Scattering Mechanisms in Twisted Electron Ionization

Ionization collisions have important consequences in many physical phenomena, and the mechanism that leads to ionization is not universal.  Understanding how and why electrons are removed from atoms and molecules is crucial to forming a complete picture of the physics.  Triple and double differential cross sections (TDCSs and DDCSs) and have been used for decades to examine the physical mechanisms that lead to ionization.  For ionization into the azimuthal plane, the TDCSs at low and intermediate energies exhibit unique qualitative features that can be used to identify single and double scattering mechanisms.  Similarly, angular DDCSs can be used to distinguish close collisions from grazing collisions.  With the recent development of sculpted electron wave packets, a new opportunity has arisen that allows a re-examination of the mechanisms that lead to ionization. We present theoretical TDCSs and DDCSs for (e,2e) ionization of atomic hydrogen and helium using electron vortex projectiles.  Our results show that the mechanisms leading to electron emission into the azimuthal plane are different for vortex and non-vortex projectiles.  Additionally, our results predict that the vortex projectile’s momentum uncertainty causes noticeable changes to the shape and magnitude of the TDCSs and DDCSs.  Our results lead to several predictions that can be experimentally tested.