Universal exciton size scaling in pi conjugated systems

The excited state properties of many oligomers or polymers are of particula r importance as they are directly related to light absorption and emission as well as to photoconductivity, which govern most of their potential appli cations. Oligomers with a finite, well-defined chain length can serve as mo del systems for the investigation of general and fundamental properties of the whole material class. We show that the primary gap excitations in a num ber of such model systems are essentially delocalized over the entire molec ules. The extension of the corresponding exciton scales with the molecule l ength only and is fully independent of the details of the corresponding mol ecular structure. (C) 2000 Elsevier Science B.V. All rights reserved.