The photoion Li 2ϩ /Li ϩ production cross section ratio of ground-state atomic lithium has been measured for photon energies ranging from 80 to 424 eV. The absolute cross sections for the Li 2ϩ and Li ϩ yield are also derived. In this energy region, the Li 2ϩ /Li ϩ ratio reaches a plateau of about 1.0% before reaching a maximum of about 4.5%, then decreases slowly. Good agreement is found between the measured total photoionization cross sections of lithium and theoretical calculations. The Li 2ϩ /Li ϩ ratio is also compared to the He 2ϩ /He ϩ ratio from excited He(1s2s) for photon energies up to 70 eV above threshold. The branching ratio of Li 2ϩ to total Li ion production is also compared to the single-ionization cross section of electron impact on Li ϩ ions.

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The photoion spectrum of atomic potassium was measured over the 3s → np excitation region with the photoion time-of-flight method and monochromatized synchrotron radiation. An unusual spectrum with paired windows structure was found instead of a simple regular Rydberg series. Such subsidiary windows have not been observed in the 3s → np resonances of Ar, which has a closed outer shell. Based on Dirac-Fock calculations, the dual window structure at 36.7 eV and at 37.4 eV was assigned to the 3s −1 3p 6 4s4p resonance. The line shape can be fitted by Fano's formula and the Fano parameters were obtained.

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