Energy and angular distributions of electrons from ion impact on atomic and molecular hydrogen. II. 20–114-keVH++H

Abstract

Results of crossed-beam measurements of cross sections differential in ejected electron energy and angle for ionization of atomic hydrogen by 20-1 14-keV protons are reported. Secondary electrons were measured over an energy range of 1.5-300 eV and an angular range of 15"-165". Atomic-hydrogen targets were produced in a radio-frequency discharge source with a dissociation fraction of about 74%. Ratios of cross sections for H targets to those for Hz targets were obtained from measurements on the mixed target. From these ratios, the measured dissociation fractions, and the absolute cross sections measured for H, targets, the cross sections for H targets were determined. These measurements are compared with the results of the first-order Born approximation, the continuum-distorted-wave eikonalinitial-state approximation, and the classical trajectory Monte Carlo (CTMC) methods. Good overall agreement is found with the CTMC results, except for slow, backward electron emission. The addition of the classically suppressed dipole transitions from the Born approximation to the CTMC results yields a good estimate of the ejected electron spectrum.PACS number (& 34.50.Fa

Theoretical total charge transfer cross sections and differential ionization cross sections for ion–atom collisions illustrated for the system

“…Differential cross section experimental results are available; in particular the momentum distribution of ejected electrons. Here, in contrast to charge transfer cross sections, CTMC and CDW calculations have generally been found to be in excellent agreement with each other and, to the point, experiment Kerby III et al, 1995). CTMC and CDW calculations are particularly convenient as they produce differential cross sections directly, whereas in FHBS and FE calculations a projection onto some appropriate momentum eigenstates must be performed.…”

Finite-Hilbert-basis-set calculations for the angular distribution of ionized electrons produced inp+Himpact at20keV

“…The cited work notwithstanding, we report here a different way of extracting differential electron cross sections from finite Hilbert basis-set (FHBS) calculations [1]; this incorporates a quantal ionization process wherein the outgoing ejected electron diffracts past the target and projectile protons. This gives rise to an interference bringing theory and experiment [9] into agreement.…”

“…Perhaps one reason for this is the quite remarkable successes of the classical trajectory Monte Carlo (CTMC) algorithm [2] and the continuum distorted wave (CDW) approximation [3]; they reproduce the Rudd group data over a wide range of proton energies [9].…”

Analytical approaches to the fragmentation of few-body Coulomb systems

“…The absolute experimental data are due to Ref. [23] where comparison with other theories can be found.…”