Theoretical interpretation of the electroabsorption spectra of polyacene crystals .1. Role of Frenkel states

The recently proposed two-dimensional model of the coupling between the Frenkel and charge transfer (CT) excitations of a molecular crystal, successfully applied for the calculation of the electroabsorption (EA) spectra of polyacenes [Petelenz et al., J. Chem. Phys. 105, 4427 (1996)], is applied to probe the influence of different intramolecular excited states on the EA signal in the CT energy range. The study highlights the preeminent role of Frenkel excitons that are energetically close to the CT manifold, even if they are inactive in conventional absorption spectroscopy. The high-energy intense excitons are found to have a lesser effect. The study suggests EA spectroscopy as a potential tool to detect and locate some of the absorption-inactive intramolecular excitations. (C) 1997 American Institute of Physics.