Femtosecond dynamics of ground-state vibrational motion and energy flow: polymers of diacetylene

In this Letter we report femtosecond (fs) dynamics of the ground-state vibrational motions and energy flow in polymers of diacetylene embedded in monomer single crystals at 8 K. The ground-state wavepackets are prepared and probed using fs-CARS methods. The observed coherence of the wavepacket among four vibrational modes, including the Fermi resonance, elucidates the time scales and the selectivity involved. From measurements of the dephasing times we establish the nature of the weak coupling to bath modes. The phase-shifted oscillatory behavior observed in the 3-D images suggests the correspondence with IVR dynamics.