To unlock materials of the future, including better photocatalysts or light-switchable superconductors, researchers need to understand how the valence electrons within materials respond to light at the atomic scale. Materials are made of atoms, and an atom’s outer electrons, or valence electrons, are responsible for chemical bonding as well as a material’s thermal, magnetic, and electronic properties.

But imaging valence electrons in bulk materials is extremely difficult because valence electrons are only a small subset of a typically large pool of electrons.

Now, researchers at the Department of Energy’s SLAC National Accelerator Laboratory have refined a way to track valence electrons using a unique method that shines both X-rays and lasers onto a material, then tracks the frequency generated by both sources. The method allows the researchers to understand more about extremely fast-moving valence electrons, including the symmetry of their local environment.