Light induced properties in chemical systems
Villy Sundstrom, Department of Chemical Physics

Most chemical reactions occur as a sequence of elementary reactions: breaking or forming chemical bonds, changing conformation, or transferring energy or charge between (or within) molecules. Such elementary reactions are associated with atomic scale motions and therefore occur on a correspondingly fast time scale–picoseconds to femtoseconds. In order to characterize, understand, and eventually exploit a certain complex reaction, a detailed knowledge of the mechanism of the constituent reactions and how they combine to yield the total event is necessary. Femtochemistry is the area of chemistry, physics and biology dealing with these topics. Femtochemistry is the collective notation for the study of elementary, often very fast, chemical reactions; the experimental methods employed in these studies are often based on the use of femtosecond laser pulses. A number of different ultrafast spectroscopic methods have been developed for studying various aspects of the dynamics in a molecular system. During the last few years, methods of femtochemistry have been very successfully applied to a variety of molecular systems, ranging from isolated molecules, molecules in clusters, molecules in the condensed phase and molecules with biological function, to obtain new detailed knowledge about the dynamics of these systems, that in combination with knowledge about structure and quantum chemistry yield new valuable knowledge of the function of many molecular systems and processes. It can be predicted that this development has just started and in the near future new and improved methods will be available that make it possible to study so far inaccessible molecular processes and phenomena.