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81.
ESUO: The European Synchrotron and FEL User Organisation: Aims & Activities
Iztok Arčon, 2018, published scientific conference contribution abstract

Abstract: The European Synchrotron and free-electron laser (FEL) User Organisation (ESUO) established in 2010 [1] today represents about 30.000 users. We aim at representing the users from all European countries. Each country is represented within ESUO by one up to four national delegate(s), depending on the size of the user community in the respective country. ESUO’s main objectives are (i) to promote an integrated approach throughout Europe for the use of European synchrotron and FEL facilities, (ii) to enable all European scientists to make use of the existing European synchrotron and FEL research infrastructures, solely based on scientific merit of their submitted proposals for beamtime requests, and this independently from the financial situation of the user (country), (iii) to facilitate open transnational access to European light sources through programmes of the European Union, (iv) to disseminate information about scientific opportunities and funding mechanisms for access to synchrotron and FEL facilities, and (v) to be a discussion and acting partner regarding the coordination of the synchrotron and FEL user activities within Europe. In the past few years, ESUO has contributed to several joint activities in the frame of successfully completed European FP7 projects such as ELISA (March 2009 - August 2011) and CALIPSO (June 2012 - May 2015). Some past ESUO activities concern, amongst others:  the user representation in e.g. the CALIPSO and BioStruct-X European projects by ESUO delegates;  the contribution to the CALIPSOplus project application;  the dissemination of ESUO activities by means of e.g. poster presentations and talks delivered at international conferences, specialized user meetings/workshops, and;  several initiatives which have been attended to promote transnational access activities [3] and to favor the continuation of transnational user access to national facilities in Europe within the new European Framework Program Horizon 2020 [4]. Today, chance is given to ESUO to keep constructively acting for the users in the frame of joint networking activities being part of the HORIZON 2020 project CALIPSOplus [5] (May 2017 – April 2021, Grant Agreement No 730872) coordinated by Helmholtz-Zentrum Dresden-Rossendorf (HZDR). In the framework of CALIPSOplus, ESUO is contributing to project networking activities which are, amongst others, shown in the present contribution. With the aim to further prepare the future science at European synchrotron and FEL user facilities, ESUO is contributing to the League of European Accelerator-based Photon Sources (LEAPS) initiative [6].
Keywords: European synchrotron user organisation, Transnational access, FEL, CALIPSO
Published in RUNG: 01.10.2018; Views: 3378; Downloads: 0
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82.
Kako lahko z različnimi vrstami svetlobo opazujemo očem nevidni svet okoli nas
Iztok Arčon, unpublished invited conference lecture

Abstract: Svetloba nam v vsakdanjem žvljenju omogoča, da vidimo in spoznavamo svet okoli nas. Kako zelo je svetloba pomembna za naše življenje opazimo še posebej, če se za nekaj časa znajdemo v popolni temi. In vendar predstavlja vidna svetloba, ki jo lahko zaznajo naše oči, le droben delček v širokem spektru razlčnih vrst svetlobe, ki nam jih ponuja narava. V predavanju si bomo ogledali, kako lahko s svetlobo različnih valovnih dolžin, od infrardeče, preko vidne, ultravijolične in rentgenske svetlobe, opazujemo očem nevidni svet okoli nas. Spomnili se bomo tudi nekaj velikih znastvenih odkritji o svetlobi v zadnjih dvesto letih. Ta osnovna odkritja o lastnostih svetlobe so nam odprla pogled neposredno v svet atomov in danes omogočajo razvoj sodobnih merskih tehnologij na atomski skali. Brez njih si skoraj ne znamo večpredstavljati razvoja novih tehnološko zanimivih materialov in različnih nanotehnologij in različnih raziskav onesnaženja okolja na atomskem nivoju.
Keywords: rentgesnka svetloba, UV, IR, slikanje, mikroskopiranje, rentgenska absorpcijska spektroskopija
Published in RUNG: 01.10.2018; Views: 3385; Downloads: 0
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83.
REBULA - KRALJICA BRIŠKIH GRIČEV
Vanesa Klinec, 2018, undergraduate thesis

