Laser-like beams at very short wavelengths (1-50nm) can now be routinely generated using high harmonic up-conversion (HHG) of tabletop femtosecond lasers. These new quantum light sources are providing powerful new tools for probing and understanding nanoscale material properties and function. The short wavelength of HHG beams are well suited to advanced spectroscopies and imaging with high...
The discovery of x-rays by Roentgen in 1895 is often taken as the starting point of modern physics, as x-rays, besides causing a revolution in medicine, allowed the first experimental determination of the atomic structure of matter, i.e. of the spatial arrangement of atoms in molecules and solids. Since the 1960's it became apparent that electron accelerators are the most brilliant X-ray...
The advent of x-ray free electron lasers (X-FELs) necessitates a re-evaluation of the adequacy of our description of x-rays and their interactions with matter. I will review the concepts used during the first 100 years of x-ray science and how they need to be modified by use of the full quantum theory of light that extends beyond a first order description of coherence.
My talk explores and...
With the installation of the fourth-generation synchrotron facility MAX IV in Sweden and XFEL facilities around the world, the Knut and Alice Wallenberg Foundation has initiated a concomitant investment in the development of theory and simulation techniques. The resulting Consortium for Theoretical X-ray Sciences (CoTXS) initiative builds on the active collaboration and synergy between seven...
Born around the turn of the new millennium, attosecond metrology has provided real-time insight into atomic-scale electron motions and light field oscillation, previously inaccessible to human observation. Until recently, this capability has relied on attosecond extreme ultraviolet pulses, generated and measured in complex vacuum systems. Next-generation attosecond metrology is now about to...
The unique capabilities of LCLS, the world’s first hard X-ray FEL, have had significant impact on advancing our understanding across a broad range of science, from fundamental atomic and molecular physics, to condensed matter, to catalysis, to structural biology. This talk will outline some of the ongoing developments at LCLS.
A major upgrade of the LCLS facility (LCLS-II project) is now...
Nowadays, free-electron lasers (FEL) are the brightest lightsources in the extreme ultraviolet and x-ray domain. The generation of multicolor multi-pulses either simultaneously or delayed with controlled frequency separation has led to experiments based on pump-probe or multiwave mixing. In addition, the generation of circularly polarized FEL light has enabled to study structural and symmetry...
I will show how laser pulses can align molecules embedded in helium nanodroplets and how the ability to place molecules in advantageous spatial orientations enables structural determination of molecular complexes. The talk will focus on the following topics:
1) Impulsive alignment with pulses much shorter than the molecular rotational periods. Here the focus is on understanding how the...
When compared to atoms and solids, the collective and correlated electron dynamics in finite systems under intense light fields can be substantially modified, enhanced and controlled by local near-fields [1-3]. Near-fields result from electronic polarization and charge separation can unfold on femtosecond or even attosecond time scales [4]. In this talk, two novel routes for characterizing the...
A novel type of grazing incidence soft X-ray spectrometer is being constructed for the SQS (Small Quantum Systems) scientific instrument at the European XFEL. It uses a cylindrical constant-line-spacing grating in Rowland mount for dispersion of the X-rays in the vertical direction. A Wolter mirror pair images the source on the detector in horizontal direction. This arrangement facilitates a...
A proposal for building a Free Electron Laser, EuPRAXIA@SPARC_LAB, at the Laboratori Nazionali di Frascati, is at present under consideration. This FEL facility will exploit plasma acceleration to produce ultra-bright photon pulses with durations of few femtoseconds down to a wavelength between 2 and 4 nm, in the so called “water window”. The project is now focused on machine development, but...
Short and intense extreme ultraviolet (XUV) pulses are a valuable tool to study ultrafast dynamics and non-linear processes in atomic and molecular systems. These XUV pulses can be generated by two complementary techniques, Free Electron Lasers (FELs) and High-order Harmonic Generation (HHG). The advantage of HHG is a pulse duration on the attosecond time scale, whereas, due to low conversion...
Until recently, the investigation of X-ray light matter interaction was limited by available X-ray intensities. These days, X-ray Free Electron Lasers (XFELS) allow for observation and examination of many non-linear effects in the X-ray regime. One of the most fundamental non-linear effects is Second Harmonic Generation (SHG). While the effect is well understood in the optical regime, the...
The replacement of hydroxyl ions by fluoride ions is determined quantitatively for the Perrenjas clay mineral. The pH of the clay suspension in contact with fluoride ions increases because of the hydroxyl ions release. This iron rich montmorillonite clay mineral is washed out almost completely from its aluminum, iron, magnesium and hydroxyl groups by sulfuric acid treatment and afterwards was...
