At what wavelength do we observe ionized gas?

[Mikkel]

TL;DR

At what wavelength do we observe ionized gas?

Hello!

My question is this: At which wavelength do we observe ionized gas?

My understanding is this: An ionized gas is basically a soup of particles flying around, because of the extreme temperatures (plasma?). So if we have particles moving around with such high velocities, I would expect to observe this in X-rays, but I lack the physical argument as to why. Gamma-rays would probably be caused by supernovae?

I find different answers when I search for it and it has something to do with the energy 13.6 eV...?

Hope someone can clarify this for me

 

[snorkack]

It has something to do with 13,6 eV.
That´ s Lyman edge. Which means the energy enough to ionize a ground state hydrogen atom.
Hydrogen atoms are very common in space. Even in quite hot gas, where most atoms are ionized, there is often an appreciable minority of atoms that are not ionized.
Now, edge absorption is very strong. Near Solar System, in Milky Way disc, the interstellar gas, sparse as it is, seems to absorb most UV with energy of just over 13,6 eV in a matter of just a few lightyears.
High energy photons of soft x-rays can still ionize atoms - they have more than enough energy for this - but they have lower probability of absorption. But it seems to be that it is only photons with energy over 100...200 eV that can get through Milky Way.
If a cloud of ionized gas is hot enough that it emits high energy UV, like 15 or 20 eV, then this far UV will be absorbed by moderately hot gas around Sun or already at the cooler edges of the hot cloud emitting such far UV. So far UV cannot be observed. What can be observed is near UV and visual light which is produced as byproducts.