Theoretical studies of the absorption spectra of polycyclic aromatic hydrocarbons

The UV-visible spectra of graphite-like fragments such as tetracene, anthanthrene, and coronene, as well as their dimers and trimers are examined using the intermediate neglect of differential overlap quantum chemical technique for comparison with the observed interstellar extinction believed to stem from graphite fragments. In general, the calculated results are in good agreement with experiment for the monomeric species which have well characterized spectra. The low-resolution interstellar extinction, however, is reproduced by several of these model systems, and in particular, a superposition of all three monomers as well as the dimers and trimers of this study at their calculated interplanar distances.