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Electronic Structure Studies Using Resonant X-ray and Photemission Spectroscopy
Uppsala University. (Tunnfilm)ORCID iD: 0000-0002-0317-0190
1999 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis addresses the electronic structure of molecules and solids using resonant X-ray emission and photoemission spectroscopy. The use of monochromatic synchrotron radiation and the improved performance of the instrumentation have opened up the possibility of detailed analyses of the response of the electronic systems under interaction with X-rays. The experimental studies are accompanied by numerical ab initio calculations in the formalism of resonant inelastic scattering. The energy selectivity has made it possible for the first time to study how the chemical bonds in a molecule break up during resonant inelastic X-ray scattering. In the conjugated polymer systems, the element selectivity of the X-ray emission process made it possible to probe the different atomic elements separately. The X-ray emission technique proved to be useful for extracting isomeric information, and for measuring the change in the valence levels at different degrees of doping. In this thesis, spectral satellite features in transition metals were thoroughly investigated for various excitation energies around a core-level threshold. By measuring the relative spectral intensity of the satellites it was possible to extract information on the partial core-level widths. Using the nickel metal system as an example, it was shown that it is possible to probe the different core-excited states close toshake-up thresholds by measuring the relative spectral intensity variation of the Auger emission.Resonant photoemission measurements showed unambiguous evidence of interference effects. Theseeffects were also thoroughly probed using angle-dependent measurements. The combination of X-rayemission and absorption were useful for studying buried layers and interfaces due to the appreciable penetration depth of soft X-rays. X-ray scattering was further found to be useful for studying low-energy excited states of rare earth metallic compounds and transition metal oxides.

Place, publisher, year, edition, pages
Uppsala: Uppsala University , 1999.
Series
Acta Universitatis Upsaliensis, ISSN 1104-232X ; 452
Keyword [en]
Electronic structure, resonant x-ray emission, photoemission spectroscopy
National Category
Physical Sciences
Identifiers
URN: urn:nbn:se:liu:diva-56480ISBN: 91-554-4463-6 (print)OAI: oai:DiVA.org:liu-56480DiVA: diva2:319606
Public defence
(English)
Opponent
Available from: 2010-05-19 Created: 2010-05-18 Last updated: 2013-11-14Bibliographically approved
List of papers
1. Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy
Open this publication in new window or tab >>Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy
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1996 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 54, 4405-4408 p.Article in journal (Refereed) Published
Abstract [en]

We measured the Mn Lα,β x-ray fluorescence spectra of MnO excited by selected photon energies near the L2,3 absorption edges. The resulting resonant inelastic x-ray scattering spectra probe low-lying electronic excited states, due to dd and charge-transfer excitations. Using a two-step model and a purely atomic approximation, we reproduce both energies and varying intensities of dd excitations relative to the electronic recombination peak. Our results show that strongly varying line shapes in resonant x-ray emission need not be due to channel interference effects.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17475 (URN)10.1103/PhysRevB.54.4405 (DOI)
Note
Original Publication:S. M. Butorin, J.-H. Guo, Martin Magnuson, P. Kuiper and J. Nordgren, Low-energy d-d excitations in MnO studied by resonant x-ray fluorescence spectroscopy, 1996, Physical Review B. Condensed Matter and Materials Physics, (54), 4405-4408.http://dx.doi.org/10.1103/PhysRevB.54.4405Copyright: American Physical Societyhttp://www.aps.org/Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
2. Resonant inelastic soft-x-ray scattering from valence-band excitations in 3d0 compounds
Open this publication in new window or tab >>Resonant inelastic soft-x-ray scattering from valence-band excitations in 3d0 compounds
1997 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 55, 4242-4249 p.Article in journal (Refereed) Published
Abstract [en]

