From abstract: "The electronic spectra arising from the excitations of pi-electrons in homo-nuclear conjugated bond systems are calculated for 37 aromatic hydrocarbons. The theoretical approach used takes into account overlap effects between different a atoms, correlation between different electrons, variations in internuclear distances, and the influence of non-conjugated neighbors, hydrogen and carbon. Four types of approximations are carried trough for the molecules in order to obtain an estimate of the inadequacies of the theory. From the calculated transition energies and oscillator strengths, theoretical spectra are synthesized and compared with observed spectra. In order to help the interpretation, a decomposition of the transition dipoles into atomic contributions is introduced. The spectra of alternant molecules are succesfully predicted, but the limits of the underlying assumptions appear to be exceeded in the applications to non-alternant systems. The calculations are markedly successful for the peri-condensed systems, which had presented an obstacle to previous treatments. It is found that the calculated spectra are fairly sensitive to small variations in interatomic distances. calculations with exact atomic positions, where available, give considerably better agreement with experimental spectra. The calculations lead to an understanding of the general spectral pattern found in all aromatic hydrocarbons. On this basis the …