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Structural Dynamics (Melville, N.Y.)

Laurent P René de Cotret, Bradley J Siwick
The general problem of background subtraction in ultrafast electron powder diffraction (UEPD) is presented with a focus on the diffraction patterns obtained from materials of moderately complex structure which contain many overlapping peaks and effectively no scattering vector regions that can be considered exclusively background. We compare the performance of background subtraction algorithms based on discrete and dual-tree complex (DTCWT) wavelet transforms when applied to simulated UEPD data on the M1-R phase transition in VO2 with a time-varying background...
July 2017: Structural Dynamics (Melville, N.Y.)
Christopher Kupitz, Jose L Olmos, Mark Holl, Lee Tremblay, Kanupriya Pande, Suraj Pandey, Dominik Oberthür, Mark Hunter, Mengning Liang, Andrew Aquila, Jason Tenboer, George Calvey, Andrea Katz, Yujie Chen, Max O Wiedorn, Juraj Knoska, Alke Meents, Valerio Majriani, Tyler Norwood, Ishwor Poudyal, Thomas Grant, Mitchell D Miller, Weijun Xu, Aleksandra Tolstikova, Andrew Morgan, Markus Metz, Jose M Martin-Garcia, James D Zook, Shatabdi Roy-Chowdhury, Jesse Coe, Nirupa Nagaratnam, Domingo Meza, Raimund Fromme, Shibom Basu, Matthias Frank, Thomas White, Anton Barty, Sasa Bajt, Oleksandr Yefanov, Henry N Chapman, Nadia Zatsepin, Garrett Nelson, Uwe Weierstall, John Spence, Peter Schwander, Lois Pollack, Petra Fromme, Abbas Ourmazd, George N Phillips, Marius Schmidt
Mix-and-inject serial crystallography (MISC) is a technique designed to image enzyme catalyzed reactions in which small protein crystals are mixed with a substrate just prior to being probed by an X-ray pulse. This approach offers several advantages over flow cell studies. It provides (i) room temperature structures at near atomic resolution, (ii) time resolution ranging from microseconds to seconds, and (iii) convenient reaction initiation. It outruns radiation damage by using femtosecond X-ray pulses allowing damage and chemistry to be separated...
July 2017: Structural Dynamics (Melville, N.Y.)
Fabio G Santomauro, Jakob Grilj, Lars Mewes, Georgian Nedelcu, Sergii Yakunin, Thomas Rossi, Gloria Capano, André Al Haddad, James Budarz, Dominik Kinschel, Dario S Ferreira, Giacomo Rossi, Mario Gutierrez Tovar, Daniel Grolimund, Valerie Samson, Maarten Nachtegaal, Grigory Smolentsev, Maksym V Kovalenko, Majed Chergui
We report on an element-selective study of the fate of charge carriers in photoexcited inorganic CsPbBr3 and CsPb(ClBr)3 perovskite nanocrystals in toluene solutions using time-resolved X-ray absorption spectroscopy with 80 ps time resolution. Probing the Br K-edge, the Pb L3-edge, and the Cs L2-edge, we find that holes in the valence band are localized at Br atoms, forming small polarons, while electrons appear as delocalized in the conduction band. No signature of either electronic or structural changes is observed at the Cs L2-edge...
July 2017: Structural Dynamics (Melville, N.Y.)
Monique M Tirion
The α and β subunits comprising the hexameric assembly of F1-ATPase share a high degree of structural identity, though low primary identity. Each subunit binds nucleotide in similar pockets, yet only β subunits are catalytically active. Why? We re-examine their internal symmetry axes and observe interesting differences. Dividing each chain into an N-terminal head region, a C-terminal foot region, and a central torso, we observe (1) that while the foot and head regions in all chains obtain high and similar mobility, the torsos obtain different mobility profiles, with the β subunits exhibiting a higher motility compared to the α subunits, a trend supported by the crystallographic B-factors...
July 2017: Structural Dynamics (Melville, N.Y.)
A Nakamura, T Shimojima, M Nakano, Y Iwasa, K Ishizaka
We report the ultrafast dynamics of electrons and lattice in transition metal thin films (Au, Cu, and Mo) investigated by a combination of ultrafast electron diffraction (UED) and pump-probe optical methods. For a single-crystalline Au thin film, we observe the suppression of the diffraction intensity occuring in 10 ps, which direcly reflects the lattice thermalization via the electron-phonon interaction. By using the two-temperature model, the electron-phonon coupling constant (g) and the electron and lattice temperatures (Te, Tl) are evaluated from UED, with which we simulate the transient optical transmittance...
November 2016: Structural Dynamics (Melville, N.Y.)
