Vector (e, e'γ) correlations in ionization-excitation of He by electron impact

The general description of simultaneous electron-impact ionization-excitation processes is reformulated in terms of an irreducible tensor representation. Using a numerical model, in which the interaction between a 'fast' ionizing projectile and the target is described by first-or second-order plane-wave and distorted-wave models, combined with a convergent close-coupling-type description of the initial bound state and the interaction between a 'slow' ejected electron and the residual ion, new benchmark calculations for the (e, e'γ) process have been performed. The predictions are compared with recent experimental data on ionization-excitation of helium. The similarity to results for excitation processes and the potential extension of propensity rules is discussed