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Author: Müller, Maria ×

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    Jitter-correction for IR/UV-XUV pump-probe experiments at the FLASH free-electron laser
    ([Bad Honnef] : Dt. Physikalische Ges., 2017-04-10) Savelyev, Evgeny; Boll, Rebecca; Bomme, Cédric; Schirmel, Nora; Redlin, Harald; Erk, Benjamin; Düsterer, Stefan; Müller, Erland; Höppner, Hauke; Toleikis, Sven; Müller, Jost; Kristin Czwalinna, Marie; Treusch, Rolf; Kierspel, Thomas; Mullins, Terence; Trippel, Sebastian; Wiese, Joss; Küpper, Jochen; Brauβe, Felix; Krecinic, Faruk; Rouzée, Arnaud; Rudawski, Piotr; Johnsson, Per; Amini, Kasra; Lauer, Alexandra; Burt, Michael; Brouard, Mark; Christensen, Lauge; Thøgersen, Jan; Stapelfeldt, Henrik; Berrah, Nora; Müller, Maria; Ulmer, Anatoli; Techert, Simone; Rudenko, Artem; Rolles, Daniel
    In pump-probe experiments employing a free-electron laser (FEL) in combination with a synchronized optical femtosecond laser, the arrival-time jitter between the FEL pulse and the optical laser pulse often severely limits the temporal resolution that can be achieved. Here, we present a pump-probe experiment on the UV-induced dissociation of 2,6-difluoroiodobenzene (C6H3F2I) molecules performed at the FLASH FEL that takes advantage of recent upgrades of the FLASH timing and synchronization system to obtain high-quality data that are not limited by the FEL arrival-time jitter. We discuss in detail the necessary data analysis steps and describe the origin of the time-dependent effects in the yields and kinetic energies of the fragment ions that we observe in the experiment.
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    Photodissociation of aligned CH3I and C6H3F2I molecules probed with time-resolved Coulomb explosion imaging by site-selective extreme ultraviolet ionization
    (Melville, NY : AIP Publishing LLC, 2018) Amini, Kasra; Savelyev, Evgeny; Brauße, Felix; Berrah, Nora; Bomme, Cédric; Brouard, Mark; Burt, Michael; Christensen, Lauge; Düsterer, Stefan; Erk, Benjamin; Höppner, Hauke; Kierspel, Thomas; Krecinic, Faruk; Lauer, Alexandra; Lee, Jason W. L.; Müller, Maria; Müller, Erland; Mullins, Terence; Redlin, Harald; Schirmel, Nora; Thøgersen, Jan; Techert, Simone; Toleikis, Sven; Treusch, Rolf; Trippel, Sebastian; Ulmer, Anatoli; Vallance, Claire; Wiese, Joss; Johnsson, Per; Küpper, Jochen; Rudenko, Artem; Rouzée, Arnaud; Stapelfeldt, Henrik; Rolles, Daniel; Boll, Rebecca
    We explore time-resolved Coulomb explosion induced by intense, extreme ultraviolet (XUV) femtosecond pulses from a free-electron laser as a method to image photo-induced molecular dynamics in two molecules, iodomethane and 2,6-difluoroiodobenzene. At an excitation wavelength of 267 nm, the dominant reaction pathway in both molecules is neutral dissociation via cleavage of the carbon-iodine bond. This allows investigating the influence of the molecular environment on the absorption of an intense, femtosecond XUV pulse and the subsequent Coulomb explosion process. We find that the XUV probe pulse induces local inner-shell ionization of atomic iodine in dissociating iodomethane, in contrast to non-selective ionization of all photofragments in difluoroiodobenzene. The results reveal evidence of electron transfer from methyl and phenyl moieties to a multiply charged iodine ion. In addition, indications for ultrafast charge rearrangement on the phenyl radical are found, suggesting that time-resolved Coulomb explosion imaging is sensitive to the localization of charge in extended molecules.
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    Correlated electronic decay in expanding clusters triggered by intense XUV pulses from a Free-Electron-Laser
    (London : Nature Publishing Group, 2017) Oelze, Tim; Schütte, Bernd; Müller, Maria; Müller, Jan P.; Wieland, Marek; Frühling, Ulrike; Drescher, Markus; Al-Shemmary, Alaa; Golz, Torsten; Stojanovic, Nikola; Krikunova, Maria
    Irradiation of nanoscale clusters and large molecules with intense laser pulses transforms them into highly-excited non- equilibrium states. The dynamics of intense laser-cluster interaction is encoded in electron kinetic energy spectra, which contain signatures of direct photoelectron emission as well as emission of thermalized nanoplasma electrons. In this work we report on a so far not observed spectrally narrow bound state signature in the electron kinetic energy spectra from mixed Xe core - Ar shell clusters ionized by intense extreme-ultraviolet (XUV) pulses from a free-electron-laser. This signature is attributed to the correlated electronic decay (CED) process, in which an excited atom relaxes and the excess energy is used to ionize the same or another excited atom or a nanoplasma electron. By applying the terahertz field streaking principle we demonstrate that CED-electrons are emitted at least a few picoseconds after the ionizing XUV pulse has ended. Following the recent finding of CED in clusters ionized by intense near-infrared laser pulses, our observation of CED in the XUV range suggests that this process is of general relevance for the relaxation dynamics in laser produced nanoplasmas.