Comparison of optical spectra for the set of 40 PAH molecules investigated by Malloci et al. (2007b). The red curve corresponds to the average spectrum computed at the TD-DFTB (reduced matrix) level using the same procedure as Malloci et al. (2007b), and the FWHM of each individual band is 0.2 eV. The blue curve corresponds to the optical absorption of small PAH grains determined by Cecchi-Pestellini et al. (2008). The black curve corresponds to the average spectrum of the set of 40 PAHs computed by Malloci et al. (2007b) at the TD-LDA level. The red and black curves were normalized as proposed by these authors.