Electron-Impact Ionization of the Si Atom

Distorted-wave calculations are made for the electron-impact ionization of the 1s2 2s2 2p6 3s2 3p2 ground configuration of the Si atom. Direct ionization of the 3s and 3p subshells contribute to single ionization, while the direct ionization of the 2p subshell contributes to double ionization. The large excitation-autoionization contributions from the 3s -> 3p transition are examined in detail. The 3s2 3p2 3P -> 3s 3p3 1D,3S,and 1P contributions are found to be located just above threshold and are found to be quite large.