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Project B.1.2

Fig. B.1.2: Transient absorption spectra of krypton ions acquired by the transmission of EUV pulses through a gas target as a function of its delay with an intense laser pulse. The data reveal intra-atomic electron wave-packet motion.

Attosecond spectroscopy of electron correlation and wavepacket dynamics in atoms

The scope of this project is to explore electron dynamics in atoms and molecules during and after the interaction with strong fields and to gain insight into fundamental atomic phenomena such as electron-electron correlation, strong-field ionisation, valence electron wavepacket formation and decay by decoherence and control of intra-atomic wavepacket dynamics by synthesised external light fields. First results in this direction have been reported in and provide motivation for the pursuit of the above goals.

We will draw on the AS-1 attosecond beamline at MPQ and utilise the tools developed in the framework of Project A.1.2 (XUV frequency combs). These tools include (a) sub-cycle pulses that will permit (i) sub-femtosecond triggering of atomic ionisation / excitation and (ii) subfemtosecond confinement of the field-atom interaction; (b) synchronised sub-100-attosecond XUV pulses. On the theoretical side, established electronic structure packages and correlated strong field theory (MCTDHF, TDCI) will be united for a description of electronic dynamics during and after excitation and ionisation processes. Electronic correlation has a drastic effect on the properties of matter.

In many molecules the correlation energy exceeds the binding energy, so that stable molecules only exist because of correlation. In atoms, the correlation energy often exceeds the ionisation potential, too, so that neutral atoms only exist because of correlation. Although it has often been pointed out that correlation strongly affects electron dynamics, time-domain access to this phenomenon has not been reported so far. Here we propose to capture electron correlation by attosecond pump-probe settings and scrutinise its controllability with synthesised external fields on a sub-femtosecond time scale.

A similar approach will be used to study and control the formation, dynamics and dephasing of electronic wavepackets created in atoms or molecules by the sudden removal of one or more electrons. The interaction of the outgoing electron(s) with the created wavepacket can result in reduced coherence. We can accurately measure the degree of coherence and its temporal evolution with the attosecond absorption technique that we developed in the previous funding period.

Project Leader