Physicists at Friedrich-Alexander-Universität Erlangen-Nürnberg (FAU) have designed a framework that allows scientists to observe interactions between light and electrons using a conventional scanning electron microscope. This procedure is much cheaper than the technique used so far and also allows for a wider range of experiments. The researchers published their findings in the journal physical examination letters.
A quantum computer is just one example of the importance of understanding the fundamental processes behind the interactions between photons and electrons. In combination with ultrashort laser pulses, it is possible to measure how photons change the energy and velocity of electrons. This photon-induced electron microscope (PINEM) has so far relied entirely on transmission electron microscopy (TEM). Although these have the accuracy needed to locate individual atoms, they are much more expensive than scanning electron microscopes (SEM), and the sample chamber is extremely small, only a few cubic millimeters.
Measure differences down to a few hundredths of a thousandths of a whole
Researchers from Professor Peter Hummelhof’s Head of Laser Physics have now succeeded in modifying a conventional SEM to perform PINEM experiments. They designed a special spectrometer based on magnetic forces embedded directly in the microscope. The basic principle is that the magnetic field deflects the electrons somewhat depending on their speed. Using a detector that converts the collision of the electron into light, an accurate reading of this deflection is given. This method allows researchers to measure even the smallest changes in energy, down to differences of a few hundred thousandths of the original value – enough to discern a single quantum contribution of light energy – a photon.
A wide range of possible future experiences
The Erlangen physicists’ discovery is groundbreaking in more ways than one. From a financial point of view, the ability to search for photon-electron interactions without using a TEM, which costs several million euros, could make the search much easier. In addition, because the SEM chamber typically has a volume of up to 20 cc, it is now possible to perform a larger range of experiments, where additional optical and electronic components such as lenses, prisms and mirrors can be placed directly next to the samples. . The researchers anticipate that within a few years, the entire field of microscopic quantum experiments will move from TEM to SEM.
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