NON-ADIABATIC DYNAMICS STUDIED BY FEMTOSECOND TIME-RESOLVED PHOTOELECTRON SPECTROSCOPY
NON-ADIABATIC DYNAMICS STUDIED BY FEMTOSECOND TIME-RESOLVED PHOTOELECTRON SPECTROSCOPY
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DOI：
10.1142/9789812813473_0003
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发表时间：
2000-06
影响因子：
1
通讯作者：
C. Hayden;A. Stolow
中科院分区：
文献类型：
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作者：
C. Hayden;A. Stolow
多烯分子的激发态动力学是特别感兴趣的，因为这些分子在生物光系统中的重要性。类似的分子对于未来的分子尺度电子器件也可能是重要的。多烯分子在光生物学系统中的功能通常取决于非常快速的非绝热转变，因为非常强的光吸收S2状态，否则会迅速再辐射，经历内部转换为弱辐射S2状态，为进一步的化学过程存储能量。尽管经过多年的研究，关于简单多烯发色团的激发态动力学的问题仍然存在。最近，各种时间分辨技术，包括光电子能谱，已经开始确定这些分子中激发态演化的途径。时间分辨光电离技术已经被用于研究孤立分子中的非绝热过程很多年了。纳秒时间尺度上的光电离产率测量首次用于测量三重态苯的寿命。这种技术已经在纳秒和皮秒的时间尺度上应用于许多其他系统。3-6利用能量分辨光电子产额分离竞争电离过程，测量了氨中里德堡态的离解寿命。随着激光脉冲的缩短，光电离产额的测量已经扩展到飞秒时间域。8-10用这种方法研究了分子激发态中的多种快非绝热过程。碘苯中导致离解的非绝热跃迁的时标，11
The excited state dynamics of polyene molecules are of special interest because of the importance of these molecules in biological photosystems. Similar molecules may also be important for future molecular scale electronic devices. The functioning of polyene molecules in photobiological systems often depends on very rapid non-adiabatic transitions, because the very strongly optically absorbing, S2, state, which would otherwise rapidly reradiate, undergoes internal conversion to a weakly radiating, S₁, state that stores the energy for further chemical processes. Despite years of study, questions about the excited state dynamics of simple polyene chromophores remain. Recently, various time-resolved techniques, including photoelectron spectroscopy, have begun to determine the pathways for excited state evolution in these molecules. Time-resolved photoionization techniques have been used for a number of years to study non-adiabatic processes in isolated molecules. Photoionization yield measurements on the nanosecond time scale were first used to measure the triplet benzene lifetime. This technique has since been applied on nanosecond and picosecond time scales to many other systems. 3-6 Using energy resolved photoelectron yield to separate competing ionization processes, dissociation lifetimes of Rydberg states in ammonia have also been measured. With the availability of shorter laser pulses, photoionization yield measurements have been extended to the femtosecond time domain. 8-10 Many types of fast non-adiabatic processes in molecular excited states have been studied with this technique. Time scales for non-adiabatic transitions leading to dissociation in iodobenzene, 11