SwePub - search: WFRF:(Urpelainen Samuli)

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1.	Aksela, S., et al. (author) Accurate free atom-solid binding energy shifts for Au and Ag 2012 In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 185:8-9, s. 273-277 Journal article (peer-reviewed)abstract Binding energy shifts between atomic and solid states have been observed with improved accuracy for All 4f and Ag 3d core levels applying a simultaneous measurement method. Also the 3d photoelectron spectrum and binding energies of free Ag atoms have been observed for the first time. New values determined as free atom to bulk solid shifts deviate considerably from previous estimate for Au but agree reasonably well for Ag. The valence bands were also found to shift rather accurately by the same amount as the core levels. (C) 2012 Published by Elsevier B.V.
2.	Chernenk, Kirill, et al. (author) Performance and characterization of the FinEstBeAMS beamline at the MAX IV Laboratory 2021 In: Journal of Synchrotron Radiation. - 0909-0495. ; 28, s. 1620-1630 Journal article (peer-reviewed)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.
3.	Fritzsche, S., et al. (author) Photoelectron satellite structure from the 3d and 4d inner-shell ionization of rubidium and cesium: Role of atomic relaxation 2008 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 78:3 Journal article (peer-reviewed)abstract The photoelectron satellite structure of rubidium and cesium has been investigated following the photoionization of an nd (n= 3,4) inner-shell electron. The intensity ratios of the nd(-1) ms monopole and nd(-1) m'p conjugated satellite lines have been measured at MAX-lab by using high-resolution electron spectroscopy. For rubidium, moreover, the energy dependence of the 3d(j)6s/3d(j)5s and 3d(j)5p/3d(j)5s intensity ratios with j=3/2 and 5/2 is measured and compared with multiconfiguration Dirac-Fock calculations. A good or at least reasonable agreement is found for both the monopole and conjugated shake-up probabilities if the relaxation of the bound-state electron density is taken into account in the computation of the photoionization cross sections. It is shown that, for the inner-shell ionization of medium and heavy atoms, the orbital relaxation accounts for a significant part of the satellite structure in the photoelectron spectra.
4.	Ghosalya, Manoj Kumar, et al. (author) Solar light driven atomic and electronic transformations in a plasmonic Ni@NiO/NiCO3 photocatalyst revealed by ambient pressure X-ray photoelectron spectroscopy 2024 In: Catalysis Science and Technology. - 2044-4753. ; 14:11, s. 3029-3040 Journal article (peer-reviewed)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.
5.	Heinasmaki, S., et al. (author) Distorted angular distribution of the 2p photoelectrons in argon 2013 In: Physica Scripta. - : IOP Publishing. - 0031-8949 .- 1402-4896. ; 87:6 Journal article (peer-reviewed)abstract Two consecutive hemispherical electron energy analyzers have been used to measure the argon angular distribution of 2p photoelectron lines over two quadrants of the dipole plane. A significant anomaly in the intensity of the photolines is observed at several electron emission angles, suggesting asymmetry with respect to the electric field vector of synchrotron light. As a possible cause for the observed behavior, we consider an external field affecting the photoelectrons, and show that it is capable of breaking the left-right asymmetry of the angular distribution, giving rise qualitatively to the observed behavior.
6.	Holappa, M., et al. (author) Atom-solid binding energy shifts for K 2p and Rb 3d sublevels 2011 In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 184:7, s. 371-374 Journal article (peer-reviewed)abstract Binding energy shifts between free and solid state atoms for K 2p and Rb 3d photolines have been determined by measuring the vapor and solid state spectra simultaneously in similar experimental conditions applying synchrotron radiation excited photoelectron spectroscopy. This method has the important benefit that the work function is not needed to correct for different reference energy levels, therefore much more accurate values for binding energy shifts are obtained. (C) 2011 Elsevier B.V. All rights reserved.
7.	Iablonskyi, D., et al. (author) 3d photoionization and subsequent decay of atomic gallium 2013 In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 46:17 Journal article (peer-reviewed)abstract We present an experimental and theoretical study of 3d photoionization and subsequent Auger decay of atomic gallium. The synchrotron radiation-induced electron spectra have been compared and analysed using multiconfiguration Dirac-Fock calculations. It has been shown that the theoretically predicted photoelectron spectrum is in rather good agreement with the experiment allowing us to identify the main spectral features. However, prediction of the Auger decay intensities fails due to calculational difficulties for the continuum wavefunctions of very low kinetic energy Auger electrons.