Ti and Mn Lα,Β x-ray fluorescence spectra of FeTiO3 and KMnO4 were measured with monochromatic photon excitation on selected energies across the L2,3 absorption edges. The resulting inelastic x-ray-scattering structures and their changes with varying excitation energies are interpreted within the framework of a localized, many-body approach based on the Anderson impurity model, where the radiative process is characterized by transitions to low-energy interionic-charge-transfer excited states. Sweeping the excitation energy through the metal 2p threshold enhances the fluorescence transitions to the antibonding states pushed out of the band of continuous states due to strong metal 3d–ligand 2p hybridization and matching the low-photon-energy satellites in the spectra. Based on the energy position of these charge-transfer satellites with respect to the recombination peak the effective metal 3d–ligand 2p hybridization strength in the ground state of the system can be estimated directly from the experiment.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17474 (URN)10.1103/PhysRevB.55.4242 (DOI)
Note
Original Publication:S. M. Butorin, J.-H. Guo, Martin Magnuson and J. Nordgren, Resonant inelastic soft-x-ray scattering from valence-band excitations in 3d0 compounds, 1997, Physical Review B. Condensed Matter and Materials Physics, (55), 4242-4249.http://dx.doi.org/10.1103/PhysRevB.55.4242Copyright: American Physical Societyhttp://www.aps.org/Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
3. Resonant inelastic soft X-ray scattering at the 4d edge of Ce-based heavy fermion materials
Open this publication in new window or tab >>Resonant inelastic soft X-ray scattering at the 4d edge of Ce-based heavy fermion materials
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1999 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 101-103, 783-786 p.Article in journal (Refereed) Published
Abstract [en]

Resonant X-ray scattering measurements were performed on CeB6, CeAl, γ-Ce, and α-Ce at various incident-photon energies near the Ce 4d threshold. A pronounced inelastic scattering structure which has 4f character is observed at about 4 eV below the elastic peak. The structure shows a distinct resonant behavior as well as a dependence on the degree of 4f hybridization and can therefore be attributed to charge-transfer excitations to the 4f0 state. The intensity of the elastic peak increases when going from the systems with low Kondo temperature TK to those with high TK which is consistent with a Kondo scale behavior. By analyzing the scattering data, a controversial issue on the validity of a single-impurity Anderson model in heavy-fermion materials is addressed.

Keyword
Resonant soft-X-ray scattering; Ce-based heavy-fermion systems; Charge-transfer excitations; X-ray absorption
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54982 (URN)10.1016/S0368-2048(98)00369-7 (DOI)
Available from: 2010-04-26 Created: 2010-04-26 Last updated: 2017-12-12Bibliographically approved
4. Resonant and nonresonant x-ray scattering spectra of some poly(phenylenevinylene)s
Open this publication in new window or tab >>Resonant and nonresonant x-ray scattering spectra of some poly(phenylenevinylene)s
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1998 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 108, no 14, 5990-5996 p.Article in journal (Refereed) Published
Abstract [en]

The electronic structure of some poly(phenylenevinylene)s have been investigated by resonant and nonresonant x-ray inelastic scattering spectroscopies. The nonresonant as well as all resonant spectra for each polymer demonstrate benzene-like features, indicating a local character of the x-ray emission in which the phenyl ring acts as a building block. Theoretical simulations of x-ray energies and intensities taking the repeat unit as a model molecule of the polymer agree with the experimental spectra fairly well. The edges of the occupied bands have been identified in the nonresonant spectra of each polymer. By subtracting the emission energy of the highest occupied molecular orbital in the nonresonant spectrum from the core excitation energy in the resonant spectrum an alternative way to determine the optical band gap is obtained. As for free benzene the outer π band in the polymer spectra show a depletion of the emission going from the nonresonant to the resonant x-ray emission spectra. It is demonstrated that this transition, which is strictly symmetry forbidden for free benzene, becomes effectively forbidden in the polymer case as a result of strong interference effects, and it is argued that this is the general case for resonant x-ray emission of conjugated polymers as far as the frozen orbital approximation holds.

