Dynamics of molten CF3SO3H·H2O probed by temperature dependent dielectric spectroscopy

Abstract

The complex permittivity of CF₃SO₃H·H₂O was investigated in the frequency range 0.3–89 GHz at temperatures from 298 to 338 K. The microwave spectra which show very broad absorption are analysed in terms of four Debye processes with relaxation times τ₁>τ₂>τ₃>τ₄. Whereas τ₂, τ₃ and τ₄ exhibit Arrhenius behaviour at all temperatures, the relaxation time of the slowest process, τ₁, exhibits an unusual temperature dependence which can be fitted by assuming two Arrhenius equations intersecting at approximately 315 K. At T315 K the τ₂ process is assigned to rotation of a mixture of the free acid and its anion. The relaxation time τ₃ arises from the reorientation of H₂O or H₃O⁺. For both relaxation processes hydrodynamic boundary conditions are close to slip. For the high-frequency process, τ₄, the comparison with results from MOPAC calculations suggests intramolecular rotation of the OH-group as the dominating contribution.