8.	Iablonskyi, D., et al. (author) High resolution study of the inner-shell 3p-3d and 3p-5s resonance regions in calcium atoms 2013 In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 186, s. 8-13 Journal article (peer-reviewed)abstract The 3p(5)4s(2)3d P-1(1) and 3p(5)(P-2(3/2))4s(2)5s (2)[3/2](1) resonance regions of Ca atoms have been studied experimentally with the aid of synchrotron radiation excited electron spectroscopy. The strong configuration interaction of the 3p(5)4s(2)3d, 3p(5)4s(2)5s and several other nearly degenerate configurations leads to complex structures observed in the photoelectron yield spectrum. Multiconfiguration Dirac-Fock (MCDF) calculations have been performed for these 3p-excited resonances of neutral calcium and compared to experimental results. The excitation and subsequent autoionization of these resonances lead to the final ionic 3p(6)nl states from which new high-lying members of the Rydberg p-series have been resolved experimentally. These new levels agree reasonably well with calculations as well as with the extrapolation of the Rydberg formula. The post collision interaction (PCI) effect has been observed in the transition Ca+ 3p(5)3d4s P-2(1/2,3/2)-> Ca2+ 3p(6) S-1(0) + e(Auger)(-) and explained by means of the rather long core-hole lifetime, while the decay of Ca+ 3p(5)3d4s P-4(1/2),(3/2,5/2) states is not affected by PCI. (c) 2013 Elsevier B.V. All rights reserved.
9.	Jankala, K., et al. (author) Analysis of 3d photoionization and subsequent Auger decay of atomic germanium 2011 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 84:5 Journal article (peer-reviewed)abstract Experimental and theoretical study of the 3d photoionization and subsequent Auger decay of initially neutral atomic germanium is presented. The features of the high-resolution photoelectron and Auger electron spectra are interpreted with the aid of multiconfiguration calculations. The binding energies and relative cross sections of the 3d ionized fine-structure states of Ge are given. The complete M4,5NN Auger electron spectrum to doubly ionized final states of the Ge ion is interpreted and discussed.
10.	Jankala, K., et al. (author) Inner-shell 2p photoionization and Auger decay of atomic silicon 2008 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 77:6 Journal article (peer-reviewed)abstract A detailed experiment on 2p photoionization and subsequent Auger decay of atomic silicon is presented. Fine-structure-resolved photoelectron and Auger electron spectra are interpreted with the aid of large-scale multiconfiguration calculations. Energy separation and the relative cross sections of the 2p ionized fine-structure states of Si+ are given. The complete 2p Auger electron spectrum of Si is interpreted, and the intensity distribution to individual doubly ionized final states is studied.
11.	Karpenko, A., et al. (author) Behavior of relative state selective photoionization cross sections of RbBr molecules in the valence region 2014 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 90:6 Journal article (peer-reviewed)abstract The photon energy dependence of relative photoionization cross sections in the valence ionization energy region of 5 to 45 eV for 4p and 4s orbitals of Rb and Br ions in RbBr vapors has been investigated. The behavior of state selective cross sections of molecular valence orbitals has been analyzed by comparing the observed 4p to 4s photoelectron intensity branching ratios with atomic state selective photoionization cross sections of Kr, taking into account the mixing between Br 4s(-1) and Rb 4p(-1) molecular states. Using atomic dipole matrix elements to calculate the photoionization intensity of alkali halides has been suggested.
12.	Karpenko, A., et al. (author) Breakdown of ionic character of molecular alkali bromides in inner-valence photoionization 2014 In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 140:20 Journal article (peer-reviewed)abstract The inner-valence region of alkali bromide XBr (X=Li, Na, K, Rb) vapours has been studied experimentally by means of synchrotron radiation excited photoelectron spectroscopy. Experimental spectra were analyzed by comparing them with available theoretical results and previous experiments. Ionic character of alkali bromides is seen to change in the inner-valence region with increasing atomic number of the alkali atom. A mechanism involving mixing between Br 4s and Rb 4p orbitals has been suggested to account for the fine structure observed in inner-valence ionization region of RbBr. (C) 2014 AIP Publishing LLC.
13.	Kettunen, J. A., et al. (author) Dissociation of As-4 clusters following valence photoionization and 3d core excitation 2012 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 86:2 Journal article (peer-reviewed)abstract The VUV-induced photofragmentation of As-4 clusters was studied using photoelectron-photoion-coincidence (PEPICO) spectroscopy. The fragmentation pathways subsequent to outer and inner valence photoionization and resonant photoexcitation were studied by examining the cationic production as a function of electron energy. In addition, regular photoelectron spectroscopy and partial ion yield absorption spectroscopy were employed. In order to enhance the weak signal from the inner valence states, resonant core 3d excitation was used in the PEPICO experiment. The fragmentation pathways were inspected with the aid of ab initio and thermochemical calculations. The many-electron effects were found to play a major role in the observed inner valence structure and resulting photofragmentation.
