Effect of Projectile Charge State on Electron Emission Spectra from He Atom

Abstract

The single ionization of He atom by the impact of highly charged dressed projectile nucleus is investigated by applying the three-body formalism of three-Coulomb wave (3CW) model and the first Born approximation (FBA). In the 3CW formalism, the interaction between the dressed projectile and the active electron is represented by a model potential containing both the long-range and short-range part of the Coulomb potential. The target is treated as a one-electron atom, where the interaction of the active electron with the rest of the target is represented by a similar type of model potential. The correlated motion of each pair of particles, interacting through long-range Coulomb potential, is taken into account in the final state. In addition, an independent particle model and a single-zeta Roothaan-Hartree-Fock 1s wavefunction, describing helium in its ground state, is used to carry out the calculations, where the effective charge of the target nuclei is obtained from the initial orbital energy. The energy distributions of the double-differential cross sections (DDCS) at low and intermediate energy electron emission from helium atom have been investigated. Our theoretical results are compared with both the available experimental measurements and theoretical calculations using other methods. There is good overall agreement of the present calculations with experimental data except for low-energy electron emission (less than 10 eV). For target ionization by a dressed projectile, we find that the cross sections depend on the projectile charge. For distant collisions involving high energy ions, the primary effect of bound projectile electrons is to screen the projectile nuclear charge, thereby reducing the strength of the interaction potential. Finally, the energy distribution of DDCS ratio at different angles has also been studied.