One- and two-electron models for electron capture by He⁺ions from Li⁰at intermediate energies

Total cross sections are calculated using a two-centred atomic orbital expansion for electron capture by He + ions of energies between 1 and 400 keV from neutral lithium atoms. Two models are compared: a two-electron model in which the electrons originally in the 1s level of the He + and the 2s level of Li 0 are treated explicitly, and a one-electron model in which the captured electron moves in effective potentials due to the He + (1s) and Li + (1s 2 ) cores. It is found that the two-electron model agrees well with the available experimental data up to 100 keV, while the one-electron model provides only fair agreement. Above 100 keV, capture from the K shell of Li 0 is the dominant process and is estimated by a two-state approximation.