Submit to Applied Sciences Review for Applied Sciences Propose a Special Issue

Journal Menu

Journal Browser

► Journal Browser

Ultrafast X-ray Spectroscopies

Print Special Issue Flyer
Special Issue Editors
Special Issue Information
Published Papers

A special issue of Applied Sciences (ISSN 2076-3417). This special issue belongs to the section "Optics and Lasers".

Deadline for manuscript submissions: closed (1 December 2020) | Viewed by 33843

Share This Special Issue

Special Issue Editors

Prof. Dr. Christian Bressler

E-Mail Website
Guest Editor

1. European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld; Germany
2. University Hamburg, Notkestrasse 85, 22607 Hamburg
Interests: ultrafast time-dependent processes in the solid state; chemical dynamics studies using ultrashort pulse X-ray spectroscopies

Dr. Thomas Tschentscher

E-Mail Website
Guest Editor

European XFEL GmbH, Holzkoppel 4, 22869 Schenefeld, Germany
Interests: ultrafast time-dependent processes in the solid state; chemical dynamics studies using ultrashort pulse X-ray spectroscopies

Special Issue Information

Dear Colleagues,

This Special Issue aims to showcase the current state-of-the-art research activities using advanced ultrafast X-ray spectroscopies employing both soft and hard pulsed X-radiation. It will comprise contemporary scientific studies exploiting the rich variety and information content available by means of these time-resolved spectroscopy tools. Applications cover a wide range of fields from atomic molecular physics, chemistry, and biology to condensed matter and material sciences, and include highly excited plasma states. These have been applied to both crystalline materials and bulk liquid solutions doped with chromophores.

Ultrafast time-resolved X-ray spectroscopy is a highly active field of research experiencing further development. X-ray absorption near-edge structure (XANES) was first applied in the ultrafast time domain nearly 20 years ago. The technique has been implemented with tabletop and synchrotron radiation as well as X-ray free-electron laser (FEL) sources. The first steps have been taken toward establishing extended X-ray absorption fine structure (EXAFS) spectroscopy in the femtosecond time domain. X-ray emission spectroscopy (XES), including its variants nonresonant XES and resonant inelastic x-ray scattering (RIXS), are more recent developments that have already delivered new insights into evolving processes on the 100 femtosecond (XFELs) to 100 picosecond (SR) time scales. The recent availability of high repetition rate X-ray FELs enables the use of time-resolved X-ray Raman spectroscopy techniques due to the unprecedented large X-ray flux available. Nonlinear XES applications, including stimulated X-ray emission, have been performed at the LCLS and SACLA FELs, exploiting their large excitation fluences.

By “ultrafast” we mean the regime from femtoseconds to nanoseconds. X-ray FELs deliver coherent X-ray pulses, combining unprecedented power densities of up to 10²⁰W/cm², high flux, and extremely short pulse durations down to a few femtoseconds. Synchrotron sources provide high flux and stability, but their time resolution is typically limited to tens of picoseconds. Although tabletop X-ray sources enable femtosecond resolution, they are often characterized by a much smaller flux, precluding their application in photon-hungry techniques. Comprehensive theoretical modeling of time-dependent signals is important to guide and interpret experimental results.

Following on from the successes of the first Special Issue “X-ray Free-Electron Laser” and the second Special Issue “Science at X-ray Free-Electron Lasers”, this latest Special Issue in this series aims to cover recent developments in X-ray spectroscopy at FEL, synchrotron, and tabletop sources. Papers will address scientific applications, experimental results, or relevant instrumentation developments as well as theoretical studies.

Prof. Dr. Christian Bressler
Dr. Thomas Tschentscher
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Applied Sciences is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Published Papers (11 papers)

Download All Papers

Order results

Result details

Show export options Show export options

Select all

Export citation of selected articles as:

Research

Jump to: Review

15 pages, 1667 KiB

Open AccessArticle

Photon-In/Photon-Out X-ray Free-Electron Laser Studies of Radiolysis

by Linda Young, Emily T. Nienhuis, Dimitris Koulentianos, Gilles Doumy, Anne Marie March, Stephen H. Southworth, Sue B. Clark, Thomas M. Orlando, Jay A. LaVerne and Carolyn I. Pearce

