Model sensitivity of theoretical results for ionization–excitation of helium

Abstract

The total cross section for ionization and simultaneous ionization–excitation of helium by electron impact has been revisited within the framework of first-order approximations for the projectile–target interaction. A systematic study of the sensitivity of theoretical results on the details of the computational model, specifically the treatments of the projectile–target interaction, the initial bound state and the ejected-electron–residual-ion interaction reveals the difficulties of making highly reliable predictions.

Out-of-Plane (e,2e) Experiments on HeliumL=0, 1, 2 Autoionizing Levels

“…However, even these theories did not do so well for the case of symmetric energy sharing [9]. In fact, even the calculation of the total He ionizationexcitation cross section remains a significant problem [10].…”

Benchmark calculation of total cross sections for ionization–excitation of helium

“…times smaller cross sections compared to earlier absolute normalizations [26,27]. The previously available theoretical predictions (see [19] for a larger selection) are scattered and cannot resolve the problem. Our BSRMPS results, however, clearly favour the original normalizations [26,27].…”

“…The magnitude of this cross section has been a widely debated issue over the years. A detailed analysis at the level of the firstorder approximation for the projectile-target interaction was carried out by Vorov and Bartschat [19]. They ultimately concluded that theoretical predictions for the ionizationexcitation process were extremely sensitive to the details of the model (in sharp contrast to ionization without excitation), and that highly sophisticated approaches would be required to make further progress.…”