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Structural Dynamics (Melville, N.Y.)

Peter Hamm, Markus Meuwly, Steve L Johnson, Paul Beaud, Urs Staub
Recent years have seen dramatic developments in the technology of intense pulsed light sources in the THz frequency range. Since many dipole-active excitations in solids and molecules also lie in this range, there is now a tremendous potential to use these light sources to study linear and nonlinear dynamics in such systems. While several experimental investigations of THz-driven dynamics in solid-state systems have demonstrated a variety of interesting linear and nonlinear phenomena, comparatively few efforts have been made to drive analogous dynamics in molecular systems...
November 2017: 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 review provides a comprehensive overview of the structural dynamics in topical gas- and condensed-phase systems on multiple length and time scales. Starting from vibrationally induced dissociation of small molecules in the gas phase, the question of vibrational and internal energy redistribution through conformational dynamics is further developed by considering coupled electron/proton transfer in a model peptide over many orders of magnitude. The influence of the surrounding solvent is probed for electron transfer to the solvent in hydrated I-...
November 2017: Structural Dynamics (Melville, N.Y.)
S L Johnson, M Savoini, P Beaud, G Ingold, U Staub, F Carbone, L Castiglioni, M Hengsberger, J Osterwalder
We present a non-comprehensive review of some representative experimental studies in crystalline condensed matter systems where the effects of intense ultrashort light pulses are probed using x-ray diffraction and photoelectron spectroscopy. On an ultrafast (sub-picosecond) time scale, conventional concepts derived from the assumption of thermodynamic equilibrium must often be modified in order to adequately describe the time-dependent changes in material properties. There are several commonly adopted approaches to this modification, appropriate in different experimental circumstances...
November 2017: Structural Dynamics (Melville, N.Y.)
I Crassee, L Gallmann, G Gäumann, M Matthews, H Yanagisawa, T Feurer, M Hengsberger, U Keller, J Osterwalder, H J Wörner, J P Wolf
In the present review, laser fields are so strong that they become part of the electronic potential, and sometimes even dominate the Coulomb contribution. This manipulation of atomic potentials and of the associated states and bands finds fascinating applications in gases and solids, both in the bulk and at the surface. We present some recent spectacular examples obtained within the NCCR MUST in Switzerland.
November 2017: Structural Dynamics (Melville, N.Y.)
F Carbone, M Hengsberger, L Castiglioni, J Osterwalder
Modern ultrafast techniques provide new insights into the dynamics of ions, charges, and spins in photoexcited nanostructures. In this review, we describe the use of time-resolved electron-based methods to address specific questions such as the ordering properties of self-assembled nanoparticles supracrystals, the interplay between electronic and structural dynamics in surfaces and adsorbate layers, the light-induced control of collective electronic modes in nanowires and thin films, and the real-space/real-time evolution of the skyrmion lattice in topological magnets...
November 2017: Structural Dynamics (Melville, N.Y.)
Joël Teuscher, Jan C Brauer, Andrey Stepanov, Alicia Solano, Ariadni Boziki, Majed Chergui, Jean-Pierre Wolf, Ursula Rothlisberger, Natalie Banerji, Jacques-E Moser
Electron transfer and subsequent charge separation across donor-acceptor heterojunctions remain the most important areas of study in the field of third-generation photovoltaics. In this context, it is particularly important to unravel the dynamics of individual ultrafast processes (such as photoinduced electron transfer, carrier trapping and association, and energy transfer and relaxation), which prevail in materials and at their interfaces. In the frame of the National Center of Competence in Research "Molecular Ultrafast Science and Technology," a research instrument of the Swiss National Science Foundation, several groups active in the field of ultrafast science in Switzerland have applied a number of complementary experimental techniques and computational simulation tools to scrutinize these critical photophysical phenomena...
November 2017: Structural Dynamics (Melville, N.Y.)
L Gallmann, I Jordan, H J Wörner, L Castiglioni, M Hengsberger, J Osterwalder, C A Arrell, M Chergui, E Liberatore, U Rothlisberger, U Keller
Ionization and, in particular, ionization through the interaction with light play an important role in fundamental processes in physics, chemistry, and biology. In recent years, we have seen tremendous advances in our ability to measure the dynamics of photo-induced ionization in various systems in the gas, liquid, or solid phase. In this review, we will define the parameters used for quantifying these dynamics. We give a brief overview of some of the most important ionization processes and how to resolve the associated time delays and rates...
November 2017: Structural Dynamics (Melville, N.Y.)
Konstantin Karandashev, Zhen-Hao Xu, Markus Meuwly, Jiří Vaníček, Jeremy O Richardson
We review several methods for computing kinetic isotope effects in chemical reactions including semiclassical and quantum instanton theory. These methods describe both the quantization of vibrational modes as well as tunneling and are applied to the ⋅H + H2 and ⋅H + CH4 reactions. The absolute rate constants computed with the semiclassical instanton method both using on-the-fly electronic structure calculations and fitted potential-energy surfaces are also compared directly with exact quantum dynamics results...
