Optical Emission Spectroscopy is the only
diagnostic method that could determine:

- Particle densities

- Electron densities

- Electron temperature

The Line intensity correlates with particle density and electron density.

The Intensity ratio yields particle density. Clever combination of lines of the same electron energy absorption compared to a third line gives back the correlation of the electron temperature.

Now we have erverything we need to control fully all of our plasma process relavant parameters.