Fully differential cross sections for the single ionization of helium by ion impact

Abstract

We present experimental and theoretical fully differential cross sections for single ionization of He by heavy-ion impact for electrons emitted into the scattering plane.Data were obtained for 2 MeV/amu C 6+ and 3.6 MeV/amu Au Q+ (Q = 24, 53) projectiles, corresponding to perturbations (projectile charge to velocity ratio) ranging from 0.7 to 4.4, a regime which is not accessible for electron-impact ionization. We observe a decreasing recoil peak intensity (relative to the binary peak) and at the same time an increasing peak in the forward direction with increasing perturbation. Large discrepancies between experiment and theory are found, which can at least partly be attributed to the use of hydrogenic wavefunctions.2

CDW and CDW-EIS calculations for FDCSs in highly charged ion impact ionization of helium

“…Theoretical results reported by these authors using a CDW-EIS model exhibited differences between experiment and theory on an absolute scale for emission in the scattering plane [11]. Their calculations were made using the active electron approximation and hydrogenic wavefunctions for the initial and final states of the active electron [11]. Indeed, the simplest description for the He bound initial state is to assume it has one 'active' and one 'passive' electron and that the 'active' electron can be described as moving in the effective Coulomb field of the atomic core with an effective charge chosen (a) to reproduce the ionization energy or (b) so that the continuum wave is orthogonal to the initial state.…”

“…Theoretical results reported by these authors using a CDW-EIS model exhibited differences between experiment and theory on an absolute scale for emission in the scattering plane [11]. Their calculations were made using the active electron approximation and hydrogenic wavefunctions for the initial and final states of the active electron [11].…”

“…Fischer et al [11] have reported absolute experimental measurements for 2 MeV/amu C 6+ single ionization of helium in the scattering plane, i.e., that defined by the initial and final projectile momenta, for various momentum transfers and ejected-electron energies. Theoretical results reported by these authors using a CDW-EIS model exhibited differences between experiment and theory on an absolute scale for emission in the scattering plane [11].…”

Post–prior discrepancies in CDW–EIS calculations for ion impact ionization fully differential cross sections

“…Even when η = 0.1 both FBA and post CDW-EIS fail to accurately describe the experimental results, although they broadly reproduce the angular distribution. Figures 3 and 4 show results for 3.6 MeV amu −1 Au 24+ impact ionization of He (Fischer et al 2003), calculated in prior and post CDW-EIS. For E e = 4.0 eV, results for prior version are in reasonable agreement with experiment, However both theories fail to correctly reproduce the strong forward emission peak, which is due to the strong projectile electron post collisional interaction (PCI).…”

“…The first measurements of the FDCS, for various momentum transfers and ejectedelectron energies, were reported in 2001 by Schulz et Fischer et al (2003) have reported absolute experimental measurements for 2 MeV amu −1 C 6+ single ionization of helium in the scattering plane for various momentum transfers and ejected-electron energies. Foster et al (2004) have presented 3DW-EIS results for the single ionization of helium by 3.6 MeV amu −1 Au 24+ and Au 53+ ions.…”