November 2017: Structural Dynamics (Melville, N.Y.)
Marius Schmidt, Dilano K Saldin
[This corrects the article DOI: 10.1063/1.4869472.].
November 2017: Structural Dynamics (Melville, N.Y.)
S W Epp, M Hada, Y Zhong, Y Kumagai, K Motomura, S Mizote, T Ono, S Owada, D Axford, S Bakhtiarzadeh, H Fukuzawa, Y Hayashi, T Katayama, A Marx, H M Müller-Werkmeister, R L Owen, D A Sherrell, K Tono, K Ueda, F Westermeier, R J D Miller
A common challenge for pump-probe studies of structural dynamics at X-ray free-electron lasers (XFELs) is the determination of time zero (T0)-the time an optical pulse (e.g., an optical laser) arrives coincidently with the probe pulse (e.g., a XFEL pulse) at the sample position. In some cases, T0 might be extracted from the structural dynamics of the sample's observed response itself, but generally, an independent robust method is required or would be superior to the inferred determination of T0. In this paper, we present how the structural dynamics in ultrafast melting of bismuth can be exploited for a quickly performed, reliable and accurate determination of T0 with a precision below 20 fs and an overall experimental accuracy of 50 fs to 150 fs (estimated)...
September 2017: Structural Dynamics (Melville, N.Y.)
A Jarnac, Xiaocui Wang, Å U J Bengtsson, J C Ekström, H Enquist, A Jurgilaitis, D Kroon, A I H Persson, V-T Pham, C M Tu, J Larsson
We have studied an X-ray switch based on a gold coated indium antimonide crystal using time-resolved X-ray diffraction and demonstrated that the switch could reduce the pulse duration of a 100 ps X-ray pulse down to 20 ps with a peak reflectivity of 8%. We have used a dynamical diffraction code to predict the performance of the switch, which was then confirmed experimentally. The experiment was carried out at the FemtoMAX beamline at the short-pulse facility of the MAX IV laboratory. The performance and limitation of the switch are discussed in terms of acoustic transport properties between the two materials and the electron transport properties of gold...
September 2017: Structural Dynamics (Melville, N.Y.)
Abid Hussain, Nils Huse, Oriol Vendrell
Ab initio quantum chemistry calculations have been performed to probe the influence of hydrogen bonding on the electronic structure of hydrogen cyanide (HCN). Our calculations determine the origin of nitrogen-specific Raman spectral features from resonant inelastic X-ray scattering occurring in the presence of a water molecule and an electric dipole field. The similarity of the two interactions in altering the electronic structure of the nitrogen atom differs only in the covalent contributions from the water molecule...
September 2017: Structural Dynamics (Melville, N.Y.)
Markus Kubin, Jan Kern, Sheraz Gul, Thomas Kroll, Ruchira Chatterjee, Heike Löchel, Franklin D Fuller, Raymond G Sierra, Wilson Quevedo, Christian Weniger, Jens Rehanek, Anatoly Firsov, Hartawan Laksmono, Clemens Weninger, Roberto Alonso-Mori, Dennis L Nordlund, Benedikt Lassalle-Kaiser, James M Glownia, Jacek Krzywinski, Stefan Moeller, Joshua J Turner, Michael P Minitti, Georgi L Dakovski, Sergey Koroidov, Anurag Kawde, Jacob S Kanady, Emily Y Tsui, Sandy Suseno, Zhiji Han, Ethan Hill, Taketo Taguchi, Andrew S Borovik, Theodor Agapie, Johannes Messinger, Alexei Erko, Alexander Föhlisch, Uwe Bergmann, Rolf Mitzner, Vittal K Yachandra, Junko Yano, Philippe Wernet
X-ray absorption spectroscopy at the L-edge of 3d transition metals provides unique information on the local metal charge and spin states by directly probing 3d-derived molecular orbitals through 2p-3d transitions. However, this soft x-ray technique has been rarely used at synchrotron facilities for mechanistic studies of metalloenzymes due to the difficulties of x-ray-induced sample damage and strong background signals from light elements that can dominate the low metal signal. Here, we combine femtosecond soft x-ray pulses from a free-electron laser with a novel x-ray fluorescence-yield spectrometer to overcome these difficulties...
September 2017: Structural Dynamics (Melville, N.Y.)
Mattis Fondell, Sebastian Eckert, Raphael M Jay, Christian Weniger, Wilson Quevedo, Johannes Niskanen, Brian Kennedy, Florian Sorgenfrei, Daniel Schick, Erika Giangrisostomi, Ruslan Ovsyannikov, Katrin Adamczyk, Nils Huse, Philippe Wernet, Rolf Mitzner, Alexander Föhlisch
We present a setup combining a liquid flatjet sample delivery and a MHz laser system for time-resolved soft X-ray absorption measurements of liquid samples at the high brilliance undulator beamline UE52-SGM at Bessy II yielding unprecedented statistics in this spectral range. We demonstrate that the efficient detection of transient absorption changes in transmission mode enables the identification of photoexcited species in dilute samples. With iron(II)-trisbipyridine in aqueous solution as a benchmark system, we present absorption measurements at various edges in the soft X-ray regime...
