http://journals.iucr.org/a/issues/2010/02/00/isscontsbdy.html Acta Crystallographica Section A: Foundations of Crystallography publishes papers reporting fundamental advances in all areas of crystallography in the broadest sense. The central themes are, on the one hand, experimental and theoretical studies of the properties and arrangements of atoms, ions and molecules in condensed matter, ideal or real, and of their symmetry and, on the other, the theoretical and experimental aspects of the various methods to determine these arrangements. en Copyright (c) 2010 International Union of Crystallography 2010-03-01 International Union of Crystallography International Union of Crystallography http://journals.iucr.org urn:issn:0108-7673 Acta Crystallographica Section A: Foundations of Crystallography publishes papers reporting fundamental advances in all areas of crystallography in the broadest sense. The central themes are, on the one hand, experimental and theoretical studies of the properties and arrangements of atoms, ions and molecules in condensed matter, ideal or real, and of their symmetry and, on the other, the theoretical and experimental aspects of the various methods to determine these arrangements. text/html Acta Crystallographica Section A: Foundations of Crystallography, Volume 66, Part 2, 2010 text yearly 6 2002-01-01T00:00+00:00 2 66 2010-03-01 Copyright (c) 2010 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography 133 urn:issn:0108-7673 med@iucr.org March 2010 2010-03-01 http://journals.iucr.org/logos/rss10a.gif http://journals.iucr.org/a/issues/2010/02/00/isscontsbdy.html Still image http://scripts.iucr.org/cgi-bin/paper?xd5030 A perspective on the new developments of structural dynamics is presented. The scope of applications and advances, from microscopy to diffraction and spectroscopy, defines the new age of endeavour. Copyright (c) 2010 International Union of Crystallography urn:issn:0108-7673 Zewail, A.H. 2010-02-09 doi:10.1107/S0108767309047801 International Union of Crystallography A perspective on the new developments of structural dynamics is presented. The scope of applications and advances, from microscopy to diffraction and spectroscopy, defines the new age of endeavour. en structural dynamics electron diffraction electron microscopy spectroscopy A perspective on the new developments of structural dynamics is presented. The scope of applications and advances, from microscopy to diffraction and spectroscopy, defines the new age of endeavour. text/html The new age of structural dynamics text 2 66 2010-02-09 Copyright (c) 2010 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 0 0 http://scripts.iucr.org/cgi-bin/paper?xd5029 Recent advances in high-intensity electron and X-ray pulsed sources now make it possible to directly observe atomic motions as they occur in barrier-crossing processes. These rare events require the structural dynamics to be triggered by femtosecond excitation pulses that prepare the system above the barrier or access new potential energy surfaces that drive the structural changes. In general, the sampling process modifies the system such that the structural probes should ideally have sufficient intensity to fully resolve structures near the single-shot limit for a given time point. New developments in both source intensity and temporal characterization of the pulsed sampling mode have made it possible to make so-called `molecular movies', i.e. measure relative atomic motions faster than collisions can blur information on correlations. Strongly driven phase transitions from thermally propagated melting to optically modified potential energy surfaces leading to ballistic phase transitions and bond stiffening are given as examples of the new insights that can be gained from an atomic level perspective of structural dynamics. The most important impact will likely be made in the fields of chemistry and biology where the central unifying concept of the transition state will come under direct observation and enable a reduction of high-dimensional complex reaction surfaces to the key reactive modes, as long mastered by Mother Nature. Copyright (c) 2010 International Union of Crystallography urn:issn:0108-7673 Miller, R.J.D. Ernstorfer, R. Harb, M. Gao, M. Hebeisen, C.T. Jean-Ruel, H. Lu, C. Moriena, G. Sciaini, G. 2010-02-09 doi:10.1107/S0108767309053926 International Union of Crystallography The long-held dream of directly observing atomic motions during the primary events governing structural dynamics has been realized using high-number-density electron pulses, and soon ultrabright X-ray pulses from fourth-generation light sources, to light up the atomic motions on 100 fs timescales. There are many surprises in store for us as we attain the fundamental limits to observe dynamical phenomena at the atomic level – as they occur. en femtosecond electron diffraction pulsed