Temperature Dependence of the Primary Relaxation in 1 Hexyl 3 methylimidazolium bis trifluoromethyl sulfonyl imide

We present results from complementary characterizations of the primary relaxation rate of a room temperature ionic liquid RTIL , 1 hexyl 3 methylimidazolium is trifluoromethyl sulfonyl imide, [C6mim][Tf2N], over a wide temperature range. This extensive data set is successfully merged with existing literature data for conductivity, viscosity, and NMR diffusion coefficients thus providing, for the case of RTILs, a unique description of the primary process relaxation map over more than 12 decades in relaxation rate and between 185 and 430 K. This unique data set allows a detailed characterization of the VTF parameters for the primary process, that are B 890 K, T0 155.2 K, leading to a fragility index m 71, corresponding to an intermediate fragility. For the first time neutron spin echo data from a fully deuteriated sample of RTIL at the two main interference peaks, Q 0.76 and 1.4 1 are presented. At high temperature T gt; 250 K , the collective structural relaxation rate follows the viscosity behavior; however at lower temperatures it deviates from the viscosity behavior, indicating the existence of a faster proces