Spectrally Resolved Femtosecond Nonlinear Spectroscopy for the Study of Vibrational Dynamics of Carotenoid Light Harvesting Molecules

摘要

In photosynthesis, carotenoid (Car) molecules play a number of roles:(1) light harvesting via singlet-state energy transfer to Bacteriochlorophyll, (2)photon protection via the quenching of the chlorophyll singlet state, and (3)scavenging of singlet oxygen. In the antenna complexes of photosynthesis, Car molecules absorb the photon energy and transfer it with high efficiency (up to100% Ill) to a photochemical reaction center where a light-induced electron-transfer reaction takes place. Because of the C2h symmetry of the molecular structures the ground state of Car molecules is the I As- state, and the lowest optically allowed singlet state is the 1B:. Two or three other optically forbidden states, e.g. 3Ag", 1B.", 2A5", exist below the 1B: state 2,3 depending on the length of the molecular chain.