electron sources ponderomotive scattering structural phase transitions homogeneous nucleation nonthermal melting warm dense matter molecular movies atomically resolved structural dynamics Recent advances in high-intensity electron and X-ray pulsed sources now make it possible to directly observe atomic motions as they occur in barrier-crossing processes. These rare events require the structural dynamics to be triggered by femtosecond excitation pulses that prepare the system above the barrier or access new potential energy surfaces that drive the structural changes. In general, the sampling process modifies the system such that the structural probes should ideally have sufficient intensity to fully resolve structures near the single-shot limit for a given time point. New developments in both source intensity and temporal characterization of the pulsed sampling mode have made it possible to make so-called `molecular movies', i.e. measure relative atomic motions faster than collisions can blur information on correlations. Strongly driven phase transitions from thermally propagated melting to optically modified potential energy surfaces leading to ballistic phase transitions and bond stiffening are given as examples of the new insights that can be gained from an atomic level perspective of structural dynamics. The most important impact will likely be made in the fields of chemistry and biology where the central unifying concept of the transition state will come under direct observation and enable a reduction of high-dimensional complex reaction surfaces to the key reactive modes, as long mastered by Mother Nature. text/html `Making the molecular movie': first frames text 2 66 2010-02-09 Copyright (c) 2010 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 0 0 http://scripts.iucr.org/cgi-bin/paper?xd5018 The timescales for structural changes in a single crystal of bismuth after excitation with an intense near-infrared laser pulse are studied with femtosecond pump-probe X-ray diffraction. Changes in the intensity and reciprocal-lattice vector of several reflections give quantitative information on the structure factor and lattice strain as a function of time, with a resolution of 200 fs. The results indicate that the majority of excess carrier energy that remains near the surface is transferred to vibrational modes on a timescale of about 10 ps, and that the resultant increase in the variance of the atomic positions at these times is consistent with the overall magnitude of lattice strain that develops. Copyright (c) 2010 International Union of Crystallography urn:issn:0108-7673 Johnson, S.L. Beaud, P. Vorobeva, E. Milne, C.J. Murray, É.D. Fahy, S. Ingold, G. 2010-02-09 doi:10.1107/S0108767309053859 International Union of Crystallography Grazing-incidence femtosecond X-ray diffraction is used to study the non-equilibrium structural dynamics in bismuth after intense near-infrared laser excitation on timescales ranging from 200 fs to 400 ps. The data indicate that at times earlier than 10 ps there are significant deviations from local thermal equilibrium due to incomplete electronic relaxation. en phonon dynamics grazing-incidence femtosecond X-ray diffraction bismuth lattice strain The timescales for structural changes in a single crystal of bismuth after excitation with an intense near-infrared laser pulse are studied with femtosecond pump-probe X-ray diffraction. Changes in the intensity and reciprocal-lattice vector of several reflections give quantitative information on the structure factor and lattice strain as a function of time, with a resolution of 200 fs. The results indicate that the majority of excess carrier energy that remains near the surface is transferred to vibrational modes on a timescale of about 10 ps, and that the resultant increase in the variance of the atomic positions at these times is consistent with the overall magnitude of lattice strain that develops. text/html Non-equilibrium phonon dynamics studied by grazing-incidence femtosecond X-ray crystallography text 2 66 2010-02-09 Copyright (c) 2010 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 0 0 http://scripts.iucr.org/cgi-bin/paper?xd5020 Femtosecond X-ray diffraction allows for real-time mapping of structural changes in condensed matter on atomic length and timescales. Sequences of diffraction patterns provide both transient geometries and charge-density maps of crystalline materials. This article reviews recent progress in this field, the main emphasis being on experimental work done with laser-driven hard X-ray sources. Both Bragg diffraction techniques for bulk and nanostructured single crystals as well as the recently implemented powder diffraction from polycrystalline samples are discussed. In ferroelectric superlattice structures, coherent phonon motions and the driving stress mechanisms are observed in real time. In molecular crystals