Fully differential cross sections for four-body scattering processes

While the original concept of the atom can be traced back to the ancient Greeks, current knowledge of the atom is due largely to the study of atomic collisions. The structure of atoms is now fairly well understood, but the understanding of their interactions remains incomplete. In atomic collisions, the particles involved in the collision interact through the Coulomb force, which is known exactly. However, for Coulomb forces, the solution of the Schrödinger equation can only be obtained analytically for two mutually interacting particles. As a result, when more than two particles are involved, theory must resort to approximations. The validity of these approximations is then determined by comparison with experiment. Three new fully quantum-mechanical models that include all relevant two-particle interactions are presented here, and used to study fully differential cross sections (FDCS) of four-body collisions. In particular, this work focuses on electron-impact excitation-ionization of helium, as well as single charge transfer, transfer-excitation, and double charge transfer in proton + helium collisions. The calculations required for this work result in nine-dimensional integrals that are performed numerically. For excitation-ionization, the projectile-ejected electron interaction is found to be important in correctly predicting the shape of the FDCS. However, the projectile-atom and projectile-ion interactions play a much smaller role in this process. For single charge transfer and transfer-excitation, the current model does a reasonable job of predicting the shape and magnitude of experiment. However, for double charge transfer, the theoretical results overestimate experiment by several orders of magnitude. For all of the charge transfer collisions, calculations show that the interaction of the electrons within the target atom has little effect on the FDCS --Abstract, page iii