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

Abstract

We extend application of our lowest-order perturbative approach (in electron-electron correlation) for analysis of photo-double-ionization (PDI) of He [A.Y. Istomin et al., J. Phys. B 35, L543 (2002)] to excess energies up to 450 eV and to analysis of circular dichroism. We find that account of electron correlation in the final state to first order provides predictions for the triply differential cross section and circular dichroism that are in reasonable agreement with absolute data for excess energies up to 80 eV. For an excess energy of 450 eV, account of electron correlation in both initial and final states is necessary and the predicted triply differential cross sections are in agreement with absolute data only for large mutual ejection angles. We find that at excess energies of a few tens of eV, the PDI is dominated by the "virtual" knock-out mechanism, while the "direct" (on-shell) knock-out process gives only small contributions for large mutual ejection angles. As a result, we conclude that the circular dichroism effect at these energies originates from the nonzero electron Coulomb phase shifts.

Circular dichroism at equal energy sharing in photo-double-ionization of He

“…Up to now, all theoretical treatments of CD have employed the EDA (Refs. [1,3,4,[6][7][8][9][10][11][12][13]) and their predictions are generally in agreement with experiments [12][13][14][15][16]. Measurement of CD provides a sensitive means for probing two-electron dynamics in PDI, since the photon-helicity-dependent CD term in the TDCS originates from an interference between real and imaginary parts of particular components of the (generally non-Hermitian) PDI amplitude [4,7].…”

“…This approach has been shown in Refs. [11,21] to provide reasonable predictions for the dipole TDCS (except for small mutual angles, ഛ 60°).…”

“…As in Refs. [11,21], for excess energies of the order of tens of eV, final state electron correlations are taken into account perturbatively to lowest order, and the He ground state is represented by the variational (uncorrelated) wave function having the effective nuclear charge Z = 27/ 16. This approach has been shown in Refs.…”

Parametrizations and dynamical analysis of angle-integrated cross sections for double photoionization including nondipole effects

“…III.A we analyze these cross sections for DPI of He quantitatively (including the lowest-order nondipole corrections to the EDA) by means of two methods: (i) the convergent close-coupling (CCC) theory [20], whose EDA predictions for the TDCS are in excellent agreement with existing experiments for He (see, e.g., Ref. [21]), and (ii) the LOPT, which provides EDA results for the TDCS of reasonable accuracy for low excess energies [22,23] and which has been used recently for analyses of nondipole effects in the TDCS for E exc ≤ 450 eV [6][7][8]). These results thus allow us: (i) to provide reliable CCC predictions for the dipole and nondipole asymmetry parameters (and thus for the magnitude of nondipole effects at particular excess energies), and (ii) to assess the accuracy of the LOPT predictions for these pa-rameters by comparing them to the CCC results.…”

Nonlinear Dichroism in Back-to-Back Double Ionization of He by an Intense Elliptically Polarized Few-Cycle Extreme Ultraviolet Pulse

“…(1), we see that ΔW ξ is comprised of two very different parts. One of them, ΔW D1 , results from the interference of different terms in the first-order amplitude A 1 ; it is the analog of conventional circular dichroism in single photon double ionization of He [1,[35][36][37][38][39][40][41] and is linear in the pulse intensity I. The second part, ΔW D12 , is due to interference of the first-and second-order amplitudes, as occurs in single electron shortpulse ionization [25].…”