Using a grazing-incidence spectrometer and a low-inductance 14-µF, 12–15-kV spark source, we have observed spectra of Mg X, Al XI, and Si XII. About 50 new lines are reported between 25 and 65 Å, arising from transitions between the lowest 2<i>s</i> and 2<i>p</i> configurations and <i>ns</i>, <i>np</i>, and <i>nd</i> configurations, where <i>n</i>≥3.
URI FELDMAN, LEONARD COHEN, and WILLIAM BEHRING, "Lithium-Like Spectra in Mg, Al, and Si," J. Opt. Soc. Am. 60, 891-893 (1970)