The core-excited quartet and doublet spectra of B III, produced by foil excitation of fast B+-ion beams, have been studied in the wavelength region 300-6300 Å. A large number of new transitions have been observed, for the first time allowing a detailed test ot theoretically predicted core-excited B III 4L- and 2L-term schemes. For a number of quartet states, the line assignments are supported by lifetime measurements. All the assigned, core-excited spectral lines are in excellent agreement with theoretical predictions by Chung et al. These predictions have been extended to include quartet states with L > 2.

A study of the ns0np6 1S0 states in the rare gas ions is described. A large cross section for the production of two vacancies in the ns shell in certain ion-atom collisions is used to settle the dispute over the identifications of the ns0np6 states in Auger spectroscopy. The identifications due to McGuire of the 3s03p6 1S0 and 4s04p6 1S0 states in Ar III and Kr III, respectively, are confirmed. Optical spectroscopy is used to obtain accurate values for the energies of these levels. The large cross sections for the production of two ns vacancies in the rare gases in ion-atom collisions are assumed to be the reason that the ns0np6 1S0 levels are found to be strongly populated in the hollow-cathode discharge compared to light sources where electron-impact excitation dominates.

Optical emission from the (2p2p2p) 4S0 states in three-electron systems has been studied both experimentally and theoretically. The wavelengths and transition rates have been calculated for the (2p2p2p) 4S0-(1s2p2p) 4P transition for the lithium-like ions ranging from Z=2 to Z=9. In foil-excited fast beams this transition has been observed for Li I and Be II at 145.02+or-0.05 AA and 80.85+or-0.03 AA, respectively. The experimental and theoretical data for Li I and Be II agree closely.

Optical-emission spectra of core-excited Be I 5L and core-excited Be II 2L and 4L states have been studied by means of the beam-foil-excitation method. Multiconfigurational Hartree-Fock calculations have been performed for the optical transitions between the lower-lying Be I 5L states and between 1s2pnl (n = 2-4, l = 0-3) 2P0, 2Pe, 2D0, 2De, and 2Fe states in core-excited Be II 2L to facilitate the identifications. Some previously assigned core-excited Be II 4L transitions are shown to belong to either the core-excited Be I 5L or the core-excited Be II 2L spectrum. Additional identifications of core-excited Be II 2L transitions explain the main features of this spectrum. The identifications of Be II 1s2p4l4L states are discussed.