Time- and space-resolved spectroscopy of electron transport in low-frequency discharge plasma in argon

The authors have observed the temporal and spatial profiles of optical emissions in low-frequency (100 kHz) discharge plasma at 1.0 Torr and 10 sccm in argon. Intermediate- and high-energy electron transport has been investigated by monitoring the emissions, Ar I (3p⁵5p to 3p⁵4s) and Ar II (3p⁴4p to 3p⁴4s), of the excited species with very short lifetimes compared with the external field period. It is emphasised that the power spectrum analysis of the emission intensity serves as an effective new method to investigate the plasma structure, i.e. the bulk and the sheath. Evidence is given that the electron in the bulk of plasma is driven only by the sinusoidal field with the same frequency as the external field. The metastable Ar(³P_0,2) and the ion Ar⁺(²P ₁2,3/2/) are also investigated by using the second positive and the first negative emissions in the argon plasma with 0.1% of N₂ added as a probe.