Davydov Splitting of Excitons in Anthracene Single Crystals in Megagauss Fields

Abstract

Frenkel-type excitons, which are generally observed in molecular solids, have small spacial extension and are highly localized within each molecule. Consequently magnetooptical studies of Frenkel excitons are extremely difficult, since very large magnetic fields are required to achieve a significant perturbation of the exciton wavefunction. Anthracene (C₁₄H₁₀) is one of best studied molecular crystals. The crystal has a monoclinic structure with C_2h ⁵ space group symmetry and contains two molecules in each unit cell; each molecule has an anisotropic optical transition dipole moment. Recent developments in the sample preparation has enabled sufficiently pure and thin single crystals to be grown. This has enabled a study of various interesting phenomena, such as free, self trapped and quasi-free exciton dynamics and their co-existence, particularly by photoluminescence studies in a high pressure cell.