Triple differential cross-section measurements for electron-impact ionization of methane from a coplanar geometry to the perpendicular plane

Abstract

A new study of electron-impact single ionization of the HOMO 1t2 state of CH4 has been conducted at incident electron energies 20 eV and 40 eV above the ionization energy of the state. Triple differential cross sections were measured from a coplanar symmetric geometry, where scattered and ionized electrons were detected at equal angles, through to the perpendicular geometry where the outgoing electrons emerged orthogonal to the incident electron beam. At the lower energy, the electrons were detected with equal energies of 10 eV, whereas at the higher energy, data were obtained for equal energies of 20 eV and for unequal energies of 5 eV and 35 eV. The results are compared to a molecular 3-body distorted wave approximation that used a full averaging procedure to allow for the random orientation of the target, an orientation averaged molecular orbital model that averages the target wavefunction over all orientations prior to the collision, and a distorted wave Born approximation that does not include postcollisional interactions.

Measurement of argon (e,2e) differential cross sections in the perpendicular plane from 5 to 200 eV above the ionization threshold

“…This trend continues until at 160 eV above the IP the cross section becomes almost flat, with little angular variation as the mutual angle changes. This has also been observed in xenon [30] as well as in some molecular targets in this geometry [31] and so it appears not to be due directly to the target. It is not at present clear why this flattening occurs.…”

An iterative deep learning procedure for determining electron scattering cross-sections from transport coefficients

“…However, argon and helium do not exhibit vibration and attachment collisions that are generally important in bio-molecules. Here, we use methane as a case study for the influence of vibration and attachment processes, as has been widely studied in the literature [25][26][27][28][29]. For example, the strong excitation processes demonstrated by methane lead to a breakdown of the two-term approximation that is often employed in the solution of Boltzmann's equations [29][30][31].…”