Theory of the exciton states of molecular crystals

A new approach to the analysis of the electronic absorption spectra of molecular crystals has been presented. It is analogous to the calculation of the π-electron spectra of molecules and has been applied to the analysis of the spectrum of crystalline anthracene. According to this calculation, several complicated absorption features observed by Lyons and Morris in the shorter ultra-violet region are reasonably assigned to the mixed states composed of the B 1u +, B 2u +, B 1u + and B 1u + excited configurations of anthracene molecular orbitals. In addition, it is shown that crystal-field mixing between exciton configurations has a large effect on the state energies and oscillator strengths.