【摘要】 利用飞秒抽运 探测技术及时间分辨荧光 (TRPL)等光谱技术对高等植物LHCⅡ中的超快光动力学过程进行了研究。在其时间分辨荧光光谱中表现出了明显的各向异性特性。实验上观察了LHCⅡ中色素间的能量传递过程 ,由飞秒动力学发现 ,单体内Chlb到邻近的Chla之间的能量传递在 2 0 0～ 30 0fs的时间尺度 ,Chla激子带间的能量弛豫发生在几百飞秒 ,不同单体Chla分子间能量分布过程在几个皮秒。而时间分辨荧光和飞秒动力学过程中上百皮秒的慢过程归属于不同聚集体间的能量平衡过程或分子构象变化更多还原

【Abstract】 The determination of the structure of light harvesting complex Ⅱ and the development of ultrafast technique provide us the possibility to investigate the mechanisms in primary process of photosynthesis. Femtosecond (fs) pump probe technique at different wavelengths and time resolved photoluminescence technique (TRPL) were used to study photoinduced ultrafast dynamics processes in the LHCⅡisolated from the leaf of soybean. A mode locked Nd∶YAG laser served as the excitation source in the TRPL measurements, and the excitation wavelength could be tuned from 570 nm to 610 nm with 10 ps pulse duration. The anisotropic dynamics were observed from TRPL spectra of LHCⅡ at different temperature, indicating that the energy transfer among pigments is affected by temperature. In the femtosecond pump probe measurements, Ti∶sapphire laser and an optical parametric amplifier (OPA)were used as excitation source to generate tunable infrared laser pulses at wavelength from 1.1 μm to 1.4 μm. By using a YCOB crystal, second harmonic beam at visible light was obtained to be applied as the laser source in our measurements, which could be tuned from 550 nm to 700 nm with 150 fs pulse duration and 1 kHz repetition rate. From the femtosecond dynamical results, it could be observed the energy transfer processes between Chl a Chl b and Chl a Chl a pigments at different sites. The dynamical traces demonstrated that the energy relaxation from Chl b to its neighboring Chl a takes place in 200～300 fs time region, the excitation relaxation between the excitonic states of Chl a in several hundreds of femtoseconds, and the energy equilibrium process of intermolecular of Chl a in several picoseconds. The observed slower decay component with the time constant up to hundred picoseconds from time resolved fluorescence and femtosecond dynamics traces could be assigned to the change of molecular conformation or energy equilibrium in LHCⅡ. These results have some significance in understanding the photophysical and photochemical mechanism in primary process of photosynthesis.更多还原