Absolute triple differential cross section for electron-impact ionization of helium at 40 eV

We present a combined experimental and theoretical study of ionization of the ground state of helium by 40 eV incident electrons. Absolute in-plane and out-of-plane measurements are provided for the case of 4 eV slow electron energy. These are found to be in good agreement with the convergent close-coupling (CCC) calculations. Three calculations are presented, in order to demonstrate convergence, which couple a total of 87, 99 and 103 states. These also simultaneously yield results for the equal energy sharing kinematics which are found to be in good agreement with the available relative coplanar symmetric measurements.