Magyar
Publications
Femtosecond X-ray Fourier holography imaging of free-flying nanoparticles
Gorkhover T, Ulmer A, Ferguson K, Bucher M, Maia FRNC, Bielecki J, Ekeberg T, Hantke MF, Daurer BJ, Nettelblad C, Andreasson J, Barty A, Bruza P, Carron S, Hasse D, Krzywinski J, Larsson DSD, Morgan A, Muhlig K, Muller M, Okamoto K, Pietrini A, Rupp D, Sauppe M, van der Schot G, Seibert M, Sellberg JA, Svenda M, Swiggers M, Timneanu N, Westphal D, Williams G, Zani A, Chapman HN, Faigel G, Moller T, Hajdu J, Bostedt C
Nature Photonics 12, 150-153 (2018)
DOI: 10.1038/s41566-018-0110-y
Ultrafast X-ray imaging on individual fragile specimens such as aerosols, metastable particles, superfluid quantum systems and live biospecimens provides high-resolution information that is inaccessible with conventional imaging techniques. Coherent X-ray diffractive imaging, however, suffers from intrinsic loss of phase, and therefore structure recovery is often complicated and not always uniquely defined. Here, we introduce the method of in-flight holography, where we use nanoclusters as reference X-ray scatterers to encode relative phase information into diffraction patterns of a virus. The resulting hologram contains an unambiguous three-dimensional map of a virus and two nanoclusters with the highest lateral resolution so far achieved via single shot X-ray holography. Our approach unlocks the benefits of holography for ultrafast X-ray imaging of nanoscale, non-periodic systems and paves the way to direct observation of complex electron dynamics down to the attosecond timescale.
Oxidized pentacene micro-rods obtained by thermal annealing of pentacene thin films in air
Tomović AŽ, Savić JJ, Bakić NLj, Bortel G, Faigel G, Zikic R, Jovanović VP
Vacuum 144, 36-42 (2017)
DOI: 10.1016/j.vacuum.2017.07.012
Prolonged annealing of pentacene thin films in air leads to the formation of nano- and micro-scale rod-shaped structures at temperatures equal to or higher than 130 °C. Scanning electron microscopy measurements indicated their crystalline structure, while UV–vis absorption spectra revealed presence of different species of oxidized pentacene, including 6,13-pentacenequinone. The mechanism of growth of microcrystals from oxidized pentacene molecules is discussed. Raman and UV–vis absorption spectra dependences on film thickness (in 30–300 nm range) and on thermal annealing conditions (in air and nitrogen at ambient pressure at 100 and 150 °C) were also studied. These spectra are not largely affected by annealing if it is performed in nitrogen at any of studied temperatures and annealing times (few hours to few days). However, if annealing is performed in air, at temperatures 130 °C and higher, changes in spectral features are significant due to film oxidation.
Measurement of synchrotron-radiation-excited Kossel patterns
G. Bortel, G. Faigel, M. Tegze and A. Chumakov
J. Synchrotron Rad. 23, 214-218 (2016)
DOI: 10.1107/S1600577515019037
Kossel line patterns contain information on the crystalline structure, such as the magnitude and the phase of Bragg reflections. For technical reasons, most of these patterns are obtained using electron beam excitation, which leads to surface sensitivity that limits the spatial extent of the structural information. To obtain the atomic structure in bulk volumes, X-rays should be used as the excitation radiation. However, there are technical problems, such as the need for high resolution, low noise, large dynamic range, photon counting, two-dimensional pixel detectors and the small spot size of the exciting beam, which have prevented the widespread use of Kossel pattern analysis. Here, an experimental setup is described, which can be used for the measurement of Kossel patterns in a reasonable time and with high resolution to recover structural information.
Experimental phase determination of the structure factor from Kossel line profile
G. Faigel, G. Bortel and M. Tegze
Scientific Reports 6, 22904 (2016)
DOI: 10.1038/srep22904
Kossel lines are formed when radiation from point x-ray sources inside a single crystal are diffracted by the crystal itself. In principle, Kossel line patterns contain full information on the crystalline structure: phase and magnitude of the structure factors. The phase is coded into the profile of the lines. Although this was known for a long time, experimental realization has not been presented. In this work we demonstrate experimentally that phases can be directly determined from the profile of the Kossel lines. These measurements are interesting not only theoretically, but they would facilitate structure solution of samples within extreme conditions, such as high pressure, high and low temperatures, high magnetic fields and extremely short times. The parallel measurement of many diffraction lines on a stationary sample will allow a more efficient use of the new generation of x-ray sources the X-ray free electron lasers (XFELs).
Atomistic three-dimensional coherent x-ray imaging of nonbiological systems
Phay J. Ho, Chris Knight, Miklos Tegze, Gyula Faigel, C. Bostedt, and L. Young
Phys. Rev. A 94, 063823 (2016)
DOI: 10.1103/PhysRevA.94.063823
We computationally study the resolution limits for three-dimensional coherent x-ray diffractive imaging of heavy, nonbiological systems using Ar clusters as a prototype. We treat electronic and nuclear dynamics on an equal footing and remove the frozen-lattice approximation often used in electronic damage studies. We explore the achievable resolution as a function of pulse parameters (fluence level, pulse duration, and photon energy) and particle size. The contribution of combined lattice and electron dynamics is not negligible even for 2 fs pulses, and the Compton scattering is less deleterious than in biological systems for atomic-scale imaging. Although free-electron scattering represents a significant background, we find that recovery of the original structure is in principle possible with 3 Å resolution for particles of 11 nm diameter.
Orienting single-molecule diffraction patterns from XFELs using heavy-metal explosion fragments
Zoltán Jurek, Gyula Faigel
EPL (Europhysics Letters) 101, 16007 (2013)
DOI: 10.1209/0295-5075/101/16007
Single-molecule imaging is one of the main target areas of X-ray free-electron lasers. It relies on the possibility of orienting the large number of low-counting-statistics 2D diffraction patterns taken at random orientations of identical replicas of the sample. This is a difficult process and the low statistics limits the usability of orientation methods and ultimately it could prevent single-molecule imaging. We suggest a new approach, which avoids the orientation process from the diffraction patterns. We propose to determine sample orientation through identifying the direction of ejection fragments. The orientation of the sample is measured together with the diffraction pattern by detecting some fragments of the Coulomb explosion. We show by molecular-dynamics simulations that from the angular distribution of the fragments one can obtain the orientation of the samples.