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Techniques and Application of Electron Spectroscopy Based on Novel X-ray Sources
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics and Astronomy, Surface and Interface Science.
2012 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

The curiosity of researchers to find novel characteristics and properties of matter constantly pushes for the development of instrumentation based on X-radiation. I present in this thesis techniques for electron spectroscopy based on developments of X-ray sources both in time structure and energy. One part describes a laser driven High-Harmonic Generation source and the application of an off-plane grating monochromator with additional beamlines and spectrometers. In initial experiments, the source is capable of producing harmonics between the 13th and 23rd of the fundamental laser 800 nm wavelength. The intensity in the 19th harmonic, after monochromatization, was measured to be above 1.2·1010 photons/second with a repetition rate of 5 kHz. 

The development of a chopper system synchronized to the bunch clock of an electron storage ring is also presented. The system can be used to adjust the repetition rate of a synchrotron radiation beam to values between 10 and 120 kHz, or for the modulation of continuous sources. The application of the system to both time of flight spectroscopy and laser pump X-ray probe spectroscopy is shown. It was possible to measure triple ionization of Kr and in applied studies the valence band of a laser excited dye-sensitized solar cell interface. The combination of the latter technique with transient absorption measurements is proposed.

The organic molecule maleic anhydride (MA) and its binding configuration to the three anatase TiO2 crystals (101), (100), (001) has been investigated by means of Xray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine structure Spectroscopy (NEXAFS). The results provide information on the binding configuration to the 101 crystal. High Kinetic Energy Photoelectron Spectroscopy was used to investigate multilayers of complexes of iron, ruthenium and osmium. The benefit of hard X-rays for ex-situ prepared samples is demonstrated together with the application of resonant valence band measurements to these molecules.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2012. , 53 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 903
Keyword [en]
High Harmonic Generation HHG, HELIOS, X-ray Beam Chopper, Dye-sensitized Solar Cell, Ultra High Vacuum UHV, Photoelectron Spectroscopy, Pump-Probe, XUV
National Category
Physical Sciences
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
URN: urn:nbn:se:uu:diva-168799ISBN: 978-91-554-8283-1 (print)OAI: oai:DiVA.org:uu-168799DiVA: diva2:503401
Public defence
2012-03-30, Pol/1311, Polacksbacken, Lägerhyddsvägen 2, Uppsala, 10:15 (English)
Opponent
Supervisors
Available from: 2012-03-09 Created: 2012-02-15 Last updated: 2012-09-18Bibliographically approved
List of papers
1. HELIOS-A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy
Open this publication in new window or tab >>HELIOS-A laboratory based on high-order harmonic generation of extreme ultraviolet photons for time-resolved spectroscopy
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2015 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 86, no 12, 123107Article in journal (Refereed) Published
Abstract [en]

In this paper, we present the HELIOS (High Energy Laser Induced Overtone Source) laboratory, an in-house high-order harmonic generation facility which generates extreme ultraviolet (XUV) photon pulses in the range of 15-70 eV with monochromatized XUV pulse lengths below 35 fs. HELIOS is a source for time-resolved pump-probe/two-color spectroscopy in the sub-50 fs range, which can be operated at 5 kHz or 10 kHz. An optical parametric amplifier is available for pump-probe experiments with wavelengths ranging from 240 nm to 20 000 nm. The produced XUV radiation is monochromatized by a grating in the so-called off-plane mount. Together with overall design parameters, first monochromatized spectra are shown with an intensity of 2 . 10(10) photons/s (at 5 kHz) in the 29th harmonic, after the monochromator. The XUV pulse duration is measured to be <25 fs after monochromatization.

National Category
Accelerator Physics and Instrumentation
Research subject
Physics
Identifiers
urn:nbn:se:uu:diva-168798 (URN)10.1063/1.4937463 (DOI)000368594900008 ()26724006 (PubMedID)
Funder
Knut and Alice Wallenberg FoundationKnut and Alice Wallenberg FoundationCarl Tryggers foundation Swedish Research Council
Note

De två första författarna delar förstaförfattarskapet.

