Ionisation differential cross section measurements for N₂at low incident energy in coplanar and non-coplanar geometries

Abstract

Abstract.Ionization triple differential cross sections (TDCS) have been determined experimentally and theoretically for the neutral molecule N 2 over a range of geometries from coplanar to the perpendicular plane. Data were obtained at incident electron energies ~10 eV and ~20 eV above the ionization potential (IP) of the 3σ g , 1π u and 2σ g states, using both equal and non-equal outgoing electron energies. The data were taken with the incident electron beam in the scattering plane (ψ = 0°), at 45° to this plane and orthogonal to the plane (ψ = 90°).The set of nine measured differential cross sections at a given energy were then internormalised to each other. The data are compared to new calculations using various distorted wave methods, and differences between theory and experiment are discussed.

Electron-impact ionization of H2O at low projectile energy: Internormalized triple-differential cross sections in three-dimensional kinematics

“…We used two theoretical methods to describe the present electron-impact ionization process. Although they have been described previously [35][36][37][38] we summarize the essential ideas and the particular ingredients for the current cases of interest in order to make this paper self-contained. More detailed information can be found in the references given.…”

Differential cross section measurements for ionisation of N2in coplanar geometry

“…This doubly-symmetric geometry is particularly challenging, since under these conditions the TDCS is highly sensitive to both initial and final states of the system. In the previous work [17] it was found that the models did not predict the data well for the lowest energy studied ( E 1 = E 2~5 eV ), however as the energy was raised to E 1 = E 2 = 20 eV , better agreement was found in the overall shape of the calculated cross sections. It was suggested that further work was needed, including measurements at higher energies to establish if the models improved under these conditions.…”

“…In a previous set of experiments carried out in Manchester, TDCS data were obtained for ionization of N 2 in a doubly-symmetric geometry, where both electron detectors were set so that θ 1 = θ 2 and E 1 = E 2 . These results were compared to calculations from the Missouri group of Don Madison and co-workers [17]. This doubly-symmetric geometry is particularly challenging, since under these conditions the TDCS is highly sensitive to both initial and final states of the system.…”

“…A description of the theory was presented in [17] with more detail in [5], so it will not be repeated The important similarities and differences between these approximations are the following. Finally, we use the orientation averaged molecular orbital approximation to calculate averaging over all molecular orientations [25].…”

“…Following from the low energy results detailed in previous work [17], experiments were carried out at higher energies in both a coplanar doubly-symmetric geometry and with the electron gun set to 45° to the detection plane. The motivation for this work was to establish if the comparison between theory and experiment improved as the incident electron energy was increased.…”