Coherent phonons in quasi-one-dimensional organic crystals

Coherent phonon oscillations in quasi-1D organic crystals of MePTCDI (N-N′-dimethylperylene-3,4,9,10-dicarboximide) are directly time-resolved by femtosecond pump–probe experiments. We observe both oscillations caused by intra-molecular vibrations (internal phonons) and, for the first time in a quasi-1D organic system, modulations which are related to coherent lattice phonons (external phonons). From the observed phonon coherence of a few picoseconds, we assign the observed phonon oscillations to the electronic ground state potential.