Abstract: Vitis vinifera L. cv 'Rebula' je najpomembnejša sorta za pridelavo vina v vinorodnem okolišu Goriška brda (tudi Brda). Je del bogate zgodovinske in kulturne dediščine ter velja za sinonim Brd. Ker postaja 'Rebula' zanimiva tudi izven meja Goriških brd, so se briški pridelovalci vina, skupaj s Konzorcijem Brda, odločili za zaščito vina sorte 'Rebula' z oznako PTP. Poleg tega se zadnje čase vedno bolj uveljavlja generična predstavitev sorte 'Rebula' pod skupnimi blagovnimi znamkami, ki so pomembne za povečanje prepoznavnosti tako sorte kot tudi teritorija pridelovanja. V diplomski nalogi smo opisali sorto 'Rebula'; značilnosti vinske trte in vina, njeno zgodovinsko pot ter predstavili pridelavo vina danes. Osredotočili smo se tudi na pomembnost te sorte za Goriška brda, v smislu promocije sorte in teritorija. Drugi del diplomske naloge zajema marketinško raziskavo in pregled situacije na vinskem trgu, pri čemer smo izvedli spletno anketiranje med potrošniki vina. Na podlagi teoretičnih osnov in rezultatov marketinške raziskave smo zasnovali marketinški načrt. Podani so tudi ukrepi in priporočila, ki so pomembni pri uspešni predstavitvi sorte 'Rebula' širši publiki.
Keywords: sorta 'Rebula', Goriška brda, geografska zaščita vina, blagovna znamka, promocija
Published in RUNG: 27.09.2018; Views: 4694; Downloads: 217
.pdf Full text (1,86 MB)

84.
Sulfur based batteries studied by in-operando S K-edge RIXS and XAS spectroscopy
Matjaž Kavčič, Ana Robba, Janez Bitenc, Alen Vižintin, Iztok Arčon, Matjaž Žitnik, Klemen Bučar, Robert Dominko, 2018, published scientific conference contribution abstract

Abstract: Sulfur based batteries are considered as very attractive energy storage devices. Sulfur is one of the most abundant elements in the earth, it is electrochemically active material which can accept up to two electrons per atom. In combination with alkali metals, sulfur forms electrochemical couples with much higher theoretical energy density compared to Li-ion batteries commonly available today. At the moment, the electrochemical couple with Li is most extensively studied. While the main principle of operation is known the relevant operation mechanism(s) is not completely clear. Even more promising is the electrochemical couple with Mg providing almost twofold higher volumetric energy density due to its ability to provide two electrons during oxidation. However, Mg-S batteries are still in the very early stage of research and development and the complex mechanism of sulfur conversion has been less extensively studied. In order to improve the understanding of sulfur electrochemical conversion and its interactions within electrode, we need to apply new experimental approaches capable to provide precise information about local environment of S in the cathode during battery operation. In our work, resonant inelastic X-ray scattering (RIXS) and XAS measurements at the sulfur K-edge performed in operando mode were used to study the lithium-polysulfide formation during the discharge process. Measurements were performed at ID26 beamline of the ESRF synchrotron using tender X-ray emission spectrometer [1]. Resonant excitation condition enhanced the sensitivity for the lithium−polysulfide detection. On the other hand, the sulfate signal from the electrolyte was heavily suppressed and the self-absorption effects minimized due to fixed excitation energy. This experimental methodology was used to provide quantitative analysis of sulfur compounds in the cathode of a Li−S battery cell during the discharge process [2]. The high-voltage plateau in the discharge curve was characterized by a rapid conversion of solid sulfur into liquid phase Li polysulfides reaching its maximum at the end of this plateau. At this point the starting point for the precipitation of the Li2S from the liquid polysulfide phase was observed. The same approach has been used also for the Mg-S battery revealing similar mechanism as in case of Li-S battery [3]. The electrochemical conversion of sulfur with magnesium proceeds through two well-defined plateaus, which correspond to the equilibrium between sulfur and Mg polysulfides (high-voltage plateau) and polysulfides and MgS (low-voltage plateau).
Keywords: Mg-Sulphur batteries, XANES, RIXS
Published in RUNG: 13.09.2018; Views: 4385; Downloads: 0
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85.
K-edge absorption spectra of isoelectronic gaseous hydrides: a combination of atomic and molecular channels
Robert Hauko, Jana Padežnik Gomilšek, Alojz Kodre, Iztok Arčon, Giuliana Aquilanti, 2018, published scientific conference contribution abstract

