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Double Excitations of Helium in Weak Static Electric Fields
Uppsala University, Disciplinary Domain of Science and Technology, Physics, Department of Physics.
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2006 In: Physical Review Letters, ISSN 0031-9007, Vol. 96, 043002- p.Article in journal (Refereed) Published
Place, publisher, year, edition, pages
2006. Vol. 96, 043002- p.
Identifiers
URN: urn:nbn:se:uu:diva-95805OAI: oai:DiVA.org:uu-95805DiVA: diva2:170149
Available from: 2007-04-24 Created: 2007-04-24 Last updated: 2016-04-26Bibliographically approved
In thesis
1. Soft X-ray Scattering Dynamics Close to Core Ionization Thresholds in Atoms and Molecules
Open this publication in new window or tab >>Soft X-ray Scattering Dynamics Close to Core Ionization Thresholds in Atoms and Molecules
2007 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this Thesis studies of highly excited states in gas-phase atoms and molecules (He, Ne, N2, O2, N2O and CO2) using a variety of synchrotron-radiation based techniques are presented. The three techniques used most frequently are X-ray-emission-threshold-electron coincidence (XETECO), X-ray emission spectroscopy (XES) and X-ray photoelectron spectroscopy (XPS) and they are all given a brief introduction.

The fluorescence yield (FY) from doubly excited states in helium near the N=2 threshold(s) has been investigated in weak static external magnetic and electric fields, but also in a field free environment. The FY spectra in weak static magnetic fields show the importance of including the diamagnetic interaction in the theoretical models. The presence of weak static electric fields shows that even weak fields (as low as 44 V/cm) has a great impact on the observed FY spectra. Resonant XES spectra from some of the first doubly excited states in helium has been recorded in a field free environment, and compared to theory.

The XETECO technique is presented and the first XETECO results from Ne, N2, O2, CO2 and N2O are shown, together with interpretations of possible threshold dynamics. I show that XETECO can be interpreted as threshold photoelectron spectra free from post collision interaction, and can hence be compared to above threshold XPS measurements. The observed below-threshold structures in the XETECO spectra are discussed and given a tentative explanation. The results from the analysis of the N2O XETECO spectrum lead to further investigations using XPS. Results showing the vibrational parameters and vibrationally resolved cross-sections and asymmetry parameters for N2O are presented together with theoretical predictions.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2007. 106 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 297
Keyword
Physics, Soft X-ray emission, Resonant inelastic X-ray scattering, Double excitations, Helium, X-ray-emission-threshold-electron coincidence, Fysik
Identifiers
urn:nbn:se:uu:diva-7832 (URN)978-91-554-6874-3 (ISBN)
Public defence
2007-05-16, Polhemsalen, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:15
Opponent
Supervisors
Available from: 2007-04-24 Created: 2007-04-24 Last updated: 2011-01-24Bibliographically approved
2. Applications of Soft X-Ray Spectroscopy
Open this publication in new window or tab >>Applications of Soft X-Ray Spectroscopy
2011 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Soft X-ray emission spectroscopy is an old experimental technique that has seen a strong revival since the advent of new high brilliance soft X-ray sources in the shape of synchrotrons.  This thesis covers a range of applications where soft x-ray techniques have been applied. I have looked at fluorescence yield from doubly excited helium in field free conditions as well as in the presence of weak electric and magnetic fields. Using soft X-ray emission spectroscopy (SXES) I have explored scattering mechanisms in molecular systems. Quenching of symmetry breaking transitions by detuning of the excitation energy was observed in CO2. Bond-length dependence was seen for symmetry breaking transitions in a series of hydrocarbons. Dissociation dynamics was explored in OCS and HCl. I have also applied SXES to liquid water exploring the properties of hydrogen bonding.  Buried layers of AlAs under 100 Å GaAs(100) was studied and thickness dependence and interface effects observed. The technique was also used to study the electronic structure of yttrium and vanadium hydrides. dd-excitations and accompanying spin flip excitations was observed in Cu M resonant x-ray Raman emission from Sr2CuO2Cl2.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2011. 61 p.
Series
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 860
National Category
Atom and Molecular Physics and Optics Condensed Matter Physics
Research subject
Physics with spec. in Atomic, Molecular and Condensed Matter Physics
Identifiers
urn:nbn:se:uu:diva-159369 (URN)978-91-554-8173-5 (ISBN)
Public defence
2011-11-11, Å4001, Ångströmlaboratoriet, Lägerhyddsvägen 1, Uppsala, 10:00 (English)
Opponent
Supervisors
Available from: 2011-10-21 Created: 2011-09-29 Last updated: 2011-11-04Bibliographically approved

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