4D-Structural Dynamics of the Transition State: Free Molecules, Clusters and Nanocrystals

Study of the structural dynamics of matter by methods with high spatially-temporal resolution represents new direction in modern science and provides the understanding of relationship inside the "structure – dynamics – property" triad in the field of physics, chemistry, biology and materials science. Application of femto and attosecond laser pulses for excitation and formation of synchronized ultrashort photoelectron bunches for probing makes it possible to observe coherent dynamics of nuclei and electrons in samples on necessary space-time scales. Using laser spectroscopy one can determine energy levels of the sample and trace their evolution over time. However, the extraction of the structural dynamics of matter from this information is achieved by indirect methods. In the paper authors demonstrate the direct approaches to the study of the coherent dynamics of the nuclei of laser-excited matter in the space-time continuum (4D), based on probing the object with ultra-short electron or X-ray pulses, and describe their experiments, which were carried out using ultrafast electron diffractometer and transmission electron microscope at the Institute of Spectroscopy RAS.