Modern light sources continue to improve our knowledge of the natural world, from the subtle workings of life to matter under extreme conditions. Free-electron lasers, for instance, have enabled the characterization of biomolecular structures with sub-ångström spatial resolution, and paved the way to controlling the molecular functions. However, to broaden our scope of the ultrafast world, we...
Nearly all chemical processes involved in energy conversion utilize catalytic chemical transformations at interfaces between solids and liquids or gases. While most of the existing understanding is based on a static view of reactions at interfaces, the X-ray Free Electron Laser (FEL) opens up the dynamic regime where studies of the reaction mechanism to observe transformations on timescales...
The concept of single-particle-imaging (SPI) of macromolecules using ultrashort intense x-ray pulses (proposed [6] and studied in detail [5]) have been corroborated by a series of experimental demonstrations [2–4, 7]. These demonstrations focussed on different aspects of SPI (e.g. algorithms, signal to noise ratio, sample delivery, etc), but have been silent on the general and crucial question...
Understanding the reaction paths and transition states of catalytic reactions is a key issue in order to design highly reactive and selective catalysts. Ultrashort free-electron laser (FEL) soft x-ray pulses are a novel tool ideally suited for investigating time-dependent surface processes, due to the femtosecond resolution and tunability of the excitation energy to specific adsorbate...
Strain and stresses influence the diffraction properties of crystals significantly. We analyze the effect of strong bending on the energy resolution of a reflection using an ultra-thin, strongly bent single crystal diamond to be implemented as a spectrometer at the European XFEL. The device is designed to measure the energy distribution in the self-amplified spontaneous emission (SASE) beam...
ABSTRACT
Crystallization of liquid water and aqueous solutions is a common phenomenon which occurs frequently in our natural environment. Therefore, it is important to understand the dynamics of ice nucleation on a microscopic level. This will significantly promote the progress of science in relevant research fields such as biology, chemistry, atmospheric science and astronomy. The prevention...
We demonstrate that emission of coherent transition radiation by a 1 GeV energy-electron beam is enhanced in intensity and extended in frequency, by the energy correlation established along the beam by coherent synchrotron radiation (CSR), in the presence of a proper electron optics in the beam delivery system. Analytical and numerical models, based on experimental electron beam parameters...
Y. Ovcharenko$^{1,9,*}$, A. LaForge$^2$, B. Langbehn$^1$, O. Plekan$^3$, R. Cucini$^3$, P.Finetti$^3$, P.O’Keeffe$^4$, D. Iablonskyi$^5$, N. Toshiyuki$^6$, K. Ueda$^5$, P. Piseri$^7$, M. DiFraia$^3$, R. Richter$^3$, M.Coreno$^{3,4}$, C.Callegari$^3$, K. C. Prince$^{3,8}$, F.Stienkemeier$^2$, T. Möller$^{1,*}$ and M. Mudrich$^{10}$
$^1$Technische Universität Berlin, Germany; $^2$Universität...
The capabilities of XFEL sources enable scientific investigations at the frontiers of spatial and temporal resolutions. One of the key procedures in time resolved experiments combining XFEL and optical lasers is the establishment of temporal overlap, i.e. “time zero”, between the ultrafast X-ray and optical laser pulses with sub-picosecond accuracy. In order to determine time zero, several...
We report on a direct time-domain measurement of the temporal properties of a seeded free-electron laser pulse in the extreme ultraviolet spectral range. Utilizing the oscillating electromagnetic field of terahertz radiation, a single-shot THz streak-camera was applied for measuring the duration as well as spectral chirp of the generated intense XUV pulses in a fully parasitic way. The...
Intense extreme ultraviolet (XUV) light generated in a high-order harmonic generation (HHG) process or delivered by a Free Electron Laser (FEL) allows the investigation of multiphoton ionization processes on a femtosecond timescale in the gas phase$^{1,2}$. The investigation of the underlying ionization and fragmentation processes can be facilitated by obtaining the correlated momentum...
The ultrafast demagnetization is a fundamental problem of modern magnetism, with its microscopic origin remaining intensely debated. Particularly, the role played by the spin-orbit interaction in the moment dissipation to the lattice and that of the exchange interaction in the collapse of long-range order call for measurements capable of resolving the charge, spin and the orbital moment...
M. Makita a, I. Vartiainen a, I. Mohacsi a, C. Caleman b, c, A. Diaz a, H. O. Jönsson c, P. Juranić a,
N. Medvedev d, e, A. Meents b, A. Mozzanica a, N. Opara a, C. Padeste a, V. Panneels a, V. Saxena b, f,
M. Sikorski g, S. Song g, L. Vera a, P. R. Willmott a, P. Beaud a, C.J. Milne a, B. Ziaja-Motyka b, h,
and C. David a
(a) Paul Scherrer Institut, CH-5232 Villigen PSI,...
