Triple differential cross sections for ionization of some heliumlike ions by electron impact

Triple differential cross sections (TDCS) have been studied for ionization of some heliumlike ions by fast electron impact in the coplanar geometry using a final-state correlated wave function that satisfies the asymptotic three-body boundary condition. The electron exchange effect between the two outgoing electrons in the final channel has also been incorporated properly. The initial channel wave function involves a Coulomb wave due to long-range Coulomb attraction between the incident electron and the screened ionic nucleus. TDCS have been computed in asymmetric geometry for a Li⁺ ion at different incident energies (E_i) 150–1000 eV for fixed values of the ejected energies (E_b=5 and 10 eV) and scattering angles (θ₁=4° and 10°). Symmetric geometry has also been studied for a Li⁺ ion for incident energies (E_i=150–500eV) for fixed scattering angle 45°. The behavior of the scaled TDCS (Z_t⁴σ) with respect to the variation of the ionic charge (Z_t) for different ions in the helium isoelectronic series has been studied for asymmetric geometry at different incident energies in units of respective thresholds (3, 6, and 10) for a scaled ejected energy (E_bsc) and a fixed scattering angle (4°), while for the symmetric geometry, scaled TDCS have been studied only at three times the respective threshold. The binary to recoil peak ratio (b/r) is studied against the momentum transfer |q| in the asymmetric geometry for all the ionic targets. A strong recoil peak is noted at low incident energy for all the ions except for the ions of high charge (e.g., Z_t=20).