Spectra of a selected set of conjugated cyclic and aromatic molecules. Upper panel: Conjugated, non-planar molecules 1,3-cyclohexadiene (blue), 1,4-cyclohexadiene (violet), and cyclooctatetraene (green; see also Fig. 3). Lower panel: planar, aromatic molecules naphthalene (green), pyrene (rose), anthracene (cobalt), and phenanthrene (blue). The black lines are the normalised spectra of the blended sub-components in the relative fractions $\frac{1}{2},\frac{1}{4},\frac{1}{4}$ (upper) and $\frac{1}{6},\frac{1}{3},\frac{1}{6},\frac{1}{3}$ (lower). The yellow and grey boxes give the usual ranges for the functional groups: aromatic and olefinic CH, olefinic cis^H C=C <^H, the aliphatic CH₂ symmetric and antisymmetric modes, and tertiary (3°) aliphatic CH.