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Öhrwall, Gunnar
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Publications (10 of 47) Show all publications
Bergersen, H., Marinho, R. R., Pokapanich, W., Björneholm, O., Sæthre, L. J., Lindblad, A. & Öhrwall, G. (2007). A photoelectron spectroscopic study of aqueous tetrabutylammonium iodide. Journal of Physics: Condensed Matter, 19(32), 326101
Open this publication in new window or tab >>A photoelectron spectroscopic study of aqueous tetrabutylammonium iodide
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2007 (English)In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 19, no 32, p. 326101-Article in journal (Refereed) Published
Abstract [en]

Photoelectron spectra of tetrabutylammonium iodide (TBAI) dissolved in water have been recorded using a novel experimental set-up, which enables photoelectron spectroscopy of volatile liquids. The set-up is described in detail. Ionization energies are reported for I 5p, I 4d, C 1s and N 1s. The C 1s spectrum shows evidence of inelastic scattering of the photoelectrons, that differs from the case of TBAI in formamide.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-97066 (URN)10.1088/0953-8984/19/32/326101 (DOI)000248185800005 ()
Available from: 2008-04-18 Created: 2008-04-18 Last updated: 2017-12-14
Rosso, A., Pokapanich, W., Öhrwall, G., Svensson, S., Björneholm, O. & Tchaplyguine, M. (2007). Adsorption of polar molecules on krypton clusters. Journal of Chemical Physics, 127(8), 084313-084313-5
Open this publication in new window or tab >>Adsorption of polar molecules on krypton clusters
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2007 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 8, p. 084313-084313-5Article in journal (Refereed) Published
Abstract [en]

The formation process of binary clusters has been studied using synchrotron based core level photoelectron spectroscopy. Free neutral krypton clusters have been produced by adiabatic expansion and doped with chloromethane molecules using the pickup technique. The comparison between the integrated intensities, linewidths, and level shifts of the cluster features of pure krypton and of chloromethane-krypton clusters has been used to obtain information about the cluster geometry. We have shown that most of the chloromethane molecules remain on the surface of the clusters.

Keywords
Spectroscopy and geometrical structure of clusters, Line shapes, widths, and shifts, Line and band widths, shapes, and shifts, X-ray photoelectron spectra
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-97633 (URN)10.1063/1.2771147 (DOI)000249156300034 ()
Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2017-12-14
Rander, T., Schulz, J., Huttula, M., Mäkinen, A., Tchaplyguine, M., Svensson, S., . . . Aksela, H. (2007). Core-level electron spectroscopy on the sodium dimer Na 2p level. Physical Review A. Atomic, Molecular, and Optical Physics, 75(3), 032510
Open this publication in new window or tab >>Core-level electron spectroscopy on the sodium dimer Na 2p level
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2007 (English)In: Physical Review A. Atomic, Molecular, and Optical Physics, ISSN 1050-2947, E-ISSN 1094-1622, Vol. 75, no 3, p. 032510-Article in journal (Refereed) Published
Abstract [en]

The lifetime broadening and molecular field splitting of the sodium dimer 2p core level is studied by x-ray photoelectron spectroscopy and by Auger electron spectroscopy. The lifetime of the Na 2p core hole has been determined to be 15±8fs , much shorter than what has previously been reported for solid sodium. The molecular field splitting of this core level has been determined to be 42±10meV . The Auger measurements have experimentally confirmed that the sodium dimer is a good example of when the Coulomb explosion mechanism determines the spectral shape.

Keywords
Fine and hyperfine structure, Ionization potentials, electron affinities, molecular core binding energy, X-ray photoelectron spectra, Autoionization, photoionization, and photodetachment
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-96540 (URN)10.1103/PhysRevA.75.032510 (DOI)000245326300093 ()
Available from: 2007-11-28 Created: 2007-11-28 Last updated: 2017-12-14
Tchaplyguine, M., Peredkov, S., Rosso, A., Schulz, J., Öhrwall, G., Lundwall, M., . . . Björneholm, O. (2007). Direct observation of the non-supported metal nanoparticle electron density of states by X-ray photoelectron spectroscopy. European Physical Journal D: Atomic, Molecular and Optical Physics, 45(2), 295-299
Open this publication in new window or tab >>Direct observation of the non-supported metal nanoparticle electron density of states by X-ray photoelectron spectroscopy
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2007 (English)In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 45, no 2, p. 295-299Article in journal (Refereed) Published
Abstract [en]

Synchrotron-based X-ray photoelectron spectroscopy on copper and silver cluster beams created by a magnetron-based gas-aggregation source has allowed mapping the electron density of states (DOS) of free metallic nanoparticles. The cluster DOS profiles obtained in the experiments strongly resemble the infinite solid DOS shapes, but the extracted cluster work-functions are lower than those for the bulk metal. The latter observation is explained by the initial negative charge on most of the clusters, created by the source.

