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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.)
Sergey V Antipov, Swarnendu Bhattacharyya, Krystel El Hage, Zhen-Hao Xu, Markus Meuwly, Ursula Rothlisberger, Jiří Vaníček
Several strategies for simulating the ultrafast dynamics of molecules induced by interactions with electromagnetic fields are presented. After a brief overview of the theory of molecule-field interaction, we present several representative examples of quantum, semiclassical, and classical approaches to describe the ultrafast molecular dynamics, including the multiconfiguration time-dependent Hartree method, Bohmian dynamics, local control theory, semiclassical thawed Gaussian approximation, phase averaging, dephasing representation, molecular mechanics with proton transfer, and multipolar force fields...
November 2017: Structural Dynamics (Melville, N.Y.)
Thomas Feurer, Ursula Keller
No abstract text is available yet for this article.
November 2017: Structural Dynamics (Melville, N.Y.)
Hans Jakob Wörner, Christopher A Arrell, Natalie Banerji, Andrea Cannizzo, Majed Chergui, Akshaya K Das, Peter Hamm, Ursula Keller, Peter M Kraus, Elisa Liberatore, Pablo Lopez-Tarifa, Matteo Lucchini, Markus Meuwly, Chris Milne, Jacques-E Moser, Ursula Rothlisberger, Grigory Smolentsev, Joël Teuscher, Jeroen A van Bokhoven, Oliver Wenger
The transfer of charge at the molecular level plays a fundamental role in many areas of chemistry, physics, biology and materials science. Today, more than 60 years after the seminal work of R. A. Marcus, charge transfer is still a very active field of research. An important recent impetus comes from the ability to resolve ever faster temporal events, down to the attosecond time scale. Such a high temporal resolution now offers the possibility to unravel the most elementary quantum dynamics of both electrons and nuclei that participate in the complex process of charge transfer...
November 2017: 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.)
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