Available from: 2012-02-15 Created: 2012-02-15 Last updated: 2017-12-07Bibliographically approved
2. Versatile high-repetition-rate phase-locked chopper system for fast timing experiments in the vacuum ultraviolet and x-ray spectral region
Open this publication in new window or tab >>Versatile high-repetition-rate phase-locked chopper system for fast timing experiments in the vacuum ultraviolet and x-ray spectral region
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2012 (English)In: Review of Scientific Instruments, ISSN 0034-6748, E-ISSN 1089-7623, Vol. 83, no 1, 013115- p.Article in journal (Refereed) Published
Abstract [en]

A novel light chopper system for fast timing experiments in the vacuum-ultraviolet (VUV) and x-ray spectral region has been developed. It can be phase-locked and synchronized with a synchrotron radiation storage ring, accommodating repetition rates in the range of ∼8 to ∼120 kHz by choosing different sets of apertures and subharmonics of the ring frequency (MHz range). Also the opening time of the system can be varied from some nanoseconds to several microseconds to meet the needs of a broad range of applications. Adjusting these parameters, the device can be used either for the generation of single light pulses or pulse packages from a microwave driven, continuous He gas discharge lamp or from storage rings which are otherwise often considered as quasi-continuous light sources. This chopper can be utilized for many different kinds of experiments enabling, for example, unambiguous time-of-flight (TOF) multi-electron coincidence studies of atoms and molecules excited by a single light pulse as well as time-resolved visible laser pump x-ray probe electron spectroscopy of condensed matter in the valence and core level region.

National Category
Natural Sciences
Identifiers
urn:nbn:se:uu:diva-168797 (URN)10.1063/1.3677329 (DOI)000300594900016 ()
Available from: 2012-02-15 Created: 2012-02-15 Last updated: 2017-12-07Bibliographically approved
3. Comparing Surface Binding of the Maleic Anhydride Anchor Group on Single Crystalline Anatase TiO2 (101), (100), and (001) Surfaces
Open this publication in new window or tab >>Comparing Surface Binding of the Maleic Anhydride Anchor Group on Single Crystalline Anatase TiO2 (101), (100), and (001) Surfaces
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2010 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 35, 15015-15020 p.Article in journal (Refereed) Published
Abstract [en]

We report on the surface binding of the maleic anhydride (C4H2O3, MA) on the TiO2 anatase (101), (100), and (001) single crystal surfaces. The MA anchor group has recently been used for dye adsorption in solar cells based on nanostructured anatase, and the results reported here are partly discussed with respect to such systems. MA was deposited simultaneously onto the (101), (100), and (001) TiO2 single crystal surfaces in UHV, and the surface binding was investigated with electron spectroscopy. The O1s and C1s core-level spectra were compared to a multilayer of MA to investigate the differences in bonding to the anatase surfaces. The results suggest a surface chemistry where the molecule reacts and the MA ring opens when adsorbed at the (101) and (100) surfaces. The molecule anchors via four oxygen atoms, similar to bonding with two carboxylic groups on TiO2. For the (001) surface, the spectra indicated a different adsorption geometry. A small amount of electronic states in the bandgap of the TiO2 surfaces was observed both before and after MA was deposited onto the surfaces, and on the (101) and (100) surfaces, the intensity of these surface states was slightly enhanced after deposition of MA.

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-139398 (URN)10.1021/jp104897k (DOI)000284520100051 ()
Available from: 2010-12-27 Created: 2010-12-23 Last updated: 2017-12-11Bibliographically approved
4. Spin-Orbit Coupling and Metal-Ligand Interactions in Fe(II), Ru(II), and Os(II) Complexes
Open this publication in new window or tab >>Spin-Orbit Coupling and Metal-Ligand Interactions in Fe(II), Ru(II), and Os(II) Complexes
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2010 (English)In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 114, no 22, 10314-10322 p.Article in journal (Refereed) Published
Abstract [en]

The purpose of the present paper is to experimentally map the energy levels governing the trends observed in oxidation potentials and absorption spectra of M(bpy)(3)(2+) complexes (bpy = 2,2'-bipyridine, M = Fe(II), Ru(II), and Os(II)). Molecular films of the transition metal complexes were investigated with element specific methods using photoelectron spectroscopy (PES) at high kinetic energy using hard X-rays and by X-ray absorption spectroscopy (XAS). The results were compared to electronic structure calculations on the complexes and the ligand. The approach allows us to experimentally measure and interpret the energy levels in terms of spin orbit coupling and metal ligand interactions. Specifically, it was verified that the anomaly in the trend in oxidation potentials could be explained by a large spin orbit coupling for the Os(bpy)(3)(2+). The influence of the different metal ions on the state formed upon light absorption was also investigated by N Is X-ray absorption, and from the spectra we could determine the relative position of the levels originating from d-sigma and pi contributions. The results for the occupied and unoccupied electronic levels explain the lower energy of the MLCT transition of the Os(bpy)(3)(2+) in comparison to the Ru(bpy)(3)(2+).

National Category
Physical Sciences
Identifiers
urn:nbn:se:uu:diva-136087 (URN)10.1021/jp103884c (DOI)000278301200032 ()
Available from: 2010-12-10 Created: 2010-12-09 Last updated: 2017-12-11Bibliographically approved

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