Electron correlation in fast ion-impact single ionization of helium atoms

Abstract

A four-body distorted-wave approximation is applied for theoretical analysis of the fully differential cross sections (FDCS) for proton-impact single ionization of helium atoms in their ground states. The nine-dimensional integrals for the partial amplitudes are analytically reduced to closed-form expressions or some one-dimensional integrals which can be easily calculated numerically. Calculations are performed in the scattering and perpendicular planes. The influence of the target static electron correlations on the process is investigated using a number of different bound-state wave functions for the ground state of the helium targets. An illustrative computation is performed for 75-keV proton-helium collisions and the obtained results are compared with experimental data and other theoretical predictions. Although for small momentum transfers, the comparison shows a reasonable agreement with experiments in the scattering and perpendicular planes, some significant discrepancies are still present at large momentum transfers in these planes. However, our results are compatible and for some cases, better than those of the other sophisticated calculations.

Triple differential cross sections for single ionization of an atom by bare ion impact

“…Figure 2 shows the angular distribution of the TDCS for 75 keV p − He collision system with an energy of 5.4 eV for the ejected electron in both the scattering plane (figure 2(a)) and the perpendicular plane (figure 2(b)) for transverse momentum transfers (q t ) 0.13, 0.41, 0.73, and 1.38 a.u. These figures show a comparison of the present FBA (green curve), 2CW (red curve) and 3CW (black curve) cross sections with the corresponding four-body formalism of FBA with 2CW (FBA-2CW) approximation [45] (blue curve) and the experimental results of Schulz et al [34] (filled circle). This experiment is an extension of the previous work [35] done by almost the same group for same impact energy and the difference in the electron emission energy of 0.1 eV.…”

“…A double peak structure in the angular distribution has been found in their calculations. Subsequently, the first order four-body distorted-wave theory [45] has been employed to calculate the cross sections for the same collision system at impact energies of 2 MeV/amu and 100 MeV/amu. They showed static correlation and the effective charge of the target ion affects in the angular regions around peak structures along with values of the cross sections.…”

Single ionization of helium atoms by energetic fully stripped carbon ions

“…As the details were explained in Ref. [26], these wave functions are referred to as the Hylleraas, Silverman, and Byron-Joachain wave functions. Further, our study shows that the cross sections are affected by the target ion effective charge Z e that takes into account the presence of the passive electron.…”

Four-body modified Coulomb-Born calculation for 2 MeV/amu C 6+ + He fully differential single ionization cross-section

“…Nevertheless, the agreement between experiment and theory is still not as good as one would hope, particularly for the highest ejected electron energy. It suggested that some physical effects, for example, the screening effects [20] or the interelectronic correlations effects [18,19], not contained in the theories might improve the agreement with the experiment. Consequently, a more complete description of the passive electron is needed for a quantitative agreement of the theories and experiment.…”

“…Furthermore, based on the results in refs. [18,19], the effects due to the passive electron might be more pronounced in the final channel than that in the initial channel. Therefore, a proper account of the passive electron may be an important component for the future theoretical calculation of the atomic few-body problem, particularly for intermediate and low impact energies.…”