Lichtgedanken 04

S C HW E R P U N K T 20 Green plants, algae and bacteria use light energy to convert carbon dioxide into high-energy biomolecules and oxy- gen. This process has been known as photosynthesis for over 200 years and has been the subject of extensive re- search: the starting materials, reaction and intermediate products have been Many chemical processes occur so quickly that, until now, we only had an approximate idea of what is going on. The available methods to analyse them are simply too slow to capture the decisive ultra-short moments. A team of physicists from Munich and Jena has now succeeded in combining two different spectroscopic techniques to visualize a key part of chemical processes, the ionization of atoms, to the degree of several quintillionth of a second (attosecond) and control it on the quadriollionth time scale (femtoseconds). This pump-probe spectroscopy produces snapshots, which can be put together to create a film in super-slow motion. The new technology is intended to help provide a better understanding of processes such as photo­ synthesis and to develop faster computer chips. Chemical reactions in super-slow motion BY ANJA WAGNER clarified, as has the chronology of the chemical reactions. However, little is known about the ele- mentary processes, which take place in the molecules within the plant cells that are involved in the photosynthesis. »We know that during photosynthesis, and during numerous other photochemi­ cal reactions, atoms or molecules are ionized«, reports Junior Professor Dr Birgitta Bernhardt. »Yet it has not yet been possible to fully track the process of the ionization reactions.« The reason: these reactions, which see electrons be- ing pulled out of atoms or molecules, can take place extremely quickly. They