Keyword
Polymers, elastomers, and plastics, X-ray emission spectra and fluorescence, Electron density of states and band structure of crystalline solids
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54988 (URN)10.1063/1.476011 (DOI)
Available from: 2010-04-26 Created: 2010-04-26 Last updated: 2017-12-12
5. Probing surface states of Cu/Ni thin films using x-ray absorption spectroscopy
Open this publication in new window or tab >>Probing surface states of Cu/Ni thin films using x-ray absorption spectroscopy
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2001 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 63, no 113401Article in journal (Refereed) Published
Abstract [en]

Surface and interface properties of Cu thin films (1–4 monolayers) deposited on Ni(100) have been extracted by means of x-ray absorption spectroscopy and analyzed in combination with ab initio density-functional calculations. An unoccupied Cu surface state is identified in an x-ray absorption spectra and studied as a function of film thickness. Experimental data is supported by calculations of the layer-resolved density of states and the results from this combined theoretical-experimental effort show that the surface state is almost entirely located on the atomic layer closest to the vacuum. Our results also indicate strong hybridization between unoccupied states at the Cu/Ni interface boundary.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17468 (URN)10.1103/PhysRevB.63.113401 (DOI)
Note
Original Publication:O. Karis, Martin Magnuson, T. Wiell, M. Weinelt, N. Wassdahl, A. Nilsson, N. Mårtensson, E. Holmström, A. M. N. Niklasson, O. Eriksson and B. Johansson, Probing surface states of Cu/Ni thin films using x-ray absorption spectroscopy, 2001, Physical Review B. Condensed Matter and Materials Physics, (63), 113401.http://dx.doi.org/10.1103/PhysRevB.63.113401Copyright: American Physical Societyhttp://www.aps.org/Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
6. Observation of short- and long-range hybridization of a buried Cu monolayer in Ni
Open this publication in new window or tab >>Observation of short- and long-range hybridization of a buried Cu monolayer in Ni
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2000 (English)In: Physical Review B Condensed Matter, ISSN 0163-1829, E-ISSN 1095-3795, Vol. 62, no 24, R16239-R16242 p.Article in journal (Refereed) Published
Abstract [en]

The electronic structure of a Cu monolayer buried in Ni fcc(100) is studied by means of x-ray emission and absorption spectroscopies in combination with first principles calculations. The local character of the x-ray probes allows us to investigate changes in the chemical interaction for these ultrathin film systems. In comparison to bulk Cu, the occupied d states of a buried Cu monolayer, as mapped in the x-ray emission spectrum, remain mostly unaltered. The absorption spectrum on the other hand shows that the empty states of the buried Cu monolayer are modified, and instead resemble the unoccupied electronic density of bulk Ni. These findings agree well with our first principle electronic structure calculations and the results are interpreted in terms of short- and long-range hybridization.

Keyword
X-ray absorption spectra, X-ray emission spectra and fluorescence, Methods of electronic structure calculations
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54981 (URN)10.1103/PhysRevB.62.R16239 (DOI)
Note
Original Publication: O. Karis, Martin Magnuson, T Wiell, M. Weinelt, N. Wassdahl, A. Nilsson, N. Mårtensson, E. Holmström, A. M. N. Niklasson and Olle Eriksson, Observation of short- and long-range hybridization of a buried Cu monolayer in Ni, 2000, Physical Review B Condensed Matter, (62), 24, R16239-R16242. http://dx.doi.org/10.1103/PhysRevB.62.R16239 Copyright: American Physical Society http://www.aps.org/ Available from: 2010-04-26 Created: 2010-04-26 Last updated: 2017-12-12
7. Angular-dependent resonant-photoemission processes at the 2p thresholds in nickel metal
Open this publication in new window or tab >>Angular-dependent resonant-photoemission processes at the 2p thresholds in nickel metal
1999 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 60, 2436-2440 p.Article in journal (Refereed) Published
Abstract [en]