A localized optical excitation of a metal/insulator heterostructure induces
ultrafast dynamics in its individual compounds, which can involve
charge and spin transfer processes as well as coupling to low
energy excitations mediated by e.g. electron-electron and electron-phonon
scattering. Femtosecond soft x-ray spectroscopy facilitates to
separate and identify these electronic and lattice...
At the plane grating monochromator beamline PG2 at FLASH a new referencing scheme for X-ray absorption spectroscopy (XAS) has been successfully tested. Similar to the approaches realized at SACLA [1] and LCLS [2], it employs a nanofabricated diffractive transmission grating to split the FEL beam into two identical copies (signal & reference) for single shot intensity normalization. The...
The variable micro-focus beamline FL24 of the Free-electron LASer in Hamburg FLASH consist of a bending mirror focusing system. This Kirkpatrick-Beaz Active Optics System (KAOS) is a product of Fermi@Elettra. The open port beamline FL24 of the second SASE FEL branch of FLASH with variable gap undulators is designed to deliver the full fundamental wavelengths range of 4-90nm, distinguished...
In the High-order Harmonic Generation (HHG) process, an intense laser field is used to create subfemtosecond pulses with photon energies up to hundreds of eV. At the High Intensity XUV beamline, high energy infrared (IR) pulses are used with a loose focusing geometry to produce intense extreme ultraviolet (XUV) attosecond pulse trains. The generated XUV radiation can be focused to high enough...
X-ray free-electron lasers have recently been shown to produce radiation pulses with sub-fs duration. Ultimately they have the potential to deliver pulses with duration significantly shorter than ~50 as that is delivered by the present leading technique - high harmonic generation (HHG) - and so extend the frontiers of ultrafast science. Several techniques have been proposed to extend the...
We introduce a novel method for soft x-ray absorption spectroscopy (XAS) featuring high sensitivity and compatibility with time resolved ultrafast short-pulse FEL experiments. As a demonstration, we have measured the optically induced insulator to metal transition in VO2 with time resolved XAS. Probing the oxygen electronic system, we observe a fast sub-100 fs response in VO2 followed by a...
Photoemission spectroscopy (PES) is a powerful technique, which allows to investigate the electronic properties of solid systems and molecules. If used in combination with high repetition rate free electron lasers (FEL) in the XUV and soft X-ray regime such as FLASH, DESY, Hamburg or with table-top laser systems based on the high harmonic generation (HHG), it offers unique possibilities for...
Native mass spectrometry (MS) enables the ionization and transfer of intact non-covalent protein complexes into the gas phase. As such, it is a perfect tool to study proteins and their assemblies in a mass and conformation specific manner. This enables MS to probe structural transitions which proteins and their complexes undergo, e.g. during a viral lifecycle. Such transient states are of high...
Superfluid helium droplets do not rotate as a solid body; instead, the droplet’s rotation is manifested through the presence of quantized vortices. The vortices have a diameter of ~2 Å and their detection remain an outstanding experimental problem. Here, we report on X-ray coherent diffraction imaging of free, single, rotating superfluid $^4$He droplets (diameter D = 200 - 2000 nm, temperature...
Results of investigation on interaction of intense nanosecond extreme ultraviolet (EUV) pulses with gases and solids are presented. EUV is generated using laser plasma sources based on plasma produced by irradiation of a gas puff target with nanosecond laser pulses. Commercially available Nd:YAG lasers (EXPLA) generating 4 ns/0.8 J or 10 ns/10 J at 10 Hz were used to irradiate the...
Myoglobin is a small protein consisting of a single polypeptide chain of 153 amino acid residues and a heme as its active center. It plays a central role in many biological functions based on detection, transport, release and/or binding of molecular ligands such as O2, CO, NO, CN, etc. The unligated high-spin form (deoxyMb) binds the ligand at the Fe of the heme, leading to a change to the...
The unique properties of hard X-ray laser beams generated by the European XFEL will enable completely new experiments in materials science. In particular, the Materials Imaging and Dynamics (MID) station will offer extended capabilities for scattering and imaging experiments, e.g. coherent X-ray diffractive imaging (CXDI) and X-ray photon correlation spectroscopy (XPCS), compared to present...
Water is one of the most critical substances on earth for life. Many important biological and geological reactions important for life take place in water. It has anomalous properties like increased specific heat capacity and isothermal compressibility on cooling at ambient conditions. These become more pronounced on supercooling. These thermodynamic properties are a result of the unique...
