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# Saha ionization equation

(Redirected from Saha equation)

Developed by the Indian astrophysicist Meghnad Saha in 1920, this formula describes the degree of ionization of a gas as a function of the temperature T, density, and ionization energy.

Let X = ne / n be the ionization fraction, i.e., the electron density relative to the total density of atoms and ions. Then the Saha equation is

$\frac{X^2}{1-X} = \frac{1}{nh^3} \left(2\pi m_ek_BT\right)^{3/2} e^{-I/k_BT}$

where h is Planck's constant and I is the ionization energy.