title: Temperature-dependent electronic and vibrational structure of the 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide room-temperature ionic liquid surface: a study with XPS, UPS, MIES, and HREELS.
abstract: The near-surface structure of the room-temperature ionic liquid 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide has been investigated as a function of temperature between 100 and 620 K. We used a combination of photoelectron spectroscopies (XPS and UPS), metastable induced electron spectroscopy (MIES), and high-resolution electron energy loss spectroscopy (HREELS). The valence band and HREELS spectra are interpreted on the basis of density functional theory (DFT) calculations. At room temperature, the most pronounced structures in the HREELS, UPS, and MIES spectra are related to the CF3 group in the anion. Spectral changes observed at 100 K are interpreted as a change of the molecular orientation at the outermost surface, when the temperature is lowered. At elevated temperatures, early volatilization, starting at 350 K, is observed under reduced pressure.
authors.affiliation: Institut für Physik and Institut für Mikro- und Nanotechnologien, Technische Universität Ilmenau, P.O. Box 100565, D-98684 Ilmenau, Germany. stefan.krischok@tu-ilmenau.de
authors.forename: S
authors.initials: S
authors.lastname: Krischok
authors.forename: M
authors.initials: M
authors.lastname: Eremtchenko
authors.forename: M
authors.initials: M
authors.lastname: Himmerlich
authors.forename: P
authors.initials: P
authors.lastname: Lorenz
authors.forename: J
authors.initials: J
authors.lastname: Uhlig
authors.forename: A
authors.initials: A
authors.lastname: Neumann
authors.forename: R
authors.initials: R
authors.lastname: Ottking
authors.forename: W J D
authors.initials: WJ
authors.lastname: Beenken
authors.forename: O
authors.initials: O
authors.lastname: Höfft
authors.forename: S
authors.initials: S
authors.lastname: Bahr
authors.forename: V
authors.initials: V
authors.lastname: Kempter
authors.forename: J A
authors.initials: JA
authors.lastname: Schaefer
mesh_terms: D004583:Electrons; D007093:Imidazoles / Q000737:chemistry*; D052578:Ionic Liquids / Q000737:chemistry*; D008854:Microscopy, Electron / Q000379:methods*; D012680:Sensitivity and Specificity; D013053:Spectrophotometry / Q000379:methods; D046590:Spectroscopy, Electron Energy-Loss / Q000379:methods*; D013449:Sulfonamides / Q000737:chemistry*; D013499:Surface Properties; D013696:Temperature; D014732:Vibration; D014965:X-Rays
chemical_list: C500270:1-ethyl-3-methyl-imidizolium bis((trifluoromethyl)sulfonyl)amide; D007093:Imidazoles; D052578:Ionic Liquids; D013449:Sulfonamides