Development and applications of spectroscopic determinations of the electron distribution function in discharges

Abstract

A spectroscopic method based on the analysis of molecular and atomic spectra of nitrogen and atomic spectra of He was used for the determination of electron distribution functions (EDFs) in glow discharges and electron cyclotron resonance (ECR) discharges. The EDF between 1.5 and 4.5 eV was determined from the vibrational distribution of excited molecular states of nitrogen. The EDFs in the energy range above 11 eV (glow discharge) and above 8.5 eV (ECR discharge) were evaluated from the intensities of different emission lines and bands of He, N I, N II and N2. The shape of the EDF in the energy range between 4.5 and 8.5 eV (ECR discharge) was interpolated by using the electron density measured with Langmuir probes and normalizing the EDF to the same density. Due to the low gas pressure of 2 × 10-5 Torr, vibrational relaxation processes on the discharge chamber wall had to be taken into account. The spectroscopic and probe methods for the EDF determination were compared over a wide energy range. The results agree within the limits of the experimental errors with the EDF measured directly by the probe.