journal menu
issue contents
March 2010 issue
Dynamical structural science
Cover illustration: Recent advances in pulsed electron and X-ray sources make it now possible to obtain atomic level views of transient phenomena in matter. A broad spectrum of recent advances in the field of dynamical structural science, including examples from solid-state physics, molecular materials, biological molecules and molecules in solution, is presented here.
dynamical structural science
Free 
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.
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.
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.
Real-time studies of structural dynamics by femtosecond X-ray diffraction are reviewed, discussing results for single-crystal and polycrystalline polar materials.
Excited-state geometries determined by time-resolved synchrotron diffraction are summarized with emphasis on their comparison with a series of theoretical results. The relative merits of monochromatic and polychromatic (Laue) techniques are discussed.
A recent investigation by 100 ps X-ray diffraction of the structural dynamics in multifunctional spin-crossover materials, which are prototypes of molecular bistability, is presented. This illustrates how the dynamics of molecular photoswitching between low-spin and high-spin states follows a complex pathway from molecular to material scales through a sequence of processes.
Open access
access
Here it is demonstrated how five-dimensional crystallography can be used to determine a comprehensive chemical kinetic mechanism in concert with the atomic structures of transient intermediates that form and decay during the course of the reaction.
Open access
access
Time-resolved structural studies of proteins have undergone several significant developments during the last decade. Recent developments using time-resolved X-ray methods, such as time-resolved Laue diffraction, low-temperature intermediate trapping, time-resolved wide-angle X-ray scattering and time-resolved X-ray absorption spectroscopy, are reviewed.
The ligand migration dynamics in myoglobin are visualized by cryogenic X-ray crystallography under continuous or pulsed laser illumination.
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.
A decade of development in X-ray transient absorption spectroscopy of metal complexes and interfacial systems for light-activated processes in the authors' institution is summarized through several examples and future prospective.
The reaction dynamics of molecular bromine in CCl4 are studied by time-resolved X-ray scattering with 100 ps pulses from a synchrotron.
This article describes a robust analysis methodology developed primarily with a focus on determining structural parameters for the excited states of medium-sized molecules in solution using time-resolved X-ray scattering. Emphasis is given to structure determination in terms of model comparisons and to the information content of difference scattering signals as well as the related experimental variables.
The present status of reaction dynamics studies using the time-resolved X-ray diffraction technique and the future prospects combining the X-ray free-electron laser with the technique are discussed. Examples of femtosecond X-ray diffraction experiments that can be implemented using sub-100 fs X-ray pulses from the free-electron laser are presented with the prospect of directly probing ultrafast structural dynamics of chemical reactions and coherent wave packet motions.