14.	Kettunen, J. A., et al. (author) Electron-ion coincidence study of photofragmentation of the CdCl2 molecule 2011 In: Journal of Mass Spectrometry. - : Wiley. - 1076-5174. ; 46:9, s. 901-907 Journal article (peer-reviewed)abstract In this work, the photofragmentation subsequent to valence and Cd4d photoionization of cadmium dichloride (CdCl2) were studied using He I and synchrotron excitation. The measurements were performed with a photoelectron-photoion coincidence (PEPICO) setup, and the connection between the singly ionized electronic states and cationic fragments was investigated. The valence-ionized states were found to lead to CdCl2+, Cd+ and CdCl+. The Cd4d(-1) states were found to lead only to Cl+ ions. The observed charge transfer effect between Cd and Cl was concluded to take place due to internal conversion or fluorescence decay to dissociating valence states either directly or through consecutive fragmentation. The fragmentation energetics were investigated with molecular ab initio calculations, and the calculated energies were found to agree with the detected fragment appearances. Copyright (C) 2011 John Wiley & Sons, Ltd.
15.	Kettunen, J. A., et al. (author) Valence electronic structure and photofragmentation of 1,1,1,2-tetrafluoroethane (CF3-CH2F) 2012 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 85:6 Journal article (peer-reviewed)abstract The electronic structure and fragmentation of the hydrofluorocarbon compound 1,1,1,2-tetrafluoroethane (CF3-CH2F) were studied using spectroscopical methods and quantum chemical calculations. Valence photoelectron spectra and the ionic fragmentation products were recorded with synchrotron radiation in the vacuum ultraviolet (VUV) region. The geometric and electronic structures of the CF3-CH2F molecule were calculated using the complete active space perturbation theory of second order. The calculated vertical ionization energies were used to interpret the experimental photoelectron spectrum. VUV photodissociation of the sample molecule was studied with photoelectron-photoion coincidence spectroscopy. Coincident ion yields are shown for several cations as a function of electron binding energy. The experimental data are discussed in comparison with theory and previous work.
16.	Klyushin, Alexander, et al. (author) Photocatalytic setup for in situ and operando ambient-pressure X-ray photoelectron spectroscopy at MAX IV Laboratory 2023 In: Journal of Synchrotron Radiation. - 0909-0495. ; 30:3, s. 613-619 Journal article (peer-reviewed)abstract The Ambient-Pressure X-ray Photoelectron Spectroscopy (APXPS) endstation at the SPECIES beamline at MAX IV Laboratory has been improved. The latest upgrades help in performing photo-assisted experiments under operando conditions in the mbar pressure range using gas and vapour mixtures whilst also reducing beam damage to the sample caused by X-ray irradiation. This article reports on endstation upgrades for APXPS and examples of scientific cases of in situ photocatalysis, photoreduction and photo-assisted atomic layer deposition (photo-ALD).
17.	Kokkonen, E., et al. (author) Ambient pressure x-ray photoelectron spectroscopy setup for synchrotron-based in situ and operando atomic layer deposition research 2022 In: Review of Scientific Instruments. - : AIP Publishing. - 1089-7623 .- 0034-6748. ; 93:1 Journal article (peer-reviewed)abstract An ambient pressure cell is described for conducting synchrotron-based x-ray photoelectron spectroscopy (XPS) measurements during atomic layer deposition (ALD) processes. The instrument is capable of true in situ and operando experiments in which it is possible to directly obtain elemental and chemical information from the sample surface using XPS as the deposition process is ongoing. The setup is based on the ambient pressure XPS technique, in which sample environments with high pressure (several mbar) can be created without compromising the ultrahigh vacuum requirements needed for the operation of the spectrometer and the synchrotron beamline. The setup is intended for chemical characterization of the surface intermediates during the initial stages of the deposition processes. The SPECIES beamline and the ALD cell provide a unique experimental platform for obtaining new information on the surface chemistry during ALD half-cycles at high temporal resolution. Such information is valuable for understanding the ALD reaction mechanisms and crucial in further developing and improving ALD processes. We demonstrate the capabilities of the setup by studying the deposition of TiO2 on a SiO2 surface by using titanium(IV) tetraisopropoxide and water as precursors. Multiple core levels and the valence band of the substrate surface were followed during the film deposition using ambient pressure XPS.
18.	Kokkonen, Esko, et al. (author) Upgrade of the SPECIES beamline at the MAX IV Laboratory 2021 In: Journal of Synchrotron Radiation. - 1600-5775. ; 28, s. 588-601 Journal article (peer-reviewed)abstract The SPECIES beamline has been transferred to the new 1.5 GeV storage ring at the MAX IV Laboratory. Several improvements have been made to the beamline and its endstations during the transfer. Together the Ambient Pressure X-ray Photoelectron Spectroscopy and Resonant Inelastic X-ray Scattering endstations are capable of conducting photoelectron spectroscopy in elevated pressure regimes with enhanced time-resolution and flux and X-ray scattering experiments with improved resolution and flux. Both endstations offer a unique capability for experiments at low photon energies in the vacuum ultraviolet and soft X-ray range. In this paper, the upgrades on the endstations and current performance of the beamline are reported.
