Spectroscopic observation of electronically excited SO (A″3Σ+)

The radiation produced in an afterglow due to the reaction of Ar(3P0, 2) with SO2 has been studied between 230 and 600 nm. Two progressions are assigned to SO species. Aside from SO (c1Σ− → X3Σ−), a new SO emission band located closely to the peak lines of SO (c1Σ− → X3Σ−) in the range of 400 and 600 nm was also discovered and assigned to the SO (A″3Σ+ → X3Σ−) transition. A set of spectroscopic constants for the A″3Σ+ state was deduced as T00 = 30 460 ± 18.0 cm−1, ω e ′ = 685 ± 8.0 cm − 1 , ω e ′ χ e ′ = 7.7 ± 0.8 cm − 1 .