A. Raeker et al., IONIZATION AND SIMULTANEOUS EXCITATION OF HELIUM-ATOMS BY ELECTRON-IMPACT, Journal of physics. B, Atomic molecular and optical physics, 27(14), 1994, pp. 3129-3138
Total and single differential cross sections for electron impact ioniz
ation of helium are calculated within the R-matrix method. In addition
to ionization of ground state atoms He (1s2) 1S, we consider the init
ial metastable states He (1s2s) 1S and He (1s2S) 3S for incident proje
ctile energies ranging from threshold to 350 eV. Our calculations incl
ude the processes which leave the residual ion in an excited state He (nl) up to n = 3. The results are compared with experiments and other
theoretical data.