The electron impact ionization of one- and two-electron atoms and ions close to the ionization threshold

Abstract

We present triple differential cross-sections for the electron impact ionization of hydrogen and helium in energy sharing coplanar constant Θ12 = 180° and coplanar energy sharing perpendicular plane geometries at impact energies of a few eV's above ionization threshold. We investigate the role of incident channel effects in determining the shape of the cross-section. We present cross-sections in the same geometries for the isoelectronic sequence of hydrogenic and helium-like ions with nuclear charges up to Z = 10.

Electron-impact-ionization cross sections ofH2for low outgoing electron energies from1to10Al-Hagan1, Murray2, Kaiser3 et al. 2010Phys. Rev. A192170View full textAdd to dashboardCite

“…Although the MDW 180 • minimum becomes less shallow with decreasing energy, disagreement between experiment and theory increases with decreasing energy, the MDW predicting a minimum at 1 eV in contrast to the data. It is important to note that Martinez et al [10] found very good agreement with the comparable 1-eV data for He using the atomic equivalent of the MDW, so the MDW is good for atoms at this energy but not molecules! The lowest energy calculated using the TDCC theory was at 2 eV, and the TDCC still exhibits a shallow minimum at this energy while the data indicate a maximum at 180 • .…”

“…However, we are close enough to this region at (1 eV, 1 eV) so that PCI is still dominant for the FDCS. Martinez et al [10] very recently showed that PCI was not dominant for these same energies for atomic targets, so this finding appears to be a phenomena associated with molecules. To our knowledge, this is the first direct observation of the transition from Wannier physics to nonthreshold physics for fully differential cross sections of H 2 .…”

The Distorted-Wave Born Approach for Calculating Electron-Impact Ionization of Molecules

“…Frequently, a radial density is used for which the integral over radius only yields the number of electrons in the target (we used this definition in the past for atoms where the angular dependence is simply a spherical harmonic). The difference is replacing 8πρ ave with 2ρ ave (see also, e.g., Martinez et al [97]).…”

Electron- and positron-impact ionization of inert gases

“…In the approximation (2) the electron-electron interaction occurs exactly once and no account is taken of PCI between the two final-state electrons. In our calculations below, the full nonlocal exchange potential is not used but rather a localized version [19,[28][29][30][31] is employed. Its use greatly simplifies the static-exchange calculations in that one needs only solve differential equations rather than integrodifferential equations.…”