Edoardo Baldini, Andreas Mann, Simone Borroni, Christopher Arrell, Frank van Mourik, Fabrizio Carbone
A femtosecond pump-probe setup is described that is optimised for broadband transient reflectivity experiments on solid samples over a wide temperature range. By combining high temporal resolution and a broad detection window, this apparatus can investigate the interplay between coherent collective modes and high-energy electronic excitations, which is a distinctive characteristic of correlated electron systems. Using a single-shot readout array detector at frame rates of 10 kHz allows resolving coherent oscillations with amplitudes <10(-4)...
November 2016: Structural Dynamics (Melville, N.Y.)
A S Johnson, L Miseikis, D A Wood, D R Austin, C Brahms, S Jarosch, C S Strüber, P Ye, J P Marangos
We use a high harmonic generated supercontinuum in the soft X-ray region to measure X-ray absorption near edge structure (XANES) spectra in polythiophene (poly(3-hexylthiophene)) films at multiple absorption edges. A few-cycle carrier-envelope phase-stable laser pulse centered at 1800 nm was used to generate a stable soft X-ray supercontinuum, with amplitude gating limiting the generated pulse duration to a single optical half-cycle. We report a quantitative transmission measurement of the sulfur L2,3 edge over the range 160-200 eV and the carbon K edge from 280 to 330 eV...
November 2016: Structural Dynamics (Melville, N.Y.)
Mizuho Fushitani, Akiyoshi Hishikawa
We present applications of extreme ultraviolet (XUV) single-order laser harmonics to gas-phase ultrafast photoelectron spectroscopy. Ultrashort XUV pulses at 80 nm are obtained as the 5th order harmonics of the fundamental laser at 400 nm by using Xe or Kr as the nonlinear medium and separated from other harmonic orders by using an indium foil. The single-order laser harmonics is applied for real-time probing of vibrational wavepacket dynamics of I2 molecules in the bound and dissociating low-lying electronic states and electronic-vibrational wavepacket dynamics of highly excited Rydberg N2 molecules...
November 2016: Structural Dynamics (Melville, N.Y.)
Marie Preuße, Sergey I Bokarev, Saadullah G Aziz, Oliver Kühn
The Frenkel exciton model was adapted to describe X-ray absorption and resonant inelastic scattering spectra of polynuclear transition metal complexes by means of the restricted active space self-consistent field method. The proposed approach allows to substantially decrease the requirements on computational resources if compared to a full supermolecular quantum chemical treatment. This holds true, in particular, in cases where the dipole approximation to the electronic transition charge density can be applied...
November 2016: Structural Dynamics (Melville, N.Y.)
Isabella Gierz, Andrea Cavalleri
We review our recent time- and angle-resolved photoemission spectroscopy experiments, which measure the transient electronic structure of optically driven graphene. For pump photon energies in the near infrared ([Formula: see text]), we have discovered the formation of a population-inverted state near the Dirac point, which may be of interest for the design of THz lasing devices and optical amplifiers. At lower pump photon energies ([Formula: see text]), for which interband absorption is not possible in doped samples, we find evidence for free carrier absorption...
September 2016: Structural Dynamics (Melville, N.Y.)
G Salvatella, R Gort, K Bühlmann, S Däster, A Vaterlaus, Y Acremann
Ultrafast demagnetization of ferromagnetic metals can be achieved by a heat pulse propagating in the electron gas of a non-magnetic metal layer, which absorbs a pump laser pulse. Demagnetization by electronic heating is investigated on samples with different thicknesses of the absorber layer on nickel. This allows us to separate the contribution of thermalized hot electrons compared to non-thermal electrons. An analytical model describes the demagnetization amplitude as a function of the absorber thickness...
September 2016: Structural Dynamics (Melville, N.Y.)
Daniel Schick, Sebastian Eckert, Niko Pontius, Rolf Mitzner, Alexander Föhlisch, Karsten Holldack, Florian Sorgenfrei
We present an X-ray-optical cross-correlator for the soft ([Formula: see text]) up to the hard X-ray regime based on a molybdenum-silicon superlattice. The cross-correlation is done by probing intensity and position changes of superlattice Bragg peaks caused by photoexcitation of coherent phonons. This approach is applicable for a wide range of X-ray photon energies as well as for a broad range of excitation wavelengths and requires no external fields or changes of temperature. Moreover, the cross-correlator can be employed on a 10 ps or 100 fs time scale featuring up to 50% total X-ray reflectivity and transient signal changes of more than 20%...
September 2016: Structural Dynamics (Melville, N.Y.)
