Berakdar, J., Klar, H.

In this report we review recent progress in the understanding of the role of chirality in the multi-electron emission. A brief account of the chiral single-electron photoemission is given. In this case the chirality of the experimental set-up is brought about by an initial orientation of the target or/and by specifying a certain projection of the photoelectron spin. The dependence of the photoelectron spectrum on the chirality of the experiment is probed by changing the initial orientation of the target or by inverting the photoelectron spin projection. In a further section we envisage the direct transition of chiral electron pairs from an isotropic bound initial state into a double continuum state following the absorption of a circularly polarized photon. We work out the necessary conditions under which the spectrum of the correlated photoelectron pair shows a chiral character, i.e. a dependence on the chirality of the exciting photon. The magnitude and the general behaviour of the chiral effects are estimated from simple analytical models and more elaborate numerical methods are presented for a more quantitative predictions. As a further example for the chiral multi-electron emission we study the photoelectron Auger-electron coincidence spectrum. The Auger hole is created by ionising a randomly oriented target by a circular polarised photon. We investigate how the helicity the photon is transferred to the emitted photoelectron pair. The theoretical findings are analysed and interpreted in light of recent experiments. In a final section we focus on the emission of correlated electrons where the initial state is already oriented, e.g. via optical pumping by circularly polarized light. The initial orientation of the atom is transferred to the continuum states following the ionisation of the target by low energy electrons. We formulate and analyse the theoretical concepts for the transition of the screw sense of the initially bound atomic electron to the continuum electron pair. Numerical methods for the calculations of the cross sections for the electron-impact ionisation of oriented atoms are presented and their results are contrasted against recent experimental data.

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