Collisions transfer coherence

Ultrafast photoexcitation of molecules prepares coherent superpositions of vibrational states, forming wave packets. We show direct experimental evidence that impulsive collisions of photo-fragments with large energy loss generate new coherent superpositions of vibrational states, causing coherence among previously unoccupied states. We demonstrate the effect in the model system of I-2 molecules in Kr solids. This coherence transfer-even in the presence of very strong dissipation-may be used for control strategies in condensed-phase photoreactions.