19.	Kooser, Kuno, et al. (author) Operando high-temperature near-ambient pressure X-ray photoelectron spectroscopy and impedance spectroscopy study of Ni−Ce0.9Gd0.1O2−δ solid oxide fuel cell anode 2020 In: International Journal of Hydrogen Energy. - : Elsevier BV. - 0360-3199. ; 45:46, s. 25286-25298 Journal article (peer-reviewed)abstract In this study we present the results of operando high temperature near-ambient-pressure x-ray photoelectron spectroscopy (HT-NAP-XPS) measurements of a pulsed laser deposited thin film Ni−Ce0.9Gd0.1O2−δ model electrode. In our measurements, we have used the novel three electrode dual-chamber electrochemical cell developed in our previous work at different H2 pressures and at different electrochemical conditions at around 650 °C. The possible redox reactions on the anode surface (Ni2+↔Ni0,Ce4+↔Ce3+) were investigated by HT-NAP-XPS technique simultaneously with electrochemical impedance spectroscopy measurements. The oxygen partial pressure in counter and reference electrode compartment was controlled at 0.2 bar. Changes in electronic structure of the Ce3d and Ni2p photoelectron spectra caused by electrode potential and H2 pressure variations were observed and estimated by curve fitting procedure. The O1s and valence band photoelectron signals were used for depth probing of the chemical composition and redox changes at Ni-GDC and for studying the influence of the electrochemical polarization on the chemical state of Ni-GDC surface atoms. As a result changes in oxidation state of electrode surface atoms caused by electrode polarization and oxide ion flux through the membrane were detected with simultaneous significant variation of electrochemical impedance.
20.	Kooser, K., et al. (author) Size selective spectroscopy of Se microclusters 2012 In: Journal of Chemical Physics. - : AIP Publishing. - 0021-9606 .- 1089-7690. ; 137:4 Journal article (peer-reviewed)abstract The electronic structure and photofragmentation in outer and inner valence regions of Se-n (n <= 8) clusters produced by direct vacuum evaporation have been studied with size-selective photoelectron-photoion coincidence technique by using vacuum-ultraviolet synchrotron radiation. The experimental ionization potentials of these clusters were extracted from the partial ion yield measurements. The calculations for the possible geometrical structures of the Se-n microclusters have been executed. The ionization energies of the clusters have been calculated and compared with the experimental results. In addition, theoretical fragment ion appearance energies were estimated. The dissociation energies of Se-n clusters were derived from the recurrent relation between the gas phase enthalpies of the formation of corresponding cationic clusters and experimental ionization energies. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4737633]
21.	Kyhl, Line, et al. (author) Exciting H2 Molecules for Graphene Functionalization 2017 In: ACS Nano. - : American Chemical Society (ACS). - 1936-086X .- 1936-0851. Journal article (peer-reviewed)abstract Hydrogen functionalization of graphene by exposure to vibrationally excited H2 molecules is investigated by combined scanning tunneling microscopy, high-resolution electron energy loss spectroscopy, X-ray photoelectron spectroscopy measurements, and density functional theory calculations. The measurements reveal that vibrationally excited H2 molecules dissociatively adsorb on graphene on Ir(111) resulting in nanopatterned hydrogen functionalization structures. Calculations demonstrate that the presence of the Ir surface below the graphene lowers the H2 dissociative adsorption barrier and allows for the adsorption reaction at energies well below the dissociation threshold of the H–H bond. The first reacting H2 molecule must contain considerable vibrational energy to overcome the dissociative adsorption barrier. However, this initial adsorption further activates the surface resulting in reduced barriers for dissociative adsorption of subsequent H2 molecules. This enables functionalization by H2 molecules with lower vibrational energy, yielding an avalanche effect for the hydrogenation reaction. These results provide an example of a catalytically active graphene-coated surface and additionally set the stage for a re-interpretation of previous experimental work involving elevated H2 background gas pressures in the presence of hot filaments.
22.	Lin, Jack J., et al. (author) Pre-deliquescent water uptake in deposited nanoparticles observed with in situ ambient pressure X-ray photoelectron spectroscopy 2021 In: Atmospheric Chemistry and Physics. - : Copernicus GmbH. - 1680-7316 .- 1680-7324. ; 21:6, s. 4709-4727 Journal article (peer-reviewed)abstract We study the adsorption of water onto deposited inorganic sodium chloride and organic malonic acid and sucrose nanoparticles at ambient water pressures corresponding to relative humidities (RH) from 0 % to 16 %. To obtain information about water adsorption at conditions which are not accessible with typical aerosol instrumentation, we use surface-sensitive ambient pressure X-ray photoelectron spectroscopy (APXPS), which has a detection sensitivity starting at parts per thousand. Our results show that water is already adsorbed on sodium chloride particles at RH well below deliquescence and that the chemical environment on the particle surface is changing with increasing humidity. While the sucrose particles exhibit only very modest changes on the surface at these relative humidities, the chemical composition and environment of malonic acid particle surfaces is clearly affected. Our observations indicate that water uptake by inorganic and organic aerosol particles could already have an impact on atmospheric chemistry at low relative humidities. We also establish the APXPS technique as a viable tool for studying chemical changes on the surfaces of atmospherically relevant aerosol particles which are not detected with typical online mass-and volume-based methods.
