Phys. Rev. Lett. 95, 157403 (2005) [4 pages]Ultrafast Relaxation in Quasi-One-Dimensional Organic Molecular CrystalsReceived 16 July 2004; revised 25 January 2005; published 4 October 2005 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. © 2005 The American Physical Society URL:
http://link.aps.org/doi/10.1103/PhysRevLett.95.157403
DOI:
10.1103/PhysRevLett.95.157403
PACS:
78.55.Kz, 71.35.−y, 78.47.+p
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