Delayed Reikbination Fluorescence and Production of Triplet Charge Transfer and Exciton States in VUV-Excited Molecular Crystals

Abstract

Abstract At sufficiently high excitation energies, the molecular crystals exhibit a new, slowly decaying magnetic field sensitive fluorescent component. The experimentally observed properties of this special luminescence component in anthracene and p-terphenyle are discussed, considering in particular the excitation spectra of the intensity for energies up to 40 eV. According to the characteristic magnetic modulation of the intensity, the light emission follows the recombination of long lived electron-hole pairs created initially in a triplet spin state via a deep valence hole. The nature of the photodynamic processes responsible for such recombination fluorescence precursors is suggested to be connected with the well documented mechanism of photoinduced exciton fission in triplet pair states, which involves intermolecular charge transfer transitions within a pair of neighboring molecules. It is shown that the measured excitation spectra are fairly interpreted on the whole explored energy domain; at the h...