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S C HW E R P U N K T 21 04 | LICHT GEDANKEN Contact Junior Professor Dr Birgitta Bernhardt Institute of Applied Physics Albert-Einstein-Straße 6, D-07745 Jena, Germany Phone: +49 36 41 9-47 818 Email: Birgitta.Bernhardt@uni-jena.de www.iap.uni-jena.de Original Publication Ultrafast Quantum Control of Ionization Dy- namics in Krypton. Nature Communications (2018), DOI: 10.1038/s41467-018-03122-1 only last a few femto- or attoseconds (a quintillionth of a second). It is such an inconceivably short space of time that physicists often make this striking com- parison: one attosecond is to a second what a second is to the age of the uni- verse—and that is almost fourteen bil- lion years old. Molecule cinema: 300 femtoseconds are turned into 35 minutes The team of scientists working with the 37-year-old physicist from the Institute of Applied Physics and colleagues from the Technical University of Munich has now succeeded in making it possible to watch ultrafast ionization processes in a level of detail that has previously been unheard of. As they write in the renowned specialist journal Nature Communications , the researchers use the so-called pump-probe spectroscopy and do so twice over. This method sees the sample—in this case the noble »If we can simulate and even influence rapid ionization processes, we can learn a lot about light-controlled processes like photosynthesis—including about those first moments when this complex machinery bursts into action; things that there has been little understanding of to date.« Controlling the ionization of silicon facilitates the production of better computer chips The technology developed by Bernhardt and her colleagues is also of interest for the development of new, faster com- puter chips, for which the ionization of silicon plays a key role. If you cannot just prompt but also control the ioniza- tion state of silicon within such a short time window—as the first experiments with krypton suggest—then scientists will possibly be able to use this tech- nique to develop innovative and even faster computer technologies. gas krypton—be stimulated by an ul- tra-short laser pulse to stimulate the ionization process. A second, time- delayed laser pulse detects the status of the process. »In this way we can measure the change to the absorption and the ion formation in the noble gas in relation to the time delay of this second pulse«, explains Bernhardt. Repeating the measurement with different time delays results in lots of individual snapshots, which are put together to create one single video. The researchers have put together 70 of such snapshots by recording a video sequence of around 35 minutes, which covers a period of just 300 femtoseconds of the actual chemical process By combining the two measuring tech- niques, the scientists can record more than just ultra-fast ionization processes: by varying the intensity of the second, interrogating laser pulse, the ionization dynamics can also be controlled and in- fluenced. »This control represents a very strong instrument«, explains Bernhardt. Image left shows one of the three vacuum chambers at the TU Munich, in which the iso­ lated attosecond flashes of light are generated. Image right: Junior Professor Dr Birgitta Bernhardt in her Jena laboratory at the Institute of Applied Physics. F E AT U R E