Abstract
The time-dependent close-coupling method and a distorted-wave approach are used to explore deep minima discovered in the non-coplanar triple differential cross sections for the electron-impact ionization of helium. This phenomenon has been well studied experimentally but so far has not been investigated by a non-perturbative theoretical approach. We find that our time-dependent calculations reproduce very well the experimental minima, and that the distorted-wave calculations also confirm this phenomenon. Further investigations reveal that the minima appear to be due to deep destructive interference between the partial wave contributions which make up the cross sections. We also show that similar minima may be found in triple differential cross sections arising from the electron-impact ionization of atomic and molecular hydrogen.