| 1. |
- Abid, Abdul Rahman, et al.
(författare)
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Forming Bonds While Breaking Old Ones : Isomer-Dependent Formation of H3O+ from Aminobenzoic Acid During X-ray-Induced Fragmentation
- 2023
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Ingår i: Journal of Physical Chemistry A. - : American Chemical Society (ACS). - 1089-5639 .- 1520-5215. ; 127:6, s. 1395-1401
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Tidskriftsartikel (refereegranskat)abstract
- Intramolecular hydrogen transfer, a reaction where donor and acceptor sites of a hydrogen atom are part of the same molecule, is a ubiquitous reaction in biochemistry and organic synthesis. In this work, we report hydronium ion (H3O+) production from aminobenzoic acid (ABA) after core-level ionization with soft X-ray synchrotron radiation. The formation of H3O+ during the fragmentation requires that at least two hydrogen atoms migrate to one of the oxygen atoms within the molecule. The comparison of two structural isomers, ortho- and meta-ABA, revealed that the production of H3O+ depends strongly on the structure of the molecule, the ortho-isomer being much more prone to produce H3O+. The isomer-dependency suggests that the amine group acts as a donor in the hydrogen transfer process. In the case of ortho-ABA, detailed H3O+ production pathways were investigated using photoelectron-photoion-photoion coincidence (PEPIPICO) spectroscopy. It was found that H3O+ can result from a direct two-body dissociation but also from sequential fragmentation processes.
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| 2. |
- Abid, Abdul Rahman, et al.
(författare)
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The effect of relative humidity on CaCl2 nanoparticles studied by soft X-ray absorption spectroscopy
- 2021
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Ingår i: RSC Advances. - : Royal Society of Chemistry. - 2046-2069. ; 11:4, s. 2103-2111
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Tidskriftsartikel (refereegranskat)abstract
- Ca- and Cl-containing nanoparticles are common in atmosphere, originating for example from desert dust and sea water. The properties and effects on atmospheric processes of these aerosol particles depend onthe relative humidity (RH) as they are often both hygroscopic and deliquescent. We present here a study of surface structure of free-flying CaCl2 nanoparticles (CaCl2-NPs) in the 100 nm size regime prepared at different humidity levels (RH: 11–85%). We also created mixed nanoparticles by aerosolizing a solution ofCaCl2 and phenylalanine (Phe), which is a hydrophobic amino acid present in atmosphere. Information of hydration state of CaCl2-NPs and production of mixed CaCl2 + Phe nanoparticles was obtained using soft X-ray absorption spectroscopy (XAS) at Ca 2p, Cl 2p, C 1s, and O 1s edges. We also report Ca 2p andCl 2p X-ray absorption spectra of an aqueous CaCl2 solution. The O 1s X-ray absorption spectra measured from hydrated CaCl2-NPs resemble liquid-like water spectrum, which is heavily influenced by the presence of ions. Core level spectra of Ca2+ and Cl- ions do not show a clear dependence of % RH, indicating that the first coordination shell remains similar in all measured hydrated CaCl2-NPs, but they differ from aqueous solution and solid CaCl2.
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| 3. |
- Boudjemia, Nacer, et al.
(författare)
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Deep core photoionization of iodine in CH3I and CF3I molecules : how deep down does the chemical shift reach?
- 2019
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Ingår i: Physical Chemistry, Chemical Physics - PCCP. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 21:10, s. 5448-5454
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Tidskriftsartikel (refereegranskat)abstract
- Hard X-ray electron spectroscopic study of iodine 1s and 2s photoionization of iodomethane (CH3I) and trifluoroiodomethane (CF3I) molecules is presented. The experiment was carried out at the SPring-8 synchrotron radiation facility in Japan. The results are analyzed with the aid of relativistic molecular and atomic calculations. It is shown that charge redistribution within the molecule is experimentally observable even for very deep levels and is a function of the number of electron vacancies. We also show that the analysis of Auger spectra subsequent to hard X-ray photoionization can be used to provide insight into charge distribution in molecules and highlight the necessity of quantum electrodynamics corrections in the prediction of core shell binding energies in molecules that contain heavy atoms.
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| 4. |
- Cao, Wei, et al.
(författare)
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X-ray photoemission electron microscope determination of origins of room temperature ferromagnetism and photoluminescence in high co-content coxzn1-xo films.
- 2014
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Ingår i: Surface Review and Letters. - 0218-625X. ; 21:4
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Tidskriftsartikel (refereegranskat)abstract
- In this paper, we reported on the X-ray photoemission electron microscope (XPEEM) determination of magnetic and luminescence origins for two CoxZn1-xO films. The cobalt fraction x of radio frequency co-sputtered samples were 0.86(2) and 0.92(2), respectively. Films were ferromagnetic and semiconductive. Unique narrow green color lines beside the ZnO intrinsic emissions were found with a decay time in microsecond range at room temperature. Origins of magnetic and luminescence properties were determined with XPEEM. The X-ray absorption near edge structure at the CoL3-edge denoted that Co was partially oxidized, and phase-contrast images together with chemical composition identification further proved that Co and CoO co-existed in the samples. The ferromagnetism was attributed to ferromagnetism of Co clusters partially canceled by the antiferromagnetism of its oxide, and the photoluminescence to bound exciton in ZnO nanoclusters and defect related centers of ZnO nanoclusters in a Co-rich matrix. Present results show possibilities for adjusting magnetic and luminescence properties of Co-ZnO compounds by changing the cobalt concentration.
