Spectroscopic Investigation of the Argon Metastable State Through Optical Emission From Pulsed Argon Discharge

摘要

A plasma diagnostic technique has been experimentally demonstrated where optical emission measurements of relative intensities of spectral lines in the violet range were combined with available electron-impact cross sections to yield absolute Ar metastable species concentration. An enabling factor of this analysis was that the electron excitation pattern was quite different between the Ar ground state and the metastable state. The result of this pattern was that the optical spectrum was unique depending on whether the emission was generated by direct excitation from the ground state, or by stepwise excitation from one of the metastable states. This study has shown that a model combining Ar excitation cross sections can fit the experimental spectral distributions by varying the ratio of the metastable state density and the E/N within the discharge. The absolute density obtained through optical emission spectroscopy was compared to measurements using laser diode absorption in order to confirm the results.