Lasers are used to see the movement of electrons

Physicists create shorter and shorter light flashes whose duration go below 10-18 s. These flashes are produced by exciting atoms or molecules with laser impulses whose duration is 1000 times as long as the flash obtained. A model has been proposed to describe the process: when the laser impulse reaches its crest, an electron is drawn away from the excited atom. This electron is accelerated then it comes back toward the atom and it collides with it releasing energy under the form of a series of electromagnetic waves whose frequency is a multiple of the frequency of the initial wave that exited the atom. These flashes are used to see the movement of electrons in atoms and molecules and the flashes begin to be short enough to see ultra-fast dynamics occurring in interactions between electrons or in the ionization process. (A.C.)