Femtosecond time resolved molecular dynamics of a polydiacetylene backbone

We report the observation of the molecular motion corresponding to the CC stretching vibrations along the backbone of a polydiacetylene, using time resolved pump-probe spectroscopy with 9 fs optical pulses. The associated wavepacket oscillates with 23 fs period before it is damped on the excited state potential. Detailed features of the wavepacket motion are observed like a π dephasing in the spectral region of induced absorption to higher excited states.