In this chapter we analyze the multiple ionization by impact of |Z|=1
projectiles: electrons, positrons, protons and antiprotons. Differences and similarities
among the cross sections by those four projectiles allows us to have an insight on the
physics involved. Mass and charge effects, energy thresholds, and relative importance
of collisional and post-collisional processes are discussed. For this purpose, we
performed a detailed theoretical-experimental comparison for single up to quintuple
ionization of Ne, Ar, Kr and Xe by particles and antiparticles. We include an extensive
compilation of the available data for the sixteen collisional systems, and the theoretical
cross sections by means of the continuum distorted wave eikonal initial state
approximation. We underline here that post-collisional ionization is decisive to
describe multiple ionization by light projectiles, covering almost the whole energy
range, from threshold to high energies. The normalization of positron and antiproton
measurements to electron impact ones, the lack of data in certain cases, and the future
prospects are presented and discussed.
Keywords: Antiparticle, Antiproton, Electron, Ionization, Multiple ionization,
Noble gases, Positron, Proton, Particle, Ne, Ar, Kr, Xe.