6.2 μm band of astronomical features (top panel) of the NGC 1333 svs 3 (A-class PAH), HD 44179 (B-class PAH), and DH 100764 (C-class PAH), and that of the experimental spectra of both non-processed (middle panel) and UV-processed (bottom panel) HACs. The hatched regions in the top panel are peaks of the B- and C-classes while in the middle and the bottom they are the corresponding peaks from the laboratory data. The vertical lines represent the band positions of the C=C structure at 6.21, 6.27 and 6.3 μm of the interstellar spectra of A-, B- and C-classes PAHs, respectively.