.1002/aenm.201802977 \n\n\n 
URL:https://xrayabsorption.org/events/journalclub-li-song/
CATEGORIES:XAFS Journal Club
END:VEVENT
BEGIN:VEVENT
DTSTART;VALUE=DATE:20200716
DTEND;VALUE=DATE:20200717
DTSTAMP:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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:20260416T035412
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
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BEGIN:VEVENT
DTSTART;VALUE=DATE:20200525
DTEND;VALUE=DATE:20200526
DTSTAMP:20260416T035412
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
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BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200521T090000
DTEND;TZID=America/Los_Angeles:20200521T100000
DTSTAMP:20260416T035412
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
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BEGIN:VEVENT
DTSTART;TZID=America/Los_Angeles:20200518T090000
DTEND;TZID=America/Los_Angeles:20200518T100000
DTSTAMP:20260416T035412
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
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