title: Coherent external and internal phonons in quasi-one-dimensional organic molecular crystals.
abstract: 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.
authors.affiliation: Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden, Germany.
authors.forename: T
authors.initials: T
authors.lastname: Hasche
authors.forename: T W
authors.initials: TW
authors.lastname: Canzler
authors.forename: R
authors.initials: R
authors.lastname: Scholz
authors.forename: M
authors.initials: M
authors.lastname: Hoffmann
authors.forename: K
authors.initials: K
authors.lastname: Schmidt
authors.forename: T
authors.initials: T
authors.lastname: Frauenheim
authors.forename: K
authors.initials: K
authors.lastname: Leo