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Author: Kornilov, Oleg × End date: 2022 × Start date: 2020 × Type: article × Publisher: Bristol : IOP Publ. × WGL Institute: MBI ×

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    Population transfer to high angular momentum states in infrared-assisted XUV photoionization of helium
    (Bristol : IOP Publ., 2020) Mayer, Nicola; Peng, Peng; Villeneuve, David M.; Patchkovskii, Serguei; Ivanov, Misha; Kornilov, Oleg; Vrakking, Marc J.J.; Niikura, Hiromichi
    An extreme-ultraviolet (XUV) laser pulse consisting of harmonics of a fundamental near-infrared (NIR) laser frequency is combined with the NIR pulse to systematically study two-color photoionization of helium atoms. A time-resolved photoelectron spectroscopy experiment is carried out where energy- A nd angle-resolved photoelectron distributions are obtained as a function of the NIR intensity and wavelength. Time-dependent Schrödinger equation calculations are performed for the conditions corresponding to the experiment and used to extract residual populations of Rydberg states resulting from excitation by the XUV + NIR pulse pair. The residual populations are studied as a function of the NIR intensity (3.5 × 1010-8 × 1012 W cm-2) and wavelength (760-820 nm). The evolution of the photoelectron distribution and the residual populations are interpreted using an effective restricted basis model, which includes the minimum set of states relevant to the features observed in the experiments. As a result, a comprehensive and intuitive picture of the laser-induced dynamics in helium atoms exposed to a two-color XUV-NIR light field is obtained. © 2020 The Author(s). Published by IOP Publishing Ltd.
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    Retrieval of attosecond pulse ensembles from streaking experiments using mixed state time-domain ptychography
    (Bristol : IOP Publ., 2020) Witting, Tobias; Furch, Federico J.; Kornilov, Oleg; Osolodkov, Mikhail; Schulz, Claus P.; Vrakking, Marc J.J.
    The electric field of attosecond laser pulses can be retrieved from laser-dressed photoionisation measurements, where electron wavepackets that result from single-photon ionisation by the attosecond pulse in the presence of a dressing field are produced. In case of fluctuating dressing laser and/or attosecond pulses, e.g. due to pulse-to-pulse fluctuations of the carrier envelope phase of the infrared laser pulse, commonly applied retrieval algorithms result in the erroneous extraction of the pulse fields. We present a mixed state time-domain ptychography algorithm for the retrieval of pulse ensembles from attosecond streaking experiments. © 2020 The Author(s). Published by IOP Publishing Ltd.