Calculation of the Davydov splitting in pyrene crystal

Abstract

We have calculated the intensities of the transition to the two optically accessible triplet exciton states of a pyrene crystal using the Hochstrasser procedure. Using the charge-transfer contribution and taking into consideration non-orthogonality between molecular π orbitals belonging to different neighbour molecules together with multicentre integrals calculation we calculate a Davydov splitting value of approximately + 1.8 cm −1 which compares reasonably with the + 2.4 cm −1 reported by Arnold et al. The charge-transfer contribution is shown to be largely predominant. Diffusion tensor anisotropy in a simple isotropic scattering time approximation is given which shows the two dimensional structure of the pyrene crystal for the diffusion of triplets.