Coplanar equal energy-sharing 64.6 eV e-He triple differential cross sections

Electron-impact ionization of the ground state of helium is measured and calculated for the case of 64.6 eV incident electrons with coplanar outgoing 20 eV electrons. Various geometries are considered: symmetric, fixed θA and fixed θB -θA. The method of calculation is the convergent close-coupling theory. This theory is able to reproduce the angular profiles in essentially all of these geometries, yet it yields cross sections which are a constant factor of approximately two lower than experiment. (Author)