Do you know what an electron looks like? You can forget the usual image of a miniscule spherical particle which orbits around an atomic nucleus. In quantum physics, the electron is both a particle and a wave similar to those produced on the surface of a liquid when a drop of water comes into contact with it. Such waves are extremely small and fast and thus difficult to observe which has led researchers to develop a technique inspired by the cinema to film them.

Before we solve the mysteries of electrons, we should first consider the cinema. Around 120 years ago in the very centre of Lyon in a street in the Monplaisir neighbourhood, the Lumiere brothers, Auguste and Louis, made the first film in the history of cinema. The principle is simple - staying with our example involving a drop of water, a high-speed camera can take successive images of its fall, the instant it comes into contact with the surface of the liquid and the movement of the water as the wave ripples outwards. Once put together, the successive snapshots give an overall view of the whole action.

With cinema cameras, a shutter which opens and closes to let light in 24 times per second is sufficient but this is not the case if the aim is to observe an electron's movement on the scale of the attosecond (1 billionth of a billionth of a second). At such a small scale, matter is made up of particles which move at extremely high speeds. Scientists therefore use an alternative method based on laser flashes. The first starts up the mechanism, the second "lights" the subject and photographs it. This operation is repeated several times with increasingly long pauses between the two pulses to obtain a film. This process has made it possible to photograph electrons and find out that they do not in fact orbit around the atom's nucleus. They can also remain immobile or start moving on attosecond time scales.

This research has a dual objective. It firstly aims to develop a technique capable of filming electrons and secondly the goal is to find out more about their nature and behaviour. The overall objective is to develop new applications particularly in the fields of chemistry or electronics such as optimizing certain equipment by replacing the diodes involved with molecular or atomic components.

Thanks to Franck Lépine for his contribution.