The Quasi-Liquid Layer on ice observed with NEXAFS

2021 ◽  
Author(s):  
Jérôme Gabathuler ◽  
Yanisha Manoharan ◽  
Huanyu Yang ◽  
Anthony Boucly ◽  
Luca Artiglia ◽  
...  
Keyword(s):  
Liquid Layer ◽  
Environmental Science ◽  
Paul Scherrer Institute ◽  
Comprehensive Treatment ◽  
Interfacial Region ◽  
Data Set ◽  
X Ray ◽  
Quasi Liquid Layer ◽  
Paul Scherrer ◽  
X Ray Absorption

<p><strong>The Quasi-Liquid Layer on ice observed with NEXAFS</strong></p><p><em>Gabathuler, Y. Manoharan, H. Yang, A. Boucly, A. Luca, M. Ammann, T. Bartels-Rausch</em></p><p>Paul Scherrer Institute, Villigen, Switzerland</p><p> </p><p> </p><p>As temperature approaches the melting point of ice from below, the hydrogen-bonding network at the air – ice interface evolves from a well-defined hexagonal structure towards more randomly spatialized interactions. The general agreement is that a Quasi-Liquid-Layer (QLL) exists at the surface of the ice, and reports on the thickness of this disordered interfacial layer range from 2 nm to 25 nm at 271 K, depending on the probing technique (atomic force microscopy (AFM), ellipsometry, optical reflectivity, sum-frequency generation (SFG)) [1]. These large differences partly arise from the fact that the different techniques are probing different properties of the interface, and the delicate calibration into the thickness of the QLL contributes greatly to the uncertainty.</p><p> </p><p>We investigate the QLL using Near Edge X-ray Absorption Fine Structure (NEXAFS) spectroscopy, as Bluhm and his group did in 2002 [2]. The technique probes Auger electrons emitted upon X-ray absorption, thus, NEXAFS becomes inherently sensitive to the upper few nm of the air-ice interfacial region. This work focuses on the probing depth associated with this method and proposes a comprehensive treatment of the data, to help resolve the discrepancy of current thickness data. The importance of the QLL’s thickness comes from its contribution to environmental science as a reservoir for chemical impurities and as a host of chemical reactions with an impact on atmospheric and cryospheric composition.</p><p> </p><p>We will present a first data set of NEXAFS from neat ice between – 40 °C and 0°C acquired at the ISS endstation at the Swiss Light Source of the Paul Scherrer Institute. Results including error bars will be compared to earlier studies. The preliminary analysis suggests that the interfacial disorder seems to be less pronounced than reported in many earlier studies, very much in agreement with recent SFG [3] and AFM data [4].</p><p> </p><p> </p><p> </p><p>Literature References:</p><p> </p><p> </p><p>Acknowledgment:</p><p>We thank A. Laso for technical help, SNF for funding (grant 178962)</p><p> </p>

scholarly journals Non-negative matrix analysis for effective feature extraction in X-ray spectromicroscopy

2014 ◽  
Vol 171 ◽  
pp. 357-371 ◽  
Author(s):  
Rachel Mak ◽  
Mirna Lerotic ◽  
Holger Fleckenstein ◽  
Stefan Vogt ◽  
Stefan M. Wild ◽  
...  
Keyword(s):  
Large Scale ◽  
Environmental Science ◽  
Matrix Analysis ◽  
Matrix Approximation ◽  
New Approach ◽  
X Ray ◽  
Rich Information ◽  
Preliminary Study ◽  
X Ray Absorption ◽  
Calculated Image

X-Ray absorption spectromicroscopy provides rich information on the chemical organization of materials down to the nanoscale. However, interpretation of this information in studies of “natural” materials such as biological or environmental science specimens can be complicated by the complex mixtures of spectroscopically complicated materials present. We describe here the shortcomings that sometimes arise in previously-employed approaches such as cluster analysis, and we present a new approach based on non-negative matrix approximation (NNMA) analysis with both sparseness and cluster-similarity regularizations. In a preliminary study of the large-scale biochemical organization of human spermatozoa, NNMA analysis delivers results that nicely show the major features of spermatozoa with no physically erroneous negative weightings or thicknesses in the calculated image.

Scanning Transmission X-ray Spectromicroscopy of Actinide Complexes

2008 ◽  
Vol 1104 ◽  
Author(s):  
David Shuh ◽  
Roy Copping ◽  
Tolek Tyliszczak ◽  
Ingrid Castro-Rodriguez ◽  
David K. Shuh
Keyword(s):  
Environmental Science ◽  
Light Element ◽  
Reference Spectrum ◽  
Donor Ligand ◽  
X Ray ◽  
Nitrogen Donor Ligand ◽  
Nitrogen Donor ◽  
Scanning Transmission ◽  
X Ray Absorption ◽  
Uranium Complex

AbstractThe fundamental characterization and understanding of 5f electron behavior in actinide complexes is imperative to provide an enhanced basis for the rational and accelerated development of improved processes relevant to nuclear energy. Soft x-ray absorption spectroscopy utilizing the scanning transmission x-ray microscope (STXM) at the Advanced Light Source-Molecular Environmental Science (ALS-MES) Beamline 11.0.2 has been used to probe the electronic characteristics of a nitrogen donor ligand 2,6-Bis(2-benzimidazyl)pyridine (BBP) and its resulting U(IV) complex. The nitrogen K- and carbon K-edges have been collected from both ligand and uranium complex, as well as the uranium 4d-edge from the complex. Upon complexation, the light element absorption spectra change markedly and the uranium spectra from the complex is compared to the reference spectrum obtained from U(IV)Cl4. The evolution of the spectral features are described and interpreted within a simple conceptual framework. Based on spectral evidence alone, the uranium is bound through the pyridine-like nitrogens and the oxidation state of the uranium is consistent with a U(IV) species.

