(e, 2e) Ionization Measurements from the 3σg and 2σu* States of N₂—comparison Between Experiment and Theoretical Predictions of the Effects of Exchange, Polarization and Interference

Gao et al (2005 Phys. Rev. A 72 032721) have predicted a Young's type interference effect in the fully differential cross sections for ionization of the 3σg state of N2 for highly asymmetric collisions with one electron detector fixed at very small scattering angles (1° or 10°). The purpose of this work was to look for this interference effect at a larger scattering angle. (e, 2e) ionization measurements have been conducted from the 3σg and 2σu* states of N2 in a coplanar asymmetric geometry, where one electron emerges in the forward direction and the correlated electron is measured as a function of scattering angle. Both final-state electrons have an energy of 30 eV, and the forward scattering angle was θa = 22° relative to the incident beam direction. The theoretical prediction is that there should be a strong interference peak near 180°. The measurements were carried out from the 3σg state over a range of scattering angles from θb ∼ 10° to θb ∼ 170° using a magnetic angle changing spectrometer. The present experimental results for 3σg find a normal binary peak plus another peak at back angles in the vicinity of 180°. Consequently, this work supports the possibility of a strong Young's type interference effect for small fixed scattering angles.