Observation of non-first-order effects in an (e, 3-1e) investigation of the double ionization of helium and molecular hydrogen

Abstract

New coplanar (e, 3-1e) experiments on double ionization (DI) of helium and molecular hydrogen at about 600 eV incident energy, and with asymmetric energy sharing among the two ejected electrons are presented. The results are compared with state-of-the-art first-order theories, and are discussed in terms of DI mechanisms. Evidence is given of the great importance of second- or higher-order effects in the projectile-target interaction, even at the high incident energy considered.