Radical cations, dications and oxidized intermediate species of three carotenoids, namely, β-carotene,
lycopene and norbixin, were generated in CH2Cl2 solutions via chemical oxidation using anhydrous
FeCl3. UV–vis, fluorescence and fluorescence-excitation spectroscopic studies were performed to
understand and compare the nature of intermediate species generated during the chemical oxidation
process and subsequent degradation. The intense emission observed at 550 nm can be assigned to the
S2- S0 (1 1Bu- 1 1Ag) transition of the carotenoid molecules. The 350 nm excitation during the oxidation
process for β-carotene, lycopene and norbixin exhibit intense fluorescence peaks at 492 nm, 493 nm and
500 nm, respectively. These peaks are assigned to intermediate peroxy/epoxy compounds of the three
molecules that are formed with molecular oxygen prior to the formation of oxidized short-chain stable
compounds.