The open inductively coupled plasma (ICP) is used as an emission source for determining transition probabilities (A-values) of highly excited argon states. These higher states are proved to be populated according to the Saha formula.
To establish the Saha densities we use the electron temperature from Thomson scattering together with the densities of three well-known levels by absolute line
intensity (ALI) measurements. The obtained A-values are used to map electron density and temperature fields in closed and open ICP's.