Publication

Isotopic Fingerprints of Proton-Mediated Dielectric Relaxation in Solid and Liquid Water

2026

Abstract

We report cross-validated measurements of the isotope effect on dielectric relaxation for four isotopologues of ice and water, including the 1–105 Hz region, in which only sporadic and inconsistent measurements were previously available. In ice, the relaxation rates exhibit an activated temperature dependence with an isotope-independent activation energy. Across 248–273 K, the H2O-to-D2O relaxation rate ratio remains constant at 2.0±0.1. This scaling agrees with Kramers’ theory in the high-friction limit if the moving mass is the proton or deuteron, indicating that dielectric relaxation is governed by a classic proton transfer over an energy barrier rather than molecular reorientation.

Official source

https://infoscience.epfl.ch/entities/publication/83b79f27-9324-4177-92c2-e44e123be111

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2026

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/83b79f27-9324-4177-92c2-e44e123be111

About this result

Related concepts (32)

Activation energy

In chemistry and physics, activation energy is the minimum amount of energy that must be provided for compounds to result in a chemical reaction. The activation energy (Ea) of a reaction is measured in joules per mole (J/mol), kilojoules per mole (kJ/mol) or kilocalories per mole (kcal/mol). Activation energy can be thought of as the magnitude of the potential barrier (sometimes called the energy barrier) separating minima of the potential energy surface pertaining to the initial and final thermodynamic state.

Kinetic isotope effect

In physical organic chemistry, a kinetic isotope effect (KIE) is the change in the reaction rate of a chemical reaction when one of the atoms in the reactants is replaced by one of its isotopes. Formally, it is the ratio of rate constants for the reactions involving the light (kL) and the heavy (kH) isotopically substituted reactants (isotopologues): This change in reaction rate is a quantum mechanical effect that primarily results from heavier isotopologues having lower vibrational frequencies compared to their lighter counterparts.

Reaction rate

The reaction rate or rate of reaction is the speed at which a chemical reaction takes place, defined as proportional to the increase in the concentration of a product per unit time and to the decrease in the concentration of a reactant per unit time. Reaction rates can vary dramatically. For example, the oxidative rusting of iron under Earth's atmosphere is a slow reaction that can take many years, but the combustion of cellulose in a fire is a reaction that takes place in fractions of a second.

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Isotopic Fingerprints of Proton-Mediated Dielectric Relaxation in Solid and Liquid Water

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