Ion and gas temperatures of 0.46MHz inductive plasma discharges

The ion and gas temperatures of inductively coupled plasma discharges, operated with low nitrogen gas pressures, are studied with optical emission spectroscopy. The nonresolved gas and ion rotational temperatures are estimated by comparing the measured and calculated spectra of selected transitions with a least-square procedure. The measured gas and ion temperatures increase weakly with gas pressure, and somewhat stronger with rf power. The ion temperatures (∼0.1eV) consistently exceed the corresponding gas temperatures by factors of 2–2.5, in contrast with past results. This may be due in part to ion heating by the low-frequency rf fields.