23.	Maibach, Julia, et al. (author) Probing a battery electrolyte drop with ambient pressure photoelectron spectroscopy 2019 In: Nature Communications. - : NATURE PUBLISHING GROUP. - 2041-1723. ; 10 Journal article (peer-reviewed)abstract Operando ambient pressure photoelectron spectroscopy in realistic battery environments is a key development towards probing the functionality of the electrode/electrolyte interface in lithium-ion batteries that is not possible with conventional photoelectron spectroscopy. Here, we present the ambient pressure photoelectron spectroscopy characterization of a model electrolyte based on 1M bis(trifluoromethane)sulfonimide lithium salt in propylene carbonate. For the first time, we show ambient pressure photoelectron spectroscopy data of propylene carbonate in the liquid phase by using solvent vapor as the stabilizing environment. This enables us to separate effects from salt and solvent, and to characterize changes in electrolyte composition as a function of probing depth. While the bulk electrolyte meets the expected composition, clear accumulation of ionic species is found at the electrolyte surface. Our results show that it is possible to measure directly complex liquids such as battery electrolytes, which is an important accomplishment towards true operando studies.
24.	Mikkela, M-H, et al. (author) Photoelectron spectroscopy of unsupported bismuth clusters: Size related effects of metallic properties 2012 In: Applied Physics Reviews. - : AIP Publishing. - 1931-9401. ; 112:8 Journal article (peer-reviewed)abstract Evolution of metallic properties of free and initially neutral nanoscale Bi clusters has been studied using synchrotron radiation excited photoelectron spectroscopy. The 4f and 5d core as well as the valence levels have been probed. The cross-level analysis indicates metallic properties in Bi clusters in the observed size range from 0.5 nm to 1.4 nm. The behavior of the core-level and valence binding energies as a function of cluster size has been observed to be smooth and relatively consistent. Valence responses for the largest clusters have their shape and width similar to those of the polycrystalline solid Bi. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4759324]
25.	Niskanen, Johannes, et al. (author) Valence photoionization of the LiCl monomer and dimer 2010 In: Physical Review A. Atomic, Molecular, and Optical Physics. - 1050-2947 .- 1094-1622. ; 81:4, s. 043401- Journal article (peer-reviewed)abstract This paper reports a study of valence photoionization of the LiCl monomer and dimer. The behavior of the photoionization partial cross section for molecular valence orbitals was measured as a function of photon energy between 15 and 35 eV. A square-integrable-function method was used to model the ionization partial cross section in both the LiCl monomer and dimer.
26.	Nurk, Gunnar, et al. (author) Near ambient pressure X-ray photoelectron - and impedance spectroscopy study of NiO - Ce 0.9 Gd 0.1 O 2-δ anode reduction using a novel dual-chamber spectroelectrochemical cell 2018 In: Journal of Power Sources. - : Elsevier BV. - 0378-7753. ; 378, s. 589-596 Journal article (peer-reviewed)abstract This paper reports an experimental study, where the reduction of NiO-GDC to Ni-GDC is monitored using high temperature (HT) near ambient pressure (NAP) X-ray photoelectron spectroscopy (XPS) in combination with simultaneous impedance spectroscopy (IS). The experiment is carried out using a dual chamber (DC)-HT-NAP-XPS cell designed for membrane electrode studies. The dual chamber measurement cell enables adequate electrochemical feedback, i.e. the possibility of measuring the working electrode potential against a Pt reference electrode in a well-known environment (pO2 = 0.2 bar) and of monitoring the pO2 value on the studied electrode through open circuit voltage (OCV) measurements. Simultaneous changes of electrode impedance and O 1s, Ce 4d and Ni 3p electron binding energies are observed and discussed. The shape of the O 1s photoelectron peak is significantly influenced by the equilibria of Ce4+ ↔ Ce3+ and Ni2+ ↔ Ni0, influenced by pO2, in analysis chamber.
