Abstract:
In this work we study several definitions of free and bound states in plasmas and the consequences of Onsager's bookkeeping rule for the thermodynamic functions. In particular we investigate Onsager's rule of balance between the contributions of free and bound charges. We show that this rule guarantees at low densities the independence (stationarity) with respect to the fine details of the definition of bound states (chemical species). The Brillouin-Planck-Larkin atomic partition function which is the most natural choice is modified and the consequences of such changes are investigated. We study the free energy landscape in dependence on different choices of the mass action constant and formulate the condition of stationarity with respect to free parameters. We show that at high densities the condition of stationarity is violated (except in certain saddle points) so that in general the chemical description of plasmas can be applied only with great care.
Similar content being viewed by others
Author information
Authors and Affiliations
Additional information
Received 28 July 2001 / Received in final form 28 February 2002 Published online 28 June 2002
Rights and permissions
About this article
Cite this article
Ebeling, W., Hilbert, S. On Saha's equation for partially ionised plasmas and Onsager's bookkeeping rule. Eur. Phys. J. D 20, 93–101 (2002). https://doi.org/10.1140/epjd/e2002-00109-0
Issue Date:
DOI: https://doi.org/10.1140/epjd/e2002-00109-0