Ionization and ionization–excitation of helium to the n = 1 – 4 states of He + by electron impact

摘要: We present experimental and theoretical results for the electron-impact-induced ionization of ground-state helium atoms. Using a high-sensitivity toroidal electron spectrometer, we measured cross-section ratios transitions leading to first three excited states residual ion relative transition leaving in ground state. Measurements were performed both symmetric- asymmetric-energy-sharing kinematics. By presenting as ratio, direct comparison can be made between predictions without recourse normalization. The data are compared employing various first-order models second-order hybrid distorted-wave $+$ convergent $R$ matrix with pseudostates (close-coupling) approach. All fail predicting even approximate size ratios. calculations found describe reasonable fidelity, although significant disparities evident symmetric-energy-sharing cases. These comparisons demonstrate need further developments, which all four charged particles treated on an equal footing.