A procedure to extract the complex amplitudes of He photodouble ionization from experimental data

A procedure to extract the two complex amplitudes that govern the He photodouble ionization process from the experimental data is proposed. The results are compared with the predictions of the convergent close coupling and hyperspherical R-matrix with semiclassical outgoing wave theories

Double photoionization of He and H2 at unequal energy sharing

A recently developed single-center model of double photoionization (DPI) of the H2 molecule [ Kheifets Phys. Rev. A 71 022704 (2005)] has been extended to represent the DPI process at unequal energy sharing. The model is applied to describe the shape of the fully-differential cross-section (FDCS) of a randomly oriented hydrogen molecule in the isotopic form of D2 at the kinematics of recent experiments. Comparison with analogous FDCS for the He atom helps to elucidate the molecular effects

Double shake-off model for the triple photoionization of beryllium

We propose a model for the triple photoionization of Be in which a core 1s electron absorbs the photon γ + 1s22s2Be → epsilon 1p + 1s2s2Be+ and the valence 2s2 electrons are shaken off into continuum due to the sudden change of the core potential. We decompose the double shake-off amplitude into a single shake-off 2s2 → nsepsilons and a subsequent electron impact ionization of the doubly charged Be2+ ion epsilons + 1sns Be2+ → epsilon 2l + epsilon3l + 1s Be3+. The latter process is described by the T-matrix of inelastic electron scattering on the 'semi-hollow' 1sns Be2+ ion in the monopole singlet channel. The convergent close-coupling method is used to evaluate the T-matrix

Nondipole effects in double photoionization of He at 450 eV excess energy

Convergent close-coupling results for the triply differential cross section for double photoionization of He that include dipole-quadrupole terms are shown to have improved agreement (as compared to dipole approximation results) with recent experiments using linearly polarized light (Knapp A et al 2005 J. Phys. B: At. Mol. Opt. Phys. 38 615) for a number of kinematical configurations

Electrons and photons colliding with atoms: development and application of the convergent close-coupling method

The substantial progress that has occurred during the 1990s in the field of electron-atom-collision theory is discussed. We show how a solution of a small-model three-body problem, using the convergent close-coupling method, has led to numerous applications involving real atomic collision systems. Consequently many fundamental electron-atom collision processes are considered as 'solved', and accurate collision data of interest to science and industry have become available. However, we suggest that the present has only just seen the birth of modern atomic collision theory. There are many more important collision problems to be tackled, with guidance coming from experiment being as important as ever

Orientation-dependent stereo Wigner time delay and electron localization in a small molecule

Attosecond metrology of atoms has accessed the time scale of the most fundamental processes in quantum mechanics. Transferring the time-resolved photoelectric effect from atoms to molecules considerably increases experimental and theoretical challenges. Here we show that orientation- and energy-resolved measurements characterize the molecular stereo Wigner time delay. This observable provides direct information on the localization of the excited electron wave packet within the molecular potential. Furthermore, we demonstrate that photoelectrons resulting from the dissociative ionization process of the CO molecule are preferentially emitted from the carbon end for dissociative 2Σ states and from the center and oxygen end for the 2Π states of the molecular ion. Supported by comprehensive theoretical calculations, this work constitutes a complete spatially and temporally resolved reconstruction of the molecular photoelectric effect.J.V., L.C., C.C., and U.K. acknowledge support by the ERC advanced grant AttoClock-320401 within the Seventh Framework Program of the European Union and by the NCCR MUST, funded by the Swiss National Science Foundation. A.S.L. acknowledges the Max Planck Center for Attosecond Science (MPC-AS), MPK, and the National Research Foundation of Korea (grant 2016K1A4A4A01922028

Solving close-coupling equations in momentum space without singularities for charged targets

The analytical treatment of the Green's function in the convergent close-coupling method (Bray et al., 2016) has been extended to charged targets. Furthermore, we show that this approach allows for calculation of cross sections at zero channel energy. For neutral targets this means the electron scattering length may be obtained from a single calculation with zero incident energy. For charged targets the non-zero excitation cross sections at thresholds can also be calculated by simply setting the incident energy to the exact threshold value. These features are demonstrated by considering electron scattering on H and He+