Quantum vortices in ionization processes by impact of positrons and ions.

The appearance of quantum vortices in the ionization of atoms and molecules due to the impact of electrons, positrons, protons, and photons, has been theoretically studied, and experimentally observed for the first of these cases. In general, restrictive geometries were used to analyze these varieties of codimension 2 in quadruple differential cross sections. On the other hand, in the case of proton impact, only the evolution of the electronic distribution for a fixed impact parameter and slow velocities was analyzed. In this communication we present a comparative study of quantum vortices free of any restrictive geometries, both for the case of positrons and ions, and in similar ranges of impact velocities. Finally, we discuss strategies to experimentally observe these fascinating quantum structures.