Optical study of anthracene molecules doped in fluorene single crystals

Properties of two luminescence centers, which are observed in anthracene-doped fluorene crystal as concentration increases, have been investigated to clarify their origin. Excitation spectra and concentration dependence of absorption spectra were measured and two types of luminescence are attributed to anthracene molecule pair centers with weak and strong interaction. Dipole-dipole interactions between two anthracence molecules of various configurations are estimated and possible configuration for two types of luminescence is proposed.