Electron density and temperature determination in an ICP using a non-equilibrium concept

We present a detailed analysis of an argon inductively coupled plasma in terms of electron density and temperature. We have measured local profiles of these parameters using two spectroscopic methods, namely the Stark broadening of the Hß line and absolute intensities of highly excited argon states. The first method yields directly the electron density, whereas the second method gives an electron density value for an equilibrium assumption. By comparing these two methods, deviations from LTE have been determined. Ionizing and recombining plasma conditions have been clearly distinguished from each other. For a wide range of operating parameters, the ICP may be described in terms of a close-to-LTE concept.