Core-excited autoionizing states in the alkali metals

An extension of projectile-electron spectroscopy to keV-energy alkali-metal beams has permitted the first observations of the energies of a number of optically forbidden core-excited autoionizing states of the alkali metals. For example, we have located the $\left(1s2\mathrm{}{s}^2\right){}_{}{}^2{}_{}{}^{}S$ and the $\left(1s2\mathrm{}{p}^2\right){}_{}{}^2{}_{}{}^{}D$ states of Li which lie at 56.31±0.03 eV and 61.04±0.03 eV, respectively, above the ground state. Energies for theoretically less-well-established doublet and quartet states in Na, ${\mathrm{Mg}}^{+}$, and K are also presented.