Minima in the triple differential cross sections for the electron-impact ionization of helium

Abstract

We examine unusual minima found in the triple differential cross sections for the electron-impact ionization of helium for configurations where the incident electron is out-of-plane with respect to the plane in which the outgoing electrons are detected. The position of the experimentally determined minima are confirmed by time-dependent close-coupling calculations. An analysis is made of the origin of the minima in the cross section, where it is found they are due to deep destructive interference between the partial-wave amplitudes which contribute to the differential cross section.