Calculation of the Exciton Band Structure of the 3800- and 2500-Å Singlet Transitions of Crystalline Anthracene

The exciton band structure of the 3800- and 2500-Å transitions of anthracene has been calculated in the dipole approximation. It is found that the branches of both transitions are flat for wave vectors k normal to the (001) plane. In other directions considered the exciton energy exhibits dispersion. The calculations also reveal that for all the directions considered the lowest energy of the 2500-Å exciton band is not a k = 0 state.