Boron-Like Spectra: Mg viii, Al ix, and Si x

Ninety new line classifications and 70 new energy levels have been determined in the B i-like spectra, Mg viii, Al ix, and Si x. The results presented here extend the previous studies of Söderqvist and Ferner to the higher series members. Both doublet and quartet lines are observed but no intercombination lines were found. These lines lie between 30 and 70 Å. For Si x, seven lines from 250 to 290 Å, which have been previously seen in the sun, were measured to permit a more precise determination of the positions of the low-lying levels previously found.