Saha Equation for Ionization Equilibrium in Thermal Plasma

Saha Equation for Ionization Equilibrium in Thermal Plasma 

The Boltzmann distribution (3-9) can be applied to describe ionization equilibrium A+ + e A in plasma (Smirnov, 1982a,b Fridman Kennedy, 2004)  

In this relation, / is the ionization potential ga, gi, and ge are the statistical weights of atoms, ions, and electrons N, and are their number densities and m is the electron mass. Formula (3-14) is known as the Saha equation and is widely used for calculations of ionization degree in thermal plasmas. 

According to the Saha formula, the effective statistical weight of the continuum spectrum is very high. As a result, the Saha equation predicts very high values of degree of ionization, 7Ve/7Va, which can be close to unity even when temperature is still much less than the ionization potential, T I. 

The Saha formula is commonly used for quasi-equihbrium thermal plasma. It can also be applied, however, for estimations of non-thermal discharges assuming the temperature in (3-14) is that of electrons, 7),. One should take into account in this case that the Saha equation describes ionization equilibrium A+ + e A, which corresponds to a detailed balance of ionizationby electron impact and three-body recombination e - - e + e + A+. As was 

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