Triple differential cross section calculation for the helium autoionization by electron impact

Abstract

The triple differential cross section and autoionization a and b parameters, as functions of ejected electron angle, have been calculated for the helium (2s2)1S, (2s2p)1P and (2p2)1D resonances in the coplanar asymmetric (e,2e) reaction for the incoming electron energy/scattering angle kinematical conditions of 400 eV/16 degrees , 200 eV/13 degrees and 100 eV/13 degrees . Configuration interaction expansions for the resonances and helium ground state which employed hydrogenic and multiconfiguration Hartree-Fock orbitals, respectively, were used in the present study. The distorted wave Born approximation, with exchange, was employed for the (e,2e) cross section calculation with the distorted waves being calculated in the Hartree-Fock potential of the helium neutral atom or the positive ion. Calculated parameters agree well with experimental 400 eV/16 degrees data whereas only a qualitative resemblance exists for 200 eV/13 degrees and 100 eV/13 degrees kinematics.