Luminescence from anthracene single crystals with photoinduced local centres

Abstract

AbstractA new series in the fluorescence spectra (4.2 K) red‐shifted by 32 cm−1 from bottom of the exciton band is found in anthracene single crystals irradiated by light with λ ≧ 320 nm at temperatures 353 K and higher. The intermolecular frequencies of this series coincide with those in the exciton fluorescence spectrum. The series is ascribed to the local states in an anthracene crystal (the L‐series). From a number of experiments it is concluded that the L‐series arises from the deformation of the lattice due to the formation of dianthracene from a photochemical reaction. The disappearance of the L‐series upon secondary irradiation with λ = 250 nm is believed to be a convincing argument for the above conclusion (dianthracene is known to decompose to anthracene upon irradiation with λ = 250 nm). The temperature dependence of the L‐series intensity is measured; the local centre concentration is estimated.