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The nature of the low-lying electronic states in carotenoids has been debatedfor decades. We use excitation-dependent transient absorption spectroscopy andcomparison with published results on \b{eta}-carotene to demonstrate that theso-called S* feature in astaxanthin, echinenone and spheroidenone spectra isdue to an impurity in the sample. Excitation at the absorption band-edgeresults in a transient absorption spectrum dominated by the pure S1photo-induced absorption, with no contribution from impurities (S*). We findthat this S1 absorption resembles the triplet excited-state absorptionspectrum, shifted by ~200meV. To explain this, we suggest that the individualtriplets that make up the dominant triplet-pair (TT) configuration of 2A$_g^-$contribute strongly to the S1 absorption band. Comparison with recentliterature on molecular polycrystalline films which undergo singlet fissionsuggests the shift could be related to the binding energy of the triplet pairstate. These findings have implications for understanding triplet-pair statesin organic semiconductors and the excitation-energy dependence of singletfission in carotenoid aggregates and biological systems.

Band-edge Excitation of Carotenoids Removes S* Revealing Triplet-pair Contributions to the S1 Absorption Spectrum