Zero-Phonon Lines Associated with Self-Trapped Exciton States and Exciton Dynamics in β-Perylene

Abstract

Low temperature luminescence and absorption spectra in β-perylene crystals are investigated. Zero-phonon transitions in which self-trapped exciton states participate in as the initial or final state are found below 30 K. The self-trap depth for the shallower self-trapped exciton state is found to be 95 cm⁻¹ and for the deeper self-trapped exciton state 187 cm⁻¹. Lattice configurations for self-trapped states are suggested to be one-center type for the deeper self-trapped exciton state and two-center type for the shallower self-trapped exciton state. Based on the discussion about the intensities of zero-phonon lines, it is suggested that phonons of the energies of 13.3 cm⁻¹ are taking part in relaxating free excitons into the shallower self-trapped excitons and 22 cm⁻¹ into the deeper self-trapped excitons.