Appl. Sci. 2021, 11(2), 701; https://doi.org/10.3390/app11020701 - 13 Jan 2021

Cited by 1 | Viewed by 4044

Abstract

Understanding the origin of reactive species following ionization in aqueous systems is an important aspect of radiation–matter interactions as the initial reactive species lead to production of radicals and subsequent long-term radiation damage. Tunable ultrafast X-ray free-electron pulses provide a new window to probe events occurring on the sub-picosecond timescale, supplementing other methodologies, such as pulse radiolysis, scavenger studies, and stop flow that capture longer timescale chemical phenomena. We review initial work capturing the fastest chemical processes in liquid water radiolysis using optical pump/X-ray probe spectroscopy in the water window and discuss how ultrafast X-ray pump/X-ray probe spectroscopies can examine ionization-induced processes more generally and with better time resolution. Ultimately, these methods will be applied to understanding radiation effects in complex aqueous solutions present in high-level nuclear waste. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

11 pages, 1562 KiB

Open AccessArticle

Time-Resolved XUV Absorption Spectroscopy and Magnetic Circular Dichroism at the Ni M_2,3-Edges

by Marcel Hennes, Benedikt Rösner, Valentin Chardonnet, Gheorghe S. Chiuzbaian, Renaud Delaunay, Florian Döring, Vitaliy A. Guzenko, Michel Hehn, Romain Jarrier, Armin Kleibert, Maxime Lebugle, Jan Lüning, Gregory Malinowski, Aladine Merhe, Denys Naumenko, Ivaylo P. Nikolov, Ignacio Lopez-Quintas, Emanuele Pedersoli, Tatiana Savchenko, Benjamin Watts, Marco Zangrando, Christian David, Flavio Capotondi, Boris Vodungbo and Emmanuelle Jal Show full author list Hide full author list

Appl. Sci. 2021, 11(1), 325; https://doi.org/10.3390/app11010325 - 31 Dec 2020

Cited by 18 | Viewed by 3990

Abstract

Ultrashort optical pulses can trigger a variety of non-equilibrium processes in magnetic thin films affecting electrons and spins on femtosecond timescales. In order to probe the charge and magnetic degrees of freedom simultaneously, we developed an X-ray streaking technique that has the advantage of providing a jitter-free picture of absorption cross-section changes. In this paper, we present an experiment based on this approach, which we performed using five photon probing energies at the Ni

M_{2, 3}

-edges. This allowed us to retrieve the absorption and magnetic circular dichroism time traces, yielding detailed information on transient modifications of electron and spin populations close to the Fermi level. Our findings suggest that the observed absorption and magnetic circular dichroism dynamics both depend on the extreme ultraviolet (XUV) probing wavelength, and can be described, at least qualitatively, by assuming ultrafast energy shifts of the electronic and magnetic elemental absorption resonances, as reported in recent work. However, our analysis also hints at more complex changes, highlighting the need for further experimental and theoretical studies in order to gain a thorough understanding of the interplay of electronic and spin degrees of freedom in optically excited magnetic thin films. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

13 pages, 2152 KiB

Open AccessArticle

X-ray Spectroscopic Studies of a Solid-Density Germanium Plasma Created by a Free Electron Laser

by Gabriel Pérez-Callejo, Sam M. Vinko, Shenyuan Ren, Ryan Royle, Oliver Humphries, Thomas R. Preston, Bruce A. Hammel, Hyun-Kyung Chung, Tomas Burian, Vojtěch Vozda, Ming-Fu Lin, Tim Brandt van Driel and Justin S. Wark

Appl. Sci. 2020, 10(22), 8153; https://doi.org/10.3390/app10228153 - 18 Nov 2020

Cited by 1 | Viewed by 2201

Abstract

The generation of solid-density plasmas in a controlled manner using an X-ray free electron laser (XFEL) has opened up the possibility of diagnosing the atomic properties of hot, strongly coupled systems in novel ways. Previous work has concentrated on K-shell emission spectroscopy of low Z (<= 14) elements. Here, we extend these studies to the mid-Z(=32) element Germanium, where the XFEL creates copious L-shell holes, and the plasma conditions are interrogated by recording of the associated L-shell X-ray emission spectra. Given the desirability of generating as uniform a plasma as possible, we present here a study of the effects of the FEL photon energy on the temperatures and electron densities created, and their uniformity in the FEL beam propagation direction. We show that good uniformity can be achieved by tuning the photon energy of the XFEL such that it does not overlap significantly with L-shell to M-shell bound-bound transitions, and lies below the L-edges of the ions formed during the heating process. Reasonable agreement between experiment and simulations is found for the emitted X-ray spectra, demonstrating that for these higher Z elements, the selection of appropriate XFEL parameters is important for achieving uniformity in the plasma conditions. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

