Abstract
The valence pi->pi* excited states of anthracene and naphthacene are studied with multireference perturbation theory with complete active space self-consistent field reference functions. The predicted spectra provide a consistent assignment of all one- and two-photon spectral and T-T spectra of low-lying valence pi->pi* excited states of anthracene and naphthacene. The present theory predicts the valence pi->pi* excitation energies with an accuracy of 0.15 eV for anthracene and of 0.25 eV or better for naphthacene. The excited states of anthracene and naphthacene are compared with those of previously studied benzene and naphthalene. The present calculations predict that, going from anthracene to naphthacene, there is a symmetry reversal of the two lowest singlet state transitions, but none for triplet, just as indicated by the experimental data. Some general trends of polyacene excited states are discussed based on the calculated results of benzene through naphthacene. Conclusive results obtained for anthracene and naphthacene can be used as a model for understanding the feature of excited states of other larger polyacenes.