scholarly journals Imaging conical intersection dynamics during azobenzene photoisomerization by ultrafast X-ray diffraction

2021 ◽  
Vol 118 (3) ◽  
pp. e2022037118
Author(s):  
Daniel Keefer ◽  
Flavia Aleotti ◽  
Jérémy R. Rouxel ◽  
Francesco Segatta ◽  
Bing Gu ◽  
...  
Keyword(s):  
Transition Density ◽  
Real Space ◽  
Conical Intersection ◽  
X Rays ◽  
X Ray Diffraction ◽  
Photochemical Process ◽  
X Ray ◽  
Space Phase ◽  
Diffraction Signal

X-ray diffraction is routinely used for structure determination of stationary molecular samples. Modern X-ray photon sources, e.g., from free-electron lasers, enable us to add temporal resolution to these scattering events, thereby providing a movie of atomic motions. We simulate and decipher the various contributions to the X-ray diffraction pattern for the femtosecond isomerization of azobenzene, a textbook photochemical process. A wealth of information is encoded besides real-time monitoring of the molecular charge density for the cis to trans isomerization. In particular, vibronic coherences emerge at the conical intersection, contributing to the total diffraction signal by mixed elastic and inelastic photon scattering. They cause distinct phase modulations in momentum space, which directly reflect the real-space phase modulation of the electronic transition density during the nonadiabatic passage. To overcome the masking by the intense elastic scattering contributions from the electronic populations in the total diffraction signal, we discuss how this information can be retrieved, e.g., by employing very hard X-rays to record large scattering momentum transfers.

scholarly journals Electronic Excitations and Radiation Damage in Macromolecular Crystallography

Crystals ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 273 ◽  
Author(s):  
José Brandão-Neto ◽  
Leonardo Bernasconi
Keyword(s):  
Chemical Information ◽  
X Rays ◽  
Electronic Excitations ◽  
Macromolecular Crystallography ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Successful Approach ◽  
Structural Research

Macromolecular crystallography at cryogenic temperatures has so far provided the majority of the experimental evidence that underpins the determination of the atomic structures of proteins and other biomolecular assemblies by means of single crystal X-ray diffraction experiments. One of the core limitations of the current methods is that crystal samples degrade as they are subject to X-rays, and two broad groups of effects are observed: global and specific damage. While the currently successful approach is to operate outside the range where global damage is observed, specific damage is not well understood and may lead to poor interpretation of the chemistry and biology of the system under study. In this work, we present a phenomenological model in which specific damage is understood as the result of a single process, the steady excitation of crystal electrons caused by X-ray absorption, which acts as a trigger for the bulk effects that manifest themselves in the form of global damage and obscure the interpretation of chemical information from XFEL and synchrotron structural research.

scholarly journals Electronic Excitations and Radiation Damage in Macromolecular Crystallography

2018 ◽  
Author(s):  
José Brandão-Neto ◽  
Leonardo Bernasconi
Keyword(s):  
Chemical Information ◽  
X Rays ◽  
Electronic Excitations ◽  
Macromolecular Crystallography ◽  
X Ray Diffraction ◽  
X Ray ◽  
Atomic Structures ◽  
Successful Approach ◽  
Structural Research

Macromolecular crystallography at cryogenic temperatures has so far provided the majority of the experimental evidence that underpins the determination of the atomic structures of proteins and other biomolecular assemblies by means of single crystal X-ray diffraction experiments. One of the core limitations of the current methods is that crystal samples degrade as they are subject to X-rays, and two broad groups of effects are observed: global and specific damage. While the currently successful approach is to operate outside the range where global damage is observed, specific damage is not well understood and may lead to poor interpretation of the chemistry and biology of the system under study. In this work, we present a phenomenological model in which specific damage is understood as the result of a single process, the steady excitation of crystal electrons caused by X-ray absorption, which acts as a trigger for the bulk effects that manifest themselves in the form of global damage and obscure the interpretation of chemical information from XFEL and synchrotron structural research.

2D real space visualization of d values in polycrystalline bulk materials of different hardness

2021 ◽  
Vol 54 (2) ◽  
pp. 597-603
Author(s):  
Mari Mizusawa ◽  
Kenji Sakurai
Keyword(s):  
Lattice Distortion ◽  
Structural Information ◽  
Hardness Test ◽  
Real Space ◽  
Polycrystalline Materials ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Imaging ◽  
D Values

Conventional X-ray diffraction measurements provide some average structural information, mainly on the crystal structure of the whole area of the given specimen, which might not be very uniform and may include different crystal structures, such as co-existing crystal phases and/or lattice distortion. The way in which the lattice plane changes due to strain also might depend on the position in the sample, and the average information might have some limits. Therefore, it is important to analyse the sample with good lateral spatial resolution in real space. Although various techniques for diffraction topography have been developed for single crystals, it has not always been easy to image polycrystalline materials. Since the late 1990s, imaging technology for fluorescent X-rays and X-ray absorption fine structure has been developed via a method that does not scan either a sample or an X-ray beam. X-ray diffraction imaging can be performed when this technique is applied to a synchrotron radiation beamline with a variable wavelength. The present paper reports the application of X-ray diffraction imaging to bulk steel materials with varying hardness. In this study, the distribution of lattice distortion of hardness test blocks with different hardness was examined. Via this 2D visualization method, the grains of the crystals with low hardness are large enough to be observed by X-ray diffraction contrast in real space. The change of the d value in the vicinity of the Vickers mark has also been quantitatively evaluated.

