Coherent external and internal phonons in quasi-one-dimensional organic molecular crystals.
We have directly time resolved coherent phonon oscillations in quasi-one-dimensional organic crystals of MePTCDI ( N-N'-dimethylperylene-3,4,9,10-dicarboximide), using femtosecond pump-probe experiments. We observe both higher-energy oscillations caused by intramolecular vibrations (internal phonons) and, for the first time in a quasi-one-dimensional organic system, lower-energy modulations which are related to coherent lattice phonons (external phonons). For internal A(g) vibrations, the coherence decay time of about 2 ps is almost independent of the mode. In contrast, the damping time of the external phonons increases strongly with decreasing energy.
Hasche
T
T
Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden, Germany.
Canzler
T W
TW
Scholz
R
R
Hoffmann
M
M
Schmidt
K
K
Frauenheim
T
T
Leo
K
K