Local Excitons and Exciton Band Structure in Naphthalene

Positions of the electron levels of the local exciton energy in a naphthalene crystal doped with thionaphthene, indole, and benzofurane are calculated. The guest molecule is assumed to change the excitation energy of one host molecule nearest to the impurity. Also it is considered that the main contribution to the exciton dispersion law comes from the matrix elements of resonance interaction between nearest naphthalene molecules which are in inequivalent positions in the ab plane of the crystal. Good agreement between the theoretical and experimental values favours the validity of the chosen local centre model and exciton dispersion law employed.