Chemical reactions are usually described in terms of the movement of nuclei between the potential energy surfaces of ground and excited electronic states. Crossings known as conical intersections permit efficient transitions between the surfaces. It is shown here that ultrafast optical spectroscopy, with sub-20-fs time resolution and spectral coverage from the visible to the near-infrared, can map the isomerization of rhodopsin with sufficient resolution to shown that a conical intersection is important in this crucial event in vision.
- Dario Polli
- Piero Altoè
- Giulio Cerullo