Angle-resolved valence-band resonant-photoemission of nickel metal has been measured close to the 2p core-level thresholds with synchrotron radiation. The well-known 6-eV correlation satellite has an intensity enhancement of about two orders of magnitude at resonance. The angular dependence of the photoemission intensity has been studied as function of photon energy and provides unambiguous evidence for interference effects all the way up to the resonance maximum. The observation of different angular asymmetries, β, for the valence band and the satellite is discussed in connection to the origin of the resonant-photoemission process and the character of the satellite.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17469 (URN)10.1103/PhysRevB.60.2436 (DOI)
Note

Original Publication:M. Magnuson, A. Nilsson, M. Weinelt, N. and N. Mårtensson, Angular-dependent resonant-photoemission processes at the 2p thresholds in nickel metal, 1999, Physical Review B. Condensed Matter and Materials Physics, (60), 2436-2440.http://dx.doi.org/10.1103/PhysRevB.60.2436Copyright: American Physical Societyhttp://www.aps.org/

Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
8. Electronic-structure investigation of CeB6 by means of soft-x-ray scattering
Open this publication in new window or tab >>Electronic-structure investigation of CeB6 by means of soft-x-ray scattering
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2001 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 63, no 075101Article in journal (Refereed) Published
Abstract [en]

The electronic structure of the heavy fermion compound CeB6 is probed by resonant inelastic soft-x-ray scattering using photon energies across the Ce 3d and 4d absorption edges. The hybridization between the localized 4f orbitals and the delocalized valence-band states is studied by identifying the different spectral contributions from inelastic Raman scattering and normal fluorescence. Pronounced energy-loss structures are observed below the elastic peak at both the 3d and 4d thresholds. The origin and character of the inelastic scattering structures are discussed in terms of charge-transfer excitations in connection to the dipole allowed transitions with 4f character. Calculations within the single-impurity Anderson model with full multiplet effects are found to yield consistent spectral functions to the experimental data.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17467 (URN)10.1103/PhysRevB.63.075101 (DOI)
Note

Original Publication:Martin Magnuson, S. M. Butorin, J.-H. Guo, A. Agui, J. Nordgren, H. Ogasawara, A. Kotani, T. Takahashi and S. Kunii, Electronic-structure investigation of CeB6 by means of soft-x-ray scattering, 2001, Physical Review B. Condensed Matter and Materials Physics, (63), 075101.http://dx.doi.org/10.1103/PhysRevB.63.075101Copyright: American Physical Societyhttp://www.aps.org/

Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
9. Competition between decay and dissociation of core-excited carbonyl sulfide studied by x-ray scattering
Open this publication in new window or tab >>Competition between decay and dissociation of core-excited carbonyl sulfide studied by x-ray scattering
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1999 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 59, 4281-4287 p.Article in journal (Refereed) Published
Abstract [en]

We show evidence of dissociation during resonant inelastic soft x-ray scattering. Carbon and oxygen K-shell and sulfur L-shell resonant and nonresonant x-ray emission spectra were measured using monochromatic synchrotron radiation for excitation and ionization. After sulfur L2,3→π*, σ* excitation, atomic lines are observed in the emission spectra as a consequence of competition between de-excitation and dissociation. In contrast the carbon and oxygen spectra show weaker line-shape variations and no atomic lines. The spectra are compared to results from ab initio calculations. The discussion of the dissociation paths is based on calculated potential energy surfaces and atomic transition energies.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17470 (URN)10.1103/PhysRevA.59.4281 (DOI)
Note

Original Publication: Martin Magnuson, J. Guo, C. Såthe, J.-E. Rubensson, J. Nordgren, P. Glans, L. Yang, P. Sałek and H. Ågren, Competition between decay and dissociation of core-excited carbonyl sulfide studied by x-ray scattering, 1999, Physical Review A. Atomic, Molecular, and Optical Physics, (59), 4281-4287. http://dx.doi.org/10.1103/PhysRevA.59.4281 Copyright: American Physical Society http://www.aps.org/

