Structures in fully differential cross-sections for proton impact ionization of helium

The three-Coulomb wave (3C) model is applied to study single ionization of helium by 75 keV proton impact. Fully differential cross-sections (FDCS) are calculated in both the scattering plane and the perpendicular plane. The results are compared with experimental data and other theoretical predictions and we find that the present 3C results qualitatively reproduce the experimental peak structure, especially in the perpendicular plane. Furthermore, the contributions of various scattering amplitudes to FDCS in the present model are discussed. It turns out that the cross-section is strongly influenced by the interference of these amplitudes. In particular, the theory predicts the minimum at the largest momentum transfer in the perpendicular plane due to the interference