Double and Triple Photoionization of Ground-State Lithium

Abstract

The double and triple photoionization of ground-state lithium is investigated in the high-energy limit. Relative to the total photoionization cross section, the fraction of two-electron escape processes is 0.0325, while the fraction leading to triple escape is only $5.6\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. Double ionization via ${\mathrm{Li}}^{+}$ autoionizing states accounts for more than $40%$ of the two-electron escape processes. A comparison of the high-energy-limit calculations with experiments at 424 eV shows close agreement for double photoionization. A factor of 10 discrepancy exists for triple photoionization at 424 eV, however, which presumably indicates that the high-energy limit has not yet been reached.