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 (1s2s²)²S and the (1s2p²)²D 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, Mg⁺, and K are also presented.