FORBIDDEN SULPHUR-I-LINES IN SOLAR SPECTRUM

The [SI] lines are due to transitions within the 3s23p4 ground configuration of neutral sulphur. The results are presented from a search for the [S i] lines in the Fraunhofer spectrum. Two identifications are proposed with faint features in the Fraunhofer spectrum: 1D2-1S0 at λ⊙ = 7725.02 Å and 3P2-1D2 at λ⊙ = 10821.23 Å. Their measured equivalent widths are shown to confirm the value for the solar abundance of sulphur, log NS = 7.21 (in the scale log NH = 12.00), which is derived from the permitted high-excitation lines. These lines give the first convincing identification of [S i] lines in an astrophysical source. © 1969 D. Reidel Publishing Company.