The ionization of helium by high energy electrons

The cross section for ionization of helium by electron impact is calculated using the Born approximation. Accurate wave functions are employed for both the ground and continuum states, the l = 0, 1 and 2 partial waves of the continuum state are represented by polarized-orbitals wave functions, the l = 3, 4 and 5 partial waves are represented by Hartree-Fock wave functions, and the ground state of helium is represented by a six-parameter correlated wave function. The cross section is obtained using both the length and velocity formulations of the Born matrix element. A comparison is made with previous calculations and measurements.