Benchmark experiment for electron-impact ionization of argon: Absolute triple-differential cross sections via three-dimensional electron emission images

Abstract

Single ionization of argon by 195-eV electron impact is studied in an experiment, where the absolute tripledifferential cross sections are presented as three-dimensional electron emission images for a series of kinematic conditions. Thereby a comprehensive set of experimental data for electron-impact ionization of a many-electron system is produced to provide a benchmark for comparison with theoretical predictions. Theoretical models using a hybrid first-order and second-order distorted-wave Born plus R-matrix approach are employed to compare their predictions with the experimental data. While the relative shape of the calculated cross section is generally in reasonable agreement with experiment, the magnitude appears to be the most significant problem with the theoretical treatment for the conditions studied in the present work. This suggests that the most significant challenge in the further development of theory for this process may lie in the reproduction of the absolute scale rather than the angular dependence of the cross section.

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“…These consist of binary and recoil peaks. The experimental measurements for TDCS are made in the scattering as well as in the perpendicular plane [14] at equal and unequal energy sharing. Figure 1 presents a comparison of the present TDCS with experiment and other accurate theoretical results for equal energy sharing as a function of the ejected angle in the scattering and perpendicular planes.…”

“…We also included the experimental data obtained by Ren et al [14] in the figure. The data were obtained from double coincidence measurement between the scattered and the recoil electrons.…”

“…The absolute measurements in the coplanar geometry were normalized to obtain the absolute scale of the cross section. The results from the CCC and TDCC calculations [14] are also included in the figure for comparison. The present results calculated in the HF and SP approximations are very similar.…”

“…eV and E 5 2 = eV. In these figures we have also included the experimental results reported by Ren et al [14] and the results obtained using the CCC and TDCC approximations. In both the scattering and the perpendicular planes both HF and SP calculations agree very well, indicating that electron correlation effects between the two final state continuum electrons are relatively small.…”

“…In both equal and unequal energy cases shared by the two final state continuum electrons, the results with polarization in the initial state and the final state obtained in the SP approximation are in excellent agreement over all ranges of 1 θ considered by the experiment. Experimentally, Ren et al [14] has made both experimental and theoretical study on electron impact ionization of He by the 70.6 eV incident electron, which covers the entire solid angle for the emitted electron and the collision kinematics. They compared the absolutely normalized triple differential experimental cross section with the accurate calculations obtained using CCC and TDCC methods and found excellent agreement.…”