Absorption spectroscopy measurements of argon metastable and resonant atoms densities in atmospheric pressure Ar-He surface-wave plasmas

摘要

The absorption method for measuring metastable and resonant atom densities extended to the case of atmospheric pressure plasmas where the lines show Voigt profiles is applied to an atmospheric pressure Ar-He surface-wave discharge. A quick decrease in Argon metastable and resonant density takes place upon introduction of helium with amounts as low as 2%. Density values for the ~3P_2 and ~3P_0 (metastable) and ~3P_1 (resonant) levels reported in this work for the case of pure argon discharges are in good agreement with those reported in the literature. The behaviour of the metastable and resonant atom densities agrees with that expected from the dependence of electron density on helium percentage. This behaviour could result from the enhancement of the gas temperature that favours the decrease of the Ar molecular ions density thereby reducing the generation of metastable atoms by dissociative recombination.