Non-rotational mechanism of polarization in alcohols

Abstract

Models following the widely used Debye's phenomenological approach to dielectric relaxation aim to explain the frequency-dependent complex dielectric function. They assume rotational diffusion of the polar molecules and ad hoc dipole relaxation time models failing to cover the full dc up to THz spectral range. Here, using the illustrative case of monohydric alcohols, we show that intermolecular separation of excess protons and "proton-holes" in the polar liquid, governs its static and dynamic dielectric properties on the same footing. We performed systematic ultrabroadband (0-10 THz) spectroscopy experiments with monohydric alcohols of different (0.4-1.6 nm) molecular lengths; and we propose a model that accurately describes the dielectric response of all the studied alcohols across the entire frequency range, without any rotational diffusion mechanism nor the knowledge of a molecule's dipole moment. This substantiates the proposed intermolecular polarization mechanism.