Partial Wave Analysis of Oriented Collisions

We present fully differential cross sections (FDCSs) for two collision processes with oriented atoms. The first collision is electron-impact ionization of oriented Mg (3p), and the second collision is electron-impact excitation-ionization (EI) of helium with an oriented final state He ⁺ (2p0) ion. Surprisingly, the theoretical functional form of the FDCS is the same for both processes, despite the fact that the only physical similarity is an oriented excited state in both processes. We present FDCS as a function of orientation angle and ejected electron angle for both ionization of oriented Mg(3p) and EI of helium in order to explore possible physical similarities between the two processes. We examine the contributions to the FDCS of individual partial waves of the ionized electron and projectile. For the ionization of oriented Mg, we show that the FDCS are dominated by larger partial waves of the ejected electron, with the dominant partial waves having a dependence on scattering angle and outgoing electron energy sharing. For the EI process, the FDCS is dominated by the L =2 partial wave, independent of scattering angle or energy sharing. Also, for EI it is possible to have angular momentum transferred from either the target helium atom or the incident projectile.