Photodouble ionization of helium at an excess energy of 40 eV

Abstract

Angular correlation in the two-electron continuum of the He double photoionization has been studied, both experimentally and theoretically, for equal and unequal energy sharing conditions at the photon energy of 40 eV above the threshold. The triple differential cross sections have been measured in the plane perpendicular to the photon direction using the multi-coincidence detection technique of Reddish et al at the Daresbury Synchrotron Radiation Source. Recent modifications to the bending-magnet beam line allowed an effective cancellation of the circular polarization at the target, leaving a relatively high degree of linear polarization (Stokes parameters: S 3 = S 2 ∼ = 0, S 1 = 0.8). The measured cross sections are compared with the calculations using the 3C method of Maulbetsch and Briggs and the convergent close coupling method of Kheifets and Bray. Good agreement between theory and experiment has been found in most cases, except for the unequal energy sharing when one of the escaping electrons is detected in a direction close to the polarization axis.

Perturbative analysis of the triply differential cross section and circular dichroism in photo-double-ionization of He

“…Comparison of our calculated TDCS with the TDCC calculation of Colgan and Pindzola [45] and with the experimental data of Cvejanovic et al [54] and Bolognesi et al FIG. 4.…”

“…Full, dashed, and dotted theoretical curves are defined as in Fig. 3; dot-dashed curves, results of the CCC calculations of Kheifets and Bray [54]. The experimental data of Cvejanovic et al [54] have been normalized to the TDCC results [45] at 1 = 95°, as in Ref.…”

Photo double ionization of He by circular and linear polarized single-photon absorption

“…We note that even so impressive progress has been made in the theoretical description of the double photo ionization process, still no perfect agreement with the experimental results is achieved for an extremely simple three-body process (see also [33,55]). Furthermore, none of the theoretical approaches available so far has provided an intuitive physical explanation of what causes the predicted and observed helicity dependence.…”

Theoretical treatment of double photoionization of helium using aB-spline implementation of exterior complex scaling

“…We now turn to the case of 40 eV for which the experiments of Bologonesi et al [49] and those of Cvejanović et al [50] provide only relative values of the cross sections. In each case the reported TDCS for different energy sharings and angles are internormalized within the experiment.…”

“…Turning to the experiments of Cvejanović et al [50] for a photon energy of 40 eV above threshold and E 1 = 5 eV, we again normalize the relative cross sections to our computed TDCS value at one point, namely, 1 = 130°and 2 = 250°, thereby determining the normalization of all six TDCS plots in Figs. 12 and 13.…”