Double differential cross section of helium ionization by proton impact
Abstract
A theoretical analysis for doubly differential cross sections of the single ionization of helium by proton impact as a function of the scattering angle and projectile energy loss is presented. We have used two different theoretical methods. The first approach involved an approximate solution of Faddeev-Merkuriev equations for the three-body Coulomb problem. The second approach employed the expansion of the transition amplitude in the Born series over the projectile-target interaction up to second order. A relation between these two methods was established for the case of fast collisions. It has been demonstrated that, for small scattering angles, the post-collision interaction in the final state between the charged particles strongly influences the differential cross sections, whereas double-scattering mechanisms dominate for scattering angles mrad. The results of our calculations are in a good agreement with the measurements of Schulz et al for 50-150 keV collisions.