  The contribution to electron-impact ionization cross sections from
excitations to high-nl shells and a consequent autoionization is investigated.
We perform relativistic subconfiguration-average and detailed level-to-level
calculations for this process. Ionization cross sections for the W27+ ion are
presented to illustrate the large influence of the high shells (n >= 9) and
orbitals (l >= 4) in the excitation-autoionization process. The obtained
results show that the excitations to the high shells (n >= 9) increase cross
sections of the indirect ionization process by a factor of 2 compared to the
excitations to the lower shells (n <= 8). The excitations to the shells with
orbital quantum number l = 4 give the largest contribution comparedwith the
other orbital quantum numbers l. Radiative damping reduces the cross sections
of the indirect process approximately twofold in the case of the level-to-level
calculations. Determined data show that the excitation-autoionization process
contributes approximately 40% to the total ionization cross sections.
