scholarly journals A primordial 15N-depleted organic component detected within the carbonaceous chondrite Maribo

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Christian Vollmer ◽  
Jan Leitner ◽  
Demie Kepaptsoglou ◽  
Quentin M. Ramasse ◽  
Ashley J. King ◽  
...  
Keyword(s):  
Organic Matter ◽  
Interstellar Medium ◽  
Structural Information ◽  
Carbonaceous Chondrite ◽  
Carbonaceous Chondrites ◽  
Local Interstellar Medium ◽  
Edge Structure ◽  
Electron Energy Loss ◽  
Cm Chondrite ◽  
X Ray Absorption

AbstractWe report on the detection of primordial organic matter within the carbonaceous chondrite Maribo that is distinct from the majority of organics found in extraterrestrial samples. We have applied high-spatial resolution techniques to obtain C-N isotopic compositions, chemical, and structural information of this material. The organic matter is depleted in 15N relative to the terrestrial value at around δ15N ~ -200‰, close to compositions in the local interstellar medium. Morphological investigations by electron microscopy revealed that the material consists of µm- to sub-µm-sized diffuse particles dispersed within the meteorite matrix. Electron energy loss and synchrotron X-ray absorption near-edge structure spectroscopies show that the carbon functional chemistry is dominated by aromatic and C=O bonding environments similar to primordial organics from other carbonaceous chondrites. The nitrogen functional chemistry is characterized by C-N double and triple bonding environments distinct from what is usually found in 15N-enriched organics from aqueously altered carbonaceous chondrites. Our investigations demonstrate that Maribo represents one of the least altered CM chondrite breccias found to date and contains primordial organic matter, probably originating in the interstellar medium.

scholarly journals Simultaneous two-color X-ray absorption spectroscopy using Laue crystals at an inverse-compton scattering X-ray facility

2021 ◽  
Vol 28 (6) ◽  
Author(s):  
Juanjuan Huang ◽  
Benedikt Günther ◽  
Klaus Achterhold ◽  
Martin Dierolf ◽  
Franz Pfeiffer
Keyword(s):  
Compton Scattering ◽  
Absorption Spectroscopy ◽  
Bimetallic Catalyst ◽  
Structural Information ◽  
Synergistic Effects ◽  
Edge Structure ◽  
X Ray ◽  
Inverse Compton Scattering ◽  
Inverse Compton ◽  
X Ray Absorption

X-ray absorption spectroscopy (XAS) is an element-selective technique that provides electronic and structural information of materials and reveals the essential mechanisms of the reactions involved. However, the technique is typically conducted at synchrotrons and usually only probes one element at a time. In this paper, a simultaneous two-color XAS setup at a laboratory-scale synchrotron facility is proposed based on inverse Compton scattering (ICS) at the Munich Compact Light Source (MuCLS), which is based on inverse Compton scattering (ICS). The setup utilizes two silicon crystals in a Laue geometry. A proof-of-principle experiment is presented where both silver (Ag) and palladium (Pd) K-edge X-ray absorption near-edge structure spectra were simultaneously measured. The simplicity of the setup facilitates its migration to other ICS facilities or maybe to other X-ray sources (e.g. a bending-magnet beamline). Such a setup has the potential to study reaction mechanisms and synergistic effects of chemical systems containing multiple elements of interest, such as a bimetallic catalyst system.

Multiple scattering calculations at the oxygen K-edge for SiO2

1995 ◽  
Vol 53 ◽  
pp. 602-603
Author(s):  
DJ Wallis ◽  
R Brydson ◽  
PH Gaskell
Keyword(s):  
Multiple Scattering ◽  
Structural Information ◽  
Core Loss ◽  
Calculated Data ◽  
Real Space ◽  
Edge Structure ◽  
Exchange Correlation ◽  
Valence Electrons ◽  
Electron Energy Loss ◽  
Atom Energy

Electron Energy Loss Spectroscopy (EELS) in the STEM is potentially a very powerful technique for studying the structure of materials. The Near Edge Structure (NES) in core loss edges carries information about triplet, and higher order correlation functions and under certain conditions is sensitive to long range atomic correlations. However, since the NES contains strong contributions due to multiple elastic scattering, a simple interpretation in terms of atomic structure is not possible. It is therefore necessary to perform some form of modeling to obtain structural information. One approach to modeling NES is Multiple Scattering (MS) theory.MS calculations have been performed to model the O K-edge ELNES for the α-quartz phase of SiO2 The calculations use a real-space atomic cluster and model the atomic potentials using the Muffin Tin approximation. Effects of the core hole produced upon excitation were accounted for using the (Z+1)* approximation for the excited atom. Energy scales of the calculated data have also been compressed to correct for the energy dependence of the exchange correlation between the photoelectron and the valence electrons which is not accounted for in the calculation.

The use of XANES and ELNES for the Characterisation of Stabilised Zirconia

2001 ◽  
Vol 699 ◽  
Author(s):  
David W. McComb ◽  
Sergei Ostanin ◽  
Dimitris Vlachos ◽  
Alan J. Craven ◽  
Michael W. Finnis ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Full Potential ◽  
Data Simulation ◽  
Edge Structure ◽  
Materials Analysis ◽  
X Ray ◽  
Lmto Method ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Atomic Coordinates

AbstractThe electron energy-loss near-edge structure (ELNES) and x-ray absorption near-edge structure (XANES) at the oxygen K-edge has been investigated in a range of yttria-stabilised zirconia (YSZ) materials. Analysis of near-edge structure reveals that both the crystallographic phase and the metal fraction of yttrium present can be determined directly from the oxygen K-edge data. Simulation of the ELNES/XANES was achieved using a pseudopotential based method to obtain the relaxed atomic coordinates combined with full-potential LMTO method to calculate the electronic structure.

