title: Correlation between Soft X-ray Absorption and Emission Spectra of the Nitrogen Atoms within Imidazolium-Based Ionic Liquids.
abstract: Soft X-ray absorption spectroscopy (XAS) has been performed on the N K-edge of two imidazolium-based ionic liquids (ILs), 1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)amide ([C2mim][TFSA]) and 1-ethyl-3-methylimidazolium bromide ([C2mim][Br]), to clarify the electronic structures of the ILs. Soft X-ray emission spectroscopy (XES) has also been applied to the ILs by excitation at various X-ray energies according to the XAS spectra. It was possible to fully associate the XAS peaks with the XES peaks. Additionally, both XAS and XES spectra of the ILs were well reproduced by the theoretical spectra for a single-molecule model on [C2mim](+) and [TFSA](-) using density functional theory. The assignments for the XAS and XES peaks of the ILs were accomplished from both experimental and theoretical approaches. The theoretical XAS and XES spectra of [C2mim](+) and [TFSA](-) did not significantly depend on the conformations of the ions. The reproducibility of the theoretical spectra for the single-molecule model suggested that the interactions between the cations and anions are very weak in the ILs, thus scarcely influencing the electronic structures of the nitrogen atoms.
authors.affiliation: Department of Physics and Information Science, Faculty of Science, Yamaguchi University , 1677-1 Yoshida, Yamaguchi 753-8512, Japan.|Soft X-ray Spectroscopy Instrumentation Unit, RIKEN SPring-8 Center , Sayo-cho, Sayo, Hyogo 679-5148, Japan.
authors.forename: Yuka
authors.initials: Y
authors.lastname: Horikawa
authors.affiliation: Soft X-ray Spectroscopy Instrumentation Unit, RIKEN SPring-8 Center , Sayo-cho, Sayo, Hyogo 679-5148, Japan.
authors.forename: Takashi
authors.initials: T
authors.lastname: Tokushima
authors.affiliation: Soft X-ray Spectroscopy Instrumentation Unit, RIKEN SPring-8 Center , Sayo-cho, Sayo, Hyogo 679-5148, Japan.|Institute for Sustainable Sciences and Development, Hiroshima University , 1-3-1 Kagamiyama, Higashi-Hiroshima 739-8526, Japan.
authors.forename: Osamu
authors.initials: O
authors.lastname: Takahashi
authors.affiliation: Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University , Honjo-machi, Saga 840-8502, Japan.
authors.forename: Hiroshi
authors.initials: H
authors.lastname: Hoke
authors.affiliation: Soft X-ray Spectroscopy Instrumentation Unit, RIKEN SPring-8 Center , Sayo-cho, Sayo, Hyogo 679-5148, Japan.|Department of Chemistry and Applied Chemistry, Graduate School of Science and Engineering, Saga University , Honjo-machi, Saga 840-8502, Japan.
authors.forename: Toshiyuki
authors.initials: T
authors.lastname: Takamuku