# Electron density Saha Ionization Equation

Saha-Boltzmann equation describes the ratio of number densities between any two consecutive ionization states and its product with the number electron density i.e.

$$n_e\frac{n_{i+1}}{n_{i}}$$

Here, $$n_e$$ is the electron number density, $$n_{i+1}$$ is the number density in $$i+1$$ ionization state and $$n_i$$ is the number density in the $$i$$ ionization state. My question is regarding the factor $$n_e$$. Which electron density is this actually? Is it the electron density produced as a result of ionization from $$i$$ state to $$i+1$$?

Which electron density is this actually?

The electron density in the Saha equation is the total electron number density. It does not really matter from where the electrons arose for the equation purposes, it's just the total electron density.

Is it the electron density produced as a result of ionization from $$i$$ state to $$i + 1$$?

Perhaps or perhaps not. Again, this is not the issue so much as $$n_{e}$$ corresponds to the total electron number density.

• From any ionization state? Means it is just the free electrons in the plasma?
– Shaz
Feb 19, 2019 at 4:24
• In my application the electrons are only created from ionization.
– Shaz
Feb 19, 2019 at 4:34
• As I said, it does not matter from where they came. Yes, $n_{e}$ is the number density of the free electrons in the plasma. Feb 19, 2019 at 15:24