Keywords
73.22.-f Electronic structure of nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals - 79.60.-i Photoemission and photoelectron spectra
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-97639 (URN)10.1140/epjd/e2007-00252-0 (DOI)000250136000014 ()
Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2017-12-14
Rander, T., Lundwall, M., Lindblad, A., Öhrwall, G., Tchaplyguine, M., Svensson, S. & Björneholm, O. (2007). Experimental evidence for molecular ultrafast dissociation in O2 clusters. European Physical Journal D: Atomic, Molecular and Optical Physics, 42(2), 253-257
Open this publication in new window or tab >>Experimental evidence for molecular ultrafast dissociation in O2 clusters
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2007 (English)In: European Physical Journal D: Atomic, Molecular and Optical Physics, ISSN 1434-6060, E-ISSN 1434-6079, Vol. 42, no 2, p. 253-257Article in journal (Refereed) Published
Abstract [en]

Resonant Auger spectra of O2 clusters excited at the O1s edge are reported. After excitation to the repulsive 1s-1* state, the resulting resonant Auger spectrum displays features that remain constant in kinetic energy as the photon energy is detuned. The shift between known atomic fragment features and these features is consistent with that observed for atoms and clusters in singly charged states in direct photoemission. These findings are strong evidence for the existence of molecular ultrafast dissociation processes within the clusters or on their surface.

Keywords
36.40.-c Atomic and molecular clusters - 36.40.Mr Spectroscopy and geometrical structure of clusters - 33.80.Eh Autoionization, photoionization, and photodetachment
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-96538 (URN)10.1140/epjd/e2007-00023-y (DOI)000245300500010 ()
Available from: 2007-11-28 Created: 2007-11-28 Last updated: 2017-12-14
Peredkov, S., Öhrwall, G., Schulz, J., Lundwall, M., Rander, T., Lindblad, A., . . . Tchaplyguine, M. (2007). Free nanoscale sodium clusters studied by core-level photoelectron spectroscopy. Physical Review B. Condensed Matter and Materials Physics, 75(23), 235407
Open this publication in new window or tab >>Free nanoscale sodium clusters studied by core-level photoelectron spectroscopy
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2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 23, p. 235407-Article in journal (Refereed) Published
Abstract [en]

Free sodium metal clusters have been studied by probing the Na2p core level using x-ray photoelectron spectroscopy (XPS) and Auger electron spectroscopy (AES). The development of electronic structure with size has been studied and discussed in comparison with the atom, dimer, and solid. Information on cluster metallic properties, size, and temperature has been deduced from the XPS measurements. For the large ⟨N⟩>103 Na clusters, the surface and bulk sites have been separated in the photoelectron signal. Auger spectra allowed extracting the information on the valence band. The present study introduces core-level spectroscopies XPS and AES into the field of free neutral metal cluster research.

Keywords
Nanoscale materials, Clusters, Atomic and molecular clusters, Photoemission and photoelectron spectra
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-97637 (URN)10.1103/PhysRevB.75.235407 (DOI)000247624900112 ()
Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2017-12-14
Tchaplyguine, M., Kivimäki, A., Peredkov, S., Sorensen, S., Öhrwall, G., Schulz, J., . . . Björneholm, O. (2007). Localized versus delocalized excitations just above the 3d threshold in krypton clusters studied by Auger electron spectroscopy. Journal of Chemical Physics, 127(12), 124314
Open this publication in new window or tab >>Localized versus delocalized excitations just above the 3d threshold in krypton clusters studied by Auger electron spectroscopy
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2007 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 127, no 12, p. 124314-Article in journal (Refereed) Published
Abstract [en]

We present Auger spectroscopy studies of large krypton clusters excited by soft x-ray photons with energies on and just above the 3d(52) ionization threshold. The deexcitation spectra contain new features as compared to the spectra measured both below and far above threshold. Possible origins of these extra features, which stay at constant kinetic energies, are discussed: (1) normal Auger process with a postcollision interaction induced energy shift, (2) recapture of photoelectrons into high Rydberg orbitals after Auger decay, and (3) excitation into the conduction band (or "internal" ionization) followed by Auger decay. The first two schemes are ruled out, hence internal ionization remains the most probable explanation.

