Emission Spectra of Sulphur

A NUMBER of investigators 1–4 have reported that predissociation occurs at v ′ > 9 and v ′ > 16 in the 3 Σ g − → 3 Σ u − ( X → B ) absorption spectrum of S 2 due to a radiationless 3 Σ u → 3 Π u transition in the upper state. In the emission spectrum 3,5−10 , various workers have reported a break-off at v ′ = 9, in conformity with this suggestion. Asundi 11 , however, has reported that with sulphur in a discharge tube in the presence of argon at high pressure, bands appear beyond the first limit of predissociation. He suggests that argon helps in some way to arrest the predissociation of S 2 molecules. However, Christy and Naudé 3 prefer to think that the argon helps to increase the population of the levels with v ′ > 9, and that although some dissociation does take place, there are still sufficient molecules present in the higher vibrational states to emit the bands with observable intensity.