Periodic Reporting for period 1 - ATTOPIE (Attosecond plasmon imaging with electrons)
Período documentado: 2018-03-01 hasta 2020-02-29
Scientific progress has always gone hand in hand with the development of new methods to examine nature ever more closely. Larger and more powerful telescopes are being built in order to be able to look further into space. At the same time, microscopes are improved in the other direction in order to better understand the matter around us and also ourselves. Scanning probe methods and transmission electron microscopy, for example, have made atoms visible, where imaging takes place under largely static conditions. In this way we can explore equilibrium states in detail.
However, if we want to understand how a system changes from one state to another, we are faced with a new problem: the shutter speed. We have to do our recording so quickly that the movement is kind of frozen. The recording must therefore happen much faster than the movement to be examined. This works relatively well when photographing people by choosing a fast shutter speed on the camera. However, the smaller the processes examined, the faster they usually run. When taking a closer look spatially, an ever higher time resolution is required to be able to observe dynamic processes.
Such a time-resolved method has so far been missing on the nanometer scale and below. So far it has not been possible to make small electrical currents such as photosynthesis in plants directly visible and understandable. This project addressed this problem and aimed at implementing a new method to bring today’s best time resolution to the nanoworld.
However, if we want to understand how a system changes from one state to another, we are faced with a new problem: the shutter speed. We have to do our recording so quickly that the movement is kind of frozen. The recording must therefore happen much faster than the movement to be examined. This works relatively well when photographing people by choosing a fast shutter speed on the camera. However, the smaller the processes examined, the faster they usually run. When taking a closer look spatially, an ever higher time resolution is required to be able to observe dynamic processes.
Such a time-resolved method has so far been missing on the nanometer scale and below. So far it has not been possible to make small electrical currents such as photosynthesis in plants directly visible and understandable. This project addressed this problem and aimed at implementing a new method to bring today’s best time resolution to the nanoworld.
Short flashes of light from an advanced laser system were used to extract electrons from different kinds of samples. These flashes of light were only a few 100 attoseconds short and thus made it possible to freeze even the fast movement of electrons. At the same time, a particularly high spatial resolution was achieved by recording the emission location of these electrons with an electron microscope. Being matter waves, electrons also obey Abbe’s diffraction limit, but this is significantly lower than that of the light pulses used. This combined the best of both worlds: short flashes of light for a high temporal resolution and electron microscopy for a high spatial resolution. More specifically, we were able to reach attosecond temporal resolution in a photoemission electron microscope. The publication of this exciting results is currently being prepared.
The experiments with attosecond temporal resolution performed using a photoemission electron microscope advance the state of the art and will renew the interest in this technique.