Spectra of dimers of anthracene and its derivatives. II. Stable dimers

Abstract

Stable dimers are formed by controlled softening of glasses at low temperature. The spectra of dimers of anthracene and 9,10- dichloroanthracene have been studied in detail. Polarized excitation spectra of the polarized fluorescence of the anthracene dimer show the presence of two oppositely polarized components in the absorption spectrum. An estimate of about 700 cm^-1 for the excitation exchange matrix element follows from these results. Hyperchromism is explained by configuration interaction with a second ¹B_2u state near 44000 cm^-1. This configuration mixing leads to hypochromism for the sandwich dimer. The ¹B_3u, state of anthracene near 40000 cm^-1 appears as a broad band in the dimer with a maximum at 49600 cm^-1. Neither delayed fluorescence nor phosphorescence can be observed for the stable dimers of anthracene and 9,10-dichloroanthracene.