They have managed to timing the emission of electrons

2017/09/21 Elhuyar Zientzia Iturria: Elhuyar aldizkaria

• Fisika

Physicists from the DIPC and UPV-EHU, together with scientists from several German universities, investigated what happens in the photoelectric effect in the first attoseconds. For the first time they have timed exhaustively the emission of electrons and have seen that electrons with more energy are not the first to arrive.

His work has been published in the journal Science and explained the technique used, using the sophisticated pulses of light lasers. The proper combination of these pulses allows measuring the time it takes an electron to leave a material, after being excited by a photon in the photoelectric effect. In these measures, in addition, electrons coming from different atoms and those coming from different quantum states can be distinguished, as if they were different streets of a speed race. The most surprising thing was to verify that the electrons of higher energy reached the detector in the last place.

The explanation of this unexpected behavior was due to the complex numerical calculations performed by the team of researchers of San Sebastian, led by Pedro Miguel Etxenike and Andrey Kazansky. According to these calculations, at the time of starting the “race”, each electron had to overcome an energy barrier – centrifugal barrier – specific to each quantum state. Interestingly, the "fastest" electrons met the highest energy barriers. These electrons could not overcome the barriers in the first, so they remained trapped for some time around the atomic nuclei before the escape occurred. That is, as a race full of obstacles in which the barriers of the fastest electrons would have higher height.

Researchers from DIPC and UPV have affirmed that these leading experimental teams lead us to a new frontier of physics: the world of attoseconds, trilions of a second. In recent years, much progress has been made in the miniaturization of the technological components and, in addition to their size, supporters have shown to deepen the phenomena that appear when reducing time. Attoseconds are extremely short time periods, but these intervals mark the speed limit for future electronic processes. The technological advances in this field will depend on our ability to analyze the phenomena that occur in these time scales and control the transport of electrons in different devices with the accuracy of the attoseconds.