An ultrashort history of ultrafast imaging

Investigating ultrafast processes is challenging. There simply are no cameras that would be fast enough to image a molecule in motion, so we need to rely on indirect measurements, for example by ultrashort light pulses. Such ultrashort pulses have been developed for several years and are widely applied in the study of ultrafast processes by, e.g., spectroscopy and diffraction. Depending on the specific needs of the investigation, they can be generated either in the laboratory or at the most powerful light sources that exist today, the x-ray free-electron lasers. With ultrafast movies, a second idea comes into play: once we understand the dynamics of matter on the femtosecond time scale, we can use this knowledge to control ultrafast motion with tailored light pulses. This is promising as a means to trigger reactions that are otherwise not accessible. In my talk, I will give a brief introduction to the rapidly developing field of ultrafast science. I will summarize main findings, imaging techniques and the generation of ultrashort pulses, both at lab-based light sources and large free-electron laser facilities. Finally, I will give an outlook on controlling ultrafast dynamics with light pulses, with the future goal of hacking chemical reactions.