Photoexcited breathers in conjugated polyenes: An excited-state molecular dynamics study

S. Tretiak, A. Saxena, R. L. Martin, A. R. Bishop

Research output: Contribution to journalArticlepeer-review

73 Citations (Scopus)

Abstract

π-conjugated polymers have become an important class of materials for electronic devices. Design of these devices requires understanding such processes as photochemical reactions, spatial dynamics of photoexcitations, and energy and charge transport, which in turn involve complex coupled electron-vibrational dynamics. Here we study nonlinear photoexcitation dynamics in the polyene oligomers by using a quantum-chemical method suitable for the simulation of excited-state molecular dynamics in extended molecular systems with sizes up to hundreds of atoms. The method is based on the adiabatic propagation of the ground-state and transition single-electron density matrices along the trajectory. The simulations reveal formation of a self-localized vibronic excitation ("breather" or multiquanta bound state) with a typical period of 34 fs and allows us to identify specific slow and fast nuclear motions strongly coupled to the electronic degrees of freedom. The effect of chain imperfections and chemical defects on the dynamics is also investigated. A complementary two-dimensional analysis of corresponding transition density matrices provides an efficient way to monitor time-dependent real-space localization of the photoexcitation by identifying the underlying changes in charge densities and bond orders. Possible correlated electronic and vibrational spectroscopic signatures of photoexcited breathers are predicted, and generalizations to energy localization in complex macromolecules are discussed.

Original languageEnglish
Pages (from-to)2185-2190
Number of pages6
JournalProceedings of the National Academy of Sciences of the United States of America
Volume100
Issue number5
DOIs
Publication statusPublished - 4 Mar 2003
Externally publishedYes

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