紫细菌外周捕光天线LH2中的超快光物理

Ultrafast photophysics in light-harvesting complex LH2 from purple bacterium

采用飞秒泵浦-探测技术研究了紫细菌外周捕光天线LH2中的超快光物理过程,在天然LH2中,B800到B850分子之间的能量传递时间在0.65ps左右;在B800主吸收带的兰侧激发时,观察到一个约400fs的超快弛豫过程,可归属于B800分子之间的能量分布过程;在848nm激发时观察到150fs的超快相归属于位于B850的激发能向其近邻分子的离域过程,几个皮秒的快相归属于激发能在次最低激子态和最低激子态间的分布过程.

In this paper, the ultrafast photophysical processes in light-harvesting complex LH2 from purple bacterium were investigated by using femtosecond pump-probe technique. The experimental results indicate that the energy transfer from B800 to B850 takes place with 0.65 ps time constant at room temperature. Under the excitation wavelength at blue side of B800 absorption band, the energy redistribution among B800 with 0.4 ps time constant was observed from the dynamical traces. Upon 848 nm excitation, the obtained ultrafast component with 150 fs was ascribed to the energy relaxation between the adjacent B580 molecules in LH2, and the process with several picoseconds could be assigned to the relaxation from the second lowest excitonic state to the lowest excitonic state of B850.