Phonon-Sideband Structures In Absorption And Emission Spectra Of Organic Molecule Oligomers (N=2-6)

Phonon-sideband structures in absorption and emission spectra of oligomers are investigated using a theoretical model: A Frenkel exciton (or molecular excitation) moves among molecules of oligomers with the transfer energy J and interacts with on-site intramolecular vibrations with the Haung-Rhys factor s. The intramolecular vibrations in the oligomers are coupled to each other with the coupling energy D. It is revealed that the absorption and emission spectra depend greatly on whether J is negative or positive. For the positive J case, the emission band splits off from the absorption band. Effects due to the coupling D to the absorption and emission spectra are studied. The molecular number dependence of the oligomers (N = 2-6) on the spectra is studied and the obtained emission spectra are discussed in connection with organic light-emitting substances.