Electron diffraction has been a staple technique for determining the structure of countless molecules for nearly a century [1]. However, it has only been in the last couple of decades that we have been able to use this technique to obtain time-resolved images of molecules undergoing light-induced chemical processes. Whilst numerous ultrafast electron diffraction (UED) experiments have been...
Abstract:
A Free Electron Laser (FEL) is the brightest and coherent radiation source in the world and many research interest in reducing the cost and the size of the bright future FELs by utilizing different kinds of accelerator techniques. In this work we consider Laser-Plasma accelerator as a promising future driven FEL next-generation compact light sources. In this modelling of a laser-...
Nanophotonics is based on the interaction of light with nanometer sized objects [1]. It provides formerly inaccessible sub-wavelength focusing and electro-magnetic field enhancement. Nowadays, it is broad research field with many proof-of-principle studies, especially acceleration of electrons [2] and practical applications [3]. Nanophotonics has been investigated with laser intensities up to...
The interaction between magnetism and light is receiving considerable interest in recent years, after the groundbreaking experiments that showed that ultrashort (∼100 fs) infrared light pulses can be used to demagnetise or even switch the magnetisation of thin film ferromagnets. However, to date no clear and commonly accepted understanding of the fundamental physical processes governing the...
The combination of polarization control with the unique properties of free-electron lasers in terms of high intensity and ultrashort pulse duration offer unique perspectives on non-linear and time-resolved insights in “handed” systems. Handedness, i.e. chirality, is of crucial interest for understanding the origination of life on earth but also in the spin properties of fundamental as well as...
The adsorption of the gas molecule to the transition metal or noble metal surface, through a weakly bound “precursor” state which facilitate the gas molecule to lose its rotational and translation energy before forming a stable chemisorption bond, is the most fundamental elementary surface chemical process. In particular, our previous work has demonstrated the short-live transient precursor...
Shirly Espinoza 1, Stefan Zollner 2, Steffen Richter 1, Mateusz Rebarz 1, Oliver Herrfurth 2, Rudiger Schmidt-Grund 2 and Jakob Andreasson 1
1 ELI Beamlines, Institute of Physics, Czech Academy of Science, Na Slovance 2, 18221 Prague, Czech Republic
2 Universität Leipzig, Felix-Bloch-Institut für Festkörperphysik, Linnéstr. 5, 04103 Leipzig, Germany
3 Department of Physics, New Mexico State...
The development of attosecond photoelectron spectroscopy based on two-color (XUV or, extreme-ultraviolet and NIR, or, near-infrared) interferometric techniques [1] has enabled studying the dispersion dynamics of electron wave-packets in atoms [2], molecules [3] and solids [4]. In a recent experiment, we have demonstrated that it is possible to simultaneously combine high spectral and...
The emergence of spin currents after ultrafast laser excitation of a magnetic thin film was predicted in the theory of superdiffusive spin currents, which was originally developed to describe the process of ultrafast demagnetization [1]. Experimentally, spin current pulses have been detected by magneto-optical measurements using fs-pulsed VUV radiation [2,3], or through the emission of THz...
We discuss principles and experimental verification of advanced schemes for X-ray FELs using variable gap undulators (harmonic lasing self-seeded FEL, reverse tape etc.). Harmonic lasing in XFELs is an opportunity to extend operating range of existing and planned X-ray FEL user facilities. Contrary to nonlinear harmonic generation, harmonic lasing can provide much more intense, stable, and...
Imaging individual biological particles, such as macromolecules or viruses, at high resolution is one of the most attractive challenges for x-ray free electron lasers (XFELs). It was predicted that diffraction patterns from single particles can be measured in “diffraction before destruction” experiments at XFELs before the sample is destroyed by intense radiation, and hence their damage-free...
In May 2018, all three undulators are in operation at the European XFEL, and will start opening to users from the end of 2018. The High-Energy Density (HED) science instrument is one of the two endstations at SASE 2 and is dedicated to the studies of matter at extreme conditions. Major scientific applications include dynamic and static compression studies, time-resolved femtosecond HED...
Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) facility has finished the commissioning successfully and started user operation from 2016. The NCI experimental hutch, which is one of the hard X-ray experimental stations, has been designed and prepared to perform serial femtosecond crystallography (SFX) experiments. We will present the current status of the sample...
Since the free-electron laser FLASH at DESY in Hamburg, [1] lases in Self-Amplified Spontaneous Emission (SASE) mode each pulse is “unique” and has different pulse energy, spectrum, arrival time and pulse duration. A Terahertz (THz) field driven streak camera [2,3] has the potential to deliver single-shot pulse duration information basically wavelength independent and with a high dynamic range...
