ELECTRON-IMPACT IONIZATION OF A HE+ ION FROM ITS GROUND (1S) AND EXCITED (2S, 2P) STATES

An approach is proposed to study the ionization cross sections of a hy drogenic ion by electron impact using coplanar geometry, for intermedi ate and high incident energies. The final-state wavefunction is chosen as the correlated 3-body Coulomb wavefunction satisfying the exact as ymptotic boundary condition. The long-range Coulomb interaction in the initial channel between the ionic target and the projectile has also been taken into account properly. Triple differential cross sections ( TDCSs) have been calculated for the ionization of a He+ ion in its gro und and excited states (2S and 2P). Apart from the usual double-peaked structure of the TDCS, as is found in ground-state ionization, some s econdary structures also appear for the excited states, particularly a t higher scattering angles. A strong recoil peak is noted in the TDCS structure at lower incident energies for both ground and excited state s of the ion.