Vibrational Population of Hydrogen Molecules Excited by an RF Discharge in an Expanding Thermal Arc Plasma as Determined by Emission Spectroscopy

This work is devoted to the determination of the vibrational population of hydrogen molecules in the ground and excited electronic states from the analysis of visible spectra of the H 2 molecules excited by an RF discharge in an expanding thermal arc plasma. Comparison of the experimental results on relative electron‐impact excitation cross sections for the transition H 2 (X 1 Σ   g + , υ 0 = 0)→ H 2 ( d 3 II u , υ′) with other experiments, and with calculations based on the Franck‐Condon principle, shows good agreement. This means, that for plasma under investigation: 1) in the ground electronic state H 2 (d 3 II u ,υ′), only the lowest vibrational level with υ 0 = 0 is significantly populated, and 2) direct electron exictation of H 2 ( d 3 II u , υ′, υ′) state from the ground state H 2 (X 1 Σ   g + , υ 0 = 0) dominates.