14 pages, 4885 KiB

Open AccessArticle

Femtosecond Optical Laser System with Spatiotemporal Stabilization for Pump-Probe Experiments at SACLA

by Tadashi Togashi, Shigeki Owada, Yuya Kubota, Keiichi Sueda, Tetsuo Katayama, Hiromitsu Tomizawa, Toshinori Yabuuchi, Kensuke Tono and Makina Yabashi

Appl. Sci. 2020, 10(21), 7934; https://doi.org/10.3390/app10217934 - 9 Nov 2020

Cited by 7 | Viewed by 2739

Abstract

We constructed a synchronized femtosecond optical laser system with spatiotemporal stabilization for pump-probe experiments at SPring-8 Angstrom Compact Free Electron Laser (SACLA). Stabilization of output power and pointing has been achieved with a small fluctuation level of a few percent by controlling conditions of temperature and air-flow in the optical paths. A feedback system using a balanced optical-microwave phase detector (BOMPD) has been successfully realized to reduce jitter down to 50 fs. We demonstrated the temporal stability with a time-resolved X-ray diffraction measurement and observed the coherent phonon oscillation of the photo-excited Bi without the post-processing using the timing monitor. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

13 pages, 1480 KiB

Open AccessFeature PaperArticle

URSA-PQ: A Mobile and Flexible Pump-Probe Instrument for Gas Phase Samples at the FLASH Free Electron Laser

by Jan Metje, Fabiano Lever, Dennis Mayer, Richard James Squibb, Matthew S. Robinson, Mario Niebuhr, Raimund Feifel, Stefan Düsterer and Markus Gühr

Appl. Sci. 2020, 10(21), 7882; https://doi.org/10.3390/app10217882 - 6 Nov 2020

Cited by 9 | Viewed by 2766

Abstract

We present a highly flexible and portable instrument to perform pump-probe spectroscopy with an optical and an X-ray pulse in the gas phase. The so-called URSA-PQ (German for ‘Ultraschnelle Röntgenspektroskopie zur Abfrage der Photoenergiekonversion an Quantensystemen’, Engl. ‘ultrafast X-ray spectroscopy for probing photoenergy conversion in quantum systems’) instrument is equipped with a magnetic bottle electron spectrometer (MBES) and tools to characterize the spatial and temporal overlap of optical and X-ray laser pulses. Its adherence to the CAMP instrument dimensions allows for a wide range of sample sources as well as other spectrometers to be included in the setup. We present the main design and technical features of the instrument. The MBES performance was evaluated using Kr M_4,5NN Auger lines using backfilled Kr gas, with an energy resolution ΔE/E ≅ 1/40 in the integrating operative mode. The time resolution of the setup at FLASH 2 FL 24 has been characterized with the help of an experiment on 2-thiouracil that is inserted via the instruments’ capillary oven. We find a time resolution of 190 fs using the molecular 2p photoline shift and attribute this to different origins in the UV-pump—the X-ray probe setup. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

7 pages, 1394 KiB

Open AccessArticle

Demonstration of Transmission Mode Soft X-ray NEXAFS Using Third- and Fifth-Order Harmonics of FEL Radiation at SACLA BL1

by Hiroshi Iwayama, Masanari Nagasaka, Ichiro Inoue, Shigeki Owada, Makina Yabashi and James R. Harries

Appl. Sci. 2020, 10(21), 7852; https://doi.org/10.3390/app10217852 - 5 Nov 2020

Cited by 3 | Viewed by 1946

Abstract

We demonstrate the applicability of third- and fifth-order harmonics of free-electron laser (FEL) radiation for soft X-ray absorption spectroscopy in the transmission mode at SACLA BL1, which covers a photon energy range of 20 to 150 eV in the fundamental FEL radiation. By using the third- and fifth-order harmonics of the FEL radiation, we successfully recorded near-edge X-ray absorption fine structure (NEXAFS) spectra for Ar 2p core ionization and CO₂ C 1s and O 1s core ionizations. Our results show that the utilization of third- and fifth-order harmonics can significantly extend the available photon energies for NEXAFS spectroscopy using an FEL and opens the door to femtosecond pump-probe NEXAFS using a soft X-ray FEL. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

