title: Ultrafast relaxation in quasi-one-dimensional organic molecular crystals.
abstract: We present a comprehensive study of ultrafast relaxation properties of optical excitations in thin films of quasi-1D stacked organic materials PTCDA (3,4,9,10-perylenetetracarboxylic dianhydride) and MePTCDI (N,N'-dimethylperylene-3,4,9,10-dicarboximide) over five decades of time. Pump-probe experiments reveal excitonic intraband relaxation time constants of 65 fs for MePTCDI and 100 fs for PTCDA. The initial time-resolved luminescence anisotropy is consistent with the exciton model of Davydov-split states. The subsequent decay of the anisotropy can be explained with a thermally activated exciton hopping process. A full understanding of the pump-probe experiments calls for an explanation beyond the models presently available.
authors.affiliation: Institut für Angewandte Photophysik, Technische Universität Dresden, D-01062 Dresden, Germany.
authors.forename: E
authors.initials: E
authors.lastname: Engel
authors.forename: M
authors.initials: M
authors.lastname: Koschorreck
authors.forename: K
authors.initials: K
authors.lastname: Leo
authors.forename: M
authors.initials: M
authors.lastname: Hoffmann