# Hydrogen excitation, ionisation and photon absorption

I need help with something that i seemed to remember was fairly easy, but just can't seem to find the simple formula for:

I have an amount of hydrogen atoms at a temperature of 10000 Kelvin. What percentage of them are ionised and what percentage of them are in the n=2 excited state.

Secondly, where could i find the absorption cross section of a hydrogen atom in the n=2 state for the wavelength 656.28 nm? (aka Halpha line)

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What percentage of them are ionised
That will depend on the density.

and what percentage of them are in the n=2 excited state.
See "Boltzmann factor".

Secondly, where could i find the absorption cross section of a hydrogen atom in the n=2 state for the wavelength 656.28 nm? (aka Halpha line)
The NIST database could have that, not sure.