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Wednesday, 14 December 2011

DM: Suren: Attosecond cascades and time-delays in one-electron photo-ionization

I shall present time-resolved ab-initio study of the attosecond dynamics of electron-electron correlation during single-electron, single XUV-photon ionization of an excited two-electron atom. Specifically, we aim to time-resolve the two fundamental processes that play the key role in electronic excitations of the ion created by ionization: the shake-up and the post-ionization interaction of the outgoing electron with the core (knock-up). These two processes have different time characteristics: while the shake-up is an essentially instantaneous process, the knock-up excitation due to the interaction between the ionic and the continuum electrons depends on the movement of the latter and may be significant for longer times, leading to delays in the ionization process. We observe an interplay of the initial shake-up excitation with the excitation cascades induced by the post-ionization interaction of the outgoing electron with the core. The time-scales and the structure of these excitation cascades is directly linked to the time it takes the 'active' continuum electron, lifted from a deeper bound orbital, to traverse the orbit of the 'passive' electron residing in the outer orbit. Ideas for resolving and controlling the two-electron interaction dynamics during the ionization process will be discussed.