THE ROLE OF METASTABLE ATOMS IN GLOW-DISCHARGE IONIZATION PROCESSES

Ionization processes have been studied in a glow discharge using neon and argon as discharge gases. A tunable laser served to depopulate metastable atom populations, and the effects were followed by optical galvanic spectroscopy and mass spectrometry. In the neon discharge, depopulation of the metastables caused a general reduction in all measured ion signals, while similar studies with argon showed that many species with ionization potentials greater than the metastable energies of argon were not affected by laser depopulation. These results provide evidence for the role of Penning ionization in the glow discharge.