The absorption and fluorescence properties of pyrene crystal: a theoretical approach. I. harmonic approximation

On the basis of the structure of pyrene crystal we argue that excitation in the crystals localized at sites consisting of pairs of close-spaced molecules, i.e., that we are dealing with a Frenkel exciton. We postulate potentials for ground- and excited-state pairs in which both in-plane and out-of-plane vibrations play a role. Using these potentials and selected experimental data we are able to estimate the values of several features of the absorption and fluorescene spectra of, and the energy migration in, cyrstalline pyrene. Agreement with experiment is satisfactory.