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ABSTRACT: Lithium insertion into nanoporous anatase TiO2 electrodes has been studied using resonant inelastic soft-x-ray scattering spectroscopy (RIXS). We have measured Ti 2p absorption, L2,3-emission and resonant inelastic scattering spectra of pristine anatase TiO2 and Li inserted TiO2. Inelastic scattering features in RIXS spectra of pristine TiO2 are assigned to charge-transfer excitations. Low energy-loss features for Li inserted TiO2 electrodes, appearing within t2g bands, due to d–d excitations, indicate the presence of Ti3+ states. The experimental observations suggest strong electron correlation in anatase TiO2 introduced by the Li-insertion. © 2003 American Institute of Physics.
The Journal of Chemical Physics 08/2003; 119(7):3983-3987. · 3.33 Impact Factor
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ABSTRACT: We report on the spectroscopic analysis of several samples relevant to the processes governing the behavior of oxidized uranium species in groundwater solutions under anoxic conditions. Both Fe samples with different times of exposure to the U(IV) solution and Fe metal-solution inetrfaces in the liquid cell ex-situ and in-situ, respectively. Resonant inelastic soft x-ray scattering is shown to be sensitive to the chemical state of uranium. The measurements were performed at a number of energies of the primary photon beam across the U 5d absorption edge. The results unambiguously indicate the reduction of U(VI) to U(IV) on the Fe surface.
MRS Proceedings. 12/2002; 807.
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ABSTRACT: Synchrotron radiation (SR) methods have been utilized with increasing frequency over the past several years to study topics in actinide science, ranging from those of a fundamental nature to those that address a specifically-targeted technical need. In particular, the emergence of microspectroscopic and fluorescence-based techniques have permitted investigations of actinide materials at sources of soft x-ray SR. Spectroscopic techniques with fluorescence-based detection are useful for actinide investigations since they are sensitive to small amounts of material and the information sampling depth may be varied. These characteristics also serve to simplify both sample preparation and safety considerations. Examples of investigations using these fluorescence techniques will be described along with their results, as well as the prospects for future investigations utilizing these methodologies.
MRS Proceedings. 12/2002; 802.
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ABSTRACT: A tight-binding linearized muffin-tin orbital method was applied for the calculation of the densities of states (DOS) for TiO2 with the rutile structure in the wide energy region of the conduction band. The calculated partial DOS of titanium and oxygen were compared with the experimental Ti 2p total electron yield spectrum (TEY), which was measured in the present work, and the Ti 1s x-ray absorption spectrum, O 1s TEY and bremstrahlung isochromat spectrum taken from the literature. We found that in the energy region higher than ∼6 eV above the bottom of the conduction band the fine structure of experimental absorption spectra follows the distribution of the corresponding partial DOS. In connection with this, one does not need to use any satellite mechanism for an interpretation of these spectra. In the region of vacant Ti 3d states (up to ∼6 eV), correspondence between the experimental and calculated splitting of t2g and eg subbands is observed in all spectra except Ti 2p TEY. As we showed using atomic calculations, this is connected with the Ti 2p53d1 multiplet in the final state of absorption which leads to suppression of the intensity of lower states of the t2g subband in Ti 2p TEY of TiO2. As a result, t2g–eg splitting extracted from Ti 2p3/2 and Ti 2p1/2 TEY is less than in Ti 3d DOS and other experimental spectra (Ti 1s XAS and O 1s TEY) in which an interaction of core level vacancy with photoelectron is absent owing to the delocalized character of valent states. Copyright © 2002 John Wiley & Sons, Ltd.
X-Ray Spectrometry 11/2002; 31(6):414 - 418. · 1.45 Impact Factor
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ABSTRACT: We use x-ray emission spectroscopy to examine the influence of the intermolecular interaction on the local electronic structure of liquid water. By comparing x-ray emission spectra of the water molecule and liquid water, we find a strong involvement of the a(1)-symmetry valence-orbital in the hydrogen bonding. The local electronic structure of water molecules, where one hydrogen bond is broken at the hydrogen site, is separately determined. Our results provide an illustration of the important potential of x-ray emission spectroscopy for elucidating basic features of liquids.
Physical Review Letters 10/2002; 89(13):137402. · 7.37 Impact Factor
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ABSTRACT: The Mn L_2,L_3 x-ray spectra of the Cu_2MnAl and Co_2MnZ (Z=Al,Ga, Sn, Sb) Heusler alloys have been investigated by the Resonant X-ray Emission Spectroscopy (RXES) using linearly polarized monochromatic synchrotron radiation for. The interplay between the half-metallic character of the Mn 3d electronic structure in connection with the local magnetic moment $\mu_{Mn}$ and Mn $2p\to 3d$ x-ray emission spectra is discussed.
