THE SPECTRUM AND TERM SYSTEM OF S-VIII

The spectrum of seven times ionized sulfur, S VIII, has been observed in the wavelength range 50-1200 angstrom. Both beam-foil and laser-produced plasma light sources have been used. 71 new lines representing the transitions 2p5-2p(4)3d, 2p(4)3s-3p, 3p-3d, 3d-4f 4f-5g and 5g-6h have been identified and 100 energy levels, of which 46 are new, are now accurately established. The spectral analysis is supported by isoelectronic comparisons along the F I-sequence and by parametric least-squares fits of Slater integrals to the observed levels. The ionization potential in S VIII is determined to 2651 899 +/- 60 cm-1 and estimated ionization energies are derived for the isoelectronic elements between F I and Ar X.