Impulsive (e, 2e) energy-sharing experiments on He

The triple differential cross section for electron impact ionisation of He is measured in 'energy-sharing' and 'non-coplanar symmetric' kinematics. Experiments performed at 424.5 eV incident energy and at different scattering angles are reported. The present experimental results are compared with the eikonal distorted-wave impulse approximation. They give further evidence for the inadequacy of this approximation at small scattering angles.