Possible mechanism of molecular motion in liquid water from dielectric spectroscopy data

Abstract

The broadband absorption spectrum of liquid water (103–1013Hz) contains a variety of dispersion features spread far apart on the time scale – the dc conductivity, the Debye relaxation, the relaxation-2, and the intermolecular vibration absorption peak at 5.3 THz. In the framework of the common hydrogen-bonding paradigm, the unified description of the features is not available. In an attempt to build a unified picture, we utilize the Frenkel's idea of the oscillation-translation dynamic of particles as a fundamental type of motion inherent to liquids. We develop a model of water structure, in which the dynamics is due to diffusion of particles, neutral H2O molecules and H3O+ and OH– ions - with their periodic localizations and mutual transformations. This model establishes, for the first time, a consistent link between the quoted spectral phenomena. Such currently debatable issues, as anomalous proton mobility and autoionization of water are discussed in the light of the new model. According to the model, water possesses a huge amount of short-living counter ions. This strongly contradicts to many current views on water, but meets support in individual MD simulations.