With the advent of X-ray Free Electron Lasers (XFELs) femtosecond time resolved experiments employing advanced X-ray probe techniques have become routinely possible in a wide variety of scientific domains. A significant number of these experiments concerns the relaxation dynamics following an externally supplied excitation, which is typically realized by an electromagnetic pump pulse...
Coherent time-resolved spectroscopy is a powerful tool to study ultrafast dynamics in complex systems. Extending this to the XUV spectral region is on the frontier of nonlinear spectroscopy. However, demands on interferometric stability increase when going to short wavelengths and advanced pulse manipulation in the XUV is challenging. In seeded free electron lasers (FEL) the emitted XUV pulses...
Stereospecific molecular interaction is one of the means used in nature to maximize the specificity of bio-chemical reactions. Most biomolecules are chiral, i.e. exist in two enantiomeric forms that are non-superimposable mirror images of each other. Different enantiomers of a compound may differ substantially in their bio-chemical activities and result in different biological response. The...
In model catalysis and general surface science studies the vibrational characterization of surfaces is usually performed with HREELS (high resolution electron energy loss spectroscopy) or IRAS (infrared reflection absorption spectroscopy). Both methods have disadvantages: HREELS suffers from its low resolution and (in the case of ionic samples) the presence of intense multiple phonon losses,...
The European Cluster of Advanced Laser Light Sources (EUCALL) generates collaboration and synergy between large scale sources of laser-driven and accelerator-driven x-ray radiation.
The lead project partner is European XFEL, while the other partners are DESY, the Extreme Light Infrastructure (ELI) in Czech Republic, Hungary and Romania; ESRF in Grenoble, Helmholtz Zentrum Dresden-Rossendorf,...
Joel Andersson), J. Björklund Svensson), Francesca Curbis)), Vitaliy Goryashko), Lennart Isaksson), Marija Kotur), Dionis Kumbaro), Filip Lindau), Alan Mak), Erik Mansten), David Olsson), Mihai Pop)**), Georgii Shumailov), Hamed Tarawneh), Pedro Fernandes Tavares), Sara Thorin), Alexey Vorozhtsov) and Sverker Werin)*)
*) MAX IV Laboratory, Lund University, Lund,...
Inter-molecular interactions (in particular hydrogen bonding) influence solvation and reaction pathways, and investigations of electronic structure and dynamics on the molecular level are important for a detailed understanding of chemical processes in solution.
In this presentation of a few case studies, I discuss how multi-configuration quantum chemistry (particularly RASPT2) , density...
Since the advent of x-ray free-electron lasers (XFELs), considerable
efforts have been devoted to achieve x-ray pulses with better
temporal coherence. Here, we put forward a scheme to generate
fully coherent x-ray lasers (XRLs) based on population inversion in
highly charged ions, created by fast inner-shell photoionization
using XFEL pulses in a laser-produced plasma. Numerical...
In one of the recent reviews, it has been shown that effective biomass conversion requires the integration of biochemical and thermochemical methods [1]. A catalytic pyrolysis is a promising tool for further upgrading of pyrolysis oils components to the value-added fuels and chemicals [2]. The identification of reaction products and the understanding of the mechanisms of thermal decomposition...
Diffraction before destruction using x-ray free-electron lasers (XFELs) has the capability to determine radiation damage-free structures without the need for crystallization. In this poster we present the 3D reconstruction of the Melbournevirus from single-particle x-ray diffraction patterns collected at the LINAC Coherent Light Source (LCLS) and use reconstructions from simulated data to...
At FLASH, the free electron laser in Hamburg, an unique scheme is used to laser X-ray pulse and THz pulse by the same electron bunch for pump-probe experiment. However the timing overlap is achieved at the price of losing pulse energy and bandwidth of the X-ray pulse in a back reflection, since the THz beamline is longer in optical path. A new scheme of lasing the X-ray and THz pulses are...
Time Dynamics and Spectral Resolved Emission Imaging of Colliding Laser Produced Aluminum Plasma
Haider Mahdi Al-Juboori1, Thomas McCormack1
1University College Dublin, School of Physics, Belfield, Dublin 4, Ireland.
email: haider.al-juboori@ucd.ie
Abstract
Colliding laser produced plasma have been investigated in a wide range of laser irradiance regimes (1010- 1015 W/cm2) and for several...
The XUV double stage Raman spectrometer is a permanent experimental end-station at the PG1 monochromator beamline at the free-electron laser FLASH at DESY in Hamburg, Germany [1,2]. This unique instrument is designed to cover the photon energy range from 20 to 200 eV with high energy resolution of about 2 – 20 meV (design values in additive mode) and to suppress the elastic line and stray...