Available from: 2009-06-08 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
10. The electronic structure of polyaniline and doped phases studied by soft X-ray absorption and emission spectroscopies
Open this publication in new window or tab >>The electronic structure of polyaniline and doped phases studied by soft X-ray absorption and emission spectroscopies
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1999 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 111, no 10, 4756-4761 p.Article in journal (Refereed) Published
Abstract [en]

The electronic structure of the conjugated polymer, polyaniline, has been studied by resonant and nonresonant soft x-ray emission spectroscopy using synchrotron radiation for the excitation. The measurements were made on polyaniline and a few doped (protonated) phases for both the carbon and nitrogen contents. The resonant x-ray emission spectra show depletion of the π electron bands due to the selective excitation which enhances the effect of symmetry selection rules. The valence band structures in the x-ray emission spectra attributed to the π bands show unambiguous changes of the electronic structure upon protonation. By comparing to x-ray absorption measurements, the chemical bonding and electronic configuration is characterized.

Keyword
Polymers and organic compounds, X-ray absorption spectra, X-ray emission spectra and fluorescence
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54983 (URN)10.1063/1.479238 (DOI)
Available from: 2010-04-26 Created: 2010-04-26 Last updated: 2017-12-12
11. X-ray fluorescence spectra of metals excited below threshold
Open this publication in new window or tab >>X-ray fluorescence spectra of metals excited below threshold
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2003 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 68, no 045119Article in journal (Refereed) Published
Abstract [en]

X-ray scattering spectra of Cu and Ni metals have been measured using monochromatic synchrotron radiation tuned from far above to more than 10 eV below threshold. Energy conservation in the scattering process is found to be sufficient to explain the modulation of the spectral shape, neglecting momentum conservation and channel interference. At excitation energies close to and above threshold, the emission spectra map the occupied local partial density of states. For the subthreshold excitations, the high-energy flank of the inelastic scattering exhibits a Raman-type linear dispersion, and an asymmetric low-energy tail develops. For excitation far below threshold the emission spectra are proportional to a convolution of the occupied and unoccupied local partial densities of states.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17414 (URN)10.1103/PhysRevB.68.045119 (DOI)
Note

Original Publication:Martin Magnuson, J.-E. Rubensson, A. Föhlisch, N. Wassdahl, A. Nilsson and N. Mårtensson, X-ray fluorescence spectra of metals excited below threshold, 2003, Physical Review B. Condensed Matter and Materials Physics, (68), 045119.http://dx.doi.org/10.1103/PhysRevB.68.045119Copyright: American Physical Societyhttp://www.aps.org/

Available from: 2009-03-23 Created: 2009-03-23 Last updated: 2017-12-13Bibliographically approved
12. Resonant Auger spectroscopy at the L2,3 shake-up thresholds as a probe of electron correlation effects in nickel
Open this publication in new window or tab >>Resonant Auger spectroscopy at the L2,3 shake-up thresholds as a probe of electron correlation effects in nickel
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1998 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 58, 3677-3681 p.Article in journal (Refereed) Published
Abstract [en]

The excitation energy dependence of the three-hole satellites in the L3-M45M45 and L2-M45M45 Auger spectra of nickel metal has been measured using synchrotron radiation. The satellite behavior in the nonradiative emission spectra at the L3 and L2 thresholds is compared and the influence of the Coster-Kronig channel explored. The three-hole satellite intensity at the L3 Auger emission line reveals a peak structure at 5 eV above the L3 threshold attributed to resonant processes at the 2p53d9 shake-up threshold. This is discussed in connection with the 6-eV feature in the x-ray-absorption spectrum.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17471 (URN)10.1103/PhysRevB.58.3677 (DOI)
Note

Original Publication:Martin Magnuson, N. Wassdahl, A. Nilsson, A. Föhlisch, J. Nordgren and N. Mårtensson, Resonant Auger spectroscopy at the L2,3 shake-up thresholds as a probe of electron correlation effects in nickel, 1998, Physical Review B. Condensed Matter and Materials Physics, (58), 3677-3681.http://dx.doi.org/10.1103/PhysRevB.58.3677Copyright: American Physical Societyhttp://www.aps.org/

Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
13. Energy dependence of Cu L2,3 satellites using synchrotron excited x-ray-emission spectroscopy
Open this publication in new window or tab >>Energy dependence of Cu L2,3 satellites using synchrotron excited x-ray-emission spectroscopy
1997 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 56, 12238-12242 p.Article in journal (Refereed) Published
Abstract [en]

The L2,3 x-ray emission of Cu metal has been measured using monochromatic synchrotron radiation. The self-absorption effect in the spectra is shown to be very small in our experimental geometry. From the quantitative analysis of spectra recorded at different excitation energies, the L3/L2 emission intensity ratio and the partial Auger width are extracted. High-energy satellite features on the L3 emission line are separated by a subtraction procedure. The satellite intensity is found to be slowly increasing for excitation energies between the L3, L2, and L1 core-level thresholds due to shake-up and shake-off transitions. As the excitation energy passes the L2 threshold, a step of rapidly increasing satellite intensity of the L3 emission is found due to additional Coster-Kronig processes.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-17472 (URN)10.1103/PhysRevB.56.12238 (DOI)
Note

Original Publication:Martin Magnuson, N. Wassdahl and J. Nordgren, Energy dependence of Cu L2,3 satellites using synchrotron excited x-ray-emission spectroscopy, 1997, Physical Review B. Condensed Matter and Materials Physics, (56), 12238-12242.http://dx.doi.org/10.1103/PhysRevB.56.12238Copyright: American Physical Societyhttp://www.aps.org/

Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
14. The electronic structure of poly(pyridine-2,5-diyl) investigated by soft X-ray absorption and emission spectroscopies
Open this publication in new window or tab >>The electronic structure of poly(pyridine-2,5-diyl) investigated by soft X-ray absorption and emission spectroscopies
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1998 (English)In: Chemical Physics, ISSN 0301-0104, E-ISSN 1873-4421, Vol. 237, no 3, 295-304 p.Article in journal (Refereed) Published
Abstract [en]

The electronic structure of the poly-pyridine conjugated polymer has been investigated by resonant and non-resonant inelastic X-ray scattering and X-ray absorption spectroscopies using synchrotron radiation. The measurements were made for both the carbon and nitrogen contents of the polymer. The analysis of the spectra has been carried out in comparison with molecular orbital calculations taking the repeat-unit cell as a model molecule of the polymer chain. The simulations indicate no significant differences in the absorption and in the non-resonant X-ray scattering spectra for the different isomeric geometries, while some isomeric dependence of the resonant spectra is predicted. The resonant emission spectra show depletion of the electron bands in line with symmetry selection and momentum conservation rules. The effect is most visual for the carbon spectra; the nitrogen spectra are dominated by lone pair n orbital emission of symmetry and are less frequency dependent.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54986 (URN)10.1016/S0301-0104(98)00262-6 (DOI)
Available from: 2010-04-26 Created: 2010-04-26 Last updated: 2017-12-12
15. Resonant inelastic soft X-ray scattering spectra at the nitrogen and carbon K-edges of poly(pyridine-2,5-diyl)
Open this publication in new window or tab >>Resonant inelastic soft X-ray scattering spectra at the nitrogen and carbon K-edges of poly(pyridine-2,5-diyl)
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1999 (English)In: Journal of Electron Spectroscopy and Related Phenomena, ISSN 0368-2048, E-ISSN 1873-2526, Vol. 101-103, 573-578 p.Article in journal (Refereed) Published
Abstract [en]

Resonant inelastic scattering measurements of the conjugated polymer, poly(pyridine-2,5-diyl) have been performed at the nitrogen and carbon K-edges using synchrotron radiation. For comparison, molecular orbital calculations of the spectra have been carried out with the repeat unit as a model molecule of the polymer chain. The resonant emission spectra show depletion of the π electron bands which is consistent with symmetry selection and momentum conservation rules. The depletion is most obvious in the resonant inelastic scattering spectra of carbon while the nitrogen spectra are dominated by lone pair n orbital emission of σ symmetry and are less excitation energy dependent. By comparing the measurements to calculations an isomeric dependence of the resonant spectra is found giving preference to two of the four possible isomers in the polymer.

