Vibronic Excitons in Anthracene as Investigated by Thermoreflectance Spectra

Abstract

Thermoreflectance spectra are measured for the vibronic bands of the lowest singlet exciton in anthracene at 10 K. Spectral features due to the 0–0 excitons, vibrons and the multi-particle band edges are interpreted in terms of a classical oscillator model. The characteristic profile of the two-particle absorption band associated with the 390 cm⁻¹ intramolecular vibration is compared with a model calculation by the dynamical coherent potential approximation model. It is concluded that the density of states curve for the exciton has a strong one-dimensional character near the lower band edge, but at higher energies it is of three-dimensional character having a large density of states near the upper edge.