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The fifteen spectral lines between 3 and 4 keV from a laser-irradiated Au plasma were identified by the relativistic Hartree-Fock-Slater method and were attributed to multiple inner-shell vacancies: one in the 3p1/2 or 3p3/2 shell and one or two more in the M or N shell. The splitting of two groups of lines was about 400 eV, the same as the spin-orbit splitting in the $3p$ shell.
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Kiyokawa et al. (1985) studied this question.
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