Zusammenfassung
Dielectric spectra in the frequency range of 0.1 ≤ ν/GHz ≤ 89 were recorded for acetonitrile, covering temperatures between − 5 and 65 °C. These data are accurately described by a single Debye equation. The obtained values for static relative permittivity, relaxation amplitude and relaxation time exhibit a smooth temperature dependence with low standard uncertainties. Thus, acetonitrile may serve ...
Zusammenfassung
Dielectric spectra in the frequency range of 0.1 ≤ ν/GHz ≤ 89 were recorded for acetonitrile, covering temperatures between − 5 and 65 °C. These data are accurately described by a single Debye equation. The obtained values for static relative permittivity, relaxation amplitude and relaxation time exhibit a smooth temperature dependence with low standard uncertainties. Thus, acetonitrile may serve as a dielectric reference for medium permittivities (ε ≈ 30 − 40). At 25 °C the dielectric spectrum was extended to 8 THz. Its analysis revealed that the short-time dynamics of acetonitrile is dominated by dipole libration and cage rattling. On the picosecond timescale these localized motions fade into rotational diffusion of the AN molecules, which is close to slip boundary conditions. Whilst static dipole–dipole correlations are present to some extent, dynamical correlations appear to be absent for diffusive dipole reorientation.
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