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Title: Inelastic neutron scattering study on boson peaks of imidazolium-based ionic liquids

Low energy excitations of 1-alkyl-3-methylimidazolium ionic liquids (ILs) have been investigated by means of neutron spectroscopy. In the spectra of inelastic scattering, a broad excitation peak referred to as a “boson peak” appeared at 1–3 meV in all of the ILs measured. The intensity of the boson peak was enhanced at the Q positions corresponding to the diffraction peaks, reflecting the in-phase vibrational nature of the boson peak. Furthermore the boson peak energy (EBP) was insensitive to the length of the alkyl-chain but changed depending on the radius of the anion. From the correlation among EBP, the anion radius, and the glass transition temperature Tg, we conclude that both EBP and Tg in ILs are predominantly governed by the inter-ionic Coulomb interaction which is less influenced by the alkyl-chain length. Furthermore, we also found that the EBP is proportional to the inverse square root of the molecular weight as observed in molecular glasses.
Authors:
 [1] ;  [1] ;  [2] ;  [2] ;  [1] ;  [1]
  1. Univ. of Tokyo, Chiba (Japan)
  2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
Publication Date:
OSTI Identifier:
1214030
Grant/Contract Number:
AC05-00OR22725
Type:
Accepted Manuscript
Journal Name:
Journal of Molecular Liquids
Additional Journal Information:
Journal Volume: 210; Journal Issue: 1; Journal ID: ISSN 0167-7322
Publisher:
Elsevier
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS ionic liquid; inelastic neutron scattering; boson peak; glass