The contributions of double excitation-autoionization to the electron impact ionization of Li+

We have performed 11-state and 37-state R-matrix close-coupling calculations of the contributions of double excitation followed by autoionization to the electron impact ionization cross section of Li+. Through the use of pseudo-orbitals in the configuration-interaction expansions for the bound states, we obtained energies in good agreement with observed energies for both the singly excited and doubly excited terms. The 37-state calculation, which employed a basis set with a total of 58 terms in all of the configuration-interaction expansions, is an improvement over our earlier calculation of this process and predicts a resonance structure which is in general agreement with that observed in an earlier high-resolution measurement of this process. (author)