title: Nonlinear ion transport in the supercooled ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide: Frequency dependence of third-order and fifth-order conductivity coefficients.
abstract: We have carried out nonlinear ion conductivity measurements on the supercooled ionic liquid 1-hexyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide[C6mim][NTf2] by applying ac electric fields with amplitudes up to about 200 kV/cm. At these field amplitudes, 3ω and 5ω harmonic components in the current response were detected, and the higher-order conductivity coefficients σ3 (1),σ3 (3),σ5 (3), and σ5 (5) were determined. The frequency and temperature dependence of these conductivity coefficients was analyzed in detail. The most important findings were the following: (i) The third-order spectra σ3 (1) and σ3 (3) exhibit very similar values in the dc plateau regime but differ considerably in the dispersive regime. The same was observed for the fifth order spectra σ5 (3) and σ5 (5). (ii) In the dispersive regime, the third-order spectra display a minimum, while the fifth-order spectra display a maximum. (iii) The frequencies of these minima and maxima are thermally activated with the same activation energy as the low-field dc conductivity σ1,dc, whereas the dc values of the higher-order conductivity coefficients, σ3,dc and σ5,dc, are characterized by lower activation energies.
authors: Department of Chemistry, Phillips University of Marburg, Marburg 35032, Germany.
authors: L N
authors: LN
authors: Patro
authors: Department of Chemistry, Phillips University of Marburg, Marburg 35032, Germany.
authors: O
authors: O
authors: Burghaus
authors: Department of Chemistry, Phillips University of Marburg, Marburg 35032, Germany.
authors: B
authors: B
authors: Roling