THE DETERMINATION OF THE TRIPLET EXCITON BAND STRUCTURE.
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Publisher:Ohio State University
Previously, the full width and structure of triplet exciton bands in organic molecular crystals have eluded direct experimental observation because of the symmetry restriction for electric dipole transitions to $K \neq 0$ states. Crystals, in which interactions between translationally inequivalent sites are small, may be treated as one dimensional linear chains. By substituting appropriate impurity molecules into the chain, polymers of various lengths are isolated. The optically allowed energy levels of each N-Mer fall within the bandwidth of the neat crystal. Because the triplet state is being observed, a nearest neighbor approximation to the interaction energy is valid; the exchange energy, density of states, and exciton bandwidth are then experimentally measurable. Spectral results will be presented from which these quantities may be directly obtained. This new technique readily provides the interaction between translationally equivalent molecules which in the usual case just contributes to the spectral shift.
Author Institution: Laboratory for Research on The Structure of Matter, University of Pennsylvania