title: Ultrafast exciton relaxation in microcrystalline pentacene films.
abstract: The exciton dynamics in microcrystalline pentacene films is investigated by transient absorption measurements with 30 fs time resolution. It is found that the emission from photoexcited Frenkel excitons decays within 70 fs due to the ultrafast formation of an excitonic species with a strongly reduced transition dipole to the ground state and an absorption dipole in the plane of the film. We propose that an excimer exciton is formed and stabilized by changes of the local crystal structure. The subsequent dynamics is dominated by diffusion controlled annihilation and trapping.
authors.affiliation: Lehrstuhl für BioMolekulare Optik, Physics Department, Ludwig-Maximilians-Universität, Oettingenstr. 67, 80538 München, Germany.
authors.forename: H
authors.initials: H
authors.lastname: Marciniak
authors.forename: M
authors.initials: M
authors.lastname: Fiebig
authors.forename: M
authors.initials: M
authors.lastname: Huth
authors.forename: S
authors.initials: S
authors.lastname: Schiefer
authors.forename: B
authors.initials: B
authors.lastname: Nickel
authors.forename: F
authors.initials: F
authors.lastname: Selmaier
authors.forename: S
authors.initials: S
authors.lastname: Lochbrunner