Abstract: The fine detail in the x-ray absorption spectra in the energy region of absorption edges provides the insight into the mechanism of inner-shell photoexcitation: in particular in spectra of free atoms or simple molecules, the simplest being gaseous hydrides [1-2]. Measured K edge absorption spectra of hydrides of 3p (PH3, H2S in HCl) and 4p (GeH4, AsH3, H2Se, HBr) elements, and published data of 2p hydrides (CH4, NH3, H2O, HF) as well as SiH4 [3-6] and the noble gases at the end of the isoelectronic series (Ne, Ar, Kr) are compared to the respective calculated spectra, obtained by atomic HF86, GRASP codes [7] and molecular DFT (Density functional theory) ORCA code [8]. For a clearer view of intraatomic processes, the weak and simple structural (XAFS) signal of the molecule is removed from the spectra. Among the spectral features below the continuum limit, those with the lowest energy belong to the transition of the core electron to the lowermost free orbitals with the molecular character. They are, as a rule, wider than the transitions to the higher orbitals with prevailing atomic character. The theoretical description with DFT code without specific adaptations is sufficient for a qualitative picture of the pre-edge structure. The fine structure immediately above the K edge stems from the coexcitation of valence electrons. We have proved that the coexcitations can be explained as a two-step process: the inner-shell photoeffect followed by the shake-up of a valence electron predominantly to a free atomic orbital. This process is markedly different from coexcitations of more tightly bound electrons [9]. In the collection of consecutive and homologous data, analyzed by a common procedure, the reaction channels can be identified with better precision and reliability than in analysis of individual spectra. Our analysis showed that the energies and probabilities of single-electron transitions into the molecular orbitals are strongly affected by the symmetry of the molecule, essentially in the same way in 3p and 4p homologues, but not in 2p homologues with a stronger influence of the core charge. In transitions to atomic orbitals the influence of the molecular field is negligible.
Keywords: hidridi, rentgenska spektroskopija, XAFS
Published in RUNG: 12.09.2018; Views: 3788; Downloads: 0
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86.
In-situ XAS analysis of nanoshaped CuO/CeO2 catalysts used for N2O decomposition
Iztok Arčon, Maxim Zabilsky, Petar Djinović, Albin Pintar, 2018, published scientific conference contribution abstract

Abstract: The goal of this research is to establish the working state and correlations between atomic structure and catalytic activity of nanoshaped CuO/CeO2 catalysts used in N2O decomposition reaction. The catalysts contained CuO nanoclusters dispersed over different CeO2 morphologies: nano-rods and nano-cubes. N2O is a side product of nitric and adipic acid production and a very potent greenhouse gas that is formed in amounts estimated at about 400 Mt/a of CO2 equivalent. Consequently, the development of robust, active and selective catalysts for N2O decomposition is of a great environmental and economical interest. CeO2-based materials promoted by CuO represent a new class of catalysts that exhibit considerable activity in N2O decomposition reaction between 300 and 500 °C [1-3], and are significantly cheaper and more efficient than Pt, Pd or Rh based catalysts. In order to maximize the efficiency of the catalyst, the active site in this reaction needs to be identified and the mechanism clarified. In-situ Cu K-edge and Ce L3-edge XANES and EXAFS analysis was done on a set of CuO/CeO2 catalysts with different ceria morphology (nano-cubes, nano-rods) and Cu loadings between 2 to 8 wt. %, during N2O decomposition reaction, under controlled reaction conditions at 400 °C. The XAS spectra were measured in-situ, in a tubular reactor, filled with protective He atmosphere at 1 bar, first at RT, then during heating, and at final temperature of 400 °C, during catalytic reaction, when the catalyst was exposed to a small amount (0.2 vol%) of N2O mixed with He. The Cu K-edge and Ce L3-edge XANES and EXAFS analysis reveals changes in valence and local structure of Cu and Ce in the CuO/CeO2 catalysts. In the initial state (in He at RT), copper is present in the form of CuO nanoparticles attached to the CeO2 surface. After heating in He to 400 °C, partial (10%) reduction of Ce [Ce(IV)→Ce(III)] is detected, significant part of Cu(II) is reduced to Cu(I) and Cu(0) species, and direct Cu-Cu bonds are formed. During catalytic N2O decomposition at 400°C, all Ce(III) is oxidized back to Ce(VI), and a major part of Cu is oxidized back to Cu(II), with about 5% of Cu(I) remaining in equilibrium state. Observed structural and valence changes of copper strongly depend on its loading and CeO2 morphology. With systematic In-situ XAS analysis of different nanoshaped CuO/CeO2 catalysts, we identified the structural characteristics and changes of Cu and Ce phases during catalytic N2O decomposition reaction, which could lead to identification of the active catalytic site during the reaction and further improve the performance of these promising catalytic materials.
Keywords: EXAFS, CuO/CeO2 catalyst, N2O decomposition
Published in RUNG: 12.09.2018; Views: 3678; Downloads: 0
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87.
XAS studies of Sn modified TiO2 coatings
Ksenija Maver, Iztok Arčon, Urška Lavrenčič Štangar, 2018, published scientific conference contribution abstract

