Partial wave analysis of oriented collisions

Abstract

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.

Anisotropy in excitation-ionization double-differential cross sections

“…In the bottom row, the incident electron energy is fixed at 200 eV and the scattering angle is 5°. These results show a clear dependence of FDCS on orientation of the ion, consistent with previous work [27][28]. In the case of orientation along the beam direction or along the momentum transfer direction, almost no forward ejection is observed, but a strong backward recoil peak is seen.…”

“…Experimentally, the EI process is very challenging due to small cross sections. Prior work using our 4-Body Distorted Wave (4DW) model has shown clear orientation effects in FDCS for the EI process, with some of the structures being traced to specific angular momentum components of the ejected electron and the target atom wave function [27][28].…”