One photon can trigger many reactions

A single photon can set off several molecules and dodge the second law of photochemistry.

A single photon can potentially trigger a chemical reaction involving several molecules, overcoming the second law of photochemistry. When light triggers chemical reactions, as in photosynthesis or vision, the second law holds that each photon reacts with only one molecule — although there are exceptions.

Javier Galego, Francisco Garcia-Vidal and Johannes Feist at the Autonomous University of Madrid reports a new breach of the rule, when the light exists as a standing wave contained by mirrors. They suggest that as light resonates in this optical cavity, it could trigger reactions with all of the molecules there. This would allow a single photon to interact with many molecules at the same time, inducing all of them to release stored energy. If proved experimentally, the principle could be used to develop ways to store and release solar energy, the authors say.