15 pages, 1111 KiB

Open AccessArticle

Element-Specific Magnetization Dynamics of Complex Magnetic Systems Probed by Ultrafast Magneto-Optical Spectroscopy

by Clemens von Korff Schmising, Felix Willems, Sangeeta Sharma, Kelvin Yao, Martin Borchert, Martin Hennecke, Daniel Schick, Ilie Radu, Christian Strüber, Dieter W. Engel, Vishal Shokeen, Jens Buck, Kai Bagschik, Jens Viefhaus, Gregor Hartmann, Bastian Manschwetus, Soeren Grunewald, Stefan Düsterer, Emmanuelle Jal, Boris Vodungbo, Jan Lüning and Stefan Eisebitt Show full author list Hide full author list

Appl. Sci. 2020, 10(21), 7580; https://doi.org/10.3390/app10217580 - 28 Oct 2020

Cited by 12 | Viewed by 3300

Abstract

The vision to manipulate and control magnetism with light is driven on the one hand by fundamental questions of direct and indirect photon-spin interactions, and on the other hand by the necessity to cope with ever growing data volumes, requiring radically new approaches on how to write, read and process information. Here, we present two complementary experimental geometries to access the element-specific magnetization dynamics of complex magnetic systems via ultrafast magneto-optical spectroscopy in the extreme ultraviolet spectral range. First, we employ linearly polarized radiation of a free electron laser facility to demonstrate decoupled dynamics of the two sublattices of an FeGd alloy, a prerequisite for all-optical magnetization switching. Second, we use circularly polarized radiation generated in a laboratory-based high harmonic generation setup to show optical inter-site spin transfer in a CoPt alloy, a mechanism which only very recently has been predicted to mediate ultrafast metamagnetic phase transitions. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

10 pages, 2998 KiB

Open AccessArticle

Flat Field Soft X-ray Spectrometry with Reflection Zone Plates on a Curved Substrate

by Jürgen Probst, Christoph Braig and Alexei Erko

Appl. Sci. 2020, 10(20), 7210; https://doi.org/10.3390/app10207210 - 16 Oct 2020

Cited by 10 | Viewed by 2513

Abstract

We report on the first experimental results obtained with a newly designed instrument for high-resolution soft X-ray spectroscopy, using reflection zone plates (RZPs) on a spherical substrate. The spectrometer was tested with a fluorescence source. High-resolution flat field spectra within ±50% around the design energies were measured at an interval of 150–750 eV, using only two RZPs: the first RZP, with its design energy of 277 eV, covered the band of 150–370 eV, and the second RZP, with a design energy of 459 eV, covered the band of 350–750 eV, where the upper boundary of this energy range was defined by the Ni coating of the RZPs. The absolute quantum efficiency of the spectrometer, including the optical element and the detector, was, on average, above 10%, and reached 20% at the designed energies of the RZPs. The resolving power E/∆E exceeded 600 for energies E inside the core range of 200–550 eV. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

8 pages, 1329 KiB

Open AccessArticle

Parallel Broadband Femtosecond Reflection Spectroscopy at a Soft X-Ray Free-Electron Laser

by Robin Y. Engel, Piter S. Miedema, Diego Turenne, Igor Vaskivskyi, Günter Brenner, Siarhei Dziarzhytski, Marion Kuhlmann, Jan O. Schunck, Florian Döring, Andriy Styervoyedov, Stuart S.P. Parkin, Christian David, Christian Schüßler-Langeheine, Hermann A. Dürr and Martin Beye

Appl. Sci. 2020, 10(19), 6947; https://doi.org/10.3390/app10196947 - 4 Oct 2020

Cited by 8 | Viewed by 2606

Abstract

X-ray absorption spectroscopy (XAS) and the directly linked X-ray reflectivity near absorption edges yield a wealth of specific information on the electronic structure around the resonantly addressed element. Observing the dynamic response of complex materials to optical excitations in pump–probe experiments requires high sensitivity to small changes in the spectra which in turn necessitates the brilliance of free electron laser (FEL) pulses. However, due to the fluctuating spectral content of pulses generated by self-amplified spontaneous emission (SASE), FEL experiments often struggle to reach the full sensitivity and time-resolution that FELs can in principle enable. Here, we implement a setup which solves two common challenges in this type of spectroscopy using FELs: First, we achieve a high spectral resolution by using a spectrometer downstream of the sample instead of a monochromator upstream of the sample. Thus, the full FEL bandwidth contributes to the measurement at the same time, and the FEL pulse duration is not elongated by a monochromator. Second, the FEL beam is divided into identical copies by a transmission grating beam splitter so that two spectra from separate spots on the sample (or from the sample and known reference) can be recorded in-parallel with the same spectrometer, enabling a spectrally resolved intensity normalization of pulse fluctuations in pump–probe scenarios. We analyze the capabilities of this setup around the oxygen K- and nickel L-edges recorded with third harmonic radiation of the free electron laser in Hamburg (FLASH), demonstrating the capability for pump–probe measurements with sensitivity to reflectivity changes on the per mill level. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Graphical abstract

