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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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    Perspective: Structure and ultrafast dynamics of biomolecular hydration shells
    (Melville, NY : AIP Publishing LLC, 2017) Laage, Damien; Elsaesser, Thomas; Hynes, James T.
    The structure and function of biomolecules can be strongly influenced by their hydration shells. A key challenge is thus to determine the extent to which these shells differ from bulk water, since the structural fluctuations and molecular excitations of hydrating water molecules within these shells can cover a broad range in both space and time. Recent progress in theory, molecular dynamics simulations, and ultrafast vibrational spectroscopy has led to new and detailed insight into the fluctuations of water structure, elementary water motions, and electric fields at hydrated biointerfaces. Here, we discuss some central aspects of these advances, focusing on elementary molecular mechanisms and processes of hydration on a femto-to picosecond time scale, with some special attention given to several issues subject to debate.