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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 (E BP) was insensitive to the length of the alkyl-chain but changed depending on the radius of the anion. From the correlation among E BP, the anion radius, and the glass transition temperature T g, we conclude that both E BP and T g 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 E BP 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:
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 Lab. (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
74 ATOMIC AND MOLECULAR PHYSICS; ionic liquid; inelastic neutron scattering; boson peak; glass
OSTI Identifier:
1214030
Alternate Identifier(s):
OSTI ID: 1250296