Frequency dispersion of the electric conductivity of liquid electrolytesI. Chikina1, S. Nazin2 and V. Shikin2
1 DRECAM/SCM/LIONS CEA - Saclay - 91191 Gif-sur-Yvette Cedex, France
2 ISSP RAS - Chernogolovka, Moscow district, 142432 Russia
received 19 June 2007; accepted in final form 3 September 2007; published October 2007
published online 24 September 2007
Discussed in this paper are details of the Ohmic conduction of the solution of a binary 1-1 electrolyte. The study is motivated by the desire to have a consistent equation of motion for a charged particle in a normal (non-superfluid) liquid with finite viscosity . Usually, employed for this purpose is the so-called Langevin equation where the particle mass M is assumed to be constant and the characteristic relaxation time is expressed through the viscosity . However, this scenario is not self-consistent: If the friction force has Stokes origin, the effective ion mass consisting of its bare mass and the associated hydrodynamic mass due to the arising flow of the adjacent liquid should not be constant (for example, in case of oscillatory motion it exhibits a strong frequency dispersion: ). Although the scenario with M = const is also in principle possible (we refer to it as the Drude scenario, below), in that case the friction force which is linear in the ion velocity should have a different (non-Stokes) origin. The performed analysis of frequency dispersion of electrolyte conductivity for the two scenarios reveals qualitative differences which can be detected experimentally in their behaviour allowing to distinguish between the Drude and Stokes models. An important problem for ion dynamics in liquids is the structure of charged clusters (arising around the ions) whose radius Rs is usually considered to be an adjustable parameter. We discuss the physical mechanisms governing the formation of Rs.
66.10.-x - Diffusion and ionic conduction in liquids.
66.10.Ed - Ionic conduction.
© Europhysics Letters Association 2007