Water and Ice Dielectric Spectra Scaling at 0 {\deg}C

TL;DR

This paper compares the dielectric spectra of water and ice at 0°C, revealing how proton conductivity and charge diffusion processes differ and change across the phase transition, with implications for understanding molecular dissociation and charge dynamics.

Contribution

It introduces a scaling analysis of dielectric spectra at 0°C, highlighting the role of charge diffusion and relaxation processes in water and ice, and explains the spectral transformation at the phase transition.

Findings

Debye relaxations correspond to charge diffusion in water and ice.

Charge recombination is diffusion-controlled with distinct lifetimes.

Spectral transformation is driven by a change in activation energy of charge diffusion.

Abstract

Dielectric spectra (10^4-10^11 Hz) of water and ice at 0 {\deg}C are considered in terms of proton conductivity and compared to each other. In this picture, the Debye relaxations, centered at 1/{\tau}_W ~ 20 GHz (in water) and 1/{\tau}_I ~ 5 kHz (in ice), are seen as manifestations of diffusion of separated charges in the form of H3O+ and OH- ions. The charge separation results from the self-dissociation of H2O molecules, and is accompanied by recombination in order to maintain the equilibrium concentration, N. The charge recombination is a diffusion-controlled process with characteristic lifetimes of {\tau}_W and {\tau}_I, for water and ice respectively. The static permittivity, {\epsilon}(0), is solely determined by N. Both, N and {\epsilon}(0), are roughly constant at the water-ice phase transition, and both increase, due to a slowing down of the diffusion rate, as the temperature is lowered. The transformation of the broadband dielectric spectra at 0 {\deg}C with the drastic change from {\tau}_W to {\tau}_I is mainly due to an abrupt (by 0.4 eV) change of the activation energy of the charge diffusion.