Four-body Effects On Single Ionization Of Helium By 75keV Proton-impact

The four-body modified Coulomb-Born approximation including the projectile-residual-target-ion interaction(MCBPT)is applied to calculate the fully differential cross section(FDCS)for single ionization of helium by 75 ke V proton-impact.The obtained results are compared with the experimental data and the other theoretical results and we find the small peak at negative angles in the scattering plane and the minimum at the largest momentum in the perpendicular plane are reproduced qualitatively by the MCBPT,whereas the three-body models do not.It turns out that the qualitative agreement of the four-body results with experiment shows a superiority over the three-body model.To investigate the four-body effects on single ionization process,two physical effects are studied.First,we have made calculations using the three initial state interelectronic correlation wavefunction and the interelectronic correlation effects are discussed in detail.It is shown that the interelectronic correlation effects in the scattering plane are more pronounced than that in the perpendicular plane.Second,the effects of the projectile-residual-target-ion interaction(PT interaction)in the initial(final)state on the FDCS are analyzed.It turns out that the shape(position)of the FDCS is strongly influenced by the initial(final)state PT interaction.