11 pages, 1856 KiB

Open AccessArticle

Bound-State Electron Dynamics Driven by Near-Resonantly Detuned Intense and Ultrashort Pulsed XUV Fields

by Alexander Magunia, Lennart Aufleger, Thomas Ding, Patrick Rupprecht, Marc Rebholz, Christian Ott and Thomas Pfeifer

Appl. Sci. 2020, 10(18), 6153; https://doi.org/10.3390/app10186153 - 4 Sep 2020

Cited by 5 | Viewed by 2034

Abstract

We report on numerical results revealing line-shape asymmetry changes of electronic transitions in atoms near-resonantly driven by intense extreme-ultraviolet (XUV) electric fields by monitoring their transient absorption spectrum after transmission through a moderately dense atomic medium. Our numerical model utilizes ultrashort broadband XUV laser pulses varied in their intensity (10¹⁴–10¹⁵ W/cm²) and detuning nearly out of resonance for a quantitative evaluation of the absorption line-shape asymmetry. It will be shown how transient energy shifts of the bound electronic states can be linked to these asymmetry changes in the case of an ultrashort XUV driving pulse temporally shorter than the lifetime of the resonant excitation, and how the asymmetry can be controlled by the near-resonant detuning of the XUV pulse. In the case of a two-level system, the numerical model is compared to an analytical calculation, which helps to uncover the underlying mechanism for the detuning- and intensity-induced line-shape modification and links it to the generalized Rabi frequency. To further apply the numerical model to recent experimental results of the near-resonant dressing of the 2s2p doubly excited state in helium by an ultrashort XUV free-electron laser pulse we extend the two-level model with an ionization continuum, thereby enabling the description of transmission-type (Fraunhofer-like) transient absorption of a strongly laser-coupled autoionizing state. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Figure 1

Review

Jump to: Research

16 pages, 2478 KiB

Open AccessReview

Tracking the Local Structure Change during the Photoabsorption Processes of Photocatalysts by the Ultrafast Pump-Probe XAFS Method

by Yohei Uemura, Toshihiko Yokoyama, Tetsuo Katayama, Shunsuke Nozawa and Kiyotaka Asakura

Appl. Sci. 2020, 10(21), 7818; https://doi.org/10.3390/app10217818 - 4 Nov 2020

Cited by 5 | Viewed by 4602

Abstract

The birth of synchrotron radiation (SR) facilities and X-ray free electron lasers (XFELs) has led to the development of new characterization tools that use X-rays and opened frontiers in science and technology. Ultrafast X-ray absorption fine structure (XAFS) spectroscopy for photocatalysts is one such significant research technique. Although carrier behavior in photocatalysts has been discussed in terms of the band theory and their energy levels in reciprocal space (k-space) based on optical spectroscopic results, it has rarely been discussed where photocarriers are located in real-space (r-space) based on direct observation of the excited states. XAFS provides information on the local electronic and geometrical structures around an X-ray-absorbing atom and can address photocarrier dynamics in the r-space observed from the X-ray-absorbing atom. In this article, we discuss the time dependent structure change of tungsten trioxide (WO₃) and bismuth vanadate (BiVO₄) photocatalysts studied by the ultrafast pump-probe XAFS method in the femtosecond to nanosecond time scale with the Photon Factory Advanced Ring (PF-AR) and the SPring-8 Angstrom Compact free-electron LAser (SACLA). WO₃ shows a femtosecond decay process of photoexcited electrons followed by a structural change to a metastable state with a hundred picosecond speed, which is relaxed to the ground-state structure with a nanosecond time constant. The Bi L₃ edge of BiVO₄ shows little contribution of the Bi 6s electron to the photoabsorption process; however, it is sensitive to the structural change induced by the photoexcited electron. Time-resolved XAFS measurements in a wide range time domain and with varied wavelengths of the excitation pump laser facilitate understanding of the overall details regarding the photocarrier dynamics that have a significant influence on the photocatalytic performance. Full article

(This article belongs to the Special Issue Ultrafast X-ray Spectroscopies)

► Show Figures

Journal Menu

Journal Browser

Ultrafast X-ray Spectroscopies

Share This Special Issue

Special Issue Editors

Special Issue Information

Published Papers (11 papers)

Research

Review

Further Information

Guidelines

MDPI Initiatives

Follow MDPI