Absorption spectra, carotenoid aggregates

Besides the main band, H-aggregates also exhibit weaker bands in the red part of the absorption spectrum (marked by in Figure 8.5). Although in some cases the position of these bands coincides with the vibrational bands of the monomeric carotenoid and can be therefore assigned to nonaggregated carotenoid molecules, certain spectral features do not match the vibrational bands... 

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