Theoretical reconstruction and elementwise analysis of photoelectron spectra for imidazolium-based ionic liquids

• Published in: Physical chemistry chemical physics : PCCP Vol. 13; no. 43; pp. 19526 - 19533
• Main Authors: REINMÖLLER, Markus, ULBRICH, Angela, IKARI, Tomonori, PREISS, Julia, HÖFFT, Oliver, ENDRES, Frank, KRISCHOK, Stefan, BEENKEN, Wichard J. D
• Format: Journal Article
• Language: English
• Published: Cambridge Royal Society of Chemistry 21.11.2011
• Subjects: Anions; Cations; Chemistry; Exact sciences and technology; General and physical chemistry; Ionic liquids; Nanostructure; Reconstruction; Spectra; UPS; X-ray photoelectron spectroscopy; Reconstruction; Density of states; Photoelectron spectrum; Ion pair; Theoretical study; X ray; Cross section (collision); Ionic liquid; Surface structure; Imide; Density functional; Valence; Density functional method; Photoelectron spectrometry; Room temperature; Core level
• ISSN: 1463-9076; 1463-9084
• DOI: 10.1039/c1cp22152c

We have recently measured core level and valence band XPS, UPS, and MIES spectra of two room temperature ionic liquids composed of bis(trifluoromethylsulfonyl)imide anions ([Tf(2)N](-)) and either 1-ethyl-3-methyl-imidazolium ([EMIm](+)) or 1-octyl-3-methyl-imidazolium cations ([OMIm](+)). [T. Ikari, A. Keppler, M. Reinmöller, W. J. D. Beenken, S. Krischok, M. Marschewski, W. Maus-Friedrichs, O. Höfft and F. Endres, e-J. Surf. Sci. Nanotechnol., 2010, 8, 241.] In the present work we analyze these spectra by means of partial density of states (pDOS) as calculated from a single ion pair of the respective ionic liquid using density functional theory (DFT). Subsequently we reconstruct the XPS and UPS spectra by considering photoemission cross sections and analyze the MIES spectra by pDOS, which provides us decisive hints to the ionic liquid surface structure.