Transient absorption study of peridinin and peridinin-chlorophyll a-protein after two-photon excitation

lTwo-photon excited pump-probe spectroscopy was carried out on the peridinin-chlorophyll a-protein complex (PCP) and on the peridinin molecule in methanol solution. Our data are consistent with earlier two-photon fluorescence excitation spectral(1.2) and lead to the conclusion that, for peridinin in methanol solution, a separate two-photon-allowed transition exists just to the red of the strongly allowed S-0 - S-2(B-u(+)) band. In the PCP complex, two-photon excitation at 1150 nm can also be interpreted as preparing a new state. In both cases, the new state is most likely the S-1(Ag-) state. It is not yet possible to conclude experimentally whether peridinin possesses a single low lying state with solvent dependent properties or two distinct states, the A(g)(-) and the charge transfer states.