The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies
The relaxation dynamics of the excited electronic states of retinal in bacteriorhodopsin by two-pump-probe femtosecond studies
复制标题
DOI：
10.1073/pnas.141220198
复制
发表时间：
2001-07-17
影响因子：
11.1
通讯作者：
El-Sayed, MA
中科院分区：
文献类型：
--
作者：
Logunov, SL;Volkov, VV;El-Sayed, MA
我们提出了两个泵浦和探测飞秒实验的结果，旨在遵循不同的模式填充的最低激发态（S-1）的弛豫动力学。在第一种模式中，使用基态的直接（S-0 --> S-1）辐射激发。在第二种模式中，使用间接激发，其中S-1状态通过使用具有不同颜色和它们之间的延迟时间的两个飞秒激光脉冲来填充。第一脉冲激发S-0 --> S-1跃迁，而第二脉冲激发S-1 --> S-n跃迁。从S-n态的非辐射弛豫占据最低激发态。我们的结果表明，当从S-n态非辐射填充时，S1态的弛豫速度比直接由S-0 --> S-1激发泵浦时快。此外，S-n -> S-1非辐射弛豫时间被发现通过改变两个泵浦脉冲之间的延迟时间而改变。所观察到的最低激发态人口的依赖性，以及它的依赖性的两个泵脉冲之间的延迟被发现，以适应一个动力学模型，其中的S-n状态填充不同的表面（称为Si）比一个被直接激发（S-1）。A（g）型状态，J中间体，和锥形交叉导致的S-0或异构化产物（K中间体）的可能参与的框架中提出的模型进行了讨论。
We present the results of two-pump and probe femtosecond experiments designed to follow the relaxation dynamics of the lowest excited state (S-1) populated by different modes. In the first mode, a direct (S-0 --> S-1) radiative excitation of the ground state is used. In the second mode, an indirect excitation is used where the S-1 state is populated by the use of two femtosecond laser pulses with different colors and delay times between them. The first pulse excites the S-0 --> S-1 transition whereas the second pulse excites the S-1 --> S-n transition. The nonradiative relaxation from the S-n state populates the lowest excited state. Our results suggest that the S1 state relaxes faster when populated nonradiatively from the S-n state than when pumped directly by the S-0 --> S-1 excitation. Additionally, the S-n --> S-1 nonradiative relaxation time is found to change by varying the delay time between the two pump pulses. The observed dependence of the lowest excited state population as well as its dependence on the delay between the two pump pulses are found to fit a kinetic model in which the S-n state populates a different surface (called Si) than the one being directly excited (S-1). The possible involvement of the A(g) type states, the J intermediate, and the conical intersection leading to the S-0 or to the isomerization product (K intermediate) are discussed in the framework of the proposed model.