Excited molecules can reconvert their excitation energy into other types such as electronic, chemical or thermal energy. The relevant molecular processes are ultrafast and often involve coupled electronic and nuclear dynamics not fulfilling the Born-Oppenheimer approximation. Their experimental investigation is complicated by the existence of dark 𝑛𝜋* states if the molecule contains...
We report on the first to our knowledge measurements of TRXEOL (time-resolved X-ray excited optical luminescence) with sub-picosecond time resolution. The up-conversion gating technique applied to luminescence in CsI single crystals excited by XUV pulses from FLASH allowed monitoring the energy relaxation during thermalization, self-trapping of charge carriers and formation of luminescence...
The development of the free electron laser (FEL) gives us a new way to investigate the interplay between electrons and nuclear motions with intense short wavelength pulses [1]. The pulse duration of current FELs varies from a few femtosecond of hard X-rays to around 100 femtoseconds of extreme ultraviolet (XUV) radiation. Recent works showed that the multiphoton ionization process allows to...
Polycyclic aromatic hydrocarbons (PAHs) are abundant in the interstellar medium, and understanding their fragmentation dynamics upon exposure to cosmic background radiation sheds light on key processes that affect the structure and evolution of galaxies [1,2]. Cosmic background radiation, i.e. the He II fluorescence line at 30.3nm wavelength, ionizes PAH molecules and triggers a range of...
The bright ultrafast pulses of X-ray Free-Electron Lasers allow investigation into the structure of matter under extreme conditions. We have used single pulses to ionize and probe water as it undergoes a phase transition from liquid to plasma. We report changes in the structure of liquid water on a femtosecond timescale when irradiated by single 6.86 keV X-ray pulses of more than 10$^{6}$...
BiVO4 is one of the most promising materials to be used as photoanodes in photoelectrochemical cells (PEC) for water splitting (Figure 1). To improve the light absorbance and charge carrier utilization performance of BiVO4, it is of key importance to understand charge transportation to the interface and interfacial transfer mechanism upon light absorption.
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Coherent diffractive imaging with X-ray lasers opened a bright avenue for determining atomic structure of biomolecules. It uses ultrashort and intense X-ray pulses to take snapshot pictures of biological samples, single particles or protein crystals, before these turn into a plasma due to the extreme radiation dose, aka diffraction before destruction. During destruction the atoms will ionize...
To date, experiments at x-ray free-electron lasers have generated a very large amount of raw diffraction data. Whilst current pulsed x-ray laser sources measure diffraction patterns at an already very fast rate, with unprecedented development in the instrumentation this data collection rate is projected to rise at least an order of magnitude over the next few years. These large datasets are...
The characterization of the wavefront dynamics is important for many X-ray free-electron laser (XFEL) experiments, in particular for coherent diffractive imaging (CDI), as the reconstructed image is always the product of the incoming wavefront with the object. An accurate understanding of the wavefront is also important to optimize peak power densities to make use of the tightest possible...
The design of the new monochromator beamline FL23 at FLASH, the Free-electron LASer in Hamburg, is made up of 7 optical elements: an elliptical mirror, 2 variable-line-spaced gratings in diffraction order compensation, a vertical slit, a plane mirror and a Kirkpatrick-Baez (KB) focussing system. The monochromotor is designed to work in the soft X-ray range covering a spectral range from 1-20...
Nanoscale hybrid films manifest a set of properties that can beneficial when used in dye lasers, amplifiers, switching devices, solar cells, OLEDs. Studies on the fabrication of sol-gel optical hybrid SiO2 and TiO2 films for photovoltaic devices or planar optical waveguide are continuously caring attention over the years because this materials have numerous applications in the field of...
The best way for planning user experiments would be performing start-to-endsimulations tracing radiation pulses from its origin (undulator) through a beamline (mirrors, monochromators etc) to a target, simulation of physical processes of the radiation interaction with a sample, and simulation of detection process of related debris (photon, electrons, ions, etc) by detectors. Modern FEL...
We present first XUV-pump/XUV-probe transient absorption spectroscopy experiments conducted at the free-electron laser FLASH. Exploiting the partial temporal coherence of the stochastic light fields, this scheme provides access to transient changes in the XUV spectra which are related to dynamics of electronic bound states on a timescale below the average pulse duration. Those transient...
Novel types of experiments with both high spatial and temporal resolution have become possible with the intense and short short-wavelength pulses from free-electron lasers. By measuring the diffracted light of a single non-crystallin nanoparticle, fragile objects such as isolated viruses or rotating superfluid helium nanodroplets can be directly visualized. Due to the short pulse duration also...
