AbstractThe location of the carotenoid 2Ag‐state (S1) was studied by fluorescence spectroscopy in two series of carotenoids. One consisted of natural polyenes like phytoene, phytofluene, β‐carotene, and neurosporene, and the other of minicarotenes,i.e.,compounds similar to β‐carotene, but with a smaller number of double bonds(n=3–9). A decrease of the S1‐S0energy gap withnwas observed in both series, and extrapolation ton= 11 gave the energies 14 500 and 13 200 cm−1for β‐carotene and lycopene, respectively. The neurosporene S1state was located atca16 000 cm−1. A good relationship between the nonradiative relaxation rate and the number of conjugation was observed. The rate increased by a factor of 2.5 per double bond. The possible role of the S1state in reversible carotenoid ← chlorophyll electron‐exchange energy