scholarly journals Revisiting the Sodiation Mechanism of TiO2 via Operando X-ray Absorption Spectroscopy

2020 ◽  
Vol 10 (16) ◽  
pp. 5547
Author(s):  
Marcus Fehse ◽  
Aurélien Henry ◽  
Andrea Zitolo ◽  
Bruno Boury ◽  
Nicolas Louvain ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Local Structure ◽  
Maximum Amount ◽  
Data Set ◽  
Anatase Structure ◽  
X Ray ◽  
Tio2 Anatase ◽  
Meaningful Information ◽  
X Ray Absorption ◽  
Chemometric Tools

The sodiation mechanism of TiO2 anatase was thoroughly investigated via X-ray absorption spectroscopy under operando conditions. The data set was analysed via an innovative and smart approach based on chemometric tools that allows the unbiased and reliable extraction of the maximum amount of meaningful information. The resulting data analysis reveals that the electrochemical sodiation mechanism is mainly based on the reduction of Ti4+ to Ti3+, going along with the irreversible amorphisation of the pristine anatase structure. At least one semi-amorphous intermediate is formed during the first discharge, whose local structure resembles those obtained at the end of the charge.

scholarly journals Preparing for SwissFEL: Exploring the limits of time-resolved X-ray spectroscopy

2014 ◽  
Vol 70 (a1) ◽  
pp. C129-C129
Author(s):  
Chris Milne ◽  
Jakub Szlachetko ◽  
Tom Penfold ◽  
Majed Chergui ◽  
Rafael Abela
Keyword(s):  
Structural Changes ◽  
Probe Laser ◽  
Time Resolved ◽  
X Ray ◽  
Ligand Rebinding ◽  
Femtosecond Regime ◽  
Under Construction ◽  
Paul Scherrer ◽  
Pulse Energies ◽  
X Ray Absorption

Using x-ray absorption spectroscopy (XAS) and x-ray emission spectroscopy (XES) to probe laser-excited samples we can obtain excited-state structural and electronic dynamical information not available through other techniques.[1] One of the restrictions of most synchrotron-based implementations of this technique is the three-orders of magnitude mismatch between x-ray and laser repetition rates (MHz Vs. kHz). By using a laser capable of generating significant pulse energies at MHz repetition rates we can eliminate this discrepancy, thus greatly reducing measurement times and enhancing achievable signal-to-noise ratios.[2] Several examples that demonstrate the strength of this technique will be presented, including probing the electron relaxation in photoexcited TiO2 nanoparticles in solution and resolving the dynamical structural changes associated with ligand rebinding in the protein myoglobin under physiological conditions. The ability to extend these types of measurements into the femtosecond regime at Experimental Station A[3] at the SwissFEL hard X-ray free electron laser, which is under construction at the Paul Scherrer Institute (Villigen, Switzerland), will be discussed.

Actinide Science with a Soft X-ray Scanning Transmission X-ray Microscope (STXM)

2010 ◽  
Vol 1264 ◽  
Author(s):  
Per-Anders Glans ◽  
Geza Szigethy ◽  
Dustin Demoin ◽  
Tolek Tyliszczak ◽  
Jide Xu ◽  
...  
Keyword(s):  
Environmental Science ◽  
Materials Science ◽  
Light Element ◽  
Radioactive Materials ◽  
Basic Approach ◽  
X Ray ◽  
Actinide Chemistry ◽  
Scanning Transmission ◽  
Uranium Nitride ◽  
X Ray Absorption

AbstractSoft x-ray scanning transmission x-ray microscope (STXM) spectromicroscopy has been developed and employed to investigate several aspects of actinide chemistry and materials science at the Advanced Light Source Molecular Environmental Science (ALS-MES) Beamline 11.0.2 STXM end station. The basic approach and fundamentals of STXM experiments for radioactive materials systems is discussed. Representative results from STXM spectromicroscopy investigations of a mixed phase uranium nitride, single crystals of Eu(III)[TREN(Me-3,2-HOPO)]3 2H2O and hydrated Pu2(III)(C2O4)3(6H2O) 3H2O complexes are presented. The STXM images and soft x-ray absorption spectra illustrate the capabilities and utility of soft x-ray STXM for providing information about actinide materials, especially the light element constituents. Lastly, new and future opportunities for actinide science utilizing soft x-ray STXM are discussed in light of the planned upgrades for the STXM end stations at the ALS.

Difference Fourier Analysis of Glucose Embedded and Frozen Hydrated Purple Membrane

1982 ◽  
Vol 40 ◽  
pp. 74-75
Author(s):  
Jules S. Jaffe ◽  
Robert M. Glaeser
Keyword(s):  
Purple Membrane ◽  
Data Set ◽  
High Resolution Data ◽  
X Ray ◽  
X Ray Crystallography ◽  
Fourier Techniques ◽  
Versus Protein ◽  
The Difference ◽  
Difference Fourier ◽  
Ideal Method

Although difference Fourier techniques are standard in X-ray crystallography it has only been very recently that electron crystallographers have been able to take advantage of this method. We have combined a high resolution data set for frozen glucose embedded Purple Membrane (PM) with a data set collected from PM prepared in the frozen hydrated state in order to visualize any differences in structure due to the different methods of preparation. The increased contrast between protein-ice versus protein-glucose may prove to be an advantage of the frozen hydrated technique for visualizing those parts of bacteriorhodopsin that are embedded in glucose. In addition, surface groups of the protein may be disordered in glucose and ordered in the frozen state. The sensitivity of the difference Fourier technique to small changes in structure provides an ideal method for testing this hypothesis.

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