The dynamics of liquid water feature a variety of time scales, ranging from extremely fast ballistic-like thermal motion, to slower molecular diffusion and hydrogen-bond rearrangements. Here, will be presented our recent studies[1] using ultrafast coherent X-ray diffraction to investigate the sub-100fs dynamics of water from ambient conditions down to supercooled temperatures. This novel...
Due to the coherence, high brightness and intensity of laser light sources, the observation and exploitation of non-linear effects in light-matter interaction has been a striving research field in the last decades. Now however, free electron lasers (FELs) at soft and hard x-ray wavelengths are operational which can deliver x-ray fluences on a sample that allow to study non-linear effects in...
For more than 100 years, X-rays have been used in crystallography to determine the structure of crystals and molecules via coherent diffraction methods. With the advent of accelerator-driven free-electron lasers (FEL) new avenues for high-resolution structure determination are presently explored that go far beyond conventional X-ray crystallography [1-3]. Yet, these techniques rely on coherent...
On which timescale do the band structure and spin polarization of a ferromagnet change after femtosecond laser excitation and how do they affect the magnetization dynamics? To answer these questions we perform time-, spin-, and angle-resolved photoemission experiments with optical laser pulses and higher-order harmonic radiation.
We have studied ultrafast demagnetization in the local-moment...
In non-metallic solids, heat is carried primarily by acoustic phonons. At cryogenic temperatures, the phonon mean free path (MFP) can be large, and ballistic propagation of heat over macroscopic distances has been well documented in the “phonon imaging” studies. At room temperature, the MFP of thermal phonons is small and heat typically propagates via diffusion: once the thermal conductivity...
Free-electron lasers (FELs) are currently the only ultrashort-pulsed photon sources that can provide sufficient photon flux for time-resolved pump-probe solid-state photoemission measurements in the soft and hard x-ray regime. In principle, FELs enable powerful combinations of photoemission techniques, augmented by femtosecond time resolution, in a single experiment. We particularly envision a...
Identifying the degrees of freedom that lead to the emergence of superconductivity in iron-based materials remains the subject of active research. Amongst spin-driven scenarios, it has also been suggested that electron-electron correlations enhance the electron-phonon coupling in iron chalcogenides and related pnictides, but direct experimental verification has been lacking.
Measurements of...
I will describe recent experiments using ultrafast electron diffraction and x-ray free electron lasers to probe light-induced structural dynamics in layered transition metal dichalcogenide materials. In particular the focus of this talk will be terahertz-driven atomic-scale responses in WTe2 and related materials. We show, via the measurement of structure factor changes in >200 Bragg...
The results were taken by the SLAC UED collaboration and LCLS Nucleobase collaboration (see author lists of publications below).
In this talk, I will present molecular dynamics obtained by diffraction of relativistic electrons exemplified on the rotational and vibrational modes of small model systems [1,2]. The results have been obtained at a new femtosecond ultrafast electron diffraction...
Time-resolved x-ray tools allow measuring electronic and geometric structure changes. X-Ray emission spectroscopy is sensitive to electronic changes, such as oxidation and spin states, while x-ray absorption fine structure tools deliver information about the local geometric structure around the selected absorbing atom. Combining these tools with forward scattering in one single setup allows to...
Time-resolved x-ray absorption near edge structure (TR-XANES)1 is one of most promising applications of X-ray free electron lasers (XFELs): X-ray absorption measurements combining XFELs and synchronized optical lasers enable one to probe ultrafast changes in the electronic states and the local structure around the absorbing atom during photoreactions.
Here, we report on our recent TR-XANES...
Potential energy surfaces play the central role for understanding molecular and chemical dynamics. For chemical reactions on the electronic ground state potential, transition state theory usually provides a strong foundation for understanding chemical reactivity because intra-well equilibration precedes chemical reaction and reactive trajectories proceed along adiabatic trajectories through...
Pohang Accelerator Laboratory X-ray Free Electron Laser (PAL-XFEL) facility has finished the commissioning successfully and started user operation from 2016. The NCI experimental hutch, which is one of the hard X-ray experimental stations, has been designed and prepared to perform serial femtosecond crystallography (SFX) experiments. We will present the current status of the sample...
We present first XUV-pump/XUV-probe transient absorption spectroscopy experiments conducted at the free-electron laser FLASH. Exploiting the partial temporal coherence of the stochastic light fields, this scheme provides access to transient changes in the XUV spectra which are related to dynamics of electronic bound states on a timescale below the average pulse duration. Those transient...