04/2002;
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ABSTRACT: Resonant x-ray scattering spectra of UO3 were measured at the U M5 edge using monochromatic photon excitation. Large differences in inelastic scattering profiles were observed between two 90°-scattering geometries with the polarization vector of incident synchrotron radiation parallel and perpendicular to the scattering plane, respectively. For the latter case, a ~9.5 eV energy-loss structure, associated with the O 2p→U 5f charge-transfer satellite, shows a significant intensity enhancement. The observed resonance behaviour allows an accurate estimation of the energy of this satellite, which is obscured in the other experimental geometry, and indicates the charge-transfer origin of the U M5 absorption structures at the respective excitation energies.
Journal of Physics Condensed Matter 02/2002; 14(10):2541. · 2.55 Impact Factor
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ABSTRACT: We are reporting here on the inexpensive fabrication and optical properties of an iron(III) oxide-chromium(III) oxide nanocomposite thin film of corundum crystal structure. Its novel and unique-designed architecture consists of uniformed, well-defined and oriented nanorods of Hematite (alpha-Fe2O3) of 50 nm in diameter and 500 nm in length and homogeneously distributed nonaggregated monodisperse spherical nanoparticles of Eskolaite (alpha-Cr2O3) of 250 nm in diameter. This alpha-Fe2O3-alpha-Cr2O3 nanocomposite thin film is obtained by growing, directly onto transparent polycrystalline conducting substrate, an oriented layer of hematite nanorods and growing subsequently, the eskolaite layer. The synthesis is carried out by a template-free, low-temperature, multilayer thin film coating process using aqueous solution of metal salts as precursors. Almost 100% of the light is absorbed by the composite film between 300 and 525 nm and 40% at 800 nm which yields great expectations as photoanode materials for photovoltaic cells and photocatalytic devices.
Journal of Nanoscience and Nanotechnology 01/2002; 1(4):385-8. · 1.56 Impact Factor
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ABSTRACT: The geometric and electronic structures of titanium fulleride complexes have been studied at the gradient corrected density-functional theory level by using various C60Tix (x=1,2) clusters. The cluster with the Ti atom binding on the six-ring site (η6) of the fullerene is shown to be lower in energy than those with Ti atom adsorbed on either five-ring (η5) or bridge (η2) sites. The bond formation for titanium fulleride has further been examined by calculated nonresonant, resonant, and off-resonant x-ray emission spectra of the clusters, and a comparison to the experimental counterpart. The examination shows that only the theoretical spectra of clusters with a six-ring adsorption site are in close agreement with the experimental x-ray emission spectra of titanium fulleride films. Our results indicate that off-resonant x-ray emission spectra provide an excellent basis for the probing of the bonding between metals and organic molecules.
Phys. Rev. B. 03/2001; 63(11).
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L. Qian,
M. Nyberg,
Y. Luo,
J.-E. Rubensson,
A. V. Talyzine,
C. Såthe,
D. Ding,
J.-H. Guo,
H. Högberg,
T. Kämbre,
U. Jansson, J. Nordgren
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ABSTRACT: The bonding between titanium atoms and C60 has been examined by means of resonant inelastic x-ray scattering. Using the symmetry-selection rules in the scattering process the symmetry of the orbitals involved in the bond formation was determined. It was found that the lowest unoccupied states are due to hybridization between the highest occupied orbital of C60 and Ti orbitals. A comparison between experimental and theoretical results indicates Ti bonding to the six-ring site. The method can be used to probe bonding between metal atoms and organic molecules in general.
Phys. Rev. B. 02/2001; 63(8).
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ABSTRACT: An interpretation of X-ray emission spectra for FeAl is given using the results of an augmented plane wave (APW) bandstructure calculation for the simple spectra Fe-K, Fe-L2.3 and Al-K as well as for the composite Fe-M2.3 Al-L2.3 spectrum, for which it is important to take into account non-radiative transition rates, ionisation probabilities and absorption corrections to estimate the relative intensities of these two spectra. Due to these effects the present calculation finds that the Fe-M2.3 intensity is weakened by a factor of about 200 with respect to the Al-L2.3 spectrum. The theoretical intensity ratio of these two spectra is found to be about half the experimental ratio.
Journal of Physics F Metal Physics 01/2001; 9(12):2509.
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ABSTRACT: A high resolution X-ray emission spectrum of water vapour is reported and the main lines are analysed in terms of molecular orbital theory. Seven satellites are found and discussed.
Journal of Physics B Atomic and Molecular Physics 01/2001; 8(2):L18.
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ABSTRACT: The X-ray emission of NH3 and N2O are reported and the main X-ray transitions are identified. A correlation between nitrogen 1s binding energies obtained by electron and X-ray emission spectroscopy is given and differences between measured X-ray energies and X-ray energies calculated from electron spectroscopy are discussed.
Journal of Physics B Atomic and Molecular Physics 01/2001; 9(2):295.
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ABSTRACT: The interaction of oxygen with C60 molecules was studied on a C60 film which had been exposed simultaneously to oxygen and UV-light for 190 hours, producing an approximately C60O1 stoichiometry in the bulk of the sample. C K-edge and O K-edge NEXAFS (using total fluorescence yield detection) and resonant
X-ray inelastic scattering (RIXS) spectra from the sample film were measured and the C K-edge data were compared to the spectra
from pristine C60 as reference. The C K-edge absorption and emission spectral profiles of the oxygen-doped sample are similar to those of the
C60 reference, suggesting that cage breaking of C60 under these conditions, if any, is negligible. However, the redistribution of intensities in the spectra indicates changes
in the occupancies of different molecular orbitals, possibly due to changes in electron density upon reaction. Similarities
of the O K-edge soft X-ray emission (SXES) spectra to several small oxygen-containing molecules is being discussed in terms
of bonding models.
