Ultrafast Electron Crystallography and Nanocrystallography: for Chemistry, Biology and Materials Science. Part I. Ultrafast Electron Crystallography

Abstract

The direct probing and understanding of the dynamics of chemical and biological processes occurring in condensed matter, is currently in its early stages. Progress in this field has been pushed by the development of methods for the study of the structural dynamics of matter in a state far from equilibrium, including extreme states. The forthcoming information serves as the basis for testing new theoretical approaches to the description of the substance in casually connected triad "structure-dynamics-function". Observation of the dynamic behavior of matter in the space-time continuum on ultrashort time scales is a necessary first step in the explanation and, ultimately, control of far from equilibrium processes, and functionality of the systems studied. The method of ultrafast electron crystallography (UEC) makes it possible to investigate transient nonequilibrium structures, which yield decisive information about the structural dynamics of the phase transitions and coherent dynamics of the nuclei in the solid state, on the surface, and in macromolecular systems. In recent years, the electron bunch path length in the UEC apparatus diminished significantly, while the accelerating voltage increased considerably. Therefore, femtosecond electron pulses were obtained. A technique of radio frequency grouping of electrons was proposed to increase the electron pulse brightness. The method of electron field emission was used to increase the spatial coherence, and ponderomotive wave front acceleration was applied to reduce the mismatch between the velocities of the light and electron pulses and to contract the electron bunches. These achievements have opened up new possibilities for studying the coherent structural dynamics – atomic and molecular movie with femtosecond temporal resolution. The results of several internationally renowned research groups are included and cited.

STRUCTURAL DYNAMICS OF FREE MOLECULES AND CONDENSED STATE OF MATTER. Part II. TRANSIENT STRUCTURES IN CHEMICAL REACTIONS

“…At present, the method of ultrafast diffraction is intensively developing. The great opportunities for the study of the structural dynamics are opened by 4D methods of ultrafast electron crystallography and electron microscopy with high temporal resolution from micro-to femtoseconds (please, see review articles [31,37,160,177,178] and the monograph [34]). The recent advances in the formation of ultrashort electron pulses allow us to go to the area of attosecond temporal resolution and to observe the coherent dynamics of the electrons in the molecule [22,179,180].…”