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Start date: 2020 × DDC: 530 × Subject: Electrons × Subject: Photons ×

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Now showing 1 - 2 of 2
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    Attosecond investigation of extreme-ultraviolet multi-photon multi-electron ionization
    (Washington, DC : OSA, 2022) Kretschmar, M.; Hadjipittas, A.; Major, B.; Tümmler, J.; Will, I.; Nagy, T.; Vrakking, M. J. J.; Emmanouilidou, A.; Schütte, B.
    Multi-electron dynamics in atoms and molecules very often occur on sub- to few-femtosecond time scales. The available intensities of extreme-ultraviolet (XUV) attosecond pulses have previously allowed the time-resolved investigation of two-photon, two-electron interactions. Here we study double and triple ionization of argon atoms involving the absorption of up to five XUV photons using a pair of intense attosecond pulse trains (APTs). By varying the time delay between the two APTs with attosecond precision and the spatial overlap with nanometer precision, we obtain information on complex nonlinear multi-photon ionization pathways. Our experimental and numerical results show that Ar2+ is predominantly formed by a sequential two-photon process, whereas the delay dependence of the Ar3+ ion yield exhibits clear signatures of the involvement of a simultaneous two-photon absorption process. Our experiment suggests that it is possible to investigate multi-electron dynamics using attosecond pulses for both pumping and probing the dynamics.
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    Photon-electron coincidence experiments at synchrotron radiation facilities with arbitrary bunch modes
    ([S.l.] : American Institute of Physics, 2021) Ozga, C.; Honisch, C.; Schmidt, P.; Holzapfel, X.; Zindel, C.; Küstner-Wetekam, C.; Richter, C.; Hergenhahn, U.; Ehresmann, A.; Knie, A.; Hans, A.
    We report the adaptation of an electron–photon coincidence detection scheme to the multibunch hybrid mode of the synchrotron radiation source BESSY II (Helmholtz-Zentrum Berlin). Single-event-based data acquisition and evaluation, combined with the use of relative detection times between the coincident particles, enable the acquisition of proper coincidence signals from a quasi-continuous excitation pattern. The background signal produced by accidental coincidences in the time difference representation is modeled using the non-coincident electron and photon spectra. We validate the method by reproducing previously published results, which were obtained in the single bunch mode, and illustrate its usability for the multibunch hybrid mode by investigating the photoionization of CO2 into CO+2 B satellite states, followed by subsequent photon emission. The radiative lifetime obtained and the electron binding energy are in good agreement with earlier publications. We expect this method to be a useful tool to extend the versatility of coincident particle detection to arbitrary operation modes of synchrotron radiation facilities and other excitation sources without the need for additional experimental adjustments.