27.	Partanen, L., et al. (author) 2s photoionization and subsequent Auger cascade in atomic Si 2010 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 81:6 Journal article (peer-reviewed)abstract The 2s photoionization and subsequent Auger transition cascade in atomic Si were studied by means of synchrotron-radiation-induced electron spectroscopy. After the 2s photoionization, the core hole states decay predominantly by a two-step Auger transition cascade into the triply ionized [Ne]nl states. The ionization channels of the 2s core-ionized Si+ atoms to Si3+ ions were observed by measuring the conventional Auger electron spectra of the L-1-L2,3M Coster-Kronig transitions and the L2,3M-MMM Auger transitions. The observed L-1-L2,3M and L2,3M-MMM Auger spectra were analyzed by means of extensive multiconfiguration Dirac-Fock computations. We found that the electron correlation plays a prominent role in the Auger cascade, especially for the final-step Auger L2,3M-MMM spectrum. Additionally, it was seen that the L2,3M-MMM Auger spectrum of Si includes more Auger groups than the isoelectronic L-2,L-3-MMAuger spectrum of Al. Thus, more information on the intermediate ionic states is obtained if they are produced by Auger cascade rather than by direct photoionization.
28.	Patanen, M., et al. (author) 4f photoionization and subsequent Auger decay in atomic Pb: Relativistic effects 2011 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 83:5 Journal article (peer-reviewed)abstract High-resolution 4f photoelectron and subsequent Auger-electron spectra have been measured from free Pb atoms using synchrotron radiation. The fine structure of the spectra has been investigated theoretically by calculating the energies and intensities for 4f photoionization and Auger decay processes using the multiconfigurational Dirac-Fock approach. The role of the relativistic effects in the ground and singly and doubly ionized states has been studied on the basis of computed results and their comparison with experiment.
29.	Patanen, M., et al. (author) High-resolution study of K 3p photoabsorption and resonant Auger decay in KF 2009 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 80:1 Journal article (peer-reviewed)abstract High-resolution (K3p sigma and pi)->sigma absorption spectrum of KF in the photon energy range of 18.2-19.4 eV was measured at the new FINEST beamline branch on the I3 beamline on MAX III. The experimental spectrum is presented and interpreted using nonrelativistic ab initio molecular calculations corrected with perturbation theory treatment to account for spin-orbit interaction. Resonant Auger decay recorded at the strongest resonances is also presented and reproduced by theoretical calculations. Also a brief introduction to the FINEST beamline branch is presented.
30.	Patanen, M., et al. (author) Strong molecular field effects in Auger decay of the potassium 2p core-hole state in molecular KCl, KBr and KI 2008 In: Journal of Physics B: Atomic, Molecular and Optical Physics. - : IOP Publishing. - 0953-4075 .- 1361-6455. ; 41:21 Journal article (peer-reviewed)abstract The K 2p photoionization and subsequent LMM Auger decay have been studied for molecular gas-phase KCl, KBr and KI. The detected manifold spectral structure of the Auger electron spectrum of KCl has been interpreted to originate from strong molecular field effects. This indicates that Auger decay on potassium side of originally very ionic molecules creates inner-shell hole states with a strong molecular character.
31.	Patanen, M., et al. (author) Valence photoionization and photoelectron-photoion coincidence (PEPICO) study of molecular LiCl and Li2Cl2 2012 In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 185:8-9, s. 285-293 Journal article (peer-reviewed)abstract Molecular LiCl and Li2Cl2 have been studied in the vapor phase with valence photoelectron and photoelectron-photoion coincidence spectroscopies. These two techniques determine the binding energies in fundamentally different ways. Binding energies obtained from photoelectron spectra are usually taken as the vertical ionization energies of the corresponding electronic states. In cases with several overlapping bands, corresponding to different electronic states, the coincidence measurement can separate the bands if the respective final states fragment differently. This applies well to the monomer case. To facilitate the determination of state-specific ionization energies in the dimeric molecule, a theoretical Franck-Condon analysis has been carried out. Moreover, ab initio coupled-cluster and density-functional-theory calculations have been used to analyze the fragmentation pattern based on asymptotic dissociation energies. The fragmentation pattern is largely common to all the accessible valence-ionized states of the chiller, consistent with rapid conversion to the ionic ground state before fragmentation. However, the highest-lying state of Li2Cl2+, (2)A(g). shows enhanced propensity for Li+ as dissociation product. (C) 2012 Elsevier B.V. All rights reserved.
32.	Redekop, Evgeniy A., et al. (author) Synchronizing gas injections and time-resolved data acquisition for perturbation-enhanced APXPS experiments 2021 In: Review of Scientific Instruments. - : AIP Publishing. - 0034-6748 .- 1089-7623. ; 92:4 Journal article (peer-reviewed)abstract An experimental approach is described in which well-defined perturbations of the gas feed into an Ambient Pressure X-ray Photoelectron Spectroscopy (APXPS) cell are fully synchronized with the time-resolved x-ray photoelectron spectroscopy data acquisition. These experiments unlock new possibilities for investigating the properties of materials and chemical reactions mediated by their surfaces, such as those in heterogeneous catalysis, surface science, and coating/deposition applications. Implementation of this approach, which is termed perturbation-enhanced APXPS, at the SPECIES beamline of MAX IV Laboratory is discussed along with several experimental examples including individual pulses of N2 gas over a Au foil, a multi-pulse titration of oxygen vacancies in a pre-reduced TiO2 single crystal with O2 gas, and a sequence of alternating precursor pulses for atomic layer deposition of TiO2 on a silicon wafer substrate.
