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Start date: 2010 × Subject: electron × Subject: generation × WGL Institute: MBI ×

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    Multidimensional high harmonic spectroscopy of polyatomic molecules: detecting sub-cycle laser-driven hole dynamics upon ionization in strong mid-IR laser fields
    (Cambridge [u.a.] : Soc., 2016) Bruner, Barry D.; Mašín, Zdeněk; Negro, Matteo; Morales, Felipe; Brambila, Danilo; Devetta, Michele; Faccialà, Davide; Harvey, Alex G.; Ivanov, Misha; Mairesse, Yann; Patchkovskii, Serguei; Serbinenko, Valeria; Soifer, Hadas; Stagira, Salvatore; Vozzi, Caterina; Dudovich, Nirit; Smirnova, Olga
    High harmonic generation (HHG) spectroscopy has opened up a new frontier in ultrafast science, where electronic dynamics can be measured on an attosecond time scale. The strong laser field that triggers the high harmonic response also opens multiple quantum pathways for multielectron dynamics in molecules, resulting in a complex process of multielectron rearrangement during ionization. Using combined experimental and theoretical approaches, we show how multi-dimensional HHG spectroscopy can be used to detect and follow electronic dynamics of core rearrangement on sub-laser cycle time scales. We detect the signatures of laser-driven hole dynamics upon ionization and reconstruct the relative phases and amplitudes for relevant ionization channels in a CO2 molecule on a sub-cycle time scale. Reconstruction of channel-resolved complex ionization amplitudes on attosecond time scales has been a long-standing goal of high harmonic spectroscopy. Our study brings us one step closer to fulfilling this initial promise and developing robust schemes for sub-femtosecond imaging of multielectron rearrangement in complex molecular systems.
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    Tracing dynamics of laser-induced fields on ultra-thin foils using complementary imaging with streak deflectometry
    (College Park, MD : American Physical Society, 2016) Abicht, Florian; Braenzel, Julia; Priebe, Gerd; Koschitzki, Christian; Andreev, Alexander; Nickles, Peter; Sander, Wolfgang; Schnürer, Matthias
    We present a detailed study of the electric and magnetic fields, which are created on plasma vacuum interfaces as a result of highly intense laser-matter interactions. For the field generation ultrathin polymer foils (30–50 nm) were irradiated with high intensity femtosecond (1019–1020  W/cm2) and picosecond (∼1017  W/cm2) laser pulses with ultrahigh contrast (1010–1011). To determine the temporal evolution and the spatial distribution of these fields the proton streak deflectometry method has been developed further and applied in two different imaging configurations. It enabled us to gather complementary information about the investigated field structure, in particular about the influence of different field components (parallel and normal to the target surface) and the impact of a moving ion front. The applied ultrahigh laser contrast significantly increased the reproducibility of the experiment and improved the accuracy of the imaging method. In order to explain the experimental observations, which were obtained by applying ultrashort laser pulses, two different analytical models have been studied in detail. Their ability to reproduce the streak deflectometry measurements was tested on the basis of three-dimensional particle simulations. A modification and combination of the two models allowed for an extensive and accurate reproduction of the experimental results in both imaging configurations. The controlled change of the laser pulse duration from 50 femtoseconds to 2.7 picoseconds led to a transition of the dominating force acting on the probing proton beam at the rear side of the polymer foil. In the picosecond case the (⇀vx⇀B)-term of the Lorentz force dominated over the counteracting ⇀E-field and was responsible for the direction of the net force. The applied proton deflectometry method allowed for an unambiguous determination of the magnetic field polarity at the rear side of the ultrathin foil.