The Measurement of Elastic Constants for the Determination of Stresses by X-Rays

1983 ◽  
Vol 27 ◽  
pp. 159-170 ◽  
Author(s):  
K. Perry ◽  
I.C. Noyan ◽  
P.J. Rudnik ◽  
J.B. Cohen
Keyword(s):  
Interplanar Spacing ◽  
Measuring System ◽  
Laboratory System ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Measured Change ◽  
Non Destructive ◽  
Applied Stresses

Residual and applied stresses (σij) are often measured via X-ray diffraction, by calculating the resultant elastic strains (ϵij) from the measured change in interplanar spacing (“d”). This method is non-destructive, reasonably reproducible (typically ±14 MPa), can be carried out in the field, and is readily automated to give values to an operator-specified precision , Let Li represent the axes of the measuring system with L3 normal to the diffracting planes, and Pi represent the sample axes. These axes are illustrated in Figure 1. In what follows, primed stresses and strains are in the laboratory system, while unprimed values are in the sample system.

scholarly journals Determination of structural chirality of berlinite and quartz using resonant x-ray diffraction with circularly polarized x-rays

2010 ◽  
Vol 81 (14) ◽  
Author(s):  
Yoshikazu Tanaka ◽  
Taro Kojima ◽  
Yasutaka Takata ◽  
Ashish Chainani ◽  
Stephen W. Lovesey ◽  
...  
Keyword(s):  
X Rays ◽  
X Ray Diffraction ◽  
Circularly Polarized ◽  
X Ray

Three-Dimensional Coherent X-Ray Diffraction Microscopy

MRS Bulletin ◽  
2004 ◽  
Vol 29 (3) ◽  
pp. 177-181 ◽  
Author(s):  
Ian K. Robinson ◽  
Jianwei Miao
Keyword(s):  
Electron Microscopy ◽  
Three Dimensional ◽  
Real Space ◽  
Objective Lens ◽  
X Rays ◽  
X Ray Diffraction ◽  
Space Images ◽  
Thin Sections ◽  
X Ray ◽  
Penetration Ability

AbstractX-rays have been widely used in the structural analysis of materials because of their significant penetration ability, at least on the length scale of the granularity of most materials. This allows, in principle, for fully three-dimensional characterization of the bulk properties of a material. One of the main advantages of x-ray diffraction over electron microscopy is that destructive sample preparation to create thin sections is often avoidable. A major disadvantage of x-ray diffraction with respect to electron microscopy is its inability to produce real-space images of the materials under investigation—there are simply no suitable lenses available. There has been significant progress in x-ray microscopy associated with the development of lenses, usually based on zone plates, Kirkpatrick–Baez mirrors, or compound refractive lenses. These technologies are far behind the development of electron optics, particularly for the large magnification ratios needed to attain high resolution. In this article, the authors report progress toward the development of an alternative general approach to imaging, the direct inversion of diffraction patterns by computation methods. By avoiding the use of an objective lens altogether, the technique is free from aberrations that limit the resolution, and it can be highly efficient with respect to radiation damage of the samples. It can take full advantage of the three-dimensional capability that comes from the x-ray penetration. The inversion step employs computational methods based on oversampling to obtain a general solution of the diffraction phase problem.

scholarly journals Multiple scattering in grazing-incidence X-ray diffraction: impact on lattice-constant determination in thin films

2016 ◽  
Vol 23 (3) ◽  
pp. 729-734 ◽  
Author(s):  
Roland Resel ◽  
Markus Bainschab ◽  
Alexander Pichler ◽  
Theo Dingemans ◽  
Clemens Simbrunner ◽  
...  
Keyword(s):  
Thin Films ◽  
Critical Angle ◽  
Grazing Incidence ◽  
X Rays ◽  
Organic Thin Film ◽  
X Ray Diffraction ◽  
Reliable Determination ◽  
X Ray ◽  
Out Of Plane

Dynamical scattering effects are observed in grazing-incidence X-ray diffraction experiments using an organic thin film of 2,2′:6′,2′′-ternaphthalene grown on oxidized silicon as substrate. Here, a splitting of all Bragg peaks in the out-of-plane direction (z-direction) has been observed, the magnitude of which depends both on the incidence angle of the primary beam and the out-of-plane angle of the scattered beam. The incident angle was varied between 0.09° and 0.25° for synchrotron radiation of 10.5 keV. This study reveals comparable intensities of the split peaks with a maximum for incidence angles close to the critical angle of total external reflection of the substrate. This observation is rationalized by two different scattering pathways resulting in diffraction peaks at different positions at the detector. In order to minimize the splitting, the data suggest either using incident angles well below the critical angle of total reflection or angles well above, which sufficiently attenuates the contributions from the second scattering path. This study highlights that the refraction of X-rays in (organic) thin films has to be corrected accordingly to allow for the determination of peak positions with sufficient accuracy. Based thereon, a reliable determination of the lattice constants becomes feasible, which is required for crystallographic structure solutions from thin films.