33.	Shayesteh, Payam, et al. (author) Experimental and theoretical gas phase electronic structure study of tetrakis(dimethylamino) complexes of Ti(IV) and Hf(IV) 2019 In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048. ; 234, s. 80-85 Journal article (peer-reviewed)abstract The gas phase electronic structure of two transition metal alkylamino complexes, M(N(CH3)2)4, where M = Ti, Hf, was studied using photoelectron spectroscopy and density functional theory (DFT). These studies are a first step for predicting atomic layer and chemical vapor deposition reactions on surfaces, which are common applications of these molecules. The valence photoemission spectra of these two complexes were collected with 50 and 150 eV photon energies. Comparison of calculated ionization energies and our experiments yielded good agreement. Analysis of calculated molecular orbitals provides insight into the π-donation interaction between the lone pair of electrons on the amino ligands and the empty metal orbitals. In addition to the valence structure, the core level photoemission spectra were analyzed. The π-interaction was found to influence core level ionization energies. Vibrational structure in the C 1s spectra are reported with insight from DFT calculations. The comprehensive experimental and theoretical characterization of the electronic structure of these complexes provide a robust foundation to progress to detailed spectroscopic studies of the interactions between these molecules and surfaces.
34.	Sjöblom, Peter, et al. (author) Motion control system of MAX IV Laboratory soft x-ray beamlines 2016 In: Proceedings of the 12th International Conference on Synchrotron Radiation Instrumentation, SRI 2015. - : Author(s). - 9780735413986 ; 1741 Conference paper (peer-reviewed)abstract At the MAX IV Laboratory, five new soft x-ray beamlines are under development. The first is Species and it will be used to develop and set the standard of the control system, which will be common across the facility. All motion axes at MAX IV will be motorized using stepper motors steered by the IcePAP motion controller and a mixture of absolute and incremental encoders following a predefined coordinate system. The control system software is built in Tango and uses the Python-based Sardana framework. The user controls the entire beamline through a synoptic overview and Sardana is used to run the scans.
35.	Sjöblom, Peter, et al. (author) Understanding the mechanical limitations of the performance of soft X-ray monochromators at MAX IV laboratory 2020 In: Journal of Synchrotron Radiation. - 1600-5775. ; 27:Pt 2, s. 272-283 Journal article (peer-reviewed)abstract MAX IV is a fourth-generation, or diffraction-limited, synchrotron light source with a number of state-of-the-art beamlines. The performance of a beamline is, to a high degree, set by the energy resolution it can achieve, which in turn is governed to a large extent by the monochromator. During the design phase of a monochromator, the mechanical requirements must be fully understood and met with margin. During commissioning, the performance must be verified and optimized. In this paper, six soft X-ray monochromators at MAX IV beamlines (Bloch, Veritas, HIPPIE, SPECIES, FinEstBeAMS and SoftiMAX) are examined with a focus on their resolving power, energy range and the time required to change measurement range, as those parameters are dependent on each other. The monochromators have a modern commercial design, planned and developed in close collaboration with the vendors. This paper aims to present the current status of the commissioning at MAX IV with emphasis on elucidating the mechanical limitations on the performance of the monochromators. It contains analysis of the outcome and our approach to achieve fast and high-resolution monochromators.
36.	Tchaplyguine, Maxim, et al. (author) Size-dependent evolution of electronic structure in neutral Pb clusters-As seen by synchrotron-based X-ray photoelectron spectroscopy 2014 In: Journal of Electron Spectroscopy and Related Phenomena. - : Elsevier BV. - 0368-2048 .- 1873-2526. ; 195, s. 55-61 Journal article (peer-reviewed)abstract Neutral Pb clusters in the size range from a few tens of atoms up to similar to 100 atoms are studied using synchrotron-based photoelectron spectroscopy. The electronic structure is seen to differ increasingly from that of the solid when the cluster size decreases. The valence band narrows gradually - down to about one fifth of the solid-state band width at the smallest size of few tens of atoms. Simultaneously the Fermi-edge energy shifts further away from the solid value by more than 2 eV. The Pb 5d core level binding energy also increases and the spectral features broaden and change in shape. The changes observed for the valence and for the 5d response energies and shapes are discussed in the context of the metal-to-insulator transition observed earlier in Pb clusters below the critical size of 20-30 atoms/cluster. (C) 2014 Elsevier B.V. All rights reserved.
