Spectroscopic studies of the low-lying singlet excited electronic states and photochemical properties of carotenoids

Investigations of the singlet; excited state properties of carotenoids usin g steady-state fluorescence, transient absorption pump-probe, two-photon ex citation, and resonance Raman excitation spectroscopies are described. The application of these experimental techniques to the specific problem of det ermining the S-1 excited energies of carotenoids is discussed in detail, an d the recent literature pertaining to the assignment of charge transfer sta tes in carotenoids and states described as having particular pseudoparity e lements is reviewed. Hypothetical schemes for how these states may account for some of the dynamic and photochemical behavior of carotenoids are prese nted. (C) 2001 Academic Press.