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Structural Dynamics (Melville, N.Y.)

Anne Creon, Inokentijs Josts, Stephan Niebling, Nils Huse, Henning Tidow
Calmodulin (CaM) is a very conserved, ubiquitous, eukaryotic protein that binds four Ca2+ ions with high affinity. It acts as a calcium sensor by translating Ca2+ signals into cellular processes such as metabolism, inflammation, immune response, memory, and muscle contraction. Calcium binding to CaM leads to conformational changes that enable Ca2+ /CaM to recognize and bind various target proteins with high affinity. The binding mode and binding partners of CaM are very diverse, and a consensus binding sequence is lacking...
November 2018: Structural Dynamics (Melville, N.Y.)
Brett M Marsh, Bethany R Lamoureux, Stephen R Leone
The addition of a metal overlayer to a semiconductor photocatalyst is a frequently used synthetic route to passivate the surface and, via the formation of a Schottky barrier, to enhance catalytic activity of the photocatalyst material. While it is known that Schottky junctions decrease recombination by charge separation, measurements of the depletion region dynamics have remained elusive. Here, we use ultrafast pump-probe transient photoelectron spectroscopy to measure material-specific dynamics of the Zn/n-GaP(100) system...
September 2018: Structural Dynamics (Melville, N.Y.)
Nadia L Opara, Istvan Mohacsi, Mikako Makita, Daniel Castano-Diez, Ana Diaz, Pavle Juranić, May Marsh, Alke Meents, Christopher J Milne, Aldo Mozzanica, Celestino Padeste, Valérie Panneels, Marcin Sikorski, Sanghoon Song, Henning Stahlberg, Ismo Vartiainen, Laura Vera, Meitian Wang, Philip R Willmott, Christian David
The development of X-ray free-electron lasers (XFELs) has opened the possibility to investigate the ultrafast dynamics of biomacromolecules using X-ray diffraction. Whereas an increasing number of structures solved by means of serial femtosecond crystallography at XFELs is available, the effect of radiation damage on protein crystals during ultrafast exposures has remained an open question. We used a split-and-delay line based on diffractive X-ray optics at the Linac Coherent Light Source XFEL to investigate the time dependence of X-ray radiation damage to lysozyme crystals...
September 2018: Structural Dynamics (Melville, N.Y.)
W Verhoeven, J F M van Rens, W F Toonen, E R Kieft, P H A Mutsaers, O J Luiten
The possibility to perform high-resolution time-resolved electron energy loss spectroscopy has the potential to impact a broad range of research fields. Resolving small energy losses with ultrashort electron pulses, however, is an enormous challenge due to the low average brightness of a pulsed beam. In this paper, we propose to use time-of-flight measurements combined with longitudinal phase space manipulation using resonant microwave cavities. This allows for both an accurate detection of energy losses with a high current throughput and efficient monochromation...
September 2018: Structural Dynamics (Melville, N.Y.)
N Pontius, M Beye, C Trabant, R Mitzner, F Sorgenfrei, T Kachel, M Wöstmann, S Roling, H Zacharias, R Ivanov, R Treusch, M Buchholz, P Metcalf, C Schüßler-Langeheine, A Föhlisch
We present a general experimental concept for jitter-free pump and probe experiments at free electron lasers. By generating pump and probe pulse from one and the same X-ray pulse using an optical split-and-delay unit, we obtain a temporal resolution that is limited only by the X-ray pulse lengths. In a two-color X-ray pump and X-ray probe experiment with sub 70 fs temporal resolution, we selectively probe the response of orbital and charge degree of freedom in the prototypical functional oxide magnetite after photoexcitation...
September 2018: Structural Dynamics (Melville, N.Y.)
Scott K Cushing, Michael Zürch, Peter M Kraus, Lucas M Carneiro, Angela Lee, Hung-Tzu Chang, Christopher J Kaplan, Stephen R Leone
The thermalization of hot carriers and phonons gives direct insight into the scattering processes that mediate electrical and thermal transport. Obtaining the scattering rates for both hot carriers and phonons currently requires multiple measurements with incommensurate timescales. Here, transient extreme-ultraviolet (XUV) spectroscopy on the silicon 2p core level at 100 eV is used to measure hot carrier and phonon thermalization in Si(100) from tens of femtoseconds to 200 ps, following photoexcitation of the indirect transition to the Δ valley at 800 nm...
September 2018: Structural Dynamics (Melville, N.Y.)
Christopher Corder, Peng Zhao, Jin Bakalis, Xinlong Li, Matthew D Kershis, Amanda R Muraca, Michael G White, Thomas K Allison
Time- and Angle-resolved photoelectron spectroscopy from surfaces can be used to record the dynamics of electrons and holes in condensed matter on ultrafast time scales. However, ultrafast photoemission experiments using extreme-ultraviolet (XUV) light have previously been limited by either space-charge effects, low photon flux, or limited tuning range. In this article, we describe XUV photoelectron spectroscopy experiments with up to 5 nA of average sample current using a tunable cavity-enhanced high-harmonic source operating at 88 MHz repetition rate...
