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Interactions and dynamics in ionic liquids
Journal article   Peer reviewed

Interactions and dynamics in ionic liquids

A. Stoppa, J. Hunger, R. Buchner, G. Hefter, A. Thoman and H. Helm
Journal of Physical Chemistry B, Vol.112(16), pp.4854-4858
2008
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Abstract

Precise dielectric spectra have been determined at 25°C over the exceptionally broad frequency range of 0.1 ≤ v/GHz ≤ 3000 for the imidazolium-based room-temperature ionic liquids (RTILs) [bmim] [BF 4], fbmim]-[PFO], [bmim][DCA], and [hmim][BF4]. The spectra are dominated by a low-frequency process at ∼1 GHz with a broad relaxation time distribution of the Cole-Davidson or Cole-Cole type, which is thought to correspond to the rotational diffusion of the dipolar cations. In addition, these RTILs possess two Debye relaxations at ∼5 GHz and ∼0.6 THz and a damped harmonic oscillation at ∼2.5 THz. The two higher-frequency modes are almost certainly due to cation librations, but the origin of the ∼5 GHz mode remains obscure.

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