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Resonant Inelastic Photon Scattering in Helium
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Physics, Department of Physics.
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In: In manuscriptArticle in journal (Refereed) Published
URN: urn:nbn:se:uu:diva-95804OAI: oai:DiVA.org:uu-95804DiVA: diva2:170148
Available from: 2007-04-24 Created: 2007-04-24Bibliographically 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.
Digital Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1651-6214 ; 297
Physics, Soft X-ray emission, Resonant inelastic X-ray scattering, Double excitations, Helium, X-ray-emission-threshold-electron coincidence, Fysik
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
Available from: 2007-04-24 Created: 2007-04-24 Last updated: 2011-01-24Bibliographically approved

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