September 2018: Structural Dynamics (Melville, N.Y.)
Giovanni Chillemi, Massimiliano Anselmi, Nico Sanna, Cristiano Padrin, Lodovico Balducci, Marco Cammarata, Elisabetta Pace, Majed Chergui, Maurizio Benfatto
We present a detailed analysis of the X-ray absorption near-edge structure (XANES) data on the Fe K-edge of CO Myoglobin based on a combined procedure of Molecular Dynamics (MD) calculations and MXAN (Minuit XANes) data analysis that we call D-MXAN. The ability of performing quantitative XANES data analysis allows us to refine classical force field MD parameters, thus obtaining a reliable tool for the atomic investigation of this important model system for biological macromolecules. The iterative procedure here applied corrects the greatest part of the structural discrepancy between classical MD sampling and experimental determinations...
September 2018: Structural Dynamics (Melville, N.Y.)
Dominik Ehberger, Catherine Kealhofer, Peter Baum
Time-resolved electron energy analysis and loss spectroscopy can reveal a wealth of information about material properties and dynamical light-matter interactions. Here, we report an all-optical concept for measuring energy spectra of femtosecond electron pulses with sub-eV resolution. Laser-generated terahertz radiation is used to measure arrival time differences within electron pulses with few-femtosecond precision. Controlled dispersion and subsequent compression of the electron pulses provide almost any desired compromise of energy resolution, signal strength, and time resolution...
July 2018: Structural Dynamics (Melville, N.Y.)
Kevin Bühlmann, Rafael Gort, Gerard Salvatella, Simon Däster, Andreas Fognini, Thomas Bähler, Christian Dornes, C A F Vaz, Andreas Vaterlaus, Yves Acremann
The laser-driven ultrafast demagnetization effect is one of the long-standing problems in solid-state physics. The time scale is given not only by the transfer of energy, but also by the transport of angular momentum away from the spin system. Through a double-pulse experiment resembling two-dimensional spectroscopy, we separate the different pathways by their nonlinear properties. We find (a) that the loss of magnetization within 400 fs is not affected by the previous excitations (linear process), and (b) we observe a picosecond demagnetization contribution that is strongly affected by the previous excitations...
July 2018: Structural Dynamics (Melville, N.Y.)
C Burger, A Atia-Tul-Noor, T Schnappinger, H Xu, P Rosenberger, N Haram, S Beaulieu, F Légaré, A S Alnaser, R Moshammer, R T Sang, B Bergues, M S Schuurman, R de Vivie-Riedle, I V Litvinyuk, M F Kling
We have investigated nuclear dynamics in bound and dissociating acetylene molecular ions in a time-resolved reaction microscopy experiment with a pair of few-cycle pulses. Vibrating bound acetylene cations or dissociating dications are produced by the first pulse. The second pulse probes the nuclear dynamics by ionization to higher charge states and Coulomb explosion of the molecule. For the bound cations, we observed vibrations in acetylene (HCCH) and its isomer vinylidene (CCHH) along the CC-bond with a periodicity of around 26 fs...
July 2018: Structural Dynamics (Melville, N.Y.)
R B Versteeg, J Zhu, P Padmanabhan, C Boguschewski, R German, M Goedecke, P Becker, P H M van Loosdrecht
We present a flexible and efficient ultrafast time-resolved spontaneous Raman spectroscopy setup to study collective excitation and quasi-particle dynamics in quantum materials. The setup has a broad energy tuning range extending from the visible to near infrared spectral regions for both the pump excitation and Raman probe pulses. Additionally, the balance between energy and time-resolution can be controlled. A high light collecting efficiency is realized by high numerical aperture collection optics and a high-throughput flexible spectrometer...
July 2018: Structural Dynamics (Melville, N.Y.)
Federico Pressacco, Vojtěch Uhlíř, Matteo Gatti, Alessandro Nicolaou, Azzedine Bendounan, Jon Ander Arregi, Sheena K K Patel, Eric E Fullerton, Damjan Krizmancic, Fausto Sirotti
We use time-resolved X-ray photoelectron spectroscopy to probe the electronic and magnetization dynamics in FeRh films after ultrafast laser excitations. We present experimental and theoretical results which investigate the electronic structure of FeRh during the first-order phase transition, identifying a clear signature of the magnetic phase. We find that a spin polarized feature at the Fermi edge is a fingerprint of the magnetic status of the system that is independent of the long-range ferromagnetic alignment of the magnetic domains...
May 2018: Structural Dynamics (Melville, N.Y.)