Abstract: Coatings based on TiO2 are extensively investigated material for the preparation of surfaces which are referred as self-cleaning. Under solar illumination these coatings catalyze pollutants degradation and enhance their removal from the surface due to photoinduced superhydrophilicity [1]. There are two main drawbacks of using pure TiO2 (anatase) as a photocatalyst; i) its band gap lies in the UVA region so it can exploit only a part of the sunlight spectrum, and ii) it has a high degree of recombination between photo generated electrons and holes on the surface. There are various strategies to improve the photocatalytic efficiency of TiO2, one of them is the modification with transition metals. Based on our previous experiences with sol-gel synthesis of low-temperature TiO2 thin films [2], we prepared a series of Sn modified TiO2 photocatalysts. As a starting material only organic (Ti and Sn alkoxide) precursors were used. The loadings of Sn cations were varied in the range of 0.05 to 20 mol.%. The coatings, deposited on glass substrates by dip-coating technique, were dried at 150 oC. In addition, another set of photocatalyst coatings was prepared by further calcination at 500 °C in air. The comparison of photocatalytic activities of Sn modified TiO2 to unmodified TiO2 showed that Sn loadings in the range of 1-10 mol.% improved photocatalytic activity up to 8 times. At lower loadings of Sn, the photocatalytic activity was improved only by 30 %. After the coatings are calcined, their photocatalytic activity was significantly reduced. The objective of the research was to examine the mechanism responsible for photocatalytic properties of Sn modified TiO2 and to to clarify the role of Sn cations in the TiO2 photocatalytic process. For this purpose, Sn and Ti K-edge XANES and EXAFS analysis was used to precisely determine the local structure and the site of incorporation of Sn cations on titania nanoparticles in the coatings. We examined the hypothesis that the solid-solid interface was a crucial structural feature that facilitates charge separation and enhances photocatalytic efficiency of titania.
Keywords: Sn, EXAFS, TiO2 fotokatalizator
Published in RUNG: 12.09.2018; Views: 3355; Downloads: 0
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88.
89.
K-edge absorption spectra of gaseous hydrides
Alojz Kodre, Robert Hauko, Jana Padežnik Gomilšek, Iztok Arčon, Giuliana Aquilanti, 2018, published scientific conference contribution abstract

Abstract: X-ray absorption spectra in the energy region of absorption edges reveal fine details of the mechanism of inner-shell photoexcitation: in particular in spectra of free atoms or simple molecules, the simplest being gaseous hydrides [1-2]. In a collection of data from consecutive and homologous elements, analyzed by a common procedure, the reaction channels can be identified with better precision and reliability than in analysis of individual spectra. Absorption spectra of the hydrides of 3p elements (PH3, H2S in HCl) were measured at the XAFS beamline of the Elettra synchrotron in Trieste: a new type of adjustable absorption cell for measurement of noxious gases at room temperature and at low photon energies was developed for the purpose. For the analysis, data from an earlier experiment on 4p hydrides (GeH4, AsH3, H2Se, HBr), and published data of 2p hydrides (CH4, NH3, H2O, HF) [3-4] as well as SiH4 and the noble gases concluding the isoelectronic series (Ne, Ar, Kr) were adopted. The spectra are compared to respective calculated spectra, obtained by atomic HF86, GRASP codes and molecular DFT (Density functional theory) ORCA code [5]. Our analysis of the pre-edge structures showed that the energies and probabilities of singleelectron transitions into the lowermost orbitals with the molecular character were strongly affected by the symmetry of the molecule, essentially in the same way in 3p and 4p homologues, but not in 2p homologues with a stronger influence of the core charge. In transitions to higher orbitals with prevailing atomic character the influence of the molecular field is negligible. The fine structure immediately above the K edge stems from the coexcitation of valence electrons. These coexcitations can be explained as a two-step process: the inner-shell photoeffect followed by the shake-up of a valence electron predominantly to a free atomic orbital. The process is markedly different from coexcitations of more tightly bound electrons [3]. The results of relative shake-up probabilities can be compared to results of emission spectroscopies, the probabilities of double excitation to bound states show a correlation with the dissociation probability of the molecule.
Keywords: večelektronske vzbuditve, hidridi, rentgenska absorpcijska spektroskopija
Published in RUNG: 12.09.2018; Views: 4061; Downloads: 0
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90.
Nickel coordination in hyperaccumulator plants studied by XANES and EXAFS
Jana Padežnik Gomilšek, Katarina Vogel-Mikuš, Alojz Kodre, Iztok Arčon, 2018, published scientific conference contribution abstract

Keywords: nickel, hyperaccumulator plants
Published in RUNG: 12.09.2018; Views: 3024; Downloads: 0
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