Fivefold differential cross sections for ground-state ionization of aligned H2 by electron impact

Abstract

We discuss the ionization of aligned hydrogen molecules into their ionic ground state by 200 eV electrons. Using a reaction microscope, the complete electron scattering kinematics is imaged over a large solid angle. Simultaneously, the molecular alignment is derived from postcollision dissociation of the residual ion. It is found that the ionization cross section is maximized for small angles between the internuclear axis and the momentum transfer. Fivefold differential cross sections (5DCSs) reveal subtle differences in the scattering process for the distinct alignments. We compare our observations with theoretical 5DCSs obtained with an adapted molecular three-body distorted wave model that reproduces most of the results, although discrepancies remain.

Fivefold differential cross sections for the ionization of aligned hydrogen molecule by electron and positron impact

“…For the initial state of the above model the Coulomb interaction between the projectile and the screened nuclear charge for a neutral target is contained to all orders of perturbation theory while the initial-state non spherical projectile-active-electron interaction is the first order interaction. Senftleben et al [23,28] have reported that M3DW reproduces most of the experimental results, although discrepancies remain. They have also mentioned that 3C-He failed to reproduce experimental FDCS at the ejection energy of (3.5±2.5) eV and the scattering angle of (16±4) o .…”

“…Very recently, 5DCS for 200 eV electron impact ionization of hydrogen molecule has been explored experimentally as a function of molecular alignment by Senftleben et al [23,28]. They derived the alignment of the internuclear axis from the fragmentation of the residual H + 2 ion which was produced as a result of the ionizing collision.…”

“…They derived the alignment of the internuclear axis from the fragmentation of the residual H + 2 ion which was produced as a result of the ionizing collision. In fact, Senftleben et al [23,28] considered the ground-state dissociation to study the alignment dependence of ionization into the electronic ground state of H + 2 . Moreover, they have compared their observations with the molecular three-body distorted wave model (M3DW) and the three Coulomb wave function approach.…”

“…We have compared the electron impact 5DCS with the M3DW [28] approximation, the 3C-He [23] approach and experimental data [23,28].…”

A recoil ion momentum spectrometer for molecular and atomic fragmentation studies

“…Till date, a number of theoretical and experimental investigations have been carried out using photons, 1-5 electrons, [6][7][8] and heavy ions [9][10][11][12] as probes to understand the breakup dynamics of molecules including, large biomolecules [13][14][15][16] or even free fullerene. [17][18][19][20][21] To tackle the complexity involved in the molecular break-up processes, it is necessary to have sophisticated, state-of-the-art, theoretical models and highly differential experimental measurements.…”