Title: Diagrammatic Exciton Basis Theory of the Photophysics of Pentacene Dimers,
Abstract: Covalently linked acene dimers are of interest as candidates for
intramolecular singlet fission. We report many-electron calculations of the
energies and wavefunctions of the optical singlets, the lowest triplet exciton
and the triplet-triplet biexciton, as well as the final states of excited state
absorptions from these states in a family of phenyl-linked pentacene dimers.
While it is difficult to distinguish between the triplet and the
triplet-triplet from their transient absorptions in the 500-600 nm region, by
comparing theoretical transient absorption spectra against published and
unpublished experimental transient absorptions in the near and mid infrared we
conclude that the end product of photoexcitation in these particular
bipentacenes is the bound triplet-triplet and not free triplets. We predict
additional transient absorptions at even longer wavelengths, beyond 1500 nm, to
the equivalent of the classic 2$^1$A$_g^-$ in linear polyenes.