charge-transfer processes and the concomitant changes of the lattice geometry are analyzed. Copyright (c) 2010 International Union of Crystallography urn:issn:0108-7673 Elsaesser, T. Woerner, M. 2010-02-09 doi:10.1107/S0108767309048181 International Union of Crystallography Real-time studies of structural dynamics by femtosecond X-ray diffraction are reviewed, discussing results for single-crystal and polycrystalline polar materials. en structural dynamics femtosecond X-ray diffraction charge-density maps superlattice structures charge-transfer processes Femtosecond X-ray diffraction allows for real-time mapping of structural changes in condensed matter on atomic length and timescales. Sequences of diffraction patterns provide both transient geometries and charge-density maps of crystalline materials. This article reviews recent progress in this field, the main emphasis being on experimental work done with laser-driven hard X-ray sources. Both Bragg diffraction techniques for bulk and nanostructured single crystals as well as the recently implemented powder diffraction from polycrystalline samples are discussed. In ferroelectric superlattice structures, coherent phonon motions and the driving stress mechanisms are observed in real time. In molecular crystals charge-transfer processes and the concomitant changes of the lattice geometry are analyzed. text/html Photoinduced structural dynamics of polar solids studied by femtosecond X-ray diffraction text 2 66 2010-02-09 Copyright (c) 2010 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 0 0 http://scripts.iucr.org/cgi-bin/paper?xd5025 In order to explore the ligand-migration dynamics in myoglobin induced by photodissociation, cryogenic X-ray crystallographic investigations of carbonmonoxy myoglobin crystals illuminated by continuous wave and pulsed lasers at 1–15 kHz repetition rate have been carried out. Here it is shown that this novel method, extended pulsed-laser pumping of carbonmonoxy myoglobin, promotes ligand migration in the protein matrix by crossing the glass transition temperature repeatedly, and enables the visualization of the migration pathway of the photodissociated ligands in native Mb at cryogenic temperatures. It has revealed that the migration of the CO molecule into each cavity induces structural changes of the amino-acid residues around the cavity which result in the expansion of the cavity. The sequential motion of the ligand and the cavity suggests a self-opening mechanism of the ligand-migration channel arising by induced fit. Copyright (c) 2010 International Union of Crystallography urn:issn:0108-7673 Tomita, A. Sato, T. Nozawa, S. Koshihara, S. Adachi, S. 2010-02-09 doi:10.1107/S0108767309050752 International Union of Crystallography The ligand migration dynamics in myoglobin are visualized by cryogenic X-ray crystallography under continuous or pulsed laser illumination. en ligand-migration dynamics myoglobin amino acids In order to explore the ligand-migration dynamics in myoglobin induced by photodissociation, cryogenic X-ray crystallographic investigations of carbonmonoxy myoglobin crystals illuminated by continuous wave and pulsed lasers at 1–15 kHz repetition rate have been carried out. Here it is shown that this novel method, extended pulsed-laser pumping of carbonmonoxy myoglobin, promotes ligand migration in the protein matrix by crossing the glass transition temperature repeatedly, and enables the visualization of the migration pathway of the photodissociated ligands in native Mb at cryogenic temperatures. It has revealed that the migration of the CO molecule into each cavity induces structural changes of the amino-acid residues around the cavity which result in the expansion of the cavity. The sequential motion of the ligand and the cavity suggests a self-opening mechanism of the ligand-migration channel arising by induced fit. text/html Tracking ligand-migration pathways of carbonmonoxy myoglobin in crystals at cryogenic temperatures text 2 66 2010-02-09 Copyright (c) 2010 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 0 0 http://scripts.iucr.org/cgi-bin/paper?xd5024 The need to visualize molecular structure in the course of a chemical reaction, a phase transformation or a biological function has been a dream of scientists for decades. The development of time-resolved X-ray and electron-based methods is making this true. X-ray absorption spectroscopy is ideal for the study of structural dynamics in liquids, because it can be implemented in amorphous media. Furthermore, it is chemically selective. Using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) in laser pump/X-ray probe experiments allows the retrieval of the local geometric structure of the system under study, but also the underlying photoinduced electronic structure changes that drive the structural dynamics. Recent developments in picosecond and femtosecond