The European Physical Journal D 01/2001; 16(1):357-360. · 1.48 Impact Factor
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ABSTRACT: Orbital-resolved O Kα x-ray fluorescence spectra of in-CuO2-plane [O(1)] and apical [O(2)] oxygen atoms were obtained for La1.9Sr0.1CuO4 by making an appropriate choice of the energy of incident photons and the crystal orientation relative to the polarization vector of the incoming radiation. The site origin of 2px,y and 2pz components in the Sr-doping-induced absorption prepeak near the O 1s edge, associated with states developed in the energy gap, was studied by O Kα monitoring at the excitation energy of the prepeak. The spectral analysis, based on the O Kα shape difference between inequivalent O sites, supports the assignment of the doping-induced 2px,y holes to the O(1) atoms but suggests that the 2pz holes may have both O(2) and O(1) character in contrast to assignments in prior studies.
Journal of Physics Condensed Matter 06/2000; 12(28):L463. · 2.55 Impact Factor
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M. V. Yablonskikh,
A. V. Ezhov,
V. I. Grebennikov,
Yu. M. Yarmoshenko,
E. Z. Kurmaev,
S. M. Butorin,
L. -C. Duda,
C. Sothe,
T. Kaambre,
M. Magnuson, J. Nordgren,
S. Plogmann,
M. Neumann
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ABSTRACT: The results of fluorescence measurements of magnetic circular dichroism (MCD) in Mn L_2,L_3 X-ray emission and absorption for Heusler alloys NiMnSb and Co2MnSb are presented. Very intense resonance Mn L_3 emission is found at the Mn 2p_3/2 threshold and is attributed to a peculiarity of the threshold excitation in materials with the half-metallic character of the electronic structure. A theoretical model for the description of resonance scattering of polarized x-rays is suggested. Comment: 3 pages, 2 figures. Discussed at conferences, submitting process in progress
11/1999;
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L. D. Finkelstein,
E. Z. Kurmaev,
M. A. Korotin,
A. Moewes,
B. Schneider,
S. M. Butorin,
J-H. Guo, J. Nordgren,
D. Hartmann,
M. Neumann,
D. L. Ederer
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ABSTRACT: Excitation-energy dependence of Ti L2,3 soft x-ray emission spectra (XES) of a TiO2 single crystal is measured near Ti 2p threshold using tuneable synchrotron radiation at excitation energies Eexc=458.2–476.9eV. It is found that the emission spectra exhibit normal soft x-ray emission features, which do not change with excitation energy and inelastic and resonant x-ray emission features (RXES), which strongly depend on the excitation energy. We are using a band approach in order to discuss the excitation-energy dependence of Ti L2,3RXES of TiO2. The RXES process is described as a convolution of occupied and unoccupied d states in the intermediate and final states. In this procedure the d states are limited to those which lie in the energy interval Eexc±ΔE taking into account the rule of k conservation. We calculate the curves of restricted joint density of states using the full potential linearized muffin-tin orbital method and the results are found to be in reasonable agreement with the experimental Ti L2,3, RXES of TiO2 measured at different excitation energies.
Phys. Rev. B. 07/1999; 60(4).
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B Hjörvarsson,
J -H Guo,
R Ahuja,
R C C Ward,
G Andersson,
O Eriksson,
M R Wells,
C Såthe,
A Agui,
S M Butorin, J Nordgren
Journal of Physics Condensed Matter. 01/1999; 11(14):L119-L125.
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M G Suraud,
S Bliman,
D Hitz,
J -E Rubensson, J Nordgren,
J J Bonnet,
M Bonnefoy,
M Chassevent,
A Fleury,
M Cornille,
E J Knystautas,
A Barany
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ABSTRACT: Photon emission in the wavelength intervals 17-24 AA and 100-200 AA following single and double electron capture in collisions of O6++H2 at 3.8 keV amu-1 has been analysed. The overall single electron capture features on both ion cores are similar and show dominant population of n=4 on O6+(1s2)1S0 and O6+(1s2s)3S1. At variance to the capture from He, double 'correlated' capture on O6+(1s2)1S0 appears as a minor channel.
Journal of Physics B Atomic Molecular and Optical Physics 12/1998; 25(10):2363. · 1.88 Impact Factor
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ABSTRACT: Nitrogen and oxygen K X-ray emission spectra from nitrous oxide (NNO), excited by electron impact, have been studied using the grazing incidence technique. Interpretation of spectra was made with the aid of ab initio calculated one-centre intensities and photoelectron spectra. Core electron binding energies were determined from an energy calibration using XUV emission lines.
Journal of Physics B Atomic and Molecular Physics 12/1998; 17(9):L279.
