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Nanomatrix Effects in der Ultrafast Ionisation Dynamics of Clusters in Superfluid Helium Droplets

Subject Area Optics, Quantum Optics and Physics of Atoms, Molecules and Plasmas
Term from 2018 to 2022
Project identifier Deutsche Forschungsgemeinschaft (DFG) - Project number 392530662
 
Final Report Year 2022

Final Report Abstract

Rare gas clusters and helium droplets as well core-shell systems in strong laser fields have been studied experimentally. In addition to pump-probe spectroscopy, the so-called phase-of-the-phase (PoP) approach was used and further developed. In PoP spectroscopy, the momentum-resolved photoelectron yields are analyzed as function of the relative phase between the two color-components of the laser field, in order to provide high resolution spectra in a concise manner. The method was successfully applied to rare gas clusters embedded in ultracold helium nanodroplets and evidence was found that surface back scattering and plasmon-assisted forward scattering are the dominating acceleration mechanisms which lead to the directed emission of fast electrons. The second focus was set to the final disintegration of the nanoplasma on the ps up the ns timescale. Subsequent electron recombination gives rise to transitions between He+ states, resulting in autoionization. The time-resolved analysis of the energy transfer to quasifree electrons reveals a transient depletion of the Auger emission, which allows for a temporal gate to map the distribution of delocalized electrons in the developing mean field. Furthermore, the recombination of delocalized electrons near the vacuum level into highly excited Rydberg states was traced by monitoring the highly charged ion as well as the electron observable. Transient above-threshold ionization has been introduced as a diagnostic tool to resolve the electron dynamics whose sensitivity was enhanced by applying two-color phase-of-the-phase spectroscopy.

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