X-ray absorption spectroscopy applied to molecular systems in solution are reviewed: examples on ultrafast photoinduced processes such as intramolecular electron transfer, low-to-high spin change, and bond formation are presented. Copyright (c) 2010 International Union of Crystallography urn:issn:0108-7673 Chergui, M. 2010-02-09 doi:10.1107/S010876730904968X International Union of Crystallography Picosecond and femtosecond X-ray absorption spectroscopic studies of photoinduced molecular processes in solution are presented, with examples of intramolecular electron transfer, low-to-high spin conversion and bond formation in metal-based molecular complexes. en structural dynamics ultrafast phenomena molecules EXAFS XANES The need to visualize molecular structure in the course of a chemical reaction, a phase transformation or a biological function has been a dream of scientists for decades. The development of time-resolved X-ray and electron-based methods is making this true. X-ray absorption spectroscopy is ideal for the study of structural dynamics in liquids, because it can be implemented in amorphous media. Furthermore, it is chemically selective. Using X-ray absorption near-edge structure (XANES) and extended X-ray absorption fine structure (EXAFS) in laser pump/X-ray probe experiments allows the retrieval of the local geometric structure of the system under study, but also the underlying photoinduced electronic structure changes that drive the structural dynamics. Recent developments in picosecond and femtosecond X-ray absorption spectroscopy applied to molecular systems in solution are reviewed: examples on ultrafast photoinduced processes such as intramolecular electron transfer, low-to-high spin change, and bond formation are presented. text/html Picosecond and femtosecond X-ray absorption spectroscopy of molecular systems text 2 66 2010-02-09 Copyright (c) 2010 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 0 0 http://scripts.iucr.org/cgi-bin/paper?xd5028 A time-resolved X-ray solution scattering study of bromine molecules in CCl4 is presented as an example of how to track atomic motions in a simple chemical reaction. The structures of the photoproducts are tracked during the recombination process, geminate and non-geminate, from 100 ps to 10 µs after dissociation. The relaxation of hot Br2* molecules heats the solvent. At early times, from 0.1 to 10 ns, an adiabatic temperature rise is observed, which leads to a pressure gradient that forces the sample to expand. The expansion starts after about 10 ns with the laser beam sizes used here. When thermal artefacts are removed by suitable scaling of the transient solvent response, the excited-state solute structures can be obtained with high fidelity. The analysis shows that 30% of Br2* molecules recombine directly along the X potential, 60% are trapped in the A/A′ state with a lifetime of 5.5 ns, and 10% recombine non-geminately via diffusive motion in about 25 ns. The Br—Br distance distribution in the A/A′ state peaks at 3.0 Å. Copyright (c) 2010 International Union of Crystallography urn:issn:0108-7673 Kong, Q. Lee, J.H. Lo Russo, M. Kim, T.K. Lorenc, M. Cammarata, M. Bratos, S. Buslaps, T. Honkimaki, V. Ihee, H. Wulff, M. 2010-02-09 doi:10.1107/S0108767309054993 International Union of Crystallography The reaction dynamics of molecular bromine in CCl4 are studied by time-resolved X-ray scattering with 100 ps pulses from a synchrotron. en time-resolved X-ray scattering laser pump and X-ray probe bromine recombination dynamics geminate recombination non-geminate recombination transient-state structure A time-resolved X-ray solution scattering study of bromine molecules in CCl4 is presented as an example of how to track atomic motions in a simple chemical reaction. The structures of the photoproducts are tracked during the recombination process, geminate and non-geminate, from 100 ps to 10 µs after dissociation. The relaxation of hot Br2* molecules heats the solvent. At early times, from 0.1 to 10 ns, an adiabatic temperature rise is observed, which leads to a pressure gradient that forces the sample to expand. The expansion starts after about 10 ns with the laser beam sizes used here. When thermal artefacts are removed by suitable scaling of the transient solvent response, the excited-state solute structures can be obtained with high fidelity. The analysis shows that 30% of Br2* molecules recombine directly along the X potential, 60% are trapped in the A/A′ state with a lifetime of 5.5 ns, and 10% recombine non-geminately via diffusive motion in about 25 ns. The Br—Br distance distribution in the A/A′ state peaks at 3.0 Å. text/html Photolysis of Br2 in CCl4 studied by time-resolved X-ray scattering text 2 66 2010-02-09 Copyright (c) 2010 International Union of Crystallography Acta Crystallographica Section A: Foundations of Crystallography research papers 0 0