Hydrogen Balmer lines were observed in the plasma of a plane-cathode abnormal glow discharge in mixtures of argon or neon with hydrogen and in pure hydrogen. Intense spectral-line wing development was detected whenever argon was present in the plasma. This effect is related to the formation of ${\mathrm{H}}_2^{+}$ ions in a charge-transfer reaction between metastable ${\mathrm{Ar}}^{+}$ and ${\mathrm{H}}_2$ molecules.

• Received 14 April 1992

DOI:https://doi.org/10.1103/PhysRevA.46.4429