LISA: The Italian CRG beamline for x-ray Absorption Spectroscopy at ESRF

LISA is the acronym of Linea Italiana per la Spettroscopia di Assorbimento di raggi X (Italian beamline for X-ray Absorption Spectroscopy) and is the upgrade of the former GILDA beamline installed on the BM08 bending magnet port of European Synchrotron Radiation Facility (ESRF). Within this contribution a full description of the project is provided

Comment on a recent sensitivity analysis of radial base function and multi-layer feed-forward neural network models - Response

Contains fulltext : 112420.pdf (publisher's version ) (Open Access

Archaeometric studies at the GILDA beamline at the European Synchrotron Radiation Facility

In the latest years archaeometry scientists have directed a growing interest to synchrotron radiation techniques. The Italian CRG beamline GILDA at the European Synchrotron Radiation Facility provides to the users the access to experimental techniques like X-ray absorption spectroscopy and diffraction that are of great potential usefulness in this field. Here we give a technical overview of the instrumentation available as well as some examples among the archaeometry studies presently in progress on the beamline

Synthesis of highly ordered L10 MPt alloys (M = Fe, Co, Ni) from crystalline salts: an in situ study of the pre-ordered precursor reduction strategy

The synthesis of highly ordered magnetic L1(0) alloys by means of the so-called pre-ordered precursor reduction (PPR) approach is deeply investigated by in situ X-ray absorption spectroscopy experiments. By following the chemical and structural evolution of the M(H2O)(6)PtCl6 (M = Fe, Co, Ni) precursor salts during hydrogen-assisted thermal reduction, it was possible to shed light on the key role of the crystalline initial compound whose intrinsic atomic order serves as a driving force to kinetically favor the formation of highly ordered FePt, CoPt and NiPt L1(0) alloys under milder conditions with respect to ordinary thermal treatments. The results confirm the potentiality of the PPR synthesis approach that can be suitably extended, by properly choosing the precursor salt, for the synthesis of other binary and ternary alloys where the chemical order represents a key property of the material, with a potential strong impact on several technological applications

Report on the activity of the GILDA-CRG beamline 2009-2013

Index Technical description of the beamline..................................................................................................3 Introduction ....................................................................................................................................3 Optics..............................................................................................................................................3 The XAS end station........................................................................................................................6 Standard data collection setup.....................................................................................................6 Surface XAS apparata.................................................................................................................8 Recent sample environment and Instrumentation developments................................................9 The x-ray diffraction (XRD) end-station.......................................................................................13 Beamline control...........................................................................................................................14 Administrative aspects........................................................................................................................16 Organisation..................................................................................................................................16 Beamline Staff Situation................................................................................................................17 Statistical data on Users and scientific production.............................................................................21 Future perspectives and plans for upgrade.........................................................................................25 Aim of the project.........................................................................................................................25 Design...........................................................................................................................................26 Timetable......................................................................................................................................31 Overview of the overall scientific activity.........................................................................................33 Selection of five publications........................................................................................................33 Highlights of the scientific activity................................................................................................34 Local order in semiconductors..................................................................................................34 Nanotechnology.......................................................................................................................44 Cements and porous systems....................................................................................................48 Chemistry.................................................................................................................................56 Earth Science............................................................................................................................61 Environment.............................................................................................................................67 Cultural Heritage.......................................................................................................................72 Health, medicine and life science .............................................................................................77 Acknowledgements...........................................................................................................................84 References.........................................................................................................................................85 Generic References.......................................................................................................................85 GILDA 2009-2013 Publications....................................................................................................8

Unveiling the atomic position of C in Mn5Ge3 Cx thin films

Heavily carbon-doped Mn5Ge3 is a unique compound for spintronics applications as it meets all the requirements for spin injection and detection in group-IV semiconductors. Despite the great improvement of the magnetic properties induced by C incorporation into Mn5Ge3 compounds, very little information is available on its structural properties and the genuine role played by C atoms. In this paper, we have used a combination of advanced techniques to extensively characterize the structural and magnetic properties of Mn5Ge3Cx films grown on Ge(111) by solid phase epitaxy as a function of C concentration. The increase of the Curie temperature induced by C doping up to 435 K is accompanied by a decrease of the out-of-plane c-lattice parameter. The Mn and C chemical environments and positions in the Mn5Ge3 lattice have been thoroughly investigated using x-ray absorption spectroscopy techniques (x-ray absorption near-edge structures and extended x-ray absorption fine structures) and scanning transmission electronic microscopy (STEM) combined to electron energy loss spectroscopy for the chemical analysis. The results have been systematically compared to a variety of structures that were identified as favorable in terms of formation energy by ab initio calculations. For x≤0.5, the C atoms are mainly located in the octahedral voids formed by Mn atoms, which is confirmed by simulations and seen for the first time in real space by STEM. However, the latter reveals an inhomogeneous C incorporation, which is qualitatively correlated to the broad magnetic transition temperature. A higher C concentration leads to the formation of manganese carbide clusters that we identified as Mn23C6. Interestingly, other types of defects, such as interstitial Ge atoms, vacancies of Mn, and their association into line defects have been detected. They take part in the strain relaxation process and are likely to be intimately related to the growth process. This paper provides a complete picture of the structure of Mn5Ge3Cx in thin films grown by solid phase epitaxy, which is essential for optimizing their magnetic properties

Chemical variability of artificial stone powders in relation to their health effects

The occurrence of highly severe silica-related diseases among the resin- and silica-based artificial stone workers was claimed, associated to an extremely short latency. High levels of exposure and intrinsic properties of AS are thought to modulate the development of silicosis and auto-immune diseases. This study compares parent materials and processed dusts, to shed light on changes of AS occurring in the manufacturing process, through an XRF, EPR and XAS investigation. We point out the extremely wide variability of the materials, the occurrence of chemical signatures impressed by the processing techniques, and the unprecedented generation of stable radicals associated to the lysis of the Si-O chemical bond inside the resin coated respirable crystalline silica. These results suggest that the AS processing in industrial stone workshops can create respirable dusts with peculiar physical and chemical properties, to be correlated to the observed clinical evidences