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.