Stable pure sulfur discharges and associated spectra

Abstract

Stable, self-sustained discharges in pure sulfur and He–sulfur mixtures have been achieved for the first time, at operating temperatures between 0 and 250 °C. Very intense S2 (B–X) band emission was observed. No other atomic or molecular emission was detected. This result indicates that S8 molecules are broken directly into S2 molecules and thus provides the potential for highly efficient discharge pumping of the (B–X) S2 laser transition at much lower operating temperatures (<300 °C) than previously thought. The S2 (B–X) band emission was examined in great detail and through the analysis of these spectra, the ground electronic state spectroscopic constants have been determined to the fourth order. These are w′′e=727.848 cm−1, wex′′e=3.0195 cm−1, w″ey″e=4.196×10−3 cm−1, wez″e =9.77×10−6 cm−1. The first observation of the B″ 3πu− −X 3Σg− system transitions was also made, and tentatively identified. Potential energy curves for both the X 3Σg− and B 3Σu− states are reported.