September 2017: Structural Dynamics (Melville, N.Y.)
Philippe Jonnard, Jean-Michel André, Karine Le Guen, Meiyi Wu, Emiliano Principi, Alberto Simoncig, Alessandro Gessini, Riccardo Mincigrucci, Claudio Masciovecchio, Olivier Peyrusse
Stimulated emission is a fundamental process in nature that deserves to be investigated and understood in the extreme ultra-violet (EUV) and x-ray regimes. Today, this is definitely possible through high energy density free electron laser (FEL) beams. In this context, we give evidence for soft-x-ray stimulated emission from a magnesium oxide solid target pumped by EUV FEL pulses formed in the regime of travelling-wave amplified spontaneous emission in backward geometry. Our results combine two effects separately reported in previous works: emission in a privileged direction and existence of a material-dependent threshold for the stimulated emission...
September 2017: Structural Dynamics (Melville, N.Y.)
M Kozina, M Trigo, M Chollet, J N Clark, J M Glownia, A C Gossard, T Henighan, M P Jiang, H Lu, A Majumdar, D Zhu, D A Reis
Here, we report Fourier-transform inelastic x-ray scattering measurements of photoexcited GaAs with embedded ErAs nanoparticles. We observe temporal oscillations in the x-ray scattering intensity, which we attribute to inelastic scattering from coherent acoustic phonons. Unlike in thermal equilibrium, where inelastic x-ray scattering is proportional to the phonon occupation, we show that the scattering is proportional to the phonon amplitude for coherent states. The wavevectors of the observed phonons extend beyond the excitation wavevector...
September 2017: Structural Dynamics (Melville, N.Y.)
M R Otto, L P René de Cotret, M J Stern, B J Siwick
We demonstrate the compression of electron pulses in a high-brightness ultrafast electron diffraction instrument using phase-locked microwave signals directly generated from a mode-locked femtosecond oscillator. Additionally, a continuous-wave phase stabilization system that accurately corrects for phase fluctuations arising in the compression cavity from both power amplification and thermal drift induced detuning was designed and implemented. An improvement in the microwave timing stability from 100 fs to 5 fs RMS is measured electronically, and the long-term arrival time stability ([Formula: see text]10 h) of the electron pulses improves to below our measurement resolution of 50 fs...
September 2017: Structural Dynamics (Melville, N.Y.)
K Sokolowski-Tinten, X Shen, Q Zheng, T Chase, R Coffee, M Jerman, R K Li, M Ligges, I Makasyuk, M Mo, A H Reid, B Rethfeld, T Vecchione, S P Weathersby, H A Dürr, X J Wang
We apply time-resolved MeV electron diffraction to study the electron-lattice energy relaxation in thin film Au-insulator heterostructures. Through precise measurements of the transient Debye-Waller-factor, the mean-square atomic displacement is directly determined, which allows to quantitatively follow the temporal evolution of the lattice temperature after short pulse laser excitation. Data obtained over an extended range of laser fluences reveal an increased relaxation rate when the film thickness is reduced or the Au-film is capped with an additional insulator top-layer...
September 2017: Structural Dynamics (Melville, N.Y.)
Marcel Holtz, Christoph Hauf, Jannick Weisshaupt, Antonio-Andres Hernandez Salvador, Michael Woerner, Thomas Elsaesser
Table-top laser-driven hard x-ray sources with kilohertz repetition rates are an attractive alternative to large-scale accelerator-based systems and have found widespread applications in x-ray studies of ultrafast structural dynamics. Hard x-ray pulses of 100 fs duration have been generated at the Cu K α wavelength with a photon flux of up to 10(9) photons per pulse into the full solid angle, perfectly synchronized to the sub-100-fs optical pulses from the driving laser system. Based on spontaneous x-ray emission, such sources display a particular noise behavior which impacts the sensitivity of x-ray diffraction experiments...
September 2017: Structural Dynamics (Melville, N.Y.)
Shaozheng Ji, Luca Piazza, Gaolong Cao, Sang Tae Park, Bryan W Reed, Daniel J Masiel, Jonas Weissenrieder
Efforts to understand matter at ever-increasing spatial and temporal resolutions have led to the development of instruments such as the ultrafast transmission electron microscope (UEM) that can capture transient processes with combined nanometer and picosecond resolutions. However, analysis by UEM is often associated with extended acquisition times, mainly due to the limitations of the electron gun. Improvements are hampered by tradeoffs in realizing combinations of the conflicting objectives for source size, emittance, and energy and temporal dispersion...
September 2017: Structural Dynamics (Melville, N.Y.)
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