Myoglobin is a small protein consisting of a single polypeptide chain of 153 amino acid residues and a heme as its active center. It plays a central role in many biological functions based on detection, transport, release and/or binding of molecular ligands such as O2, CO, NO, CN, etc. The unligated high-spin form (deoxyMb) binds the ligand at the Fe of the heme, leading to a change to the...
With the advent of X-ray Free Electron Lasers (XFELs) femtosecond time resolved experiments employing advanced X-ray probe techniques have become routinely possible in a wide variety of scientific domains. A significant number of these experiments concerns the relaxation dynamics following an externally supplied excitation, which is typically realized by an electromagnetic pump pulse...
Y. Ovcharenko$^{1,9,*}$, A. LaForge$^2$, B. Langbehn$^1$, O. Plekan$^3$, R. Cucini$^3$, P.Finetti$^3$, P.O’Keeffe$^4$, D. Iablonskyi$^5$, N. Toshiyuki$^6$, K. Ueda$^5$, P. Piseri$^7$, M. DiFraia$^3$, R. Richter$^3$, M.Coreno$^{3,4}$, C.Callegari$^3$, K. C. Prince$^{3,8}$, F.Stienkemeier$^2$, T. Möller$^{1,*}$ and M. Mudrich$^{10}$
$^1$Technische Universität Berlin, Germany; $^2$Universität...
The generation of intense, multicolor fields in the extreme ultraviolet spectral range at Free Electron Lasers (FELs) opens new perspectives for the characterization and control of nonlinear processes in atoms and molecules. These sources can deliver pulses with the high peak intensities enabling the observation of nonlinear processes. These pulses can also be implemented in XUV-pump-XUV-probe...
The development of x-ray free-electron lasers (XFELs) opened up a new extreme regime of light-matter interactions and provide unique novel capabilities for studying the structure and dynamics of biological systems, complex materials, and matter under extreme conditions [1,2]. Particularly intriguing is the domain of hard x-ray wavelengths and highest available intensities, since this...
The Low Density Matter (LDM) beamline of the Free Electron Laser FERMI in Trieste has been open to Users since December 2012. Members of the atomic-, molecular-, and cluster-science community worldwide have exploited its high-intensity ultrafast pulses for spectroscopy experiments. FERMI is a seeded source, in fact the only one operating in its wavelength range (100 nm–4 nm), and this results...
X-ray free electron lasers potentially have the pulse duration and intensity to probe electron motion on the intrinsic timescales found in atoms and molecules, as characterized by the Bohr orbital period of ~150 attoseconds. While sub-orbital period dynamics for deep inner-shell electrons may still out of reach using direct time-domain probes, readily available few femtosecond x-ray pulses...
First lasing at the European XFEL was demonstrated in May last year (2017). From these first photons, remarkable progress has been made in delivering beam to the instruments and conducting first user experiments only four months later in September of the same year. I will present an overview of the Single Particles, clusters and Biomolecules and Serial Femtosecond Crystallography (SPB/SFX)...
Time-resolved (TR) crystallography using X-ray free electron lasers (XFELs) is being established and increasingly applied to proteins for visualizing their structural dynamics as "molecular movies". At SACLA, we have applied this technique to study the dynamics of two respiratory enzymes, bovine cytochrome c oxidase (CcO) and fungal NO reductase (P450nor). CcO is the terminal oxidase of cell...
XFELs with their ultrashort and highly intense pulses open the sub-ps time domain for time-resolved crystallography using small crystals that can be efficiently photolyzed. This is particularly appealing for the study of photosensitive proteins, which contain a light-absorbing chromophore that allows exploitation of light energy as a resource or as a carrier of information initiating intra- or...
Despite being the subject of numerous shock compression studies, the behavior of silicon under dynamic loading is vigorously debated [1-3]. The few studies that combine shock compression and X-ray diffraction have exclusively focused on ``normal'' X-ray geometry whereby X-rays are collected along the shock propagation direction, consequently sampling numerous strain states at once, greatly...
An accurate knowledge of the properties of iron and iron alloys at high pressures and temperatures is crucial for understanding and modelling planetary interiors. While Earth-size and Super-Earth Exoplanets are being discovered in increasingly large numbers, access to detailed information on liquid properties, melting curves and even solid phases of iron and iron at the pressures and...
When solid-density matter is irradiated on 100-fsec timescales with a tightly-focussed x-ray FEL the intensities are such that the electrons are heated to temperatures of several hundred eV or more. Core holes induced in the system via photoionisation by the FEL rapidly fill and, depending on the FEL photon energy and intensity, radiation is only emitted during the FEL pulse itself: the photon...