Oxford HEXameter: Laboratory High Energy X-Ray Diffractometer for Bulk Residual Stress Analysis

2006 ◽  
Vol 524-525 ◽  
pp. 743-748 ◽  
Author(s):  
Alexander M. Korsunsky ◽  
Shu Yan Zhang ◽  
Daniele Dini ◽  
Willem J.J. Vorster ◽  
Jian Liu
Keyword(s):  
Accurate Determination ◽  
High Energy ◽  
Energy Dispersive ◽  
Detector Response ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
New Instrument ◽  
Synchrotron Beamlines

Diffraction of penetrating radiation such as neutrons or high energy X-rays provides a powerful non-destructive method for the evaluation of residual stresses in engineering components. In particular, strain scanning using synchrotron energy-dispersive X-ray diffraction has been shown to offer a fast and highly spatially resolving measurement technique. Synchrotron beamlines provide best available instruments in terms of flux and low beam divergence, and hence spatial and measurement resolution and data collection rate. However, despite the rapidly growing number of facilities becoming available in Europe and across the world, access to synchrotron beamlines for routine industrial and research use remains regulated, comparatively slow and expensive. A laboratory high energy X-ray diffractometer for bulk residual strain evaluation (HEXameter) has been developed and built at Oxford University. It uses a twin-detector setup first proposed by one of the authors in the energy dispersive X-ray diffraction mode and allows simultaneous determination of macroscopic and microscopic strains in two mutually orthogonal directions that lie approximately within the plane normal to the incident beam. A careful procedure for detector response calibration is used in order to facilitate accurate determination of lattice parameters by pattern refinement. The results of HEXameter measurements are compared with synchrotron X-ray data for several samples e.g. made from a titanium alloy and a particulate composite with an aluminium alloy matrix. Experimental results are found to be consistent with synchrotron measurements and strain resolution close to 2×10-4 is routinely achieved by the new instrument.

X-Ray Diffraction Determination of Texture and Stress in Damascene Fabricated Copper Interconnects

1999 ◽  
Vol 563 ◽  
Author(s):  
Delrose Winter ◽  
Paul R. Besser
Keyword(s):  
Incident Beam ◽  
Preferred Orientation ◽  
Copper Interconnects ◽  
X Rays ◽  
X Ray Diffraction ◽  
X Ray ◽  
Diffraction Determination ◽  
Lattice Planes ◽  
Excellent Tool

AbstractX-Ray diffraction (XRD) provides an excellent tool for the measurement of both stress and texture (preferred orientation) on fabricated damascene interconnect structures. Since x-ray diffraction provides a direct measurement of lattice spacings, film strain can be measured directly. Also, since the intensity of diffracted x-rays is proportional to the density of lattice planes oriented in diffracting condition with respect to the incident beam, both the direction and extent of preferred orientation can be accurately measured. Special techniques and considerations are necessary when examining damascene interconnect structures with XRD which are not necessary with blanket films. These techniques are discussed and described in order to aid in obtaining meaningful XRD data and a correct interpretation of the results.

Abinitiostructure determination of triphenyl phosphite by powder synchrotron X-ray diffraction

2002 ◽  
Vol 35 (2) ◽  
pp. 212-219 ◽  
Author(s):  
Olivier Hernandez ◽  
Alain Hédoux ◽  
Jacques Lefebvre ◽  
Yannick Guinet ◽  
Marc Descamps ◽  
...  
Keyword(s):  
Degrees Of Freedom ◽  
Real Space ◽  
Mirror Plane ◽  
Triphenyl Phosphite ◽  
X Ray Diffraction ◽  
X Ray ◽  
Topological Features ◽  
Lattice Space ◽  
Plane Passing

The crystal structure of the glass-forming molecular liquid triphenyl phosphite [TPP, P(OC6H5)3, six torsional degrees of freedom] has been solvedab initioat 110 K from powder synchrotron X-ray diffraction data by real-space methods (simulated annealing) followed by rigid-body Rietveld refinements. The symmetry is trigonal, with a rhombohedral lattice, space group R\bar{3}. The associated hexagonal cell, which is a sixfold multiple of the previously published less-symmetric monoclinic cell [Hédouxet al.(1999).Phys. Rev. B,60, 9390–9395], is unusually large [V= 7075.7 (4) Å3,Z= 18] and displays a noteworthy platelet-like shape [a= 37.766 (1) andc= 5.7286 (2) Å]. The TPP molecule does not exhibit the idealC3symmetric propeller shape, its conformation being on the contrary almost mirror-symmetric, with the pseudo-mirror plane passing through the P—O1 bond and two carbon atoms inparaposition with respect to the O1 atom. The hitherto unknown topological features of crystalline TPP, including unusual intermolecular weak C—H...O hydrogen-bonding networks, are presented and discussed in the scope of the `glacial state' problem.

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