Spatially Resolved Local Atomic Structure from Exelfs

1994 ◽  
Vol 332 ◽  
Author(s):  
E. A. Stern ◽  
M. Qian ◽  
M. Sarikaya
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Structural Information ◽  
Spectroscopic Techniques ◽  
Complex Materials ◽  
Spatially Resolved ◽  
Transmission Electron ◽  
Electron Energy Loss ◽  
X Ray Absorption ◽  
Potential Use

ABSTRACTEXELFS, extended energy loss fine structure, is one of the spectroscopic techniques provided by electron energy loss spectrometer in the transmission electron microscope. Here, EXELFS is described for its potential use for determining nanoscale physical properties of complex materials. It is demonstrated that EXELFS analysis, like EXAFS, extended X-ray absorption fine structure in bulk materials, provides short-range structural information such as atomic nearest-neighbors and their distances in amorphous an crystalline samples. Some of the problems that hindered the development and wide use of EXELFS were discussed and their solutions are presented. Further solutions and future prospects are discussed.

scholarly journals Core-hole effects on theoretical electron-energy-loss near-edge structure and near-edge x-ray absorption fine structure of MgO

2000 ◽  
Vol 61 (3) ◽  
pp. 2180-2187 ◽  
Author(s):  
Teruyasu Mizoguchi ◽  
Isao Tanaka ◽  
Masato Yoshiya ◽  
Fumiyasu Oba ◽  
Kazuyoshi Ogasawara ◽  
...  
Keyword(s):  
Fine Structure ◽  
Energy Loss ◽  
Electron Energy ◽  
Core Hole ◽  
Edge Structure ◽  
X Ray ◽  
Absorption Fine ◽  
Electron Energy Loss ◽  
X Ray Absorption

Energy-filtered imaging of constituent phases in polymer blends

1996 ◽  
Vol 54 ◽  
pp. 164-165
Author(s):  
E. L. Hall ◽  
G. A. Hutchins
Keyword(s):  
Spatial Resolution ◽  
Structural Damage ◽  
Chemical Nature ◽  
Phase Distribution ◽  
Core Loss ◽  
Edge Structure ◽  
X Ray ◽  
Engineering Plastics ◽  
Electron Energy Loss ◽  
X Ray Absorption

Many engineering plastics consist of complex blends of chemically-distinct constituent polymers and other additives. These components are added in order to achieve desired performance in a variety of properties, including mechanical behavior, processability, color, fire retardency, and others. The distribution of the components, as well as the nature of the interfaces between constituents, are critically important to the performance of the engineering plastic. For many years, TEM has been the key tool in determining phase distribution. However, TEM studies are often limited by the need to stain the various constituents in order to achieve contrast, and also by the inability of TEM methods to unambiguously identify the chemical nature of the various constituents in the image. In the recent past, both electron energy loss spectroscopy (EELS) in the TEM and x-ray absorption near-edge spectroscopy (XANES) using synchrotron sources have demonstrated the ability to differentiate constituents based on characteristic carbon core loss edge structure. The EELS technique has the benefit of high spatial resolution, while the XANES method causes much less structural damage and mass loss. The advent of imaging energy filters has led to a third method for phase delineation for chemically distinct components, which combines the spatial resolution of EELS with the imaging capabilities of XANES.

Extraction of local coordination structure in a low-concentration uranyl system by XANES

2016 ◽  
Vol 23 (3) ◽  
pp. 758-768 ◽  
Author(s):  
Linjuan Zhang ◽  
Jing Zhou ◽  
Jianyong Zhang ◽  
Jing Su ◽  
Shuo Zhang ◽  
...  
Keyword(s):  
Structural Information ◽  
Chemical Properties ◽  
Edge Structure ◽  
X Ray ◽  
Low Concentration ◽  
Simplified Approach ◽  
Bond Lengths ◽  
Uranyl Carbonate ◽  
X Ray Absorption ◽  
Xanes Analysis

Obtaining structural information of uranyl species at an atomic/molecular scale is a critical step to control and predict their physical and chemical properties. To obtain such information, experimental and theoreticalL3-edge X-ray absorption near-edge structure (XANES) spectra of uranium were studied systematically for uranyl complexes. It was demonstrated that the bond lengths (R) in the uranyl species and relative energy positions (ΔE) of the XANES were determined as follows: ΔE1= 168.3/R(U—Oax)2− 38.5 (for the axial plane) and ΔE2= 428.4/R(U—Oeq)2− 37.1 (for the equatorial plane). These formulae could be used to directly extract the distances between the uranium absorber and oxygen ligand atoms in the axial and equatorial planes of uranyl ions based on the UL3-edge XANES experimental data. In addition, the relative weights were estimated for each configuration derived from the water molecule and nitrate ligand based on the obtained average equatorial coordination bond lengths in a series of uranyl nitrate complexes with progressively varied nitrate concentrations. Results obtained from XANES analysis were identical to that from extended X-ray absorption fine-structure (EXAFS) analysis. XANES analysis is applicable to ubiquitous uranyl–ligand complexes, such as the uranyl–carbonate complex. Most importantly, the XANES research method could be extended to low-concentration uranyl systems, as indicated by the results of the uranyl–amidoximate complex (∼40 p.p.m. uranium). Quantitative XANES analysis, a reliable and straightforward method, provides a simplified approach applied to the structural chemistry of actinides.

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