Dresden 2011 – scientific programme
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CPP: Fachverband Chemische Physik und Polymerphysik
CPP 6: Charged Soft Matter
CPP 6.3: Talk
Monday, March 14, 2011, 14:30–14:45, ZEU 160
Theoretical Reconstruction of Photoelectron-Spectra for Imidazolium-Based Ionic Liquids — •Wichard J. D. Beenken, Markus Reinmöller, Julia Preiß, Jelena Pajovic, Angela Ulbrich, Stefan Krischok, and Erich Runge — Institute of Physics and Institute of Micro- and Nanotechnologies, Ilmenau University of Technology, P.O. Box 100 565, 98684 Ilmenau, Germany
We have previously measured valence-band XPS, UPS and MIES spectra of room-temperature ionic liquids formed by bis(trifluoromethylsulfonyl)imide anions ([Tf2N]−) and 1-ethyl-3-methyl-imidazolium ([EMIm]+) and 1-octyl-3-methyl-imidazolium ([OMIm]+) cations [1]. In the present work, we demonstrate how to reconstruct these XPS/UPS spectra in terms of orbital-specific partial densities of states (pDOS), which are calculated by density functional theory (DFT), and XPS/UPS cross-sections known from literature. This method allows us to identify not only the stoichiometry of the ionic liquid, but also to attribute spectral features to specific chemical positions within the ions. Furthermore, we extend this method to the analysis of MIES-spectra. Since the surface-sensitivity increases from XPS over UPS to MIES, we do not only obtain depth profiles for the stoichiometry but our analysis provides even information about the orientation of the ions at the ionic-liquid surface.
[1] Ikari, T.; Keppler, A.; Reinmöller, M.; Beenken, W. J. D.; Krischok, S.; Marschewski, M.; Maus-Friedrichs, W.; Höfft, O.; Endres, F. e-J. Surf. Sci. Nanotech. 2010, 8, 241.