Direct determination of the excited state energies of the xanthophylls diadinoxanthin and diatoxanthin from Phaeodactylum tricornutum

Steady-state and femtosecond time-resolved transient absorption spectra of diadinoxanthin and diatoxanthin were measured in the visible and near-infrared (NIR) regions at 293 K. The difference in energy between the visible S0 → S2 transitions from the steady-state absorption measurements and the S1 → S2 transitions observed in the transient absorption spectra in the NIR region yields precise values of the S1 energies. The data are important for evaluating the mechanism by which excess energy is dissipated by algal systems that interconvert these xanthophylls in response to changes in photon flux levels in the marine environment.