The spectra at ∼300 K are shown in Fig. . The spectra are broader in comparison to those for the model geometries in Fig. due to nuclear motion. The tetramer absorption band with a peak at 4.34 eV is blue-shifted by ∼0.17 eV with respect to the monomer absorption maximum located at 4.17 eV. The maximum tetramer absorbance is ∼3.5 times larger than the maximum monomer absorbance. Apart from the intense blue-shifted band, the tetramer spectrum exhibits a tail extending in the red direction, up to ∼3.3 eV. This demonstrates that the spectrum of the H-aggregate is more complex than merely a blueshifted absorption band, and that the aggregate may be excited not only at energies above the monomer absorption, but also below it.