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| 5. |
- Chernenk, Kirill, et al.
(författare)
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Performance and characterization of the FinEstBeAMS beamline at the MAX IV Laboratory
- 2021
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Ingår i: Journal of Synchrotron Radiation. - 0909-0495. ; 28, s. 1620-1630
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Tidskriftsartikel (refereegranskat)abstract
- FinEstBeAMS (Finnish-Estonian Beamline for Atmospheric and Materials Sciences) is a multidisciplinary beamline constructed at the 1.5 GeV storage ring of the MAX IV synchrotron facility in Lund, Sweden. The beamline covers an extremely wide photon energy range, 4.5-1300 eV, by utilizing a single elliptically polarizing undulator as a radiation source and a single grazing-incidence plane grating monochromator to disperse the radiation. At photon energies below 70 eV the beamline operation relies on the use of optical and thin-film filters to remove higher-order components from the monochromated radiation. This paper discusses the performance of the beamline, examining such characteristics as the quality of the gratings, photon energy calibration, photon energy resolution, available photon flux, polarization quality and focal spot size.
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| 6. |
- Ghosalya, Manoj Kumar, et al.
(författare)
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Solar light driven atomic and electronic transformations in a plasmonic Ni@NiO/NiCO3 photocatalyst revealed by ambient pressure X-ray photoelectron spectroscopy
- 2024
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Ingår i: Catalysis Science and Technology. - 2044-4753. ; 14:11, s. 3029-3040
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Tidskriftsartikel (refereegranskat)abstract
- This work employs ambient pressure X-ray photoelectron spectroscopy (APXPS) to delve into the atomic and electronic transformations of a core-shell Ni@NiO/NiCO3 photocatalyst - a model system for visible light active plasmonic photocatalysts used in water splitting for hydrogen production. This catalyst exhibits reversible structural and electronic changes in response to water vapor and solar simulator light. In this study, APXPS spectra were obtained under a 1 millibar water vapor pressure, employing a solar simulator with an AM 1.5 filter to measure spectral data under visible light illumination. The in situ APXPS spectra indicate that the metallic Ni core absorbs the light, exciting plasmons, and creates hot electrons that are subsequently utilized through hot electron injection in the hydrogen evolution reaction (HER) by NiCO3. Additionally, the data show that NiO undergoes reversible oxidation to NiOOH in the presence of water vapor and light. The present work also investigates the contribution of carbonate and its involvement in the photocatalytic reaction mechanism, shedding light on this seldom-explored aspect of photocatalysis. The APXPS results highlight the photochemical reduction of carbonates into -COOH, contributing to the deactivation of the photocatalyst. This work demonstrates the APXPS efficacy in examining photochemical reactions, charge transfer dynamics and intermediates in potential photocatalysts under near realistic conditions.
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| 7. |
- Hautala, Lauri, et al.
(författare)
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Probing RbBr solvation in freestanding sub-2 nm water clusters
- 2017
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9076 .- 1463-9084. ; 19:36, s. 25158-25167
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Tidskriftsartikel (refereegranskat)abstract
- Concentration dependent solvation of RbBr in freestanding sub-2 nm water clusters was studied using core level photoelectron spectroscopy with synchrotron radiation. Spectral features recorded from dilute to saturated clusters indicate that either solvent shared or contact ion pairs are present in increasing amount when the concentration exceeds 2 mol kg-1. For comparison, spectra from anhydrous RbBr clusters are also presented.
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| 8. |
- Hautala, Lauri, et al.
(författare)
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Surface site coordination dependent responses resolved in free clusters: applications for neutral sub-nanometer cluster studies
- 2015
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Ingår i: Physical Chemistry Chemical Physics. - : Royal Society of Chemistry (RSC). - 1463-9084 .- 1463-9076. ; 17:10, s. 7012-7022
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Tidskriftsartikel (refereegranskat)abstract
- In this paper we demonstrate how surface site specific experimental information can be obtained from free low nanometer scale clusters using photoelectron spectroscopy utilising synchrotron radiation. In addition, we show how it can be used to gain insight into the geometry and surface structure of the clusters. The present experiments were conducted on alkali metal halides, RbCl and CsCl, which were chosen as advantageous test cases due to their simple electronic and geometric structures. These heavy alkali metal salts provide additional clarity since the surface and bulk responses can be separated, which is not the case for clusters of lighter alkali metal salts. Computational chemical shift calculations and simple alkali halide cluster size modelling were used to interpret the experimental results.
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| 9. |
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| 10. |
- Huttula, Marko, et al.
(författare)
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Size-varied photoelectron spectroscopy of metal clusters using the Exchange Metal Cluster Source
- 2010
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Ingår i: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 181:2-3, s. 145-149
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Tidskriftsartikel (refereegranskat)abstract
- The recently developed Exchange Metal Cluster Source (EXMEC) is described. The source is designed for electron-spectroscopic studies of neutral metal clusters. Preliminary results on the rubidium and tin clusters using synchrotron radiation excited photoelectron spectroscopy show the capability for cluster production in the size regime of few tens to few hundred of atoms per cluster. A wide range of metal evaporation temperatures is covered applying resistive and induction heating methods. (C) 2010 Elsevier B.V. All rights reserved.
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