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

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 tau(1) > tau(2) > tau(3) > tau(4). Whereas tau(2), tau(3), and tau(4) exhibit Arrhenius behaviour at all temperatures, the relaxation time of the slowest process, tau(1), exhibits an unusual temperature dependence which can be fitted by assuming two Arrhenius equations intersecting at approximately 315 K. At T greater than or equal to 315 K the tau(2) process is assigned to rotation of a mixture of the free acid and its anion. The relaxation time tau(3) arises from the reorientation of H2O or H3O+. For both relaxation processes hydrodynamic boundary conditions are close to slip. For the high-frequency process, tau(4), the comparison with results from MOPAC calculations suggests intramolecular rotation of the OH-group as the dominating contribution.