National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54985 (URN)10.1016/S0368-2048(98)00354-5 (DOI)
Available from: 2010-04-26 Created: 2010-04-26 Last updated: 2017-12-12
16. Coherent and incoherent processes in resonant photoemission
Open this publication in new window or tab >>Coherent and incoherent processes in resonant photoemission
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1997 (English)In: Applied Physics A: Materials Science & Processing, ISSN 0947-8396, E-ISSN 1432-0630, Vol. 65, no 2, 159-167 p.Article in journal (Refereed) Published
National Category
Natural Sciences
Identifiers
urn:nbn:se:liu:diva-54989 (URN)10.1007/s003390050559 (DOI)
Available from: 2010-04-26 Created: 2010-04-26 Last updated: 2017-12-12Bibliographically approved
17. Electronic structure of buried Si layers in GaAs(001) as studied by soft-x-ray emission
Open this publication in new window or tab >>Electronic structure of buried Si layers in GaAs(001) as studied by soft-x-ray emission
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1995 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 52, R8643-R8645 p.Article in journal (Refereed) Published
Abstract [en]

It is demonstrated that it is possible to investigate details of the electronic structure of an internal atomic monolayer using soft-x-ray-emission spectroscopy. The local and partial density of states of one monolayer and three monolayers of Si, embedded deep below a GaAs(001) surface, was extracted. Clear differences to the density of states for bulk Si were observed.

National Category
Natural Sciences Biological Sciences
Identifiers
urn:nbn:se:liu:diva-17476 (URN)10.1103/PhysRevB.52.R8643 (DOI)
Note
Original Publication:P. O. Nilsson, J. Kanski, J. V. Thordson, T. G. Andersson, J. Nordgren, J. Guo and Martin Magnuson, Electronic structure of buried Si layers in GaAs(001) as studied by soft-x-ray emission, 1995, Physical Review B. Condensed Matter and Materials Physics, (52), R8643-R8645.http://dx.doi.org/10.1103/PhysRevB.52.R8643Copyright: American Physical Societyhttp://www.aps.org/Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved
18. Resonant Photoemission at the 2p Edges of Ni: Resonant Raman and Interference Effects
Open this publication in new window or tab >>Resonant Photoemission at the 2p Edges of Ni: Resonant Raman and Interference Effects
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1997 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 78, no 5, 967-970 p.Article in journal (Refereed) Published
Abstract [en]

Unambiguous evidence for resonant photoemission in Ni is presented. Interference effects are identified at the 2p edges for the valence band and the 6 eV satellite. A rapid transition from a resonant Raman to an Auger-like regime shows that the core-excited states above threshold are not localized enough to significantly enhance the photoemission intensity, implying a large fraction of incoherent intensity. The results indicate that the appearance of interference effects does not require strong localization of the intermediate state.

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Natural Sciences
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urn:nbn:se:liu:diva-17473 (URN)10.1103/PhysRevLett.78.967 (DOI)
Note
Original Publication:M. Weinelt, A. Nilsson, Martin Magnuson, T. Wiell, N. Wassdahl, O. Karis, A. Föhlisch, N. Mårtensson, J. Stöhr and M. Samant, Resonant Photoemission at the 2p Edges of Ni: Resonant Raman and Interference Effects, 1997, Physical Review Letters, (78), 5, 967-970.http://dx.doi.org/10.1103/PhysRevLett.78.967Copyright: American Physical Societyhttp://www.aps.org/Available from: 2009-03-26 Created: 2009-03-25 Last updated: 2017-12-13Bibliographically approved

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