Christoph Hauf, Antonio-Andres Hernandez Salvador, Marcel Holtz, Michael Woerner, Thomas Elsaesser
Quantum theory has linked microscopic currents and macroscopic polarizations of ferroelectrics, but the interplay of lattice excitations and charge dynamics on atomic length and time scales is an open problem. Upon phonon excitation in the prototypical ferroelectric ammonium sulfate [(NH4 )2 SO4 ], we determine transient charge density maps by femtosecond x-ray diffraction. A newly discovered low frequency-mode with a 3 ps period and sub-picometer amplitudes induces periodic charge relocations over some 100 pm, a hallmark of soft-mode behavior...
March 2018: Structural Dynamics (Melville, N.Y.)
T Frigge, B Hafke, T Witte, B Krenzer, M Horn-von Hoegen
The photoinduced structural dynamics of the atomic wire system on the Si(111)-In surface has been studied by ultrafast electron diffraction in reflection geometry. Upon intense fs-laser excitation, this system can be driven in around 1 ps from the insulating [Formula: see text] reconstructed low temperature phase to a metastable metallic [Formula: see text] reconstructed high temperature phase. Subsequent to the structural transition, the surface heats up on a 6 times slower timescale as determined from a transient Debye-Waller analysis of the diffraction spots...
March 2018: Structural Dynamics (Melville, N.Y.)
Armin Feist, Nara Rubiano da Silva, Wenxi Liang, Claus Ropers, Sascha Schäfer
The control of optically driven high-frequency strain waves in nanostructured systems is an essential ingredient for the further development of nanophononics. However, broadly applicable experimental means to quantitatively map such structural distortion on their intrinsic ultrafast time and nanometer length scales are still lacking. Here, we introduce ultrafast convergent beam electron diffraction with a nanoscale probe beam for the quantitative retrieval of the time-dependent local deformation gradient tensor...
January 2018: Structural Dynamics (Melville, N.Y.)
Kasra Amini, Evgeny Savelyev, Felix Brauße, Nora Berrah, Cédric Bomme, Mark Brouard, Michael Burt, Lauge Christensen, Stefan Düsterer, Benjamin Erk, Hauke Höppner, Thomas Kierspel, Faruk Krecinic, Alexandra Lauer, Jason W L Lee, Maria Müller, Erland Müller, Terence Mullins, Harald Redlin, Nora Schirmel, Jan Thøgersen, Simone Techert, Sven Toleikis, Rolf Treusch, Sebastian Trippel, Anatoli Ulmer, Claire Vallance, Joss Wiese, Per Johnsson, Jochen Küpper, Artem Rudenko, Arnaud Rouzée, Henrik Stapelfeldt, Daniel Rolles, Rebecca Boll
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...
January 2018: Structural Dynamics (Melville, N.Y.)
Krystel El Hage, Sebastian Brickel, Sylvain Hermelin, Geoffrey Gaulier, Cédric Schmidt, Luigi Bonacina, Siri C van Keulen, Swarnendu Bhattacharyya, Majed Chergui, Peter Hamm, Ursula Rothlisberger, Jean-Pierre Wolf, Markus Meuwly
[This corrects the article DOI: 10.1063/1.4996448.].
January 2018: Structural Dynamics (Melville, N.Y.)
Rafael Abela, Paul Beaud, Jeroen A van Bokhoven, Majed Chergui, Thomas Feurer, Johannes Haase, Gerhard Ingold, Steven L Johnson, Gregor Knopp, Henrik Lemke, Chris J Milne, Bill Pedrini, Peter Radi, Gebhard Schertler, Jörg Standfuss, Urs Staub, Luc Patthey
We present the main specifications of the newly constructed Swiss Free Electron Laser, SwissFEL, and explore its potential impact on ultrafast science. In light of recent achievements at current X-ray free electron lasers, we discuss the potential territory for new scientific breakthroughs offered by SwissFEL in Chemistry, Biology, and Materials Science, as well as nonlinear X-ray science.
November 2017: Structural Dynamics (Melville, N.Y.)
Martin P Bircher, Elisa Liberatore, Nicholas J Browning, Sebastian Brickel, Cornelia Hofmann, Aurélien Patoz, Oliver T Unke, Tomáš Zimmermann, Majed Chergui, Peter Hamm, Ursula Keller, Markus Meuwly, Hans-Jakob Woerner, Jiří Vaníček, Ursula Rothlisberger
Due to their very nature, ultrafast phenomena are often accompanied by the occurrence of nonadiabatic effects. From a theoretical perspective, the treatment of nonadiabatic processes makes it necessary to go beyond the (quasi) static picture provided by the time-independent Schrödinger equation within the Born-Oppenheimer approximation and to find ways to tackle instead the full time-dependent electronic and nuclear quantum problem. In this review, we give an overview of different nonadiabatic processes that manifest themselves in electronic and nuclear dynamics ranging from the nonadiabatic phenomena taking place during tunnel ionization of atoms in strong laser fields to the radiationless relaxation through conical intersections and the nonadiabatic coupling of vibrational modes and discuss the computational approaches that have been developed to describe such phenomena...
November 2017: Structural Dynamics (Melville, N.Y.)
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