Keywords
atomic clusters, Auger electron spectra, krypton, Penning ionisation, Rydberg states
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-16366 (URN)10.1063/1.2770460 (DOI)000249787300026 ()
Available from: 2008-05-20 Created: 2008-05-20 Last updated: 2017-12-08
Lundwall, M., Pokapanich, W., Bergersen, H., Lindblad, A., Rander, T., Öhrwall, G., . . . Björneholm, O. (2007). Self-assembled heterogeneous argon/neon core-shell clusters studied by photoelectron spectroscopy. Journal of Chemical Physics, 126(21), 214706
Open this publication in new window or tab >>Self-assembled heterogeneous argon/neon core-shell clusters studied by photoelectron spectroscopy
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2007 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 126, no 21, p. 214706-Article in journal (Refereed) Published
Abstract [en]

Clusters formed by a coexpansion process of argon and neon have been studied using synchrotron radiation. Electrons from interatomic Coulombic decay as well as ultraviolet and x-ray photoelectron spectroscopy were used to determine the heterogeneous nature of the clusters and the cluster structure. Binary clusters of argon and neon produced by coexpansion are shown to exhibit a core-shell structure placing argon in the core and neon in the outer shells. Furthermore, the authors show that 2 ML of neon on the argon core is sufficient for neon valence band formation resembling the neon solid. For 1 ML of neon the authors observe a bandwidth narrowing to about half of the bulk value.

Keywords
Spectroscopy and geometrical structure of clusters, Electronic structure of nanoscale materials: clusters, nanoparticles, nanotubes, and nanocrystals, Photoemission and photoelectron spectra
National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-96750 (URN)10.1063/1.2735607 (DOI)000247106600033 ()
Available from: 2008-02-28 Created: 2008-02-28 Last updated: 2017-12-14
Peredkov, S., Sorensen, S. L., Rosso, A., Öhrwall, G., Lundwall, M., Rander, T., . . . Tchaplyguine, M. (2007). Size determination of free metal clusters by core-level photoemission from different initial charge states. Physical Review B. Condensed Matter and Materials Physics, 76(8), 081402
Open this publication in new window or tab >>Size determination of free metal clusters by core-level photoemission from different initial charge states
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2007 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 76, no 8, p. 081402-Article in journal (Refereed) Published
Abstract [en]

We present the study of free nanoscale lead clusters using photoelectron spectroscopy and synchrotron radiation. Pb  5d core-level spectra reveal the presence of different initial charge states of the clusters created by the magnetron-based source. We suggest a method for determining the cluster size from the charge-dependent core level binding energies. Both the core-level and the valence spectra demonstrate that we have created free metallic clusters with essentially the same electronic structure as the solid.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-97638 (URN)10.1103/PhysRevB.76.081402 (DOI)000249155400008 ()
Available from: 2008-10-23 Created: 2008-10-23 Last updated: 2017-12-14
Holland, D. M., Powis, I., Öhrwall, G., Karlsson, L. & von Niessen, W. (2006). A study of the photoionisation dynamics of chloromethane and iodomethane. Chemical Physics, 326, 535-550
Open this publication in new window or tab >>A study of the photoionisation dynamics of chloromethane and iodomethane
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2006 (English)In: Chemical Physics, Vol. 326, p. 535-550Article in journal (Refereed) Published
Abstract [en]

Angle resolved valence shell photoelectron spectra of chloromethane and iodomethane have been recorded using synchrotron radiation in the photon energy range 14–120 eV. These have allowed photoelectron angular distributions and branching ratios to be determined not only for the main bands associated with the single-hole states but also for the satellite structure due to many-electron effects. The continuum multiple scattering approach has been used to calculate photoelectron asymmetry parameters and branching ratios for the valence orbitals of CH3Cl and CH3I, and also for the I 4d subshell. A comparison between the experimental data and the theoretical predictions has enabled the influence of Cooper minima, shape resonances and intershell coupling to be assessed. The asymmetry parameters and branching ratio for the spin–orbit split components of the CH3I+ X~2E state have been measured and exhibit a spectral behaviour almost identical to that of the corresponding data for the Xe 5p3/2 and 5p1/2 levels. The many-body Green’s function approach has been employed to evaluate the ionisation energies and spectral intensities of all valence states and the results have facilitated an interpretation of the satellite structure. The I 4d shake-up, shake-off and Auger spectra of iodomethane have been recorded and many of the Auger peaks have been assigned using previously determined ionisation energies of doubly charged valence states.

National Category
Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:uu:diva-19494 (URN)doi:10.1016/j.chemphys.2006.03.017 (DOI)
Available from: 2007-02-13 Created: 2007-02-13 Last updated: 2011-01-11
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