采用时间分辨瞬态吸收光谱技术研究了假根羽藻外周天线寡聚体的光保护机制.分别以667 nm飞秒激光脉冲和白光脉冲作为泵浦光和探测光,探测光与泵浦光之间的延时范围和准确度分别为340 ps和134 fs.实验结果表明在泵浦光激发之后外周天线对探测光的吸收是动态变化的.对瞬态吸收光谱进行多指数拟合, 并结合外周天线的荧光发射谱和激发谱进行分析, 结果表明: 500~600 nm的瞬态吸收谱主要来源于类胡萝卜素分子, 外周天线寡聚体至少包含四种具有光保护作用的类胡萝卜素分子, 对应的S0→Sn跃迁光谱为511 nm和554 nm, 522 nm和541 nm, 530 nm和563 nm(对应管藻黄素), 536 nm和575 nm；类胡萝卜素分子以两种方式参与到光保护过程中: 一种是直接方式, 在几皮秒范围内猝灭叶绿素三重态；另一种是间接方式, 在几百皮秒范围内猝灭从叶绿素分子获得能量的单线态氧.

A time resolved transient absorption spectroscopy was performed to investigate the photoprotection mechanism in light harvesting complex II of broypsis corticulans. A 667 nm femotosenond laser and white light pulse were used as pump and probe lights. The range and accuracy of the delay line between probe and pump were 340 ps and 134 fs, respectively. The experiment results show that the absorption of the probe is dynamically changing after pump light exciting. The results of the multi-exponential fitting, fluorescence emission and excitation spectra show that the transient absorption spectra from 500 nm to 600 nm mainly originate from carotenoids and the aggregated light harvesting complex II contains at least four types of carotenoids functioning photoprotection which have S0→Sn transition spectral properties 511 nm and 554 nm, 522 nm and 541 nm, 530 nm and 563 nm (corresponding to siphonaxanthin), 536 nm and 575 nm. Carotenoids play the photoprotection role not only in a direct manner by quenching the triplet state of chlorophyll a in several picoseconds, but also in an indirect manner by quenching the singlet state of oxygen in several hundreds of picoseconds.