Ultrafast X-rays capture atomic movements in light-activated catalyst molecules

Catalysts facilitate crucial chemical reactions in nature and industry alike. In a subset of them, catalytic activity is triggered by light. For example, when iron pentacarbonyl—a molecule in which a central iron atom is surrounded by five carbon monoxide groups—is exposed to light, the iron sheds its carbon monoxide groups one after another, creating spots for other molecules to dock onto during a catalytic reaction.