Naphthalene dimer: Electronic states, excimers, and triplet decay

Computations have been performed for the singlet and triplet electronic sta tes of varying orientations of naphthalene dimer. The dependence of exciton splitting upon orientation and intermonomer distance was explored. Splitti ngs of triplet states are seen to be nontrivial at typical bonding distance s, commensurate with the splittings of weakly allowed singlet states. Charg e-transfer interaction with the excimer states is seen to be most significa nt in face-to-face orientations which can allow closer approach of the two monomers. Predictions of the prominent features of the singlet-singlet and triplet-triplet absorption spectra agree well with experimental findings. A spin-orbit channel-counting scheme is introduced to account for observed r adiative and nonradiative decay of the T-1 triplet state of the monomer, an d then applied to the dimer. The mechanism has been found for the observed more rapid phosphorescence of the T-1 state of the dimer when placed in ori entations lacking inversion symmetry. (C) 2000 American Institute of Physic s. [S0021-9606(00)00244-0].