title: Decoupling charge transport from the structural dynamics in room temperature ionic liquids.
abstract: Light scattering and dielectric spectroscopy measurements were performed on the room temperature ionic liquid (RTIL) [C4mim][NTf2] in a broad temperature and frequency range. Ionic conductivity was used to estimate self-diffusion of ions, while light scattering was used to study structural relaxation. We demonstrate that the ionic diffusion decouples from the structural relaxation process as the temperature of the sample decreases toward T(g). The strength of the decoupling appears to be significantly lower than that expected for a supercooled liquid of similar fragility. The structural relaxation process in the RTIL follows well the high-temperature mode coupling theory (MCT) scenario. Using the MCT analysis we estimated the dynamic crossover temperature in [C4mim][NTf2] to be T(c) ~ 225 ± 5 K. However, our analysis reveals no sign of the dynamic crossover in the ionic diffusion process.
authors.affiliation: Department of Physics and Astronomy, University of Tennessee, Knoxville, Tennessee 37996-1600, USA.
authors.forename: Philip
authors.initials: P
authors.lastname: Griffin
authors.forename: Alexander L
authors.initials: AL
authors.lastname: Agapov
authors.forename: Alexander
authors.initials: A
authors.lastname: Kisliuk
authors.forename: Xiao-Guang
authors.initials: XG
authors.lastname: Sun
authors.forename: Sheng
authors.initials: S
authors.lastname: Dai
authors.forename: Vladimir N
authors.initials: VN
authors.lastname: Novikov
authors.forename: Alexei P
authors.initials: AP
authors.lastname: Sokolov