37.	Tchaplyguine, Maxim, et al. (author) Valence-band narrowing and metallic-screening disappearance in the metal-to-insulator transition in small Pb clusters—as seen by photoelectron spectroscopy Other publication (other academic/artistic)abstract A metal-to-insulator transition in small Pb clusters within the size range from a few tens of atoms up to ~100 atoms is investigated using synchrotron-based photoelectron spectroscopy. The electronic structure is seen to differ increasingly from that of the solid when the cluster size decreases. With the cluster size decrease the valence band narrows gradually -down to 25% of that of the solid-state at the smallest size of few tens of atoms. Simultaneously the Fermi-edge energy increases. The Pb 5d core level binding energy also increases and the spectral features broaden and change the shape. The changes observed for the valence and for the 5d energies and shapes are consistent with the picture of the loss of metallicity in Pb below the critical size of 20-30 atoms/cluster.
38.	Timm, Rainer, et al. (author) Self-cleaning and surface chemical reactions during hafnium dioxide atomic layer deposition on indium arsenide 2018 In: Nature Communications. - : Springer Science and Business Media LLC. - 2041-1723. ; 9:1 Journal article (peer-reviewed)abstract Atomic layer deposition (ALD) enables the ultrathin high-quality oxide layers that are central to all modern metal-oxide-semiconductor circuits. Crucial to achieving superior device performance are the chemical reactions during the first deposition cycle, which could ultimately result in atomic-scale perfection of the semiconductor-oxide interface. Here, we directly observe the chemical reactions at the surface during the first cycle of hafnium dioxide deposition on indium arsenide under realistic synthesis conditions using photoelectron spectroscopy. We find that the widely used ligand exchange model of the ALD process for the removal of native oxide on the semiconductor and the simultaneous formation of the first hafnium dioxide layer must be significantly revised. Our study provides substantial evidence that the efficiency of the self-cleaning process and the quality of the resulting semiconductor-oxide interface can be controlled by the molecular adsorption process of the ALD precursors, rather than the subsequent oxide formation.
39.	Urpelainen, Samuli, et al. (author) Size evolution of electronic properties in free antimony nanoclusters 2013 In: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 87:3, s. 035411- Journal article (peer-reviewed)abstract The evolution of electronic properties in free antimony (Sb) nanoclusters as a function of the cluster size has been studied experimentally using synchrotron radiation. Antimony 4d core-level and valence-band regions have been probed, and the 4d binding energies and valence ionization potentials of clusters of various mean sizes have been determined. The binding-energy shifts with respect to polycrystalline solid have been used for deriving the electronic properties of the clusters. The observed results suggest that even large Sb clusters are not metallic.
40.	Urpelainen, Samuli, et al. (author) The SPECIES beamline at the MAX IV Laboratory : A facility for soft X-ray RIXS and APXPS 2017 In: Journal of Synchrotron Radiation. - 1600-5775 .- 0909-0495. ; 24:1, s. 344-353 Journal article (peer-reviewed)abstract SPECIES is an undulator-based soft X-ray beamline that replaced the old I511 beamline at the MAX II storage ring. SPECIES is aimed at high-resolution ambient-pressure X-ray photoelectron spectroscopy (APXPS), near-edge X-ray absorption fine-structure (NEXAFS), X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) experiments. The beamline has two branches that use a common elliptically polarizing undulator and monochromator. The beam is switched between the two branches by changing the focusing optics after the monochromator. Both branches have separate exit slits, refocusing optics and dedicated permanent endstations. This allows very fast switching between two types of experiments and offers a unique combination of the surface-sensitive XPS and bulk-sensitive RIXS techniques both in UHV and at elevated ambient-pressure conditions on a single beamline. Another unique property of the beamline is that it reaches energies down to approximately 27 eV, which is not obtainable on other current APXPS beamlines. This allows, for instance, valence band studies under ambient-pressure conditions. In this article the main properties and performance of the beamline are presented, together with selected showcase experiments performed on the new setup.
41.	Urpelainen, Samuli, et al. (author) Valence photoionization and resonant Auger decay of Sb-4 clusters at resonances below the 4d ionization threshold 2011 In: Physical Review A (Atomic, Molecular and Optical Physics). - 1050-2947. ; 83:1 Journal article (peer-reviewed)abstract The valence photoionization and resonant Auger decay at 4d resonances below the 4d ionization threshold in Sb-4 clusters have been studied experimentally by means of photoelectron spectroscopy. The 4d absorption spectrum in the photon energy region from 30 to 36 eV has been recorded using the constant ionic state (CIS) partial electron yield (PEY), and the CIS spectra for various ionic states are presented. The photoelectron spectra at various resonant positions are recorded, and the results and their interpretation are presented. The findings provide experimental proof of the previous assignment of the various structures of the inner valence photoelectron spectrum.

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