Coherent excited state intramolecular proton transfer probed by time-resolved fluorescence.

An ultra-fast chemical reaction can act as an impulsive excitation of the vibrations. Excited state intramolecular proton transfer in 10-hydroxybenzo[h]quinoline proceeds in 13 fs. As a result, product vibrational modes with their periods longer than (13 x 2) fs are coherently excited in the product potential surface, which can be observed most unambiguously by the oscillations in the time-resolved fluorescence signal of the product keto isomer.