EQUATION OF STATE AND SAHA EQUATION OF PARTIALLY IONIZED PLASMAS

On the basis of a generalization of the method by Uhlenbeck, Beth and Kahn to quantum plasmas, given in recent papers, the thermodynamic properties of plasmas are investigated. Using a semiclassical approximation, the free energy of low density plasmas at temperatures below a rydberg is derived. The lower bound energy states (En≲ -kT) are treated quantummechanically and the higher states (E≳ - kT) are described classically. An expression for the pressure of the plasma is obtained. From this a Saha equation is derived. Convergent expressions are given for the constant of the mass action law and the atomic partition function which depend only on the temperature. © 1968.