Kinetic dielectric decrement revisited: a theory for finite ion concentrations

With the help of a recently developed non-equilibrium approach, we investigate the ionic strength dependence of the Hubbard--Onsager dielectric decrement. We compute the depolarization of water molecules caused by the motion of ions in sodium chloride solutions from the dilute regime (0.035 M) up close to the saturation concentration (4.24 M), and find that the kinetic decrement displays a strong nonmonotonic behavior, in contrast to the prediction of available models. We introduce a modification of the Hubbard--Onsager continuum theory, that takes into account the screening due to the ionic cloud at mean field level, and, is able to predict quantitatively the value of the kinetic decrement in the whole inspected range.