Convergent calculations for simultaneous electron-impact ionization-excitation of helium

Theoretical results are presented for electron-impact ionization of He(1s²), leaving the ion in the n = 2 excited states. The projectile-target interaction is described in the first-order plane-wave Born approximation, whereas the interaction between the ejected electron and the residual ion is treated non-perturbatively within the convergent close-coupling formalism. Comparison of the predictions from two entirely independent approaches, formulated either in coordinate or in momentum space, provides a basis for further systematic improvement of the models.