The shortest pulses ever created last only 100 attoseconds (10^-16 s), which is the temporal scale of electrons and allows to measure electron motion in atoms and molecules. The project aims at the application of a novel ultrafast photography setup with the highest temporal resolution to film electron motion deep inside xenon atoms or biologically relevant organic compounds after irradiation by extreme-ultraviolet light.
Investigation of nature with high time resolution has essentially broadened our knowledge about fast mechanisms with early examples being the well-known recording of a horse in motion in 1878, the photograph of a supersonic bullet, or later the filming of chemical reactions. This ultrafast photography requires very short light flashes that freeze and capture the motion of the rapidly changing object. The continuous development of corresponding sources of light pulses delivers shorter and shorter duration, which allows the filming of faster and faster processes. At the present state of research, the shortest pulses ever created last only 100 attoseconds (10^-16 s), which is the temporal scale of electrons and allows to measure electron motion in atoms and molecules. Related investigations explored time-resolved outer electron dynamics in matter, studies of tiny time delays in ionization processes, and measurements of rapidly oscillating electric fields in optical pulses. This research is expected to contribute to faster electronics, ability to measure individual processes in atoms and molecules and development of detection techniques with enhanced chemical sensitivity.
The present project aims at the application of a novel ultrafast photography setup with the highest presently possible temporal resolution to study electron motion deep inside atoms. This setup utilizes a special laser (LWS-100 in Umeå) based on the so-called chirped-pulse amplification technique, for which that the Nobel prize 2018 has been awarded. This laser is applied to generate short and intense attosecond pulses in the extreme ultraviolet spectral range that serve to observe and control the electron motion. The first object that we want to film is xenon atom, which possesses many electrons that respond collectively to external influence and thus has a very rich electron dynamics. Utilizing a nonlinear interaction, i.e., absorption of two photons from the short light flash, it will be possible to interrogate and control how the complex electron structure of xenon behaves if a deep lying inner electron is removed. Another important application of our attosecond source is how biologically relevant organic compounds react after irradiation by extreme-ultraviolet light. The irradiation excites or ionizes the molecules and puts them into an unstable state. As the electronic structure reorganizes, charge migration from one part of the molecule to another takes place that we want to film and control. This process is the start of a light/induced chemical reaction and can in principle fundamentally determine how this reaction proceeds. Therefore, by controlling the electron dynamics we might be able to control even these chemical reactions. Furthermore, this project can result in a better understanding and control of fundamental biological processes such as photosynthesis, transport of biological signals or protein folding.