W Verhoeven, J F M van Rens, M A W van Ninhuijs, W F Toonen, E R Kieft, P H A Mutsaers, O J Luiten
We demonstrate the use of two TM110 resonant cavities to generate ultrashort electron pulses and subsequently measure electron energy losses in a time-of-flight type of setup. The method utilizes two synchronized microwave cavities separated by a drift space of 1.45 m. The setup has an energy resolution of 12 ± 2 eV FWHM at 30 keV, with an upper limit for the temporal resolution of 2.7 ± 0.4 ps. Both the time and energy resolution are currently limited by the brightness of the tungsten filament electron gun used...
September 2016: Structural Dynamics (Melville, N.Y.)
S Höfer, T Kämpfer, E Förster, T Stöhlker, I Uschmann
We explore the InSb-semiconductor lattice dynamics after excitation of high density electron-hole plasma with an ultrashort and intense laser pulse. By using time resolved x-ray diffraction, a sub-mÅ and sub-ps resolution was achieved. Thus, a strain of 4% was measured in a 3 nm thin surface layer 2 ps after excitation. The lattice strain was observed for the first 5 ps as exponentially decaying, changing rapidly by time and by depth. The observed phenomena can only be understood assuming nonlinear time dependent laser absorption where the absorption depth decreases by a factor of twenty compared to linear absorption...
September 2016: Structural Dynamics (Melville, N.Y.)
Heikki Takala, Stephan Niebling, Oskar Berntsson, Alexander Björling, Heli Lehtivuori, Heikki Häkkänen, Matthijs Panman, Emil Gustavsson, Maria Hoernke, Gemma Newby, Federico Zontone, Michael Wulff, Andreas Menzel, Janne A Ihalainen, Sebastian Westenhoff
Phytochromes sense red light in plants and various microorganism. Light absorption causes structural changes within the protein, which alter its biochemical activity. Bacterial phytochromes are dimeric proteins, but the functional relevance of this arrangement remains unclear. Here, we use time-resolved X-ray scattering to reveal the solution structural change of a monomeric variant of the photosensory core module of the phytochrome from Deinococcus radiodurans. The data reveal two motions, a bend and a twist of the PHY domain with respect to the chromophore-binding domains...
September 2016: Structural Dynamics (Melville, N.Y.)
A von Reppert, J Pudell, A Koc, M Reinhardt, W Leitenberger, K Dumesnil, F Zamponi, M Bargheer
We present a temperature and fluence dependent Ultrafast X-Ray Diffraction study of a laser-heated antiferromagnetic dysprosium thin film. The loss of antiferromagnetic order is evidenced by a pronounced lattice contraction. We devise a method to determine the energy flow between the phonon and spin system from calibrated Bragg peak positions in thermal equilibrium. Reestablishing the magnetic order is much slower than the cooling of the lattice, especially around the Néel temperature. Despite the pronounced magnetostriction, the transfer of energy from the spin system to the phonons in Dy is slow after the spin-order is lost...
September 2016: Structural Dynamics (Melville, N.Y.)
George D Calvey, Andrea M Katz, Chris B Schaffer, Lois Pollack
Knowledge of protein structure provides essential insight into function, enhancing our understanding of diseases and enabling new treatment development. X-ray crystallography has been used to solve the structures of more than 100 000 proteins; however, the vast majority represent long-lived states that do not capture the functional motions of these molecular machines. Reactions triggered by the addition of a ligand can be the most challenging to detect with crystallography because of the difficulty of synchronizing reactions to create detectable quantities of transient states...
September 2016: Structural Dynamics (Melville, N.Y.)
Michael Greif, Tibor Nagy, Maksym Soloviov, Luca Castiglioni, Matthias Hengsberger, Markus Meuwly, Jürg Osterwalder
[This corrects the article DOI: 10.1063/1.4922611.].
September 2016: Structural Dynamics (Melville, N.Y.)
Malik Muhammad Abdullah, Zoltan Jurek, Sang-Kil Son, Robin Santra
We present a generalized method to describe the x-ray scattering intensity of the Bragg spots in a diffraction pattern from nanocrystals exposed to intense x-ray pulses. Our method involves the subdivision of a crystal into smaller units. In order to calculate the dynamics within every unit, we employ a Monte-Carlo-molecular dynamics-ab-initio hybrid framework using real space periodic boundary conditions. By combining all the units, we simulate the diffraction pattern of a crystal larger than the transverse x-ray beam profile, a situation commonly encountered in femtosecond nanocrystallography experiments with focused x-ray free-electron laser radiation...
September 2016: Structural Dynamics (Melville, N.Y.)
Terry Mullins, Jochen Küpper
No abstract